EOY

Question 1

Example of physical agent mutagens (3)

Answer 1

UV Radiation

X-Ray

Gamma rays

Question 2

Unsaturated fatty acids vs saturated fatty acids (melting point)

Answer 2

U have lower melting points than S - more double bonds = lower melting point

Question 3

Growth of chlamydomonas (4)

Answer 3

produces organic molecules in photosynthesis

absorbs minerals

causes increase in size

it reaches certain size –> divide into two daughter cells

Question 4

Meiosis 1 Prohpase 1

Answer 4

chromosomes condense

nuclear envelope disintegrates

spindle fibres form on poles

crossing over - exchange of equivalent DNA between non-sister chromatids

DNA molecule of one chromatids is cut + second cut is made at same point of other chromatid from other parent (non-sister)

DNA sections are swapped between parent chromosomes

Question 5

Explain the spontaneous formation of vesicles (2)

Answer 5

fatty acids spontaneously coalesce due to hydrophobic/hydrophillic traits

formed spherical bilayer - curved to reduce hydrophobic tail exposure

Question 6

Define hydrophilic

Answer 6

substances chemically attracted to water

Question 7

Name of bond formed between glycerol and fatty acid

Answer 7

ester bond

Question 8

Importance of an amino acid order

Answer 8

gives the protein its function

Question 9

Enzyme anabolic reactions (4)

Answer 9

synthesis of complex molecules from simpler molecules

by reducing repulsion between substrates, allowing them to bond more easily

requires energy

e.g protein/DNA synthesis

Question 10

Features of beta-pleated sheet secondary structure (2)

Answer 10

hydrogen bonds form between polypeptide chains parallel to each other

form pleated sheet shape due to tetrahedral bond angles

Question 11

Define morphological concept of species (2)

Answer 11

classifying organisms based on physical traits

used for extinct species

Question 12

Reproduction of fungi cells (2)

Answer 12

budding - daughter cell (copy) buds/separates from parent cell

form ring of tissue called budding scars

Question 13

Collagen as a fibrous protein (2)

Answer 13

3 polypeptide chains twisted together in a triple helix shape

held together by hydrogen bonds

Question 14

How structure of mitochondria relates to its function (4)

Answer 14

cristae increases surface area

matrix - space between 2 membranes

matrix contains enzymes for respiration

small space of matrix allows for high concentration gradients to form

Question 15

Mature red blood cells as atypical cells (2)

Answer 15

anucleate – no nucleus (cannot repair themselves when damaged)

cell has greater haemoglobin capacity + transport more oxygen

Question 16

Structure of smooth Endoplasmic Reticulum

Answer 16

no ribosomes on outer surface

Question 17

Acetylcholine (2)

Answer 17

nuerotransmitter that triggers muscle contraction

or promotes parasympathetic responses (relaxing body after stress)

Question 18

Intracellular Receptors

Answer 18

signal molecule is hydrophobic

many are molecular switches

Question 19

Different types of ion protein channels (3)

Answer 19

voltage-gated - respond to changes in voltage

ligand-gated - respond to binding of substance

respond to pressure

Question 20

3 most common types of membrane receptor proteins

Answer 20

G-protein coupled receptors

Receptor tyrosine

Question 21

Define immunofluorescence light microscopy (4)

Answer 21

fluorescent tag (fluorophore) - attached to antibodies specific for specimen

antibody binds to the antigen –> structure ‘tagged’ with immunofluorescence

certain wavelength of light shone onto fluorescence tag –> emits light of different colour

appear as brightly coloured spots –> can locate target molecules

Question 22

Perinuclear space

Answer 22

space between inner + outer membranes of nuclear envelope

Question 23

Vacuoles in plant cells (2)

Answer 23

regulate osmotic potential of cells - stores excess water away from cytoplasm

supports structure of cell through turgor pressure

Question 24

Features of integral proteins (3)

Answer 24

embedded in lipid bilayer

channel proteins - hydrophilic interior + hydrophobic exterior allows charged particles to pass through by diffusion

carrier proteins - involved in active + passive transport by changing shape

Question 25

Define facilitated diffusion

Answer 25

movement of particles from HC to LC facilitated/assisted by transport proteins

Question 26

Allosteric binding of oxygen to haemoglobin in alveoli (2)

Answer 26

high concentration of oxygen in alveoli easier for oxygen to bind quickly

Question 27

Synaptic transmission (3)

Answer 27

neurotransmitter binds to neuroreceptors in post-synaptic membrane ligand-gated sodium channels open - sodium ions flow in creates depolarisation - may initiate action potentials if threshold reached

Question 28

Selectivity of ion protein channels (2)

Answer 28

pore size specific to certain ions hydrophillic interior of channel proteins are specific to particular ions

Question 29

Number of hydrogen bonds between adenine + thymine

Answer 29

2 hydrogen bonds

Question 30

Inhibitory synapses (2)

Answer 30

hyperpolarises (more negative) the local membrane potential of postsynaptic cell reduces likelihood that post-synaptic neuron will fire

Question 31

Describe tertiary structure hydrogen bonds between R-groups

Answer 31

hydrogen bonds form between slightly positive hydrogen and slightly negative O or N

Question 32

Function of membrane (2)

Answer 32

separate cytoplasm from external environment separate interior of organelles from each other + from cytosol

Question 33

2nd Step of PCR process (annealing) (2)

Answer 33

sample cools to 60 degrees short primer sequences bond to complementary sequences of DNA

Question 34

Features of reception in cell signalling (4)

Answer 34

complementary binding of signal molecule (ligand) to receptor water soluble (hydrophillic) - binds to outside membrane intracellular (hydrophobic) - bind to receptors inside the cell ligand binds to receptor --> protein changes shape --> initiates transduction signal

Question 35

Describe oogenesis (3)

Answer 35

primary oocyte (2n) performs cell division + releases first polar body (n) Secondary oocyte loses a second polar body and become ovum ovum fertilised by sperm cell to form zygote

Question 36

Second growth phase of interphase (3)

Answer 36

cell continues to increase in size energy stores increase duplicated DNA checked for errors

Question 37

Define prokaryotes (3)

Answer 37

unicellular organisms that lack membrane bound organelles no nucleus e.g bacteria, archaea

Question 38

Function of insulin (2)

Answer 38

regulates amount of glucose in bloodstream in response to high glucose levels binds to receptors on cells - allows glucose to enter cells to be used or stored

Question 39

Application of property of glucose being chemically stable (2)

Answer 39

improves structural role of cellulose in plants helpful in starch and glycogen for storage

Question 40

Define a phospholipid bilayer (4)

Answer 40

double layer of phospholipids phospholipid bilayers can form when phospholipids are placed in water hydrophobic fatty acids will orient towards each other hydrophilic phosphate + glycerol will orient towards water

Question 41

Define cell proliferation (2)

Answer 41

process of cellular division/replication increases cell number and/or organism size + complexity

Question 42

Define hydrolysis (2)

Answer 42

chemical reaction where water is used to break covalent bond between monomers -OH will attach to one monosaccharide, -H will attach to other

Question 43

Define the cytoskeleton (3)

Answer 43

system of protein fibres called microtubules and microfilaments holds organelles in place maintains structure of cell

Question 44

Define respiration

Answer 44

complex metabolic process to break down carbon compounds + create energy

Question 45

Root hair cells in maintaining concentration gradients (2)

Answer 45

root hairs that increase surface area for water intake

Question 46

Define non-synonymous SNPs (3)

Answer 46

change in amino acid sequence causes change in protein function non-sense - changes codon into stop codon, polypeptide is not complete + resulting protein does not function properly mis-sense = change codon into codon coding for different amino acid

Question 47

Molecular motion in forming enzyme substrate complexes (3)

Answer 47

enzyme substrate complex only form when both are close to each other random movement causes occasional successful collision increasing substrate/enzyme amount + temperature increases chances of collision

Question 48

Difficulties with speciation (2)

Answer 48

difficult to find exact point where they become separate species hybrids could be created by 2 divergin species

Question 49

Phloem sieve tube elements as atypical cells (3)

Answer 49

phloem hollow tube has sieve-like gaps anucleate = nucleus + other components broken down sieve elements connected to other cells with nuclei + mitochondria

Question 50

How CAM cells prevent cancer (2)

Answer 50

adhesion - cells stay stuck together + behave normally signals to cells to stop dividing

Question 51

Cohesion of water for water transport in plants (5)

Answer 51

water is sucked upwards in continuous columns column of water under tension from both ends tension from roots due to attraction between soil + water tension from leaves as water lost by evaporation + attraction between water and leaf cell walls water moves upwards because force in leaves > force in roots

Question 52

Define malignant tumour (2)

Answer 52

cancer cells in tumour spread to other parts of body sometimes recur after it is removed

Question 53

Define tRNA (2)

Answer 53

transfer RNA carries amino acids to ribosomes bonded together to form polypeptides

Question 54

Define gas exchange

Answer 54

exchange of oxygen and carbon dioxide between the alveoli and bloodstreams (passive diffusion) through a permeable membrane

Question 55

Structure of nuclear envelope inner membrane

Answer 55

contains nuclear lamina (fibrous protein) - provides structural support + prevents collapse from external forces

Question 56

Factors which affect permeability of biological membranes (2)

Answer 56

size of molecule - smaller molecules more likely to pass hydrophobic nature - hydrophobic molecules more likely to pass through instead of polar molecules

Question 57

Define intracellular enzymes (2)

Answer 57

enzymes used within cells synthesized by ribosomes in cytoplasm

Question 58

Name 2 types of secondary structure (2)

Answer 58

alpha helix beta pleated sheet

Question 59

Chromatin

Answer 59

fiber of nucleosomes

Question 60

Disease modelling in CRISPR Cas-9 system (3)

Answer 60

creates animal models to simulate human diseases introduces mutations or deleting genes in animals researchers gain info into disease progression + potential treatment

Question 61

Define an anticodon

Answer 61

3-base code complementary to the matching RNA codon

Question 62

Disadvantages of electron microscopes (2)

Answer 62

only give black and white images electron beams kill specimen

Question 63

Stage 2 of aerobic respiration (link reaction) (5)

Answer 63

2 pyruvates enter matrix of mitochondria through active transport pyruvates dehydrogenated + decarboxylated enzymes remove CO2 + transfer hydrogen to NAD (NADH) pyruvate bonds with acetyl group (CoA) become 2 acetyl CoA 2 NADH formed + 2CO2 produced as waste product

Question 64

Features of non-coding genome (3)

Answer 64

98% of the human genome DNA sequences within genome that do not have information to make protein. not represented within the amino acid sequence of expressed proteins.

Question 65

Features of peripheral proteins (3)

Answer 65

hydrophilic found on surface of membrane interact with hydrophilic regions of integral proteins + phospholipid heads

Question 66

Reasons for formation of phospholipid bilayer or micelle (2)

Answer 66

hydrophobic tails point inward + away from water/aqueous environment hydrophilic heads point outward + towards aqueous environment

Question 67

High concentration gradient as a feature of gas exchange (2)

Answer 67

larger concentration gradient = faster rate of diffusion concentration gradient required for gas exchange/diffusion to function

Question 68

Allosteric binding of oxygen to haemoglobin in cells to respire (2)

Answer 68

low concentration of oxygen in alveoli easier for oxygen to disattach from haem groups

Question 69

Mutations in germ cells (2)

Answer 69

passed onto offspring - mutations inherited by offspring can cause genetic disorders, change chromosome number, increase susceptibility to certain disease

Question 70

Features of ribosomes in translation (4)

Answer 70

acts as enzyme to form peptide bonds between amino acids complex structure of small + large subunit small subunit binds to mRNA large subunit has 3 binding sites for tRNA

Question 71

Describe tertiary structure ionic bonds between R-groups (4)

Answer 71

ionic bonds between positive + negatively charged R-groups R-group binding with hydrogen ion = positively charged R-group losing a hydrogen ion = negatively charged ionic bonds are more sensitive to pH due to involvement of H+

Question 72

Define cryogenic electron microscopy (4)

Answer 72

flash-freezing sample to cryogenic temperatures (placed in liquid ethane) - makes molecules more firm/stable specimen then viewed using electron microscopy computer algorithms - create 3D image of protein molecules primarily used for structure of proteins

Question 73

Define lysosomes (4)

Answer 73

sacs surrounded by membrane containing hydrolytic enzymes (break down things using water) break down (destroy) biological molecules + old cellular organelles high concentrations found in phagocytes (white blood cells)

Question 74

Describe a glycosidic bond

Answer 74

oxygen atom shared between 2 glucose molecules

Question 75

Describe tertiary structure disulphide bonds between R-groups (3)

Answer 75

disulphide bond between amino acids with sulphur atoms e.g cysteine and methionine strongest covalent bonds

Question 76

Regeneration of RuBP (4)

Answer 76

6 CO2 can make 12 triose phosphate 10 triose phosphate (30C) used to make 6 RuBP (5C each) requires 1 ATP 2 triose phosphate left over can synthesize carbon compounds

Question 77

Reasons for DNA Replication (2)

Answer 77

cell division - new cells need new DNA for growth + tissue repair reproduction - gametes require DNA to pass on genetic information

Question 78

Factors which affect respiration rate (4)

Answer 78

Temperature pH concentration of respiratory substrates oxygen concentration

Question 79

Define the smooth endoplasmic reticulum (2)

Answer 79

produces + stores lipids (including steroids) detoxification

Question 80

Why are large uncharged polar molecules mostly impermeable to a lipid bilayer (2)

Answer 80

mostly hydrophillic due to being polar hydrophobic tails of bilayer repel hydrophillic molecules

Question 81

Bases in DNA (4)

Answer 81

Adenine (A) Cytosine (C) Guanine (G) Thymine (T)

Question 82

How are chromosomes formed from nucleosomes (3)

Answer 82

nucleosomes joined together by linker DNA nucleosomes stacked onto each other stacks form chromosomes

Question 83

Receptors as a function of membrane proteins (2)

Answer 83

bind to signaling molecules like hormones + neurotransmitters binding triggers a chain of intracellular reactions

Question 84

Features of internal intercostal muscles (3)

Answer 84

contract during exhalation ribs pulled in and down to decrease volume external intercostal muscles

Question 85

No. of ATP generated by lipids (2)

Answer 85

460 ATP produce more due to having long chains of carbon + hydrogen

Question 86

Permeability as a feature of gas exchange

Answer 86

must allow substances (O2, CO2) to pass through

Question 87

Define spliceosomes

Answer 87

large enzymes found in nucleus

Question 88

Structure of glycoproteins (2)

Answer 88

covalent bonding of carbohydrate chains to protein molecules carbohydrate group sticks out into the extracellular environment

Question 89

Features of amino acid hormones (3)

Answer 89

small molecules derived from amino acids tyrosine + tryptophan water soluble - hydrophillic bind to surface receptors

Question 90

Define magnification

Answer 90

number of times larger an image is than an object image size/actual size

Question 91

Creating action potentials

Answer 91

generator potential - few sodium channels opened to create small depolarisation many generator potentials come together to reach the threshold of an action potential

Question 92

Asteroids/Comets in influencing early earth conditions (3)

Answer 92

asteroid/comets brought water + other compounds collisions + volcanoes released methane + ammonia gas earth's early atmosphere - methane, ammonia, water vapour, CO2

Question 93

Define response to stimuli/sensitivity (2)

Answer 93

responding to changes/external stimuli in environment e.g detecting chemicals in environment --> moving towards or away from area

Question 94

Uses of excess triose phosphate produced (4)

Answer 94

glucose/starch amino acids fatty acids DNA/RNA

Question 95

Name the types of quaternary structure proteins (2)

Answer 95

Globular Fibrous

Question 96

How can CO2 concentration be controlled in photosynthesis experiments

Answer 96

dissolving sodium hydrogen carbonate in water

Question 97

Allosteric binding of haemoglobin (4)

Answer 97

O2 binds to haem group causes confirmational change that increased affinity of other haem groups binding of oxygen makes it easier to bind to more oxygen loss of oxygen makes it easier to lose oxygen

Question 98

Define aerobic respiration (4)

Answer 98

complete breakdown of glucose to generate a net gain of 36 molecules of ATP in presence of oxygen takes place in cytoplasm + mitochondria can use glucose, fats and proteins as respiratory substrates produces water + carbon dioxide as waste products

Question 99

Features of estradiol (7)

Answer 99

mainly secreted by cells of ovarian follicles regulates mesntrual cycle + reproduction regulates bone density regulates brain function regulates cholesterol mobilisation develops breast tissue + sexual organ controls inflammation

Question 100

Why the universal genetic code was preserved (3)

Answer 100

genetic code has been conserved essential for the transmission of genetic information any change to this genetic code could be detrimental to organism

Question 101

Genomic Estrogen-mediated signalling

Answer 101

migration of estrogen-receptor complexes to the cell nucleus direct interaction

Question 102

Uses of ATP (3)

Answer 102

synthesizing DNA + Protein active transport of molecules + ions across membraines move things around cells (e.g chromosomes + muscle fibers)

Question 103

Advantages of photosystems having different pigments in a structured array (2)

Answer 103

variety of pigments = enough light energy for light dependent stage energy only transferred from one close pigment to another - structure allows energy to reach reaction centre

Question 104

Describe the structure of an amino acid (5)

Answer 104

amino group NH2 (basic) carboxyl group COOH (acidic) hydrogen atom central alpha carbon atom side chains called R groups

Question 105

Gas Exchange process for blood (4)

Answer 105

oxygen in air taken to alveoli in lungs diffuses into the blood in capillaries CO2 from blood diffuse into alveoli CO2 expelled out of lungs

Question 106

Directionality of translation

Answer 106

5' to 3' direction

Question 107

Describe late prophase (3)

Answer 107

centrioles move towards opposite poles of the cell nucleolus shrinks + disappears nuclear envelop disintegrates

Question 108

Myelinated neurons as a factor which impacts speed

Answer 108

prevents leakage of neurons into the axon

Question 109

3 main classes of hormones (3)

Answer 109

Amino acid/amine hormones peptide hormones lipid based hormones

Question 110

Define a fibrous protein (3)

Answer 110

elongated polypeptides - polypetide chains linked together into narrow fibres with hydrogen bonds between them insoluble in water designed for strength + stability

Question 111

Stomata of leaf (2)

Answer 111

control water + gas exchange by opening/closing guard cells regulate size of stoma

Question 112

Define adhesion for water (2)

Answer 112

hydrogen bonds forming between water + surface of solid composed of polar molecules allows water to stick to other objects

Question 113

Function of CAM cells (cell-adhesion molecules)

Answer 113

allow cells to bind together to form tissues

Question 114

Functions of glycoproteins +glycolipids

Answer 114

cell recognition

Question 115

Define telomeres (3)

Answer 115

repetitive sequences that protect ends of chromosome. ensure that DNA is replicated correctly every cell division = telomeres lose short stretches of DNA

Question 116

Cell wall of plant cells (2)

Answer 116

made of polysaccharide cellulose maintains shape of cell/protects it

Question 117

Features of eukaryotes (11)

Answer 117

plasma membrane cytoplasm mitochondria 80S ribosomes nucleus smooth endoplasmic reticulum rough endoplasmic reticulum golgi apparatus vesicle vacuole cytoskeleton

Question 118

Penicillin as mechanism-based inhibition (3)

Answer 118

bacterial cell wall protects + prevents bacteria from bursting transpeptidase - enzyme which maintains cell wall structure by forming cross-links with polysaccharide chains penicillin binds to transpeptidase irreversibly - inhibits its function + cell wall weakens

Question 119

Metabolism of chlamydomonas (2)

Answer 119

grows heterotrophically (photosynthesis) mixotrophically - absorb organic molecules

Question 120

Strands of DNA nucleotides in relation to each other (2)

Answer 120

(anti)parallel - parallel but run in opposite directions one strand ends with phosphate group other ends with deoxyribose (pentose sugar)

Question 121

Pressure and volume changes during expiration (3)

Answer 121

volume of chest cavity decreases higher pressure inside lungs pressure wants to reach equilibrium so air exits

Question 122

Relationship between LUCA, bacteria, archaea, eukaryotes (2)

Answer 122

bacteria + archaea arose from LUCA eukaryotes - endosymbiosis of bacteria + archaea

Question 123

Deoxyribose sugar nucleotide diagram

Answer 123

-- CH2 | O CH CH -- N CH CH | | OH OH

Question 124

Define taxonomy (2)

Answer 124

the classification of living things based on similarities + differences study relationships between different organisms

Question 125

Parts of nucleotides (3)

Answer 125

pentose sugar with 5 carbon atoms phosphate group : acidic and negatively charged part of nucleic acids base that contains nitrogen - has either 1 or 2 rings of atoms in its structure

Question 126

Why is there a high concentration of Rubisco (2)

Answer 126

inefficient - slow enzyme + high energy requirements can be competitively inhibited by oxygen

Question 127

Features of plant cell (3)

Answer 127

cell wall chloroplasts vacuole

Question 128

Define a population (3)

Answer 128

group of organisms of the same species in same area rely on same resources interbreed + interact with each other

Question 129

Shape which chains of carbon atoms can form (2)

Answer 129

rings zig zag shape

Question 130

Why Lipids are not used as a main respiratory substrate (4)

Answer 130

lipids must first be broken down to glycerol + fatty acids glycerol must be further broken down to be used in glycolysis fatty acids must be broken down into acetyl groups lipids are harder to digest + transport (hydrophobic)

Question 131

PCR + gel electrophoresis use in DNA profiling (5)

Answer 131

tandem repeats - short repeated DNA sequences restriction enzymes chop DNA into fragments (lengths based on number of repeats) PCR amplifies DNA fragments DNA fragments then separated using gel electrophoresis match = same number + length of DNA fragments

Question 132

Examples of hydrophobic substances (2)

Answer 132

non-polar molecules (not positive or negative) lipids

Question 133

Define neutral/silent mutations (3)

Answer 133

mutations which do not significantly affect organism neutral mutations - occur in non-coding regions of genome + regions that do not alter function of essential genes silent mutations - occur in coding regions but do not alter amino acid sequence due to degeneracy

Question 134

Define vital capacity

Answer 134

maximum amount of air a person can exhale from their lungs

Question 135

Enzyme catabolic reactions (4)

Answer 135

breaks complex molecules into simpler molecules puts strain on the bonds, making them easier to break releases energy e.g digestion, respiration

Question 136

Features of axon terminal (synaptic) knobs

Answer 136

axon terminal (synaptic) knobs - end of nerve where impulse leaves

Question 137

Metabolism of paramecium (2)

Answer 137

breaking down nutrients obtained from environment rely on external organic sources for energy

Question 138

Advantages of compartmentalisation (3)

Answer 138

ability to create higher concentrations of certain substances within organelles ability to separate toxins + potentially damaging substances from cell control conditions in organelle (pH for enzymes)

Question 139

Features of nervous system (4)

Answer 139

central nervous system - brain + spinal cord protected by bone receives + processes bodily information + activity composed of neurons that carry electrical impulses peripheral nervous system - non-CNS nerves - connects CNS to organs, muscles, sensors

Question 140

Define conserved sequences

Answer 140

sequences remain identical or similar across species or group of species

Question 141

Reduced NAD equation (3)

Answer 141

NAD+ + 2H+ + 2e- --> NADH + H+ (reduced NAD) NAD initially has one positive charge NAD accepts 2 e + 1 p from 2 hydrogen atoms

Question 142

Define a vesicle (2)

Answer 142

small sac that transports and releases substances produced in cell by fusing with cell membrane

Question 143

What blood type does not cause rejection problems and why (2)

Answer 143

O has same structure as A and B but with one monosaccharide less

Question 144

Stages of translation (3)

Answer 144

initiation elongation termination

Question 145

Role of glycoproteins as receptors (3)

Answer 145

act as receptors on cell surfaces receive signals from other cells or molecules e.g insulin binds to glycoproteins on surface of body cells

Question 146

Define paramecium (3)

Answer 146

unicellular protozoa heterotrophs located in aquatic environments

Question 147

Regions of non-coding DNA (4)

Answer 147

regulators of gene expression introns telomeres genes for tRNA + rRNA

Question 148

Structure of chromosomes (2)

Answer 148

chromosomes are only visible during cell division 2 chromatids joined at centromere to form x-shape

Question 149

Define the DNA leading strand (3)

Answer 149

strand that can be replicated in same direction as helicase (5' to 3') strand has 3' to 5' directionality can be replicated continously (completed quicker)

Question 150

What is the DNA and RNA backbone made of

Answer 150

chain between sugar and phosphate

Question 151

Define mitochondria (2)

Answer 151

double membrane bound organelle converts glucose into ATP in respiration

Question 152

Limitations of biologocial calssification of species based on reproduction (4)

Answer 152

existence of asexual reproduction not possible for extinct species limitations of environments of species potentially interfering with species behaviour

Question 153

Define harmful mutations (2)

Answer 153

mutations that cause negative consequences for organism can cause disease, abnormality, reduce organisms survival

Question 154

Define LUCA (3)

Answer 154

last universal common ancestor original life forms that gave rise to all species existing today likely that there was more than one life form --> may have gone extinct through competition from LUCA

Question 155

Features of post-translational modification (3)

Answer 155

polypeptides synthesised by ribosomes on the rough endoplasmic reticulum are packaged in vesicles vesicles carry polypeptides to the Golgi apparatus. modifications carried out in Golgi apparatus

Question 156

Define genome

Answer 156

whole genetic information of an organism

Question 157

Explain inhibitory postsynaptic potential (5)

Answer 157

opening of ion channels --> leads to hyperpoarisation makes action potential less likely inside of psot-synaptic cell becomes more negative influx of Cl- efflux of K+

Question 158

Define receptors (2)

Answer 158

specifically shaped proteins that will bind to certain signal molecules changes shape after binding ligand

Question 159

Define cell theory (3)

Answer 159

all organisms made up of one or more cells cells = smallest unit of life all cells come from pre-existing cells

Question 160

Types of switching on mechanisms in intracellular receptors (2)

Answer 160

phosphorylation - GTP binding - GDP bound = inactive, GTP bound inactive

Question 161

Role of Sodium Potassium Pump for maintaining resting potential for Na+ ions (4)

Answer 161

few Na+ channels --> Na+ ions diffuse at slower rate no pump --> more Na+ ions will enter cell due to diffusion more Na+ ions --> more positive = depolarisation pump - actively removes Na+ ions

Question 162

Impact of radiation on gene structure (3)

Answer 162

single-strand breaks - interrupts continuity of template strand --> replication errors double strand breaks chemical alterations to bases

Question 163

Factors that influence mutation rate (3)

Answer 163

exposure to mutagens DNA repair mechanisms fidelity of DNA replication - accuracy of DNA copy

Question 164

Variation of molecular motion between enzymes and substrates (3)

Answer 164

most cases substrate smaller than enzymes = substrate moves more some substrates large + dont move much = enzyme has to move in relation to substrate some enzymes embedded in membranes = substrate does all movement

Question 165

Gene therapy in CRISPR Cas-9 system (3)

Answer 165

treats genetic disorders correcting disease-causing mutations in a patient’s cells e.g sickle cell anaemia.

Question 166

Why glucose is soluble (4)

Answer 166

soluble because it is polar contains (-OH) molecules which are polar oxygen atoms are partially negative so carbon-hydrogen (C-H) atoms are partially positive

Question 167

Collagen function

Answer 167

provides structural support to tissues + maintains their shape

Question 168

Structure of pump proteins (4)

Answer 168

ATP binds to carrier protein protein undergoes a conformational change + transfers molecules to the other side of the membrane once transported, phosphate groups leaves protein restored to original shape

Question 169

region of mRNA

Answer 169

exons : protein regions

Question 170

Location of cholesterol (2)

Answer 170

hydrophobic region attaches/interacts with hydrophobic phospholipid tail hydrophillic region attaches/interacts with hydrophillic phospholipid head

Question 171

Define genetic engineering (2)

Answer 171

process of altering DNA of organisms to introduce new characteristics, modify characterstics, remove undesired characteristics

Question 172

Limiting reactants of photosynthesis (3)

Answer 172

CO2 concentration light intensity temp.

Question 173

How does the smooth endoplasmic reticulum detoxify substances (3)

Answer 173

enzymes oxidise hydrophobic toxins SER adds polar molecules to oxidised toxins - increases water solubility broken down further with enzymes - become less reactive

Question 174

Explain excitatory postsynaptic potential (4)

Answer 174

opening of channels --> leads to depolarisation + increases chances of action potential happening inside of post-synaptic cell becomes less negative Na+ channels (come in) Ca2+ comes in

Question 175

Relationship between pressure and volume (2)

Answer 175

inversely proportional pressure increases as volume decreases

Question 176

Number of different amino acids

Answer 176

20

Question 177

Define transcription in genes

Answer 177

process where one DNA strand is used as template to produce RNA

Question 178

Recycling of amino acids by proteasomes

Answer 178

unneeded/damaged proteins can be broken down + recycled for amino acids carried out by proteasome (protein complex) hydrolyses proteins by breaking the peptide bonds between amino acids

Question 179

Define highly conserved sequences

Answer 179

sequences that remain similar over long periods of evolution

Question 180

Define translation in DNA

Answer 180

process where transcribed RNA is translated by ribosomes to produce proteins

Question 181

Recognition as a function of membrane proteins (2)

Answer 181

help in cell-cell recognition distinguishes immune system from self and non-self cells

Question 182

G0 phase of interphase

Answer 182

cell moves out of the cell cycle can be permanent or temporary

Question 183

Define introns

Answer 183

DNA base sequences in eukaryotic genes that are removed at end of transcription

Question 184

Structure of cholesterol (2)

Answer 184

4 steroid rings + hydrocarbon chain - hydrophobic polar hydroxyl group - hydrophillic

Question 185

Features of cytoplasm (3)

Answer 185

water-based jelly-like fluid suspends organelles of cell site of enzymes that carry out metabolic reactions

Question 186

Orientation of alpha-glucose (2)

Answer 186

hydroxyl group (OH) is orientated downward e.g glycogen + starch

Question 187

Features of the axon for neurons (2)

Answer 187

long single fibre away from cell body covered by Schwann cells/a myelin sheath

Question 188

Aim of Miller and Urey's experiment (2)

Answer 188

proving spontaneous origin of cells simulate earth's prebiotic conditions

Question 189

Define cytokinesis (2)

Answer 189

physical process of cell division divides cytoplasm of parental cell into 2 daughter cells

Question 190

Capillaries in maintaining concentration gradients (2)

Answer 190

walls of capillary - one cell thick (short diffusion distance) constant flow of blood

Question 191

Applications of quorom sensing (3)

Answer 191

medicine - blockicng receptors of bacteria biomediation - breakdown pollutants from environment food spoilage - autoinducers block receptors of bacteria which cause food spoilage

Question 192

Stage 1 of aerobic respiration (glycolysis) (6)

Answer 192

2 molecules of ATP phosphorylate glucose (6 carbon has phosphate added to it) lysis - phosphorylated glucose split into 2 3 carbon G3P each G3P oxidised by losing hydrogen atom 2NAD uses H atoms to produce NADH (reduced NAD) 2 ATP produced from each G3P (2 net) 1 glucose will produce net 2 ATP, 2 NADH, 2 pyruvate molecules

Question 193

Name of bond between amino acids

Answer 193

peptide bond (type of covalent bond)

Question 194

Define hydrophobic (3)

Answer 194

substances not attracted to water more attracted to other hydrophobic substances insoluble in water

Question 195

Define specific heat capacity

Answer 195

energy required to raise the temperature of 1g of material by 1 C

Question 196

Define movement

Answer 196

organisms having control over their position and location

Question 197

Synaptic signalling (2)

Answer 197

nervous system neurotransmitters diffuse from one nerve cell to stimulate the next

Question 198

Define interphase (2)

Answer 198

stage where DNA is replicated occurs before mitosis

Question 199

Define unsaturated fatty acids (3)

Answer 199

hydrocarbons have one or more double bonds causes bends in shape liquid at room temp. - bends make it difficult for molecules to pack together

Question 200

Features of Transcription (4)

Answer 200

first step for cell to build protein production of RNA (mRNA) using DNA as template transcription takes place in nucleus in eukaryotic cells transcription takes place cytoplasm for prokaryotes

Question 201

Define ventilation rate (2)

Answer 201

number of inspiration-expiration spirometry used

Question 202

Define a vacuole (2)

Answer 202

maintains osmotic balance of cell may also be used to store substances

Question 203

Gene knockout technique in mice (4)

Answer 203

prepared DNA inserted into genome of embryotic mouse cells --> replaces + deletes target gene succesful procedures grown into adult mice males + females with only one copy mated - 25% expected to have no copies of target gene (knockout mice) phenotype of knockout mice investigated to find out traits changed

Question 204

Define growth (2)

Answer 204

increase in cell size + number or dry mass over period of time e.g cell division

Question 205

Define spontaneous mutation

Answer 205

mistake made when DNA is copied during production of gametes

Question 206

Define non-conjugated proteins (2)

Answer 206

proteins with only polypeptide subunits e.g collagen + insulin

Question 207

Function of Smooth Endoplasmic Reticulum (3)

Answer 207

synthesizes lipid-based molecules - phospholipids + cholesterol + steroid hormones Enzymes in SER detoxify substances stores Calcium ions in muscle cells + releases them in muscle contraction

Question 208

PCR use in Covid testing (5)

Answer 208

swab in nose/throat collects virus RNA sample rinsed of in saline solution to become liquid RNA in sample converted to DNA using enzyme reverse transcriptase PCR amplifies bases sequences which indicate prescence of covid fluorescent markers attached to produced DNA - if level of fluorescence > target = positive

Question 210

Components of CRISPR-Cas 9 (2)

Answer 210

enzyme Cas9 - cuts DNA at specific target sites on chromosome CRISPR

Question 211

Differences between DNA and RNA (3)

Answer 211

DNA is double-stranded, RNA is single-stranded RNA has uracil instead of thymine in DNA pentose sugar of DNA is deoxyribose, pentose sugar of RNA is ribose

Question 212

What happens in semi-conservative replication of DNA (3)

Answer 212

2 strands of double helix separate - hydrogen bonds break free nucleotides pair with exposed complementary bases changes 1 DNA molecule into 2 identical ones

Question 213

Why doe unsaturated fatty acids have lower melting points (2)

Answer 213

double bonds disrupt packing of fatty acid molecules makes them easier to break apart

Question 214

Orientation of beta-glucose (2)

Answer 214

hydroxyl group (OH) is orientated upward e.g cellulose

Question 215

Define cell aggregation (2)

Answer 215

individual cells cluster together --> more efficient to obtain + share nutrients, benefiting from group protection from predators cells in cluster evolved to become differentiated to have specialised roles

Question 216

Function of DNA polymerase III (2)

Answer 216

places free nucleotides complementary to bases in template strand only builds new strands in 5' to 3' directionality

Question 217

Explain the CRISPR Cas-9 procedure for bacteria (4)

Answer 217

foreign DNA matches foreign DNA matches CRISPR spacer --> corresponding RNA identifies + binds to specific viral sequences guides Cas9 to target DNA to make precise cuts in DNA causes double stranded break that can be repaired by cell's DNA repair mechanism

Question 218

Features of peptide hormones (4)

Answer 218

polypeptide chains, small proteins, glycoproteins include insulin + oxytocin water soluble - hydrophillic bind to surface receptors

Question 219

Factors which determine how much ATP can be generated (4)

Answer 219

availability of hydrogen when respiratory substrates are broken down more hydrogen = more reduced NAD more reduced NAD = more protons to be transported across IMM more ATP generated

Question 220

Define freeze-fracture in microscopy (5)

Answer 220

sample frozen then physically broken apart vapour of carbon/platinum fired onto fracture --> replica of fracture electron microscopy used to observe replica gives image of cell's internal structure

Question 221

Shape of tRNA (3)

Answer 221

single-stranded RNA molecule folds on itself to form clover-leaf structure with double stranded regions + 3 hairpin loops

Question 222

Where can gene mutations occur (2)

Answer 222

somatic cells - all cells in body except germ cells germ cells - cells that give rise to eggs + sperms

Question 223

Stages of mitosis (4)

Answer 223

prophase metaphase anaphase telophase

Question 224

System of species classification (8)

Answer 224

Domain Kingdom Phylum Class Order Family Genus Species

Question 225

Conditions of early earth (6)

Answer 225

Surface Temp: 75-95 C single global ocean (no land masses) bombarded by asteroids/comets no ozone layer hotter liquid inner core --> weaker magnetic field --> high levels of cosmic + solar (UV) radiation extreme weather - electric storms

Question 226

Define the rough endoplasmic reticulum (3)

Answer 226

has ribosomes attached to surface ribosomes produce proteins usually used outside of cell attached to nuclear envelope

Question 227

Features of end-product inhibition (2)

Answer 227

enzymes allosterically inhibited by end-product of pathway prevents over-production of certain substance

Question 228

Examples of exocytosis (2)

Answer 228

proteins in golgi apparatus released in vesicles waste products secreted by cell

Question 229

Post-synaptic neuron (2)

Answer 229

carries impulse away from synapse receiver

Question 230

How is acetylcholine made

Answer 230

made in axon terminal combines chlorine with acetate group from Acetyl CoA

Question 231

Describe G-protein cell receptor

Answer 231

cell surface transmembrane receptor ligand binds to outside passes through thr cell membrane 7 times G-protein (complex) is inside the protein

Question 232

Define homeostasis (2)

Answer 232

maintenance of constant internal conditions e.g active transport to control concentration of ions

Question 233

Diameter of axons as a factor which impacts speed

Answer 233

wider surface area for charges to hop from sections in resting potential

Question 234

Features of DNA (2)

Answer 234

contain information for cell to carry out its functions hold instructions for making proteins

Question 235

Name 2 types of starch (2)

Answer 235

amylose amylopectin

Question 236

Lipid bilayers as barriers (3)

Answer 236

lipid-soluble non-polar molecules are permeable ions are impermeable large uncharged polar molecules (glucose) are mostly impermeable

Question 237

Describe tertiary structure hydrophobic interactions between R-groups (3)

Answer 237

water forms hydrogen bonds between polar/hydrophilic amino acids non-polar amino acids will clump in hydrophobic clusters in the interior of the protein to minimise contact with surround ing water molecules

Question 238

Inductive reasoning in cell theory (2)

Answer 238

observation - parts of diverse organisms consist of cells hypothesis - all organisms consist of ells

Question 239

Define a ligand

Answer 239

specially shaped molecule that will bind to a specifically shaped larger molecule

Question 240

Define resting potential of a neuron (4)

Answer 240

membrane potential when a neuron is not transmitting a signal more Na+ outside, more K+ inside potential difference - voltage is at -70 mV sodium-potassium pump - pumps 3 Na+ out and 2 K+ in channels - K+ ions flow out at faster rate than Na+ ions flow in

Question 241

High SA:V ratio as a feature of gas exchange (2)

Answer 241

large respiratory surface for diffusion enough SA for gas exchange per volume of air

Question 242

Define cell differentiation (3)

Answer 242

involves turning on of genes necessary for function of the specialised cell and turning off of genes unecessary for function of the specialised cell regulation of gene expression can be controlled by changes in environment of the cell

Question 243

Define the CRISPR Cas-9 system for bacteria (3)

Answer 243

used by bacteria against invading foreign DNA (viruses) incorporate short segments of foreign DNA into their own genome bacteria create molecular record of previous infections

Question 244

Stages of transcription (3)

Answer 244

DNA strands separated into 2 stands + RNA polymerase binds to DNA strand RNA polyemrase builds mRNA on one of strands (complementary to template strand/antisense strand) terminator sequence ("stop" codon) in DNA reached + mRNA detached

Question 245

refractory period

Question 246

Tetranucleotide hypothesis (2)

Answer 246

DNA contains repeating sequence of 4 bases (4 nucleotides occur in equal amounts) DNA was single-stranded

Question 247

Cellulose characteristics (3)

Answer 247

structural sugar in plants strong - hydrogen bonds between chains create lattice structure 1,4 glycosidic bond

Question 248

Applications of water's thermal conductivity

Answer 248

high water content in blood --> can carry heat from parts of body to parts that need more heat or parts that dissipate heat

Question 249

Chloroplasts of plant cells (4)

Answer 249

double membrane bound organelle converts light energy into chemical energy through photosynthesis type of plastid contains pigment chlorophyll - makes it green

Question 250

Theory of endosymbiosis (2)

Answer 250

eukaryotic organisms engulfed prokaryotic cell capable of generating energy from oxygen cells remained inside host cell --> carried out aerobic respiration + providing energy to host cells (mitochondria)

Question 251

Define macromolecules

Answer 251

molecules composed of a large number of atoms

Question 252

Define the daughter cell

Answer 252

mother cell divides into 2 daughter cells

Question 253

Define a dipeptide

Answer 253

2 amino acids linked by a condensation reaction

Question 254

Cyclic photophosphorylation (3)

Answer 254

light energy causes excitation of electrons from PSI electrons move to electron carriers to pump H+ across electrons will return to same PS1 after moving along carriers

Question 255

Using a microscope (6)

Answer 255

start with lowest magnification + stage at the highest position. adjust coarse + fine focus to get clear image of specimen look through eyepiece anticlockwise to move specimen further from lens, and clockwise to move it closer use fine focus knob/wheel to image clearer adjust magnification - rotating nosepiece to use different objective lens

Question 256

Role of glycoproteins in cell to cell recognition (2)

Answer 256

acts as markers on the surface of cells so they can be identified e.g immune cells attack foreign cells with different glycoproteins

Question 257

Structure of glycolipids (4)

Answer 257

covalent bonding of carbohydrates to lipids ampiphatic located on external surface of membrane carbohydrate extends outside of membrane

Question 258

Paracrine signalling (2)

Answer 258

moleucle (neurotransmitter) released by one cell acts on neighboring target cells diverse group of hydrophillic molecules (dopamine, serotonin)

Question 259

Features of single nucleotide polymorphisms (2)

Answer 259

occur when one nucleotide is replaced by another nucleotide in DNA sequence effect on protein structure depends on whether substitution is synonymous or non-synonymous

Question 260

Pseudogenes (2)

Answer 260

non-coding gene regions leftovers from genes experiencing too much SNPs

Question 261

Number of carbon atoms for pentose (2)

Answer 261

5 e.g ribose

Question 262

ATP generation in photosytems II (2)

Answer 262

hydrogen ions accumulate in intermembrane space H+ diffuse through ATP synthase to phosphorylate ADP to ATP

Question 263

Describe early prophase (4)

Answer 263

chromosomes become more distinct coil up shorten thincken

Question 264

Domain in species classification

Answer 264

DNA contained in nucleus

Question 265

Define chemiosmosis

Answer 265

flow of protons (H+) down electrochemical gradient to generate energy

Question 266

Why are lipid-soluble non-polar molecules permeable to a lipid bilayer

Answer 266

no polarity = not repelled by hydrophobic tails

Question 267

cyclin B level of mitosis

Answer 267

essential for formation of mitotic spindles + alignment of chromatids

Question 268

Different types of R-groups (3)

Answer 268

charged R-groups which form ionic bonds R-groups with sulphur atoms that form disulphide bridges hydrophilic + hydrophobic - some are polar or charged

Question 269

Features of mechanism-based inhibition (3)

Answer 269

irreversible binding of inhibitor to A.S through covalent bond enzyme permanently loses catalytic ability harmful to organisms

Question 270

Describe the secondary structure of proteins (2)

Answer 270

the folding patterns that occur within the polypeptide chain hydrogen bonds between O and H atoms on adjacent amino acids form structure

Question 271

Reduction of GP stage of Calvin cycle (2)

Answer 271

one ATP molecule adds phosphate to GP hydrogen added to GP from NADPH to become triose phosphate

Question 272

3 Domain system of life (3)

Answer 272

bacteria archaea Eukarya (Eukaryotes)

Question 273

How ATP works (4)

Answer 273

ATP has 3 phosphates linked through high energy bonds breaking of phosphate group (hydrolysis) releases energy ATP --> ADP + one phosphate group ADP converted back into ATP through respiration

Question 274

Stage 3 of aerobic respiration (krebs cycle) (7)

Answer 274

takes place in matrix of mitochondria acetate from Acetyl CoA (2C) binds with oxaloacetate (4C) to make citrate (6C) Co-A goes back to link reaction oxidative decarboxylation - CO2 molecule removed + NAD becomes NADH + citrate becomes 5-carbon compound 2nd oxidative decarboxylation - another CO2 molecule removed + NAD becomes NADH + one molecule of ATP formed + 4-carbon compound 2H used to reduce FAD + H2O added to 4-carbon compound + NAD reduced again to make oxaloacetate per glucose 6 reduced NAD, 2 reduced FAD, 2 ATP, 4 molecules of CO2

Question 275

Define viscosity (3)

Answer 275

how easily a fluid is able to flow more viscosity --> more friction + resistance to flow due to internal friction when on part of a fluid moves faster relative to another part

Question 276

Hydrophilic signalling molecules (5)

Answer 276

proteins amino acids peptides nucleotides cannot pass through cell membrane

Question 277

Condensation Polymerisation (3)

Answer 277

two molecules join together one molecule loses a hydroxyl group (-OH), another loses a hydrogen atom (-H) causes formation of water

Question 278

Nucleolus

Answer 278

produces RNA which is made into ribosomes (move out of nucleus to produce proteins)

Question 279

Categories of cell signalling (4)

Answer 279

paracrine signalling autocrine signalling endocrine signalling signaling by direct contact

Question 280

Features of the R-group in amino acids (2)

Answer 280

R-groups vary + make amino acids different from each other affects the way the amino acid bonds with another amino acid

Question 281

Making temporary mounts of cells/tissues (onion) (5)

Answer 281

scapel to cut piece off (onion) tweezers to place onto glass slide add drop of iodine lower cover slip over specimen gently press cover slip to push out bubbles

Question 282

Pressure and volume changes during inspiration (3)

Answer 282

volume of chest cavity increases lowers pressure inside lungs (lower pressure compared to outside) pressure wants to reach equilibrium so air enters in

Question 283

Name 3 forms of RNA (3)

Answer 283

mRNA rRNA tRNA

Question 284

Role of conserved and highly conserved sequences (2)

Answer 284

provide clues about function/importance sequences for evolution of species functional constraints - selective pressures prevent mutations in these genes as they are vital for life

Question 285

Hydrophobic signalling molecules (3)

Answer 285

steroids - hormones gases can enter cell membrane

Question 286

Advantages of electron microscopes (2)

Answer 286

shorter wavelengths than light --> higher resolution magnification of 500,000x

Question 287

Function of glycoproteins (4)

Answer 287

Cell-cell recognition act as receptors on surface of cells can act as ligands structural support of cells + tissue

Question 288

Movement of carbon dioxide in body as an example of simple diffusion (3)

Answer 288

CO2 diffuses from cells (high CO2 concentration) to blood (lower CO2 concentration) CO2 reaches lungs CO2 diffuses from blood (high CO2 concentration) to alveoli (low CO2 concentration)

Question 289

CRISPR Cas-9 in gene editing (4)

Answer 289

creating single guide RNAs (sgRNA) to target specific genes for modification or deletion sgRNA molecule specifically targets + bind to a particular DNA sequence of interest guides Cas9 enzyme to location and enables it to make precise cuts in the DNA, resulting in double-strand break. scientists can add, delete or modify the DNA sequences at that point

Question 290

Define atypical cells (2)

Answer 290

contain abnormal numbers of organelles in eukaryotes do not contain some of organelles in eukaryotes

Question 291

3 Stages of cell signalling (3)

Answer 291

reception - detection of signal molecule coming from outside of cell transduction - convert signal to form that can bring about cellular response response - cellular response to signal molecule

Question 292

Application of glucose property of being easily oxidised (2)

Answer 292

oxygen important reactant for cellular respiration broken down by losing electrons to oxygen to form CO2 and H2O

Question 293

Function of NAD in respiration (2)

Answer 293

functions as coenzyme is a hydrogen carrier - able to be reduced + oxidised

Question 294

myelination

Answer 294

action potential hop between gaps of myelin sheath called nodes of ranvier

Question 295

Function of spontaneous formation of vesicles (2)

Answer 295

interior provides different chemical environment to outside allows cell to control/maintain conditions (e.g pH level, solute concentration)

Question 296

Applications of glucose being soluble (2)

Answer 296

polar so able to dissolve in water dissolves in plasma - can be transported in blood, OH groups bond with water in plasma

Question 297

Role of oxygen in electron transport chain (3)

Answer 297

electrons must go somewhere O2 split into individual oxygen atoms each O2 molecules joins with 4e- + 4H+ to form 2 H2O molecules

Question 298

Define globular proteins (4)

Answer 298

spherical shaped proteins with irregular folds soluble in water play roles as enzymes, transporters, regulators e.g insulin, haemoglobin, enzymes

Question 299

Define excretion

Answer 299

removal of metabolic waste

Question 300

Oxidisation as a property of glucose (3)

Answer 300

addition of oxygen to a molecule loss of hydrogen atom loss of electrons to another atom/ion

Question 301

Define selective permeabiltiy

Answer 301

property of cell membranes that allow certain molecules to enter a cell

Question 302

Define transpiration

Answer 302

loss of water by leaves through evaporation

Question 303

How is a respirometer used to measure the rate of reaction (6)

Answer 303

rate of oxygen consumption used as indicator of respiration organism placed in closed system alkaline solution added to absorb CO2 decrease in volume of gas in tube due to oxygen being used in respiration reduces pressure in tube due to reduced oxygen liquid will move towards tube

Question 304

cyclin E level of S phase

Answer 304

cyclin E is used for DNA replication + promotes centromere duplication

Question 305

Rf chromatography formula

Answer 305

distance travelled by sample/distance travelled by solvent

Question 306

Effect of R-group hydrophobic polarity on tertiary structure (2)

Answer 306

R-groups reside in protein interior stabilises protein - maximises hydrophobic interactions within centre + hydrogen bonding between amino acids on surface + water

Question 307

Describe metaphase (2)

Answer 307

centrioles at poles grow/produce spindle fibers spindle fibres attach to centrometre of chromosomes

Question 308

Homeostasis of paramecium/chlamydomonas

Answer 308

constant internal environment maintained by collecting excess water in contractile vacuoles + expelling it through plasma membrane (osmoregulation)

Question 309

Procedure of post-transcriptional modification (5)

Answer 309

transcription - synthesis of pre-mRNA addition of a 5' cap + poly-A tail - protect the mRNA molecule from degradation by stabilising ends 5' cap = modified nucleotide added to 5' end of RNA poly-A tail - 100-200 adenine molecules added to 3' of RNA splicing - removes (excises) introns and joins (ligates) exons to form mature mRNA.

Question 310

Synthesis phase of interphase

Answer 310

DNA is replicated in the nucleus

Question 311

Describe semi-conservative DNA replication (5)

Answer 311

hydrogen bonds between bases break through enzyme helicase DNA splits into 2 strands enzyme DNA polymerase moves along strands free floating nucleotides pair with complementary base in strands 2 DNA helixes form

Question 312

Define resolution (2)

Answer 312

ability to distinguish 2 close points as separate rather than one clarity of image

Question 313

Function of recycling amino acids by proteasomes (3)

Answer 313

proteome = total proteins made within body production of proteins + large supply of amino acids needed to maintain proteomes provides amino acids to do this

Question 314

Define trans unsaturated fatty acids (2)

Answer 314

hydrogen atoms attached to carbon atoms around double bond are on different sides linear shape + less flexible than cis

Question 315

Importance of Chargaff's experiment (3)

Answer 315

hinted at complementary base pairing helped watson and crick build their double helix model dispelled tetranucleotide hypothesis

Question 316

Define simple diffusion

Answer 316

movement of molecules from a region of high concentration to a region of low concentration down a concentration gradient

Question 317

Amylopectin property (3)

Answer 317

branch shape allows amylopectin to be more packed together - allows for more efficient storage of glucose adding + removing glucose is quicker since branch shape has more ends major component of starch

Question 318

Function of cholesterol in lipid bilayer (3)

Answer 318

low temperatures - cholesterol prevents fatty acid chains of the phospholipids from fitting closely together prevents membranes from freezing high temperatures - cholesterol reduces fluidity

Question 319

Evidence for LUCA

Answer 319

universal genetic code across all living organisms may have originated from LUCA

Question 320

Features of Gas Exchange (5)

Answer 320

permeable membrane large SA - faster diffusion ventilation to keep surface moist thin walls for short diffusion distance concentration gradient

Question 321

Features of diaphragm (3)

Answer 321

muscle that forms "floor" of lungs inhalation - contracts/flattens to increase volume of chest cavity + abdominal muscles relax exhalation - relaxes (dome shape) to decrease volume of chest cavity + abdominal muscles contract

Question 322

Nutrition of paramecium (3)

Answer 322

engulfs food particles in vacuoles where digestion takes place nutrients then absorbed into cytoplasm of the cell feeds on microorganisms (e.g bacteria, algae and yeast)

Question 323

Why proteins are not used as main respiratory substrate

Answer 323

produce toxic nitrogenous wastes (NH3)

Question 324

Mutations in somatic cells (2)

Answer 324

can cause diseases in person's lifetime (e.g cancer) not passed onto offspring

Question 325

Movement of paramecium

Answer 325

whip-like cilia propel paramecium

Question 326

Photosynthesis equation (2)

Answer 326

6CO2 + 6H2O --> C6H12O6 + 6CO2 carbon dioxide + water --> glucose + oxygen

Question 327

Define plastid (2)

Answer 327

small organelle responsible for manufacturing/storing chemical energy plant cell specific

Question 328

Evidence to support RNA first hypothesis (3)

Answer 328

RNA can self-replicate - short RNA sequences can duplicate other RNA molecules RNA has some catalytic activity - could have initially acted as genetic material + enzymes ribozymes still catalyse peptide bond formation in protein synthesis

Question 329

Features of grana (2)

Answer 329

stacks of thykaloids provide SA for as much photosystems, ETCs as possible

Question 330

How cytokinesis works in plant cells (2)

Answer 330

formation of cell plate - created by fusion of vesicles containing cell wall material (cellulose) cell plat grows outward until it reaches the existing cell wall that it fuses with

Question 331

Describe sucrose

Answer 331

alpha-glucose molecule and fructose molecule joined by a glycosidic bond

Question 332

Function of active transport for protein pumps (3)

Answer 332

take up essential nutrients remove waste material from cell maintain correct ion concentrations inside cells

Question 333

Features of insulin as a globular protein (4)

Answer 333

has 2 polypeptide chains - alpha and beta held in 3D shape by hydrogen bonds, hydrophobic interactions, disulphide bonds has hydrophilic exterior - allows insulin to react with water + other hydrophilic molecules in blood, able to travel through blood + bind to its receptors has hydrophobic interior - stabilises globular shape, allows insulin to bind to receptor

Question 334

Structures of typical cells (3)

Answer 334

plasma membrane cytoplasm DNA

Question 335

Features of the axon hillock in neurons (2)

Answer 335

connects cell body to axon site where action potential generated

Question 336

Growth of paramecium (2)

Answer 336

consumes food --> enlarges certain size reached --> divides into 2 daughter cell

Question 337

Why pH affects enzyme activity (2)

Answer 337

prescence/abscence of hydrogen ions affects ionic bonds between amino acids changes AS shape

Question 338

Features of prokaryotes (6)

Answer 338

cell wall plasma membrane cytoplasm naked DNA in a loop 70s Ribosomes plasmid

Question 339

Features of glycogen (2)

Answer 339

insoluble due to large molecular size - does not affect osmotic concentration of cells branched structure - can be easily hydrolysed to produce glucose

Question 340

Define ventilation (3)

Answer 340

involves physical movement of air into and out of lungs inhalation allows blood to become oxygenated exhalation removes CO2 in blood

Question 341

Examples of chemical mutagens (3)

Answer 341

mustard gas nitrous acid Formaldehyde

Question 342

Define metabolism

Answer 342

complex network of interacting chemical reactions in living organisms

Question 343

3rd Step of PCR process (extention phase) (2)

Answer 343

Taq polymerase replicates DNA using primers as starting point once DNA is replicated, DNA is heated to separate + cycle repeats

Question 344

Thermal conductivity as a property of water

Answer 344

high thermal conductivity = good at absorbing/transferring heat

Question 345

Adaptations of mammalian lungs (3)

Answer 345

maximise surface area through alveoli pneumocytes alveoli surrounded by capillaries

Question 346

Examples of hydrophilic substances (2)

Answer 346

glucose positive or negative ions (e.g sodium + chloride ions)

Question 347

Directionality of DNA in DNA translation (3)

Answer 347

ribosome reads RNA sequence ribosome that carries out translation moves along RNA to 3' end 5' to 3' directionality

Question 348

Stages of interphase (4)

Answer 348

first growth phase G0 phase synthesis phase second growth phase

Question 349

Function of non-coding sequences in genes (4)

Answer 349

regulators of gene expression introns : found in eukaryotes, removed after transcription telomeres : found at ends of chromosomes to ensure correct replication genes for tRNA and rRNA

Question 350

Define a specimen

Answer 350

object being viewed under a microscope

Question 351

Electron transport chain of non-cyclic photophosphorylation (5)

Answer 351

electrons released from PSII passed along electron carriers onto PSI electrons re-excited by light energy from PSI electrons passed onto protein ferrodoxin electrons from ferrodoxin react with H+ in stroma to form H atoms NADP --> reduced NADP (NADPH) (accepts 2 electrons from PSI + 2 H+ from stroma)

Question 352

Benefits of species classification (3)

Answer 352

communication of biological info between scientists species in same group likely share a common ancestor - info. on how species evolved characteristics of individual species in a group can be predicted if the group's characteristics is known

Question 353

Gonadotrophin releasing hormone (3)

Answer 353

causes pituitary gland to make + secrete hormones men - these hormones cause testicles to make testosterone women - cause ovaries to make estrogene + progesterone

Question 354

Directionality of DNA in DNA transcription (2)

Answer 354

nucleotides added to 3' end of polymer 5' phosphate of free nucleotide links to 3' end of growing polymer

Question 355

Number of possible combinations of DNA bases (2)

Answer 355

4^n where n is the number of bases

Question 356

Nutrition of chlamydomonas (2)

Answer 356

autotroph uses large cup-shaped chloroplast to photosynthesize

Question 357

Where acetylcholine is made (3)

Answer 357

stored in vesicles in axon terminal performs exocytosis in response to nerve impulse activates post-synaptic cell by binding to specific receptor

Question 358

Effects of estrogen

Question 359

Define endocytosis (3)

Answer 359

moves particles into cell cell membrane engulfs particles membrane pinches off to form vesicle with particles

Question 360

Define glycoproteins

Answer 360

proteins that have one or more carbohydrates attached to them

Question 361

Necessary steps for the spontaneous origin of cells to be brought about by evolution (5)

Answer 361

formation of simple organic compounds (amino acids + hydrocarbons) catalysis - control over chemical reactions larger organic molecules formed from simpler ones self-replication of molecules compartmentalisation - membrane to enclose cell contents

Question 362

Cell recognition of glycoproteins + glycolipids (2)

Answer 362

act as "markers" on cell surface help cell to cell communication

Question 363

Procedure of Miller and Urey (4)

Answer 363

water vaporised --> run through gases + electric sparks cooling jacket to condense water water droplets represented primordial soup water droplets collected + analysed

Question 364

Define variation

Answer 364

differences between members of a group

Question 365

Define a pyrimidine (4)

Answer 365

Thymine Cytosine Uracil has one ring

Question 366

Define beneficial mutations (2)

Answer 366

mutations that are advantageous to organism improve ability to adapt, reproductive success, resistance to disease

Question 367

Describe maltose

Answer 367

disaccharide formed from 2 alpha-glucose molecules joined by a glycosidic bond

Question 368

Name of liquid lipids at room temperature

Answer 368

oils

Question 369

Define benign tumour (2)

Answer 369

localised and does not spread to other parts of body most respond well to treatment

Question 370

Define a phosphodiester bond

Answer 370

occurs when 2 hydroxyl groups in phosphoric acid react with groups in other molecules to form 2 ester bonds

Question 371

Function of gyrase enzyme in DNA (2)

Answer 371

moves ahead of helicase relieving tension created by unwinding DNA

Question 372

Define amphipathic molecules

Answer 372

molecules with both hydrophobic and hydrophillic properties

Question 373

Pre-synaptic neuron (2)

Answer 373

carries impulse towards synapse "sender"

Question 374

Temperature as a factor which impacts neuron speed

Question 375

Describe amylose (2)

Answer 375

polysaccharide made of glucose monomers linked through alpha-1,4 -glycosidic bonds helical shaped chain

Question 376

Define sensory neurons (2)

Answer 376

long axons transmits nerve impulses from sensory receptors to CNS

Question 377

Materials used in the Hershey-Chase experiment (3)

Answer 377

virus - T2 bacteriophage bacteriophage inner DNA coated in radioactive phosphorous bacteriophage outer protein coated in radioactive sulfur

Question 378

Miller-Urey hypothesis

Answer 378

spontaneous generation of simple organic molecules in pre-earth conditions (amino acids, carbohydrates, lipids)

Question 379

Features of Thykaloids (2)

Answer 379

flattened membrane-bound sacs contain photosystems

Question 380

Evolution of chloroplasts (3)

Answer 380

endocytosis of a prokaryotic cell prokaryotic cell could convert light energy to chemical energy eventually evolved into chloroplast

Question 381

Define a mutagen

Answer 381

chemical or physical agent which can cause a mutation

Question 382

Define transmission electron microscopes (3)

Answer 382

beam of electrons passed through specimen electrons absorbed by denser parts of sample + scattered/pass through less dense areas picked up by electron detector ---> forms image

Question 383

Plasmids as components of prokaryotes

Answer 383

small/circular pieces of DNA that can be transferred from one prokaryotic cell to another (horizontal gene transfer)

Question 384

Define reproduction

Answer 384

production of offspring + passing down of genes

Question 385

Define fluorescent dye light microscopy (3)

Answer 385

dye added to sample --> attach to certain structures. dye absorbs light at one wavelength --> re-emits fluorescence labelled areas become brightly coloured spots --> can locate target molecules in specimen

Question 386

Define regulators of gene expression (4)

Answer 386

promoters DNA sequences that are binding sites for proteins e.g enhancers + silencers enhancers - increase rate of transcription silencers - decrease rate of transcription

Question 387

Define mitosis (2)

Answer 387

process of nuclear division before a cell physically divides into 2 cell's DNA is copied into 2 daughter cells before mitosis

Question 388

Define post-transcriptional modification (2)

Answer 388

process where mRNA which is produced needs to be modified before translation introns are removed using spliceosomes

Question 389

Links between bases of DNA (2)

Answer 389

Adenine forms hydrogen bonds with thymine guanine forms hydrogen bonds with cytosine

Question 390

Movement of oxygen in body as an example of simple diffusion (3)

Answer 390

red blood cells transport oxygen from lungs to body's cells oxygen diffuses from alveoli to RBCs in capillaries surrounding alveoli oxygen diffuses from high concentration in RBC to low concentration in cells

Question 391

Describe the 5' to 3' directionality of DNA (3)

Answer 391

5 and 3 = 5th + 3rd carbon on pentose phosphate binds at 5' and 3' one strand will start with 5' and end with 3', other strand will start with 3' and end with 5'

Question 392

cyclin D level of G1 phase

Answer 392

cyclin D levels gradually increase

Question 393

Define nutrition (2)

Answer 393

intake/production of nutrients nutrients obtained through external environment or produced from inorganic material

Question 394

Why water is a good solvent (5)

Answer 394

polar nature of water molecule forms shells around both charged + polar molecules prevents molecules from clumping together so they remain in solution water's partially negative oxygen pole attracted to positive ions water's partially positive hydrogen pole attracted to negative ions both dissolve

Question 395

Structure of saturated fats in membranes (3)

Answer 395

no kinks in chains chains fit together better higher melting points

Question 396

Structure of mitochondria (3)

Answer 396

has 2 membranes - outer + inner outer membrane is permeable + contains transport proteins (porins) inner membrane folded into cristae

Question 397

Types of receptors (2)

Answer 397

plasma membrane receptor intracellular receptor

Question 398

Transport as a function of membrane proteins (2)

Answer 398

facilitate movement of molecules inside + outside cell channel + carrier proteins

Question 399

Advantages of PCR in Covid testing

Answer 399

sensitive - viral RNA replicated so miniscule virus contents detected

Question 400

Nuclear pores (2)

Answer 400

channel proteins regulate mRNA leaving nucleus for rough endoplasmic reticulum + free ribosomes

Question 401

Features of post-transcriptional modification (3)

Answer 401

mRNA must be prepared for translation genes contain non-coding information --> must be removed only for eukaryotes

Question 402

Chlamydomonas (3)

Answer 402

genus of unicellular green algae located all over the world (e.g soil, fresh water, oceans, snow on mountain tops) autotrophs

Question 403

Define saturated fatty acids (3)

Answer 403

straight shape due to no double bonds between carbon atoms carbon atom in hydrocarbon bonds to 4 atoms fatty acids can pack together, forming solid at room temp.

Question 404

Define karyotype

Answer 404

complete set of chromosomes in cell

Question 405

Factors which impact speed of nerve impulse (3)

Answer 405

amount of myelinaton diameter of axon temperature

Question 406

Elongation stage of translation (5)

Answer 406

ribosome moves along mRNA, one codon at a time as each codon moves into place, new tRNA carries corresponding amino acid, attaches + moves previous tRNA molecules to the next position new amino acids are delivered = condensation reactions catalysed + peptide bonds formed repeats until termination codon reached

Question 407

Describe amylopectin (2)

Answer 407

polysaccharide made up of glucose monomers linked through alpha-1,4-glycosidic bonds with ocassional 1,6-glycosidic bonds branched shaped chain

Question 408

Define a tryglyceride (4)

Answer 408

non-polar macromolecule + most common type of lipid formed from one molecule of glycerol + 3 fatty acids glycerol stays the same but there are different fatty acids fatty acids = carboxyl groups (COOH) with a hydrocarbon tail

Question 409

Define anaerobic respiration (4)

Answer 409

partial breakdown of glucose to produce net 2 ATP in absence of oxygen takes place in cytoplasm only carbohydrates as respiratory substrates produces lactic acid/lactate as a waste product

Question 410

How much ATP is created from aerobic respiration of a glucose molecule

Answer 410

38

Question 411

Define a promoter (3)

Answer 411

section of DNA that initiates gene transcription proteins known as transcription factors bind to promotor- act as binding point for RNA polymerase enzymes that catalyse transcription

Question 412

Why are ions impermeable to a lipid bilayer (2)

Answer 412

ions have + and - charges so will interact will polar water hydrophobic tails of bilayer repel hydrophilic ions

Question 413

Features of fungal cells (3)

Answer 413

cell wall (made of chitin) large vacuoles centrioles

Question 414

Define cohesion

Answer 414

ability of water molecules to stick together

Question 415

Features of translation (3)

Answer 415

only genes transcribed into mRNA are translated into proteins mRNA moves out of nucleus via nuclear pore once transcribed mRNA combines with ribosome in cytoplasm

Question 416

Miller and Urey's closed system (3)

Answer 416

water - simulated ocean gas inlet - to add reducing gases (methane, ammonia, hydrogen) electrical sparks - simulate electric storms

Question 417

Process of divergence during speciation (4)

Answer 417

develop mutations different from each other become more different to each other as they become more compatible to the environment they are in become more genetically different to the extent where they cannot reproduce with each other --> become separate species

Question 418

Why bases are complementary to each other

Answer 418

complementary bases form hydrogen bonds with each other but not with other bases

Question 419

Role of glycoproteins as ligands

Answer 419

ligands - molecules that bind to receptors to initiate a biological response

Question 420

Define an enzyme (3)

Answer 420

biological catalysts speed up chemical reactions + increase rate of occurrence globular proteins

Question 421

Functions of membrane proteins (4)

Answer 421

Transport Recognition Receptors Enzymes

Question 422

Vacuole in animal cells (2)

Answer 422

expels excess water digest food/pathogens taken by endocytosis

Question 423

Causes of variation within a species (4)

Answer 423

mutation gene flow meiosis sexual reproduction

Question 424

Disadvantages of PCR in Covid testing (2)

Answer 424

expensive equipment results are not immediately available

Question 425

micrometers to nanometers

Answer 425

1 micrometer = 1000 nanometers

Question 426

Response to stimuli of chlamydomonas (2)

Answer 426

senses light changes using its "eye spot" (photoreceptor) moves towards brighter region to increase photosynthesis rate

Question 427

Fish gills in maintaining concentration gradients (3)

Answer 427

directly extract oxygen from water capillaries located in gills oxygenated blood flows separately from deoxygenate blood

Question 428

Define speciation

Answer 428

formation of new/distinct species due to evolution

Question 429

Inspiratory reserves

Answer 429

volume of air that can be inhaled forcefully after a normal breath

Question 430

Features of alpha-helix secondary structure (2)

Answer 430

polypeptide chain forms helical shape hydrogen bond forms between amine hydrogen of one amino acid + carboxyl oxygen of another 4 residues away

Question 431

Features of lipid-based hormones

Answer 431

derived from cholesterol insoluble in water - hydrophobic require carrier protein to attach to transport via blood remain in circulation longer

Question 432

Define non-essential amino acids (2)

Answer 432

amino acids which can be produced by the body 11/20

Question 433

Purpose of cell membrane (2)

Answer 433

separate internal components/organelles of cell from outside environment regulate movement of substances

Question 434

How is a gene expressed (3)

Answer 434

copying base sequence - copy made using RNA adenine in RNA pairs with uracil instead of thymine synthesiszing a protein - base sequence of RNA translated into amino acid sequence of protein

Question 435

Define ATP (2)

Answer 435

consist of adenine, ribose sugar, 3 phosphate groups used for temp. storage of energy + energy transfer

Question 436

First Step of PCR process (melting/denaturation) (2)

Answer 436

heating to 95 degrees for 30 to 60 seconds hydrogen bonds between DNA strands broken

Question 437

Why leaves are green (2)

Answer 437

chlorophyll a + b absorbs other lights more + reflects green light most pigments are bad absorbers of green light

Question 438

Define the DNA lagging strand (2)

Answer 438

strand that cannot allow DNA polymerase III to move in 5' to 3' directionality strand has 5' to 3' directionality

Question 439

Upper epidermis of leaf (2)

Answer 439

thin + transparent allows light to reach palisade mesophyll cells

Question 440

Define an action spectrum (2)

Answer 440

graph comparing rate of photosynthesis with wavelength of light shows which wavelengths are good for photosynthesis

Question 441

Genetic engineering of microorganisms (3)

Answer 441

make modifications to genetic material of bacteria, yeast or other microorganisms. enhance microorganisms' ability to produce valuable compounds such as pharmaceuticals, biofuels and enzymes. creation of efficient microbial factories to contribute to sustainable production

Question 442

DNA strand replication for lagging strand (3)

Answer 442

DNA polymerase III adds nucleotides away from fork movement (opposite to leading) nucleotides added in sections as replication fork exposes more of template sections called Okazaki fragments

Question 443

Factors which affect enzyme activity (4)

Answer 443

substrate concentration enzyme concentration temperature pH

Question 444

Define rRNA (2)

Answer 444

ribosomal RNA found in ribosomes decodes mRNA into amino acids

Question 445

DNA polymerase III in proofreading (2)

Answer 445

proofreads newly formed DNA strand while it is built nucleotide paired with mismatched base = incorrect nucleotide replaced with correct

Question 446

Define deductive reasoning (2)

Answer 446

starting with a rule/hypothesis testing the rule through experiments

Question 447

Chargaff's results (2)

Answer 447

concentration/amount of adenine equal/similar to thymine concentration/amount of cytosine equal/similar to guanine

Question 448

Function of respirometer (2)

Answer 448

simple devices measure rate of respiration in organism that respire aerobically

Question 449

Photosynthesis light-dependent stage (4)

Answer 449

photons of light hit pigments inside photosystems excite electrons within the molecules excited electrons transferred to reaction centre photoactivation - photochemical reaction occurs which emits excited electron

Question 450

Define an allosteric site

Answer 450

second active site for a different substance to bind/unbind to

Question 451

Function of saturated fats in membranes

Answer 451

make membrane denser + more rigid

Question 452

Specific heat capacity as a characteristic of water (2)

Answer 452

increase in temperature must have hydrogen bonds broken with energy must lose an equal amount of energy to cool down

Question 453

Directionality of DNA polymerase

Answer 453

5' carbon to 3' carbon

Question 454

How are DNA nucleotides held together (2)

Answer 454

phosphodiester bond bond between phosphate group of 5' carbon deoxyribose and hydroxyl group of 3' carbon deoxyribose on next nucleotide

Question 455

Importance of mitosis (2)

Answer 455

how organisms grow important for asexual reproduction

Question 456

Features of steroids (4)

Answer 456

lipids hydrophobic - as they are mainly hydrocarbons have 4 carbon rings able to pass through phospholipid bilayer

Question 457

Starch properties (2)

Answer 457

compact in structure due to branching and coiling - efficient storage for small space insoluble due to large size - can store lots of glucose, ensures that water is not drawn in

Question 458

Define a disaccharide

Answer 458

2 monosaccharides linked together

Question 459

Endocrine signalling (3)

Answer 459

signalling molecules (hormones) secreted by spceialised endocrine cells carried through circulation to act on target cells at distant body sites e.g lipid steroids (testosterone, estrogen)

Question 460

Define a coenzyme

Answer 460

molecule required for enzyme to carry out a function

Question 461

Describe Budding in yeast (3)

Answer 461

type of asexual reproduction bud starts small then grows until it becomes a fully developed cell daughter cell is is typically smaller than parent cell and receive less than half of cytoplasm + organelles

Question 462

Define alternative splicing (2)

Answer 462

gene can be spliced in multiple ways by combining different exons and omitting others creates different versions of proteins with different functions

Question 463

Photosystems in thykaloid membranes (2)

Answer 463

photosystem I - most sensitive to light wavelengths of 700nm photosystem II - most sensitive to light wavelengths of 680nm

Question 464

Causes of frameshift mutations (3)

Answer 464

insertion deletion duplication

Question 465

Response to stimuli of paramecium (2)

Answer 465

detect changes in water temp. move to warmer waters

Question 466

3 Different types of mutation (3)

Answer 466

Substitution Insertion Deletion

Question 467

Break-down of neurotransmitters in synaptic transmission

Answer 467

specific enzyme breaks down neurotransmitter broken-down products reabsorbed by the pre-synaptic neuron

Question 468

Appearance of nucleosome (2)

Answer 468

length of DNA wrapped twice around cores of 8 histone molecules (2 copies of 4 different histones) additional histone molecule (H1) reinforces binding of DNA to nucleosome core

Question 469

Define gene knockout technique (2)

Answer 469

specific gene is intentionally removed/changed to prevent its expression helps to discover function of specific gene

Question 470

Why purines are complementary with pyrimidines (3)

Answer 470

purine to purine bond length will be too long pyrimidine to pyrimidine bond length will be too short complementary base pairing stabilises DNA shape

Question 471

Direction of gas exchange in leaves (2)

Answer 471

O2 enters through stomata CO2 exits out of stomata

Question 472

Respiration for maintaining concentration gradient in gas exchange (4)

Answer 472

cell respiration uses oxygen + produces CO2 O2 concentration lower inside cell than outside CO2 concentration higher inside cell than outside concentration gradient allows O2 from blood to enter cell + CO2 from cells to escape to blood

Question 473

Define codons for DNA

Answer 473

group of 3 bases for mRNA (complementary to DNA triplet)

Question 474

Inner Mitochondrial Membrane (IMM) (2)

Answer 474

membrane of matrix of mitochondria contains series of 4 transmembrane proteins + 2 electron carriers

Question 475

Phosphate group nucleotide diagram

Answer 475

O- | O- -- P -- O -- || O

Question 476

Define a purine (3)

Answer 476

Adenine Guanine have 2 carbon rings

Question 477

Describe Hershey-Chase experiment (5)

Answer 477

bacteriophage added to bacteria blender separates bacteriophage capsid from DNA in bacteria centrifuge separates bacteriophage from virus to allow investigator to detect radiation location Phosphorous - virus capsid in liquid is not radioactive, bacteria are Sulfur - viruse capsid in liquid are radioactive, bacteria are not

Question 478

Kingdom in species classification

Answer 478

organism that ingests food, digests it + assimilates it

Question 479

Results of Miller and Urey (3)

Answer 479

water droplets contained basic organic monomers (amino acids) proved that non-living synthesis of organic compounds was possible could have been how carbon compounds originated

Question 480

Photosynthesis light-independent stage (Calvin cycle) (2)

Answer 480

takes place in stroma uses ATP + reduced NAD to form carbon compounds (glucose) from CO2

Question 481

Describe anaphase (3)

Answer 481

spindle fibres contract chromatids are pulled to opposite poles of cells by their centromere each pole receives one chromatid from each chromosome

Question 482

Types of unsaturated fatty acids (2)

Answer 482

monounsaturated polyunsaturated

Question 483

Features of lipids (3)

Answer 483

hydrophobic + insoluble in water - non-polar dissolve in non-polar solvents - non-polar solvents have similar polarity to lipids contains carbon, hydrogen, oxygen

Question 484

Waxy cuticle of leaf (2)

Answer 484

protects leaf prevents water loss without preventing entrance of light

Question 485

Why does pH cause protein denaturation (3)

Answer 485

high pH = excess H+ can make it difficult to form hydrogen bonds + affecting electronegativity low pH = lack of H+ reduce number of hydrogen bonds denaturation = will alter protein shape

Question 486

Breakdown of Acetylcholine (4)

Answer 486

must be continually removed from synapse - may lead to fatal convulsions + paralysis broken down by enzyme acetylcholinesterase (AChE) enzyme released into presynaptic neuron or embedded onto membrane of post-synaptic neuron

Question 487

Significance of enzyme shape to being complementary to subtrate (2)

Answer 487

interactions of amino acids determine active site shape active site created from folding of polypeptide chain

Question 488

Features of competitive enzyme inhibitors (4)

Answer 488

bind to active site of enzyme = substrate cannot bind to A.S chemically similar to substrate inhibitor competes with substrate for A.S faster rate of reaction than non-competitive inhibitor

Question 489

Functions of steroids (2)

Answer 489

provide phospholipid bilayer with stability + flexibility role in signalling

Question 490

Features of lamella

Answer 490

connects grana to each other

Question 491

How cytokinesis works for animal cells (2)

Answer 491

network of actin + myosin proteins form a contractile ring that pinches cell membrane together forms a cleavage furrow - deepens and forms 2 separate daughter cells

Question 492

Function of DNA primase (2)

Answer 492

attaches small RNA primers (RNA nucleotides) to template strand allows DNA polymerase III to attach to DNA strand

Question 493

Define monounsaturated fatty acids (3)

Answer 493

have one double bond in hydrocarbon chain causes a bend in the chain liquid state at room temp. - bends make it difficult for molecules to pack together

Question 494

Spongy mesophyll of leaf (2)

Answer 494

contains air spaces allows gases to diffuse through leaf

Question 495

How were carbon compounds formed from early earth (4)

Answer 495

reducing atmosphere due to reducing gases (ammonia + methane) able to donate electrons to other molecules --> enables chemical reactions reactions formed more complex carbon compounds (amino acids + hydrocarbons) carbon compounds could be joined to form building blocks of cells (proteins, nucleic acids, lipids)

Question 496

Features of the cell body/soma for neurons (2)

Answer 496

nucleus + cytoplasm neurons do not multiply - have no centrioles

Question 497

Define the golgi apparatus (2)

Answer 497

processes/packages proteins released in golgi vesicles

Question 498

Signal transduction (3)

Answer 498

process where external signal becomes internal cellular response cells receive signal + pass signal along using signal transduction

Question 499

Cell signalling of glycoproteins + glycolipids

Answer 499

act as receptors for enzymes + molecules in cell signalling

Question 500

Eukaryotic division

Answer 500

divide by mitosis or meiosis

Question 501

Define tidal volume

Answer 501

volume of air that moves in and out of lungs during normal breath cycle

Question 502

Define a compartmentalised cell structure (3)

Answer 502

membranes isolate certain parts of cell from the rest to form separate organelles e.g mitchochondrion matrix separated from cytoplasm by membrane

Question 503

Define the saturation point for an enzyme

Answer 503

point at which every active site is filled

Question 504

"Lipid world" hypothesis (2)

Answer 504

lipid bilayers evolved before RNA provide protective layer for RNA

Question 505

Why does ice float on water (2)

Answer 505

ice is less dense as water pattern of hydrogen bonding of ice is less dense

Question 506

Number of possible amino acid sequences for a polypeptide (3)

Answer 506

20^n 20 possible amino acids to be linked n = number of amino acids

Question 507

cyclin A level of G2 phase

Answer 507

helps induce DNA replication

Question 508

Nuclear envelope (3)

Answer 508

has nuclear pores - allows relatively large molecules to pass through dense spherical structure surrounds nucleolus

Question 509

Excretion of paramecium (4)

Answer 509

metabolic waste collects in vacuoles vacuole moves to anal pore vacuole ruptures - expels waste contents into environment contractile vacuoles pump excess water

Question 510

Define conjugated proteins (2)

Answer 510

proteins with polypeptide subunits + non-protein (prosthetic group e.g haemoglobin containing haem to bind to oxygen

Question 511

Describe the structure of glycogen (2)

Answer 511

linear glucose chains linked through alpha 1,4 glycosidic bonds and 1,6 glycosidic bonds forms compact coiled structure

Question 512

Vacuoles of fungal cells (2)

Answer 512

break down molecules in cell act as storage site for small molecules (e.g ions)

Question 513

Terms used to describe different arrangement of unsaturated fatty acids (2)

Answer 513

cis trans

Question 514

Define karyogram (2)

Answer 514

diagram/photograph of chromsomes in nucleus arranged in homologous pairs of decreasing length

Question 515

Number of codons to code for an amino acid

Answer 515

64

Question 516

Properties of enzymes

Answer 516

specific - catalyses specific reaction

Question 517

Process of translation (5)

Answer 517

mRNA attaches to ribosome at start codon (AUG) tRNA with complementary anticodon (UAC) attaches to mRNA tRNA attached to amino acid (methionine) ribosome moves along mRNA + brings 2 tRNA molecules at any one time enzyme + ATP used to join amino acids with peptide bond

Question 518

Define deletion for gene mutation

Answer 518

one or more nucleotides are removed from DNA sequence

Question 519

2 regions of pre-mRNA (2)

Answer 519

exons : protein coding regions introns : non-protein coding regions

Question 520

Glycoprotein role in ABO blood groups (2)

Answer 520

red blood cells have glycoproteins : oligosaccharides called O, A, B blood with glycoprotein A/B will be rejected by a person who does not produce it

Question 521

Where does glycolysis occur

Answer 521

takes place in cytoplasm

Question 522

Prokaryotic division

Answer 522

divide by binary fission

Question 523

Features of external intercostal muscles (3)

Answer 523

contract during inhalation lifts ribs up and out to increase volume internal intercostal muscles relax

Question 524

Conditions of PCR process (2)

Answer 524

Taq polymerase - heat-stable version of DNA polymerase primers - short single strand of DNA to allow replication to occur from desired point

Question 525

Describe equal cell division (2)

Answer 525

daughter cells receive at least 1 mitochondria + other organelles come from existing parent cells produces 2 cells of the same size

Question 526

Define an orgnanism (2)

Answer 526

biological system that functions as an individual life form composed of cells

Question 527

Define respiratory substrate (2)

Answer 527

organic nutrient oxidised in respiration e.g glucose, fats, proteins

Question 528

Purpose of gel electrophoresis (2)

Answer 528

identify key features of DNA through separating parts of DNA

Question 529

Excitatory synapses (2)

Answer 529

depolarises the local membrane potential of post-synaptic cell makes cell more prone to firing

Question 530

Functions at site of interphase (4)

Answer 530

DNA replication + checked for errors protein synthesis mitochondria + chloroplasts grow and divide metabolic functions

Question 531

Define metabolism (2)

Answer 531

chemical reactions that take place in the cells of an organism enzymes speed up these chemical reactions

Question 532

Define nucleus (3)

Answer 532

contains DNA associated with histone proteins and organised into chromosomes nucleus contains the nucleolus --> involved in production of ribosomes double membrane which contains pores through which certain molecules can pass (e.g glucose, RNA, ions)

Question 533

Rate of reaction formula

Answer 533

(product formed/reactant used up)/ time

Question 534

Define the Goldilocks Zone (2)

Answer 534

habitable zone around a star location depends on size of star, amount of energy it emits, size of planet

Question 535

Define exocytosis (3)

Answer 535

moves particles out of cell vesicles move to membrane + fuse to it particles inside released

Question 536

Hershey-Chase experiment results (3)

Answer 536

bacteriophages with radioactive phosphorous infected non-radioactive bacteria, all infected cells became radioactive next-generation of bacteriophages produced from infected bacteria were all radioactive bacteriophages coated in radioactive sulfur + virus coats separated = no radioactivity inside infected cell

Question 537

Define rubisco

Answer 537

enzyme which adds CO2 to RuBP

Question 538

Define polyunsaturated fatty acids (3)

Answer 538

have 2 or more double bonds in hydrocarbon chain causes multiple bends in chain liquid state at room-temp - bends make it more difficult for molecules to pack together

Question 539

Chargaff's experiment (3)

Answer 539

extracted DNA from cells + mixed them with acid acid breaks bonds between pentose sugar + base bases separated using paper chromatography + concentration of bases measured

Question 540

Define extracellular enzymes (2)

Answer 540

enzymes released from cell + work outside it synthesized by ribosomes attached to endoplasmic reticulum

Question 541

Define the template strand/antisense strand for DNA (2)

Answer 541

strand with directionality 3' to 5' strand connected to mRNA

Question 542

Define the mother cell

Answer 542

parent cell/original cell

Question 543

Viscosity as a physical property of water

Answer 543

pure water has low viscosity - hydrogen bonds are weak so not as much internal friction

Question 544

Structure of unsaturated fats in membranes

Answer 544

have kinks in their fatty acid chains lower melting points

Question 545

What is suggested if the hypothesis that RNA was the first genetic material is true (5)

Answer 545

RNA formed from inorganic sources able to replicate using ribozymes (RNA molecules with enzymatic activity) able to catalyse protein synthesis RNA able to produce DNA + protein DNA became main genetic material due to being more stable

Question 546

Factors which determine strength of action potential (2)

Answer 546

amount of neurotransmitter released --> more neurotransmitter = more channels open time neurotransmitter is in area

Question 547

Neuromuscular Junction (4)

Answer 547

specialised synapse between motor neuron + muscle fiber motor neuron releases acetylcholine binds to receptors on plasma membrane of muscle fiber --> initiates muscle contraction causes depolarisation of muscle membrane + release of calcium

Question 548

Expiratory reserves

Answer 548

volume of air that can be exhaled forcefully after a normal breath

Question 549

Function of Helicase enzyme in DNA (2)

Answer 549

unwinds DNA molecule by breaking hydrogen bonds between bases single strand binding proteins attach to single strand of DNA + prevent them from re-forming hydrogen bonds with comp. bases

Question 550

Why is glucose chemically stable (2)

Answer 550

ring structure - atoms are bonded to minimise strain + allows for strong covalent bonds hydroxyl groups - forms bonds with water molecules (stable in aqueous solution) + prevents glucose from undergoing reactions

Question 551

Uses of PCR in DNA (4)

Answer 551

Covid tests paternity testing DNA in crime scenes clones genes

Question 552

What happens after a polypeptide chain is synthesised (2)

Answer 552

protein folding - adopts specific 3D shape which corresponds to its function influenced by sequence of amino acids, hydrogen + ionic bonding, hydrophobic interactions

Question 553

Define stains (3)

Answer 553

distinguish between parts of cells due to them usually being transparent bind to particular structures - making it easier to identify e.g iodine for plants

Question 554

Cell adhesion of glycoproteins + glycolipids

Answer 554

help cells to bind to other cells

Question 555

Examples of signalling molecules (4)

Answer 555

proteins, small peptides, amino acids nucleotides steroids, retinoids, fatty axis derivatives nitric oxide, carbon monoxide

Question 556

Advantages of cryogenic electron microscopy (2)

Answer 556

freezing sample improves resolution + reduces damage that may occur from the electron beam captures protein at instant time

Question 557

Define a community (2)

Answer 557

populations of multiple different species occupying same geographical locations at same time

Question 558

Naked DNA as a component of prokaryotes (3)

Answer 558

single molecule of DNA as a loop not associated with histone proteins found in region called nucleoid

Question 559

Define thermal conductivity

Answer 559

the rate at which heat passes through a material

Question 560

Isomers of glucose (2)

Answer 560

alpha-glucose beta-glucose

Question 561

Carbon fixation stage of Light independent stage of photosynthesis (Calvin Cycle) (2)

Answer 561

Co2 added to RuBP (5C) - catalysed by rubisco forms 2 molecules of GP3 (3C)

Question 562

Continuous variation (4)

Answer 562

traits that vary along a quantitative continuum results from complex interactions between many different genes environment often plays a significant part in phenotype expression e.g height, body mass

Question 563

Define quaternary structure proteins

Answer 563

arrangement of 2 or more polypeptide chains to form a protein

Question 564

Centrioles of fungal cells (3)

Answer 564

producing/organising cytoskeleton significant in cell division not present in most fungi (except male gametes of some fungi)

Question 565

Buoyancy as a physical property of water (2)

Answer 565

buoyancy = force exerted upward by fluid which counteracts gravity density of object < density of liquid = buoyancy force > gravity = object will float

Question 566

Function of unsaturated fats in membranes (2)

Answer 566

prevent lipids from packign together maintains fluidity in the membrane

Question 567

Example of adaptation in membrane composition to environment (2)

Answer 567

Cold-blooded organisms increase proportion of unsaturated fatty acids in membranes regulating the fluiditity of membranes

Question 568

Evidence for the endosymbiotic theory (6)

Answer 568

mitochondria + chloroplast measure 8 micrometers, same length as other prokaryotes both have double membranes - inner membrane could be plasma membrane of prokaryote, outer membrane could be vesicle both have circular naked DNA both have 70S ribosomes both divide by binary fission susceptible to some antibiotics (that target prokaryotic structures)

Question 569

Effect of R-group hydrophilic polarity on tertiary structure (2)

Answer 569

R-groups will orient outwards towards water soluble in water = can allow them to carry out functions in aqueous solution

Question 570

CO2 binding to haemoglobin in red blood cells (Bohr Shift)(2)

Answer 570

binds to polypeptide region not haem group changes affinity of haemoglobin for oxygen - causes oxygen to be dissociated

Question 571

70S ribosomes as a component of prokaryotes (2)

Answer 571

protein synthesis smaller mass than eukaryotic ribosomes

Question 572

Excretion of chlamydomonas

Answer 572

whole surface of plasma membrane excretes waste products (diffusion)

Question 573

Features of plasma membrane (2)

Answer 573

separates cell from external environment controls what exits/enters cell

Question 574

Define capillary action

Answer 574

the ability of a liquid to flow through a narrow tube without external forces

Question 575

Explain the electron transport chain (6)

Answer 575

reduced NAD (NADH) delivered to protein I NADH --> NAD+, H+, 2e- 2 electrons passed along electron carriers electrons allow H+ ions to be pumped into intermembrane space FAD delivers electrons to 2nd protein proton (H+) gradient created between intermembrane space + matrix

Question 576

Evidence for chromosome 2 fusion from chimp chromosomes (3)

Answer 576

banding of human chromosomes matches 2 separate chromosomes in apes supposedly fused chromosome has telomere sequences in the middle + end human chromosome 2 has an inactive centromere

Question 577

Movement of chlamydomonas (2)

Answer 577

flagella of chlamydomonas rotates moves organism towards more favourable conditions e.g(higher light intensity)

Question 578

Define photosynthesis

Answer 578

production of carbon compounds in cells using light energy

Question 579

Why does temperature cause protein denaturation (2)

Answer 579

high temperatures can break weak hydrogen bonds holding proteins together protein will unfold + lose its function

Question 580

Describe lactose (2)

Answer 580

glucose + galactose molecule joined by glycosidic bond

Question 581

Importance of transcription factors (2)

Answer 581

binding of correct transcription factors --> allows the RNA polymerase to also bind + begin to transcribe the DNA into RNA. transcription factors are missing or cannot bind to the promoter = transcription will not take place and that gene cannot be expressed

Question 582

Define cover slips/slides (4)

Answer 582

small thin pieces of glass hold specimen in place prevent specimen from drying out prevent specimen from touching lens of microscope

Question 583

Define Relay neurons

Answer 583

smaller cells with more interconnections

Question 584

Define a phospholipid

Answer 584

glycerol molecule with a phosphate group and 2 fatty acids phosphate head is hydrophilic when fatty acids are hydrophobic

Question 585

Directionality of transcription

Answer 585

3' to 5'

Question 586

Structure of a neuron (4)

Answer 586

cell body/soma dendrites (one or more) long axons axon terminal (synaptic) knobs

Question 587

Define initiation stage of translation (6)

Answer 587

Translation starts - 5' terminal of mature mRNA binds to small ribosomal subunit at mRNA binding site all mRNA have start codon (AUG) which can be linked to the initiator tRNA This specific tRNA always carries methionine - all proteins start with this amino acid ribosome moves along mRNA until it finds the start codon anticodon of the initiator tRNA (amino acid methionine) binds to codon of the mRNA large ribosomal subunit joins

Question 588

Relationship between pH and enzyme activity (2)

Answer 588

ph increases = rate of reaction increases up till optimum ph beyond optimum pH = denaturation + alter shape of active site

Question 589

Features of tRNA (transfer RNA) in translation (4)

Answer 589

translates base sequence of mRNA in to amino acid sequence tRNA has anticodon at one end + attachment point at other end for amino acid corresponding to anticodon transfers corresponding amino acid to end of growing polypeptide once code on mRNA recognised tRNA has specific corresponding amino acid attached

Question 590

Long distance signalling

Answer 590

hormones

Question 591

Purpose of the Hershey-Chase experiment

Answer 591

proving that DNA made up genetic material instead of protein

Question 592

Features of dendrites for neurons (2)

Answer 592

short + branched nerve fibers from cell surface make connection with other neurons - have increased SA

Question 593

How enzymes catalyse reactions (6)

Answer 593

substrate moves randomly until close enough to active site chemical properties of enzyme surface attract substrate to active site induced fit-binding : interactions between substrate + AS change 3D shape of both if 2nd substrate, it will bind to another part of AS changed substrate molecules weaken bonds + allow new bonds to form to make products products detach from A.S + enzyme activity site returns to original shape

Question 594

Reproduction of paramecium/chlamydomonas (2)

Answer 594

sexual + asexual (more common) reproduction cell divides into 2 daughter cells

Question 595

Function of nuclear envelope (2)

Answer 595

protects genetic material regulates transport between nucleus + cytoplasm

Question 596

Fetal haemoglobin vs Adult haemoglobin (2)

Answer 596

fetal haemoglobin have gamma + alpha subunits fetal haemoglobin have greater affinity to oxygen

Question 597

Impacts of frameshift mutations (3)

Answer 597

alters amino acid sequence coded by DNA sequence addition of new nucleotides alters grouping of codons mRNA transcript produced will have different codon structures

Question 598

Local signalling (4)

Answer 598

cell-cell recognition local regulators paracrine (growth factors) synaptic (neurotransmitter)

Question 599

Define motor neurons

Answer 599

long axons transmit nerve impulses from CNS to effectors

Question 600

Describe telophase

Question 601

Function of aquaporins (2)

Answer 601

allows passage of water through cell membrane bidirectional - water can flow in from either direction (depending on CG)

Question 602

Define mRNA (2)

Answer 602

messenger RNA made as a complementary strand to one DNA strand copy of other DNA strand + contains uracil

Question 603

"Sulfur world" hypothesis

Answer 603

forms of life based on ion-sulfur chemistry

Question 604

Define insertion for gene mutation

Answer 604

one or more nucleotides added to DNA sequence

Question 605

Examples of endocytosis (2)

Answer 605

phagocytosis - white blood cells engulfing pathogens pinocytosis - cells takes in extracellular fluid

Question 606

Neuroglandular junction (2)

Answer 606

synapses between neurons + glandular cells regulate secretory activities

Question 607

Function of DNA polymerase I

Answer 607

removes RNA nucleotides of primers + replaces with correct DNA nucleotide

Question 608

micrometers to millimitres (2)

Answer 608

1 micrometer = 0.001millimitres 1 millimeter = 1000 micrometers

Question 609

How can photosynthesis be measured (4)

Answer 609

hydrogen carbonate indicator solution change colour as CO2 concentration changes less photosynthesis, more respiration = CO2 will increase + indicator turns orange/yellow more photosynthesis, less respiraton = CO2 will decrease + indicator turns purple

Question 610

Gap Junctions as direct contact cell-cell communication

Answer 610

cells are in direct contact protein channels connect 2 adjoining

Question 611

Usages of compartmentalisation in a cell (3)

Answer 611

enzymes have different optimal pH --> must be differentiated within cells isolating toxic/damaging substances from cytoplasm ability to change number/position of organelles through isolation

Question 612

Define photolysis

Answer 612

reaction which splits molecules of water using light energy

Question 613

Interdependence of light dependent + light independent (Calvin cycle) (2)

Answer 613

Calvin cycle requires ATP + reduced NADP from light dependent light dependent requires NADP + ADP to produce ATP + reduced NADP

Question 614

Trans fats vs cis fats (2)

Answer 614

cis occurs in nature, trans produced artificially cis has lower melting points than trans

Question 615

Agriculture in CRISPR Cas-9 system (3)

Answer 615

ability to transform crop breeding practices introducing precise genetic modifications to enhance desirable traits improve crop yield + nutritional content and disease resistance

Question 616

RNA first genetic material hypothesis (2)

Answer 616

basis for formation of first cell-structure acts as genetic material + catalyst

Question 617

Define a mutation (2)

Answer 617

changes to genetic composition of cell change in order of bases in DNA strand

Question 618

Process of gel electrophoresis (6)

Answer 618

electric field created by voltage applied across electrodes charged molecules move through gel DNA placed in wells in one side of gel DNA moves towards positive anode due to negative electric charge in phosphates smaller pieces slip through spaces within gels - can travel farther smaller DNA pieces will appear as a band closer to anode, while larger DNA piece will be further

Question 619

How are nucleotides linked together

Answer 619

covalent bonds formed between phosphate of one nucleotide and the pentose sugar of another

Question 620

Different pigments of a leaf (3)

Answer 620

chlorophyll beta-carotene xanthophyll

Question 621

Palisade mesophyll of leaf

Answer 621

absorbs light + carries out photosynthesis

Question 622

Features of animal cells (4)

Answer 622

centrioles - cylindrical organelles that establish/organise microtubules during cell division/metaphase lysosomes some contain cillia/flagella small temporary vacuole

Question 623

Applications of specific heat capacity of water (2)

Answer 623

aquatic habitats are more thermally stable helps mammals maintain constant body temperatures

Question 624

ATP synthase role in ATP generation

Answer 624

flow of protons (proton motive force) generates energy to phosphorylate ADP H+ ions pass through ATP synthase through diffusion --> rotates + converts ADP to ATP

Question 625

Tryglycerides function/characteristics (4)

Answer 625

energy storage - chemically stable so energy not lost used as insulators to retain heat liquid at body temperature - can act as shock absorbers release twice as much energy per gram in respiration than carbs

Question 626

Define specialised cells (2)

Answer 626

specific cells having different roles in a multicellular organism these cells work together to form tissues + muscles of organisms

Question 627

How do amino acids link with one another (2)

Answer 627

carboxyl group reacts with amino group condensation reaction - bond formed between C and N + H2O produced as by-product

Question 628

Describe the primary structure of proteins (3)

Answer 628

sequence of amino acids peptide bonds between carboxyl + amine group determines shape of protein - sequence determines how polypeptide chain will fold

Question 629

Thin layer as a feature of gas exchange (2)

Answer 629

thin to minimise diffusion distance molecules can diffuse faster with shorter distance

Question 630

Structure of haemoglobin (3)

Answer 630

2 alpha + 2 beta polypeptide chain globular protein of 4 packed polypeptide chains conjugated protein - contains protein + iron

Question 631

Define photosystems (3)

Answer 631

molecular arrays of chlorophyll + accessory pigments within protein complexes + located in membranes capture light energy + convert to chemical energy

Question 632

Features of LUCA (4)

Answer 632

single-celled autotrophic microbe possible RNA genome anaerobic existed in hydrothermal vents in ocean - hydrogen, methane, sulfur used as an energy source

Question 633

Explain repolarisation (3)

Answer 633

voltage gated sodium- ion channels close voltage-gated potassium ion channles open when 40+ reached K+ ions rush out of cell --> membrane is repolarised then hyperpolarised

Question 634

Binomial nomeclature (2)

Answer 634

first part : genus second part : species

Question 635

Structure of phospholipids (3)

Answer 635

same as triglyceride but phosphate joins to 3rd OH instead of fatty acid 2 non-polar fatty acid chains amphipathic molecules - hydrophilic phosphate head, hydrophobic fatty acids

Question 636

Differences between species chromosomes (3)

Answer 636

length - number of base pairs position of centromere genes at certain locus (location)

Question 637

Glycolysis for Anaerobic respiration in animal cells (lactic acid fermentation) (2)

Answer 637

NADH becomes NAD+ Pyruvate forms lactate/lactic acid + carbon dioxide

Question 638

Function of DNA ligase

Answer 638

catalyses formation of phosphodiester bonds between Okazaki fragments

Question 639

Structure of nuclear envelope outer membrane (2)

Answer 639

outer membrane is connected to rough endoplasmic reticulum outer membrane surface dotted with ribosomes

Question 640

Define triplet for DNA

Answer 640

group of 3 bases for DNA

Question 641

2 examples of unequal cell division

Answer 641

Oogenesis Budding in yeast

Question 642

Define synonymous SNPs (3)

Answer 642

known as neutral/same-sense mutations change one codon of amino acid into another codon of same amino acid do not affect phenotype

Question 643

Application of CRISPR Cas-9 system (4)

Answer 643

gene therapy agriculture disease modelling genetic engineering of microorganisms

Question 644

Skeletal muscles as atypical cells (2)

Answer 644

multinucleated - one single cell has multiple nuclei muscle cell formed from fusion of smaller myocytes

Question 645

Base with highest probability of mutation (3)

Answer 645

cytosine can experience chemical reaction called deamination can lose an amine group --> becomes uracil

Question 646

Reasons for G0 phase of interphase (2)

Answer 646

cell becomes specialised to carry out particular function DNA is damaged - cell division may no longer be viable

Question 647

Directionality of DNA in DNA replication (2)

Answer 647

nucleotides added to the 3' end of polymer 5' phosphate of free nucleotide links to 3' end of growing polymer

Question 648

Define essential amino acids (2)

Answer 648

amino acids which the body cannot produced + must be obtained from diet 9/20

Question 649

Moisture as a feature of gas exchange (2)

Answer 649

O2 + CO2 must dissolve in water/solution before diffusion respiratory system is moist with water

Question 650

2 types of membrane proteins (2)

Answer 650

integral proteins peripheral proteins

Question 651

Aseptate fungal hyphae as atypical cells (2)

Answer 651

long tube structures without septa (internal walls dividing cells) multinucleated - many nuclei in a singular cellular unit

Question 652

Metabolism first hypothesis (4)

Answer 652

simple metabolic reactions --> simple metabolic pathways --> formed more complex molecules --> formed basis of cells

Question 653

Define phosphorylation (2)

Answer 653

process of adding a phosphate to a molecule makes many molecules more unstable + more reactive

Question 654

Define discrete variation (3)

Answer 654

traits that can be put into distinct quantitative categories influenced by one or few genes e.g blood type, eye colour, dominance

Question 655

Examples of intracellular receptors

Answer 655

Testosterone

Question 656

Define inductive reasoning (2)

Answer 656

starting with examples attempting to form rule/hypothesis

Question 657

How do RNA nucleotide join together

Answer 657

condensation reaction - molecules combine while losing water

Question 658

Features of carbon bonds (3)

Answer 658

covalent carbon can bond to 4 atoms single carbon bonds allow atoms to rotate

Question 659

3 Types of neurons

Answer 659

Sensory neurons Motor Neurons Relay Neurons

Question 660

Bohr effect on oxygen dissociation curve

Answer 660

sigmoidal curve shifts to the right

Question 661

Role of Sodium-Potassium pump for maintaining resting potential for K+ ions (4)

Answer 661

diffusion - K+ ions will leave cell (more inside) electropotential gradient - K+ ions will re-enter (because insides is more negative from diffusion) diffusion force > electropotential gradient (gradient charge less negative hence weaker) pump - pumps K+ ions in to maintain resting potential

Question 662

Why water is able to be retained on earth (2)

Answer 662

distance between sun and earth = temperatures are not high enough to vaporize water strong gravity = oceans is held to surface, gases kept within atmosphere

Question 663

Enzymes as a function of membrane proteins

Answer 663

membrane proteins can catalyse reactions

Question 664

Intercellular signalling (2)

Answer 664

communication among cells through signalling molecules

Question 665

Define cis unsaturated fatty acids (2)

Answer 665

hydrogen atoms attached to carbon atoms around double bond are on same side creates bend

Question 666

Name of solid lipids at room temperature

Answer 666

fats

Question 667

Properties of ATP (5)

Answer 667

soluble in water - can move freely through cytoplasm stable at pH levels close to neutral cannot pass freely through phospholipid bilayer 3rd ATP phosphate group easily removed + attached through hydrolysis + condensation reaction hydrolysing ATP to ADP + phosphate releases energy

Question 668

Function of PCR in DNA (2)

Answer 668

polymerase chain reaction amplifies small fragments of DNA (increases quantity of DNA)

Question 669

Paracrine signalling

Answer 669

simultaneous response to more than one cell

Question 670

Main classes of macromolecules in living organisms (3)

Answer 670

polysaccharides polypeptides nucleic acids

Question 671

Structure of aquaporins (2)

Answer 671

4 subunit channels inner channels are hydrophillic

Question 672

First growth phase of interphase (3)

Answer 672

proteins are synthesized organelles replicate cell increases in size

Question 673

Cellulose structure (4)

Answer 673

straight chain of beta-molecules B-glucose is inverted so that -OH groups are together hydrogen bonds form between chains (polarity between O in glycosidic bond + H in glucose) microfibrils form - bundles of cellulose chains

Question 674

Cillia (2)

Answer 674

hair-like structures made of microtubules used for movement of substances past the cell

Question 675

Properties of glucose (3)

Answer 675

glucose is soluble + small --> easily transported glucose is chemically stable yields energy when oxidised

Question 676

Define codons in genes (2)

Answer 676

groups of 3 bases 64 possible codons

Question 677

Enzymes role in energy (2)

Answer 677

reduce activation energy required for a reaction - increases rate of reaction bonds in substrate weaken during enzyme-substrate complex = less energy needed to break

Question 678

Bases in RNA (4)

Answer 678

Adenine (A) Cytosine (C) Guanine (G) Uracil (U)

Question 679

Number of carbon atoms for hexose (2)

Answer 679

6 e.g glucose, fructose

Question 680

Define the tertiary structure of proteins (2)

Answer 680

folding of the polypeptide chain into a 3-dimensional structure stabilized by interactions between R-groups of amino acids

Question 681

Number of hydrogen bonds between guanine + cytosine

Answer 681

3 hydrogen bonds

Question 682

Functions of codons in genes (3)

Answer 682

most codons specify a particular amino acid one codon signals that protein synthesis should start 3 codon signal that protein synthesis should stop

Question 683

Features of sodium-potassium pump (2)

Answer 683

uses ATP 3 Na+ pumped out, 2K+ pumped in

Question 684

Features of non-competitive inhibitors (4)

Answer 684

bind to allosteric site - change shape of enzyme enzyme rate of reaction decreases changing enzyme shape = A.S no longer complementary to substrate hence fewer complementary enzymes

Question 685

Quantitative vs Qualitative data (2)

Answer 685

quantitative - numerical + objective qualitative - observations/descriptions that are more subjective

Question 686

Define gene expression (2)

Answer 686

process which genetic code in DNA translated into protein allows DNA to code for proteins

Question 687

Explain surface tension of water (2)

Answer 687

cohesion between water molecules > attraction between water and floating object object must break hydrogen bonds to break the surface of water

Question 688

Features of stroma lamella (2)

Answer 688

unstacked thykaloids form connections between thykaloids in grana

Question 689

Glycolysis for anaerobic respiration in yeast (ethanol fermentation) (2)

Answer 689

pyruvate converted to ethanol CO2 produced + NADH oxidised to NAD (H used to make ethanol)

Question 690

How oxygen is created from light dependent stage of photosynthesis (5)

Answer 690

release of electrons from reaction centre creates unstable oxidised molecule water molecules split to give up electron -->1/2 O2 + 2H+ + e- electron replaces electron lost in reaction centre protons released to thykaloid space to increase proton electrochemical gradient oxygen diffuses out

Question 691

Define CRISPR (2)

Answer 691

short repeated base sequences unique spacer sequences

Question 692

Stages of meiosis (2)

Answer 692

Meiosis 1 Meiosis 2

Question 693

Define eukaryotes (4)

Answer 693

cells with a nucleus and membrane bound organelles usually larger than prokaryotes some are multicellular (organism consists of more than one cell) e.g animal cells, plant cells, fungi cells

Question 694

Metabolism in water solvent property (2)

Answer 694

solutes can move + interact allows for substrates to touch the active sites of enzymes

Question 695

Features of mRNA in translation (4)

Answer 695

has site for ribosome to bind to has sequence of codons which codes for specific amino acids has start + stop codon to indicate when translation will stop/start mRNA can be translated multiple times but is broken down if it is damaged or if polypeptide it codes for is no longer needed