extra flashcards unit 1 + unit 2
1
Q
give one advantage and one disadvantage of the tracheal system for gas exchange in insects [2]
A
- adv =
• reduces water loss / allows them to live in arid conditions
• no (blood/circulatory system/pigment) required
• oxygen supplied directly to the cells/muscles
• tracheoles go directly to cells/tissues - disadv =
• size/shape limitation
2
Q
state how mammals maintain the concentration gradient at their gas exchange surface [2]
A
- ventilation (movement/system) / description of replacing oxygen in alveoli
- (blood/transport system) (takes oxygen away from respiratory surface) / ORA for carbon dioxiee
3
Q
state why cellular demand for oxygen is lower in a fish compared to a dog of the same size [2]
A
- low body temperature
- metabolic rate low
- less energy required for support / fish are bouyant
reject : dogs move more than fish/dogs are more active than fish/ more oxygen needed for respiration
4
Q
what does no nucleus mean for red blood cells?
A
can carry more haemoglobin (so increased O2 transport)
5
Q
how does the thin centres on a red blood cells aid its function?
A
has short diffusion distance (so faster diffusion)
6
Q
how does being small give an advantage to mammalian red blood cells?
A
- have a higher sa:vol ratio
- so more in total / total surface area large
7
Q
what is the dependent variable?
A
the variable that is being measured/tested in the experiment
8
Q
what is the independent variable?
A
the variable that you change during an experiment
9
Q
identify one possible source of error when investigating the biodiversity of animals [1]
A
- some easier to catch than others / misidentification / recounting / they move around / camoflauged
10
Q
one student calculated the diversity index in one section of a stream to be 10.24. explain what can be concluded from this result [2]
A
- there has been a mathematical error
- highest possible diversity index is 1
11
Q
the banded snail is found in a variety of habitats, such as grassland, heathland, sand dunes and the base of hedges. the shell colour can vary : yellow which looks green with the animal inside, brown, pink and white. the shell can be banded or have up to 5 bands
- these morphologically different snails are all the same species. explain why this is an example of ‘genetic polymorphism’ [2]
A
any two from:
- the existence of a number of distinct (inherited) varieties (coexisting in the same population in a single species)
- snails (are different colours/have different bands)
- different morphology
- different phenotypes
- at frequencies too great to be explained by recurrent mutations
- multiple alleles for the same gene
12
Q
questions related to ‘breathing in/inspiration’
A
- the DIAPHRAGM muscle CONTRACTS which cause it to FLATTEN
- this INCREASES THE VOLUME of the chest cavity and therefore the lungs
- at the same time the INTERCOSTAL MUSCLES between the ribs CONTRACT which causes the RIB CAGE TO MOVE UP AND OUT
- this increases the VOLUME of the chest cavity and therefore the lungs
- increasing the volume of the lungs REDUCES THE PRESSURE in the lungs, ad the pressure within the lungs is now LOWER THAN THE PRESSURE OUTSIDE the body AIR RUSHES INTO the lungs via the trachea, bronchi and bronchioles
13
Q
questions related to ‘breathing out/expiration’
A
- the diaphragm muscle relaxes which causes it to dome upwards
- this decreases the volume of the chest cavity and therefore the lungs
- at the same time the intercoastal muscles between the ribs relax which causes the rib cage to move down and in
- this decreases the volume of the chest cavity and therefore the lungs
- decreasing the volume of the lungs increases the pressure in the lungs, as the pressure within the lungs is now higher than the pressure outside the body air rushes out of the lungs via the bronchioles, bronchi and trachea
14
Q
questions related to ‘adaptation to gas exchange’
A
- the structure (lungs, gills etc) will have a large surface area which increases the rate of diffusion
- as the tissue is thin there is a short diffusion pathway which aids rapid diffusion
- the tissue is also permeable to the gases involved so diffusion is possible
- finally there is a good blood supply which means that a concentration gradient is maintained so that diffusion happens rapidly
- terrestrial organisms also have a moist gas exchange surface to allow gases to dissolve into the liquid to aid movement of the gases across membranes either into or out of cells
15
Q
questions related to ‘adaptations of xerophytes’
A
- xerophytes are adapted to reduce loss of water
- they have a reduced surface area to volume ratio so that there us less area over which water can be lost
- xerophytes also have a thick waxy cuticle which acts as a waterproofing layer
- and also possess fewer stomata per unit area which again reduces the volume of water lost
- often stomata are sunken and/or leaves are curled; in both cases this traps a layer of moist air above the stomata which reduces the concentration gradient of water and therefore water loss by diffusion
16
Q
explain why atp is sometimes referred to as the universal energy currency. include reference to the structure of the molecule in your answer [3]
A
- found in (all cells, of) all organisms
- (common) source of energy (in reactions)
- high energy BONDS / energy stored in BONDS between phosphate ions
- released when (bonds between phosphate break/hydrolysed) / exergonic
17
Q
explain why the substance used to immobilise enzymes must be inert [1]
A
- substance used for immobilisation must not affect the shape of the active site / does not react with enzyme or substrate
18
Q
it was originally proposed that one gene carried the code for one enzyme. this was revised to become the one gene-one protein hypothesis. it is now known as, the one gene-one polypeptide hypothesis.
using your knowledge of protein structure and function explain why the two previous versions of this hypothesis are no longer accepted [2]
A
- some proteins are made of more than one polypeptide/some genes code for more than one polypeptide
- not all proteins are enzymes
19
Q
there has been some debate as to whether the pseudo-thumb in red pandas and giant pandas are examples of analogous or homologous structures. distinguish between analogous and homologous structures. explain why analogous features are not considered evidence of common ancestry [3]
A
- analogous structures (evolve separately) are different structures to perform a similar function
- homologous structures (evolve from common ancestor) similar structure performing different function
- analogous structures arise through convergent evolution
20
Q
give an example of a disease caused by an organism in the kingdom:
a) prokaryotae
b) protoctista
c) fungi
A
a) any of the bacterial diseases
b) malaria etc
c) athletes food, ringworm, thrush etc
21
Q
identify two habitats where you would expect to find a high number of species [2]
A
- (tropical) rain forest
- coral reef
22
Q
questions related to ‘sexual and asexual reproduction’
A
- asexual reproduction produces offspring that are genetically identical
- cells divide by mitosis during asexual reproduction and as this process is rapid the species can reproduce rapidly is the environmental conditions are right
- however, organisms that carry ou t asexual reproduction are at a disadvantage as if the environmental conditions change e.g temperature changes markedly then the species will not be able to adapt
- if one died they all would
- sexual reproduction produces offspring that are genetically different
- gametes (sex cells) are produced by meiosis during sexual reproduction and as a partner is required sexual reproduction is slower than asexual reproduction
- however, organisms that carry out sexual reproduction are at an advantage as if the environmental conditions change e.g temperature changes markedly then the species will be able to adapt
- at least some of the species would be able to survive
23
Q
questions of ‘define counter-current flow as seen in the gills of bony fish, and explain why counter current flow makes gas exchange more efficient’ [3]
A
- counter current flow is when blood flows in the opposite direction to the water
- this happens in the gills of bony fish
- the concentration gradient is maintained across the entire surface of the gill as the blood in the capillaries is always next to water with a higher concentration of oxygen
- this means that more oxygen can be diffused into the blood from the water surrounding the gill
24
Q
questions related to ‘transpiration from leaves’
A
- transpiration is the loss of water from the leaves of plants
- this happens as water diffuses out of the leaves through the stomata as there is a water potential gradient between inside the leaf and the outside
- if the temperature is increased transpiration happens more rapidly as the water molecules in the air outside the stomata have more kinetic energy and therefore move away more quickly so that a steep water potential gradient is maintained
- if humidity is high this will reduce transpiration as the air outside will have many water molecules in it
- this would mean that there was less of a water potential gradient
- if light intensity was high this would increase transpiration because of the increase in stomatal opening which leads to a larger surface area for the water molecules to diffuse through
25
questions related to ‘the Bohr effect’
- when cells (e.g muscle cells) are aerobically respiring they release carbon dioxide as a waste product
- this means that when this gas is released as a waste product into the blood the partial pressure of carbon dioxide in the blood increases
- the increased partial pressure of carbon dioxide in the blood causes the pH to reduce as carbonic acid is formed
- the lower pH reduces haemoglobin’s affinity for oxygen so that more oxygen is released
- this means that more oxygen is released from haemoglobin in those areas where it required most i.e adjacent to cells respiring aerobically
26
questions related to ‘tape worm transmission from human to human’
- tapeworm eggs present in human faeces are consumed by the pig
- the tapeworm eggs pass into the digestive system and eventually move into muscles
- if the meat/muscle containing the tapeworm eggs is undercooked or eaten raw by the human then the human is infected
27
questions related to ‘tape worms’
- tape works attach themselves to the wall of the intestine using hooks and suckers
- they absorb the nutrients they require from the host’s intestine
- they have a large surface area compared to their volume which increases the speed of diffusion of the nutrients from the host intestine into the tape worm
- as the tape worm is very thin the diffusion pathway is short which again increases the speed of diffusion
- tape worms do not require a digestive system as their food is digested by the hosts digestive system
- to prevent the digestive enzymes in the host digestive system damaging the tapeworm, it has a thick cuticle
- tapeworms produce large numbers of eggs to increase the change of infecting a new host
28
questions related to ‘digestion in cows’ [2]
- cows have a four chambered stomach that contains cellulose digesting bacteria [2]
OR
- cows have a four chambered stomach that contains cellulose digesting bacteria
- the long gut allows more time for the cellulose to be broken down
- cows also chew the cud which means they regurgitate some of the contents do that it can be chewed again to aid further digestion
29
questions related to ‘why does the ventricular pressure fall to zero, whilst the aortic pressure does not fall below 80 mmHg?’ [2]
- as the ventricle goes into diastole the ventricular pressure falls to 0
- however, the semi lunar valves in the aorta prevents the back-flow of blood into the ventricles thus maintaining the pressure at 80mmHg
30
questions related to ‘stomatal functions’
- stomata allow gas exchange of carbon dioxide and oxygen to occur as they allow these gases to enter and leave the leaf
- stomata also control the loss of water from the plant e.g by closing at night which greatly reduces the rate of transpiration
31
questions related to ‘mechanism of stomatal opening’
- in the presence of light potassium ions are pumped into the guard cells
- the presence of the potassium ions promotes the conversion of starch to malate
- the malate causes the water potential of the guard cell to be lowered
- water therefore flows into the guard cell by osmosis from the surrounding epidermal cells
- the guard cell therefore becomes turgid and as the inner wall of the guard cell is inelastic the guard cells curve away from each other which means the stomata opens
32
questions related to ‘evolution’
- evolution happens when selection pressure happens to a population in a particular environment
- as there is variation in any population of organisms some of them will have a selective advantage over others, some of the variation in the population may also be caused by mutations
- those members of the population with the selective advantage are more likely to survive to sexual maturity and therefore breed successfully
- they will pass on their beneficial alleles, which will increase the allele frequency of this beneficial allele which will lead over generations to the vast majority of the population of this organism possessing the beneficial allele and therefore the beneficial phenotype
33
questions related to ‘digesting fat’
- the presence of bile salts causes the emulsification of lipids
- this increases the surface area of the lipids which means that the enzyme lipase can catalyse the breakdown of the lipid more quickly into fatty acids
34
questions related to ‘oxygen dissociation curves’
- oxygen dissociation curves are normally sigmoid as this is the most efficient way of obtaining oxygen in areas where there is an increasing partial pressure of oxygen such as the lungs and releasing oxygen where there is a decreasing partial pressure of oxygen such as respiring tissues in the body’s organs
- this happens because haemoglobin has a high affinity for oxygen in areas of high partial pressure of oxygen and a low affinity for oxygen in areas of lower partial pressure of oxygen
35
questions related to ‘effect of wind on transpiration’
- wind removes water vapour from the leaf’s surface
- this causes an increased diffusion gradient between the inside of the leaf (higher) and the outside of the leaf (lower)
- this means that water moves more quickly from the inside of the leaf to the outside
36
questions related to ‘how water moves up the stem’
- water is lost by transpiration from the leaves which causes tension on the water molecules in the water column in the xylem vessels
- as the water columns water molecules have cohesive forces between them and the other water molecules in the water column also have adhesive forces with the xylem vessel walls the increase in tension on the water at the top of the plant, caused by transpiration, results in the water molecules being pulled up the plant
37
for the polypeptide structure, should you use polypeptide chains or polypeptide strands?
polypeptide CHAINS
38
higher energy yield PER UNIT MASS
39
blood may be contaminated WITH A DISEASE
40
DNA CIRCULAR in prokaryotes
DNA in STRANDS in eukaryotes
41
two DNA chains CONNECTED or JOINED by base pairs
42
DNA CODES for proteins or mRNA
43
in transcription, DNA is used as a template to produce a mRNA MOLECULES
44
if a vesicle is travelling to the cell membrane to release its content, it is known as a ___?
secretory vesicle
45
biosensors detect SPECIFIC molecules
46
what happens when an enzyme becomes denatured? [2]
- the enzyme’s active site changes shape
- and the substrate no longer fits into the enzyme’s active site
- so the enzyme can’t function as no enzyme substrate complexes are formed
- and the reaction is therefore not catalysed
47
questions related to ‘transcription
- DNA is found in the nucleus of cells
- the DNA’s nitrogenous base sequence contains a code for the sequence of amino acids in a protein
- 3 nitrogenous bases code for 1 amino acid, the three nitrogenous bases are called a DNA triplet
- during transcription an enzyme called DNA helicase linkage to the DNA and unwinds it
- one of these strands called the coding strand acts as a template first the synthesis of mRNA
- the mRNA molecule is built up by complimentary base pairing with the coding strand, if the DNA nitrogenous base is adenine then the mRNA nucleotide would be uracil etc
- once the mRNA molecule is built, it leaves the nucleus through a nuclear pore
48
how to convert from nanometers to micrometers?
divide by 1000
49
using a buffer would have been inappropriate in certain experiment in question because:
- colour change/indicator dependent on change in pH
- (hydrolysis produces) fatty acids (that lower the pH/make it acid)
- buffer solution would (stabilise/maintain/control) pH (to alkaline conditions)
50
test at *smaller increments* to determine optimum (temperature) accurately
- repeat experiment with a range of intermediate values (/wider range)
51
suggest why the presence of unsaturated fatty acids in the phospholipid would increase fluidity of the membrane? [4]
- unsaturated contain (double bonds between carbons / C=C)
- produces a kink/bend in side chain
- less packing is possible / increased distance between the chains
- lower intermolecular force
- less energy needed (to break the bonds/overcome the intermolecular forces)
52
state how a diet high in animal products and cholesterol can lead to a person developing heart disease [2]
- raises level of LDLs / causes LDLs to be made
- increases incidence of atheroma in arteries
53
describe the role of calcium in plant cells and tissues [1]
(structure of)/ component of cell WALLS in plants
54
explain why the growth of a plant may be reduced if the roots have little access to oxygen [4]
- anaerobic conditions/lack of oxygen
- (less/no) ATP produced
- active transport (cannot occur/reduced), fewer ions can be transported (against concentration gradient)
- stunted growth because of a lack of ions
55
how does the cell mass change during a cell cycle of mitosis?
- interphase : mass of cell increases
- as does cell size
- mass of cell continues to increase
- due to replication of DNA / organelles
- and possibly due to formation of spindle fibres
- cell undergoes cytokinesis and mass of cell halves
56
why can’t insects use their external surface for gas exchange?
as they are covered in an impermeable cuticle to reduce water loss by evaporation
57
describe the change in fluid level in the tracheoles during flight (insects). suggest how this change benefits gaseous exchange during flight [2]
- less fluid/fluid moves into muscle fibres / fluid level decreases
- more area for gaseous exchange / shorter diffusion pathway
58
what is the outer pleural membrane attached to?
the ribcage
59
what is the inner pleural membrane attached to?
the outer surface of the lungs
60
water is a dense medium with a low oxygen content. explain how bony fish have overcome the problems of oxygen uptake in water [4]
- water forced over the gill by (ventilation mechanisms / pressure differences / continuous swimming)
- unidirectionally / one way flow
- counter-current flow of blood and water
- (diffusion / concentration) gradient is maintained (over entire gill surface)
- high affinity Hb
61
what is the function of the gill rakers? [1]
- (filter/sieve/remove/catch) (food/particles/solid) NOT molecules
- protection from debris/preventing damage to the gill filaments
62
what become constricted and inflamed during an asthma attack? [1]
bronchioles
63
what is the function of the layer of cartilage in the trachea of a human?
- prevent trachea closing
- during inspiration
64
suggest why the cartilage in the trachea of a human is not in the form of a complete ring? [1]
- to allow room for oesophagus to expand when swallowing
65
1mm = ___ µm
1000
66
- accuracy relates to the apparatus used
- reliability relates to your repeats
67
membrane 1 has phospholipids containing only saturated fatty acids and membrane 2 has phospholipids containing both saturated and unsaturated.
explain which membrane you would expect to be more permeable to small molecules [2]
- membrane 2
- bc bigger spaces between phospholipids/fatty acid tails / fit together less closely
- less densely packed
68
describe role of DNA helicase in DNA replication [1]
- unwinds DNA / breaks HYDROGEN bonds between bases / unzips DNA
69
in beetroot experiment, the beetroot in water had increased in size. explain this observation [3]
- water had entered the CELLS / moved in across CELL membrane
- by osmosis
- as the beetroot CELLS had a lower water potential than the water
70
explain the role of the rough endoplasmic reticulum in the production of fibrinogen (an enzyme) [2] - diagram of RER with ribosomes on outside
- translation of mRNA by ribosomes / production of (polypeptides / protein synthesis) on ribosomes
- packaging of polypeptide into vesicles / transport to golgi body
71
explain the role of the Golgi body in the production of fibrinogen (an enzyme) [2]
- assembly / joining of polypeptides/subunits (into quaternary structure)
- addition of other groups (e.g adding carbohydrate chains to form glycoproteins)
- packaged (into vesicles)
72
describe the biochemical structure of a glycoprotein [2]
- (globular) protein (accept polypeptide)
- with a carbohydrate (chain) / polysaccharide (attached to it)
73
glucose concentration in body fluids can be detected by using a number of tests. in one technique, known concentrations of glucose and reagents are prepared leading to a colour change. the absorbance is then measured using a colorimeter. the results are used to plot a standard (calibration) curve. unknown solutions can then be compared with the standard curve to determine their concentration.
why is it not possible to use the standard curve for glucose determination in a whole blood sample? [1]
- blood is (red/coloured) so could not get through a colorimeter reading / light cannot pass through
74
modern medicine uses immobilised enzymes, in devices called biosensors, to detect blood glucose levels. this involves the use of glucose oxidase as the enzyme and glucose as the substrate. give two advantages of using immobilised enzymes for blood glucose monitoring [2]
any two:
- only glucose will give a result / enzyme specific (to glucose)
- detects very low concentrations
- reading is more accurate / enzyme is more stable
- works at different temperatures
75
explain why it is important that the RNA which is finally translated, consists only of exons [2]
- introns do not code for the (amino acids (sequence) in / primary structure of ) protein / only exons code for the amino acide sequence in proteins
- if introns are included a different protein (structure) would be produced
76
the plasma membrane of a single human red blood cell has a surface area of approximately 140 µm^2. calculate the area of water covered by the lipids extracted from the plasma membrane of a single red blood cell [1]
explain how you calculated this value [1]
140 x 2 = 280 µm^2
- phospholipids arranged in BILAYER in cell membrane (but in a single layer on water)
77
describe the structure of a virus and explain why it is not considered to be a cell [2]
- molecule of (nucleic acid / DNA / RNA) surrounded by a (protein coat / capsid)
- (acellular as) does not have membranes / no organelles / cell membranes / cytoplasm
78
cells undergoing mitosis have been stained with a dye, which causes the DNA to be visible
explain why some stain would be seen in other parts of the cell [2]
- DNA is found (in other parts of the cell)
- in mitochondria
79
to complete the replication of the virus, capsid needs to be produced. describe how the proteins in the capsid are produced [5]
- translation
- mRNA attaches to a ribosome
- tRNA brings a (specific) amino acid
- complementary base pairing between mRNA codon and tRNA anticodon
- ribosome has room for two tRNA molecules / brings two amino acids into close proximity
- condensation reaction occurs / peptide bond formed (between amino acids)
- ribosomes moves to next codon / reference to stop codon
- post translational processing / or description of e.g folding of polypeptide chain role of Golgi
80
explain why the virus is unable to synthesise its own capsid? [2]
- it does not possess (any ribosomes / tRNA / the organelles for protein synthesis )
- it doesnt possess mitochondria / cannot produce its own ATP for the process
81
identify two differences between a eukaryotic cell and a prokaryotic cell [2]
eukaryotic vs prokaryotic
- membrane bound organelle present vs not
- DNA enclosed within nuclear membrane vs DNA free in cytoplasm
- linear DNA vs loop of DNA / plasmid
- larger/80s ribosomes vs smaller/70s ribosomes
82
describe and explain why pyrophosphatase (enzyme) can only hydrolyse pyrophosphate (substrate) [5]
- enzyme has tertiary structure
- the active site has a specific shape
- substrate has complementary shape
- fits into the active site / forms enzyme-substrate complex
- lock and key theory / induced fit
83
how is nitrate ions (NO3 -) needed in animal/plant cells?
- needed for making nucleotides
84
reducing sugars reduce blue copper II sulphate forming copper I sulphate which is a brick red ppt
85
why is sucrose called a non-reducing sugar?
because it doesnt reduce copper II sulphate
86
cellulose is unreactive and stable (due to being unbranched) and has a high tensile strength (due to the formation of microfibrils and fibres)
87
the higher the ratio of HDL:LDL in a person’s blood, the lower the risk of cardio-vascular and coronary heart disease
88
function of lipids:
- energy reserve (store) in plants and animals
- thermal insulator
- protection
- metabolic water source
- waterproofing
- low density and buoyancy
- nerve transmission
- steroids and cholesterol
- cell membrane formation
describe each one:
- energy store = triglycerides contain more carbon-hydrogen bonds than carbohydrate, twice as much energy produced as same mass
- thermal insulator - when stored under the sink acts as a thermal insulator which reduces heat loss
- protection = fat is often stored around delicate organs such as the kidneys
- metabolic water source = triglycerides produce a lot of metabolic water when oxidised. essential for desert animals
- waterproofing = insoluble in water important in e.g insects for waxy cuticle to reduce water loss. also leaves
- low density and buoyancy = fairly low density and help animals e.g polar bears float in water. seeds which store oils can be dispersed easily as they are light
- nerve transmission = triglycerides form the myelin sheath which surrounds the axon of nerve cells (neurones) in vertebrates; the myelin sheath seeps up nerve transmission
- steroids and cholesterol = steroids are lipids. have a ring structure rather than a long chain structure
- cell membrane formation = phospholipids form a bilayer which is basis of all cell membranes. allows transport of non-polar molecules across cell membrane by simple diffusion
89
amino acids can be essential or non-essential.
essential =
non essential =
essential amino acids cannot be synthesised by our bodies, and must be provided by out diet.
non essential amino acids can be synthesised by out bodies
90
where is fat stored in animals?
in plants?
- in animals, fat is stored under the skin and around organs
- in plants, triglycerides are stored as oils in seeds
91
fibrous proteins:
- consist of polypeptides in parallel chains or sheets with numerous cross linkages to form long fibres
- a single fibre consists of three identical polypeptide chains twisted together like a rope. these chains are linked by cross-bridges, making a very stable molecule
92
haemoglobin vs collagen
(globular vs fibrous)
- haemoglobin:
- 4 polypeptide molecules
- each polypeptide molecule is different (4 genes needed to code for haemoglobin)
- haemoglobin associated with non-protein groups (haem groups)
- highest level of protein structure is quaternary
- collagen:
- 3 polypeptide chains
- each polypeptide is the same (only one gene needed to code for collagen)
- collagen not associated with non-protein groups
- highest level of protein structure is secondary
93
similarities in features between mitochondria and chloroplasts:
differences:
- similarities:
- both have double membrane
- have highly folded inner membranes
- have circle of DNA for self replication
- have ribosomes
- produce ATP
differences:
- mitochondria have cristae, but chloroplasts have thylakoid membranes
- chloroplasts contain photosynthetic pigments to absorb light energy, mitochondria do not
- mitochondria have an inner matrix, but chloroplasts have a stroma
94
example of connective tissue:
collagen forms tendons which connects muscles to bones
95
1000nm = ___ µm
1 µm
96
1000 µm = ___mm
1 mm
97
1m = ___ mm
1000mm
98
nm = 10^-9 m
µm = 10^-6 m
mm = 10^-3 m
99
how does increasing sodium chloride concentration affect cell membrane permeability?
- sodium ions attach to the oxygen atoms on the hydrophilic (phosphate) heads of the phospholipid bilayer.
- this reduces mobility of the phospholipid molecules
- as sodium chloride concentration increases the permeability will decrease
100
how does increasing detergent concentration reduce surface tension?
- detergents reduce surface tension of phospholipids and disperse the membrane
- as the concentration of detergent increases the permeability of the membrane increases
101
what can facilitated diffusion be limited by?
the number of available intrinsic proteins
102
is facilitated diffusion a passive or active process?
passive
103
- co-transport is a type of facilitated diffusion
- that brings molecules and ions into cells together on the same carrier protein
- sodium-glucose co-transport is significant in absorbing glucose and sodium ions across cell membranes and into the blood in the ileum (small intestine) and kidney nephron
- sodium ions and glucose attach to a carrier protein in the cell membrane
- the carrier protein changes shape and deposits the sodium ion and glucose molecule into the cell
- the sodium ion and glucose molecule diffuse separately across the cell to the opposite membrane
- sodium ions are pumped out of the epithelial cells by active transport
- this lowers the sodium ion concentration inside the cell maintaining the concentration gradient needed for the diffusion of sodium ions from the gut lumen into the cell
- glucose leaves the epithelial cells by facilitated diffusion and enters the blood in the capillaries
104
what are some processes involving active transport?
- muscle contraction
- protein synthesus
- absorption of minerals e.g nitrates by plant root hair cells
105
the pressure potential is the hydrostatic pressure generated when the cell contents push against the cell wal (due to water entering the cell by osmosis)
106
plasmolysis is usually fatal to plant cells
107
plant cells in an isotonic medium are flaccid
108
turgid plant cells support the plant tissues and structures (optimal for plant cells)
109
isotonic mediums are optimal bathing mediums for animal cells
110
plant cells become flaccid in isotonic mediums - INCIPIENT PLASMOLYSIS
111
what does it mean that enzymes have a high turnover time?
they can convert many molecules of substrate into product per unit time
112
in an enzyme controlled reaction, the general rule is that the rate of reaction doubles for each 10°C rise in temperature
113
catalase is an enzyme found in all living cells
what does catalase break down?
the toxic waste product hydrogen peroxide into harmless water and oxygeb
114
where is ATP produced?
- in the cytoplasm
- the mitochondria (matrix and inner membranes)
- and in chloroplasts (thylakoid membranes)
115
DNA:
- is a double stranded polymer of nucleotides or polynucleotide
- the alternating phosphate groups and pentose sugars form the backbone of the polynucleotide
- the pentose sugar in DNA is always deoxyribose
- 4 diff bases, each contain nitrogen A, T, C, G
- purine bases bond with pyrimidine bases by hydrogen bonding
- adenine bonds with thymine and guanine bonds with cytosine - complementary base pairings
- base pairing links two polynucleotide chains
- polynucleotide chains are antiparallel to each other
- molecule is twisted to form a double helix. shape is maintained by hydrogen bonding
116
each strand of mRNA contains the genetic code for one gene
117
an advantage of asexual reproduction:
a disadvantage :
- adv = the ability to increase in numbers quickly to take advantage of an ideal environment
- disadv = lack of genetic variation, leading to an inability to adapt if the environment changes
118
state two uses for the energy released from ATP in a plant cell [1]
- active transport
- DNA replication
- protein synthesis
- cell division
119
describe the structure of starch and triglycerides and suggest how their structure and properties relate to their function as energy storage molecules [9QER)
starch:
- polymer of a-glucose
- composed of amylose and amylopectin
- amylose contains only 1,4 glycosidic bonds
- forms a helical structure
- amylopectin contains 1,4 and 1,6 glycosidic bonds
- forms a branched structure
triglycerides/lipids
- composed of glycerol and three fatty acids
- joined together by ester bonds
- saturated fatty acids contain only C-C single bonds
- unsaturated fatty acids contain at least one C=C double bond
- properties of triglycerides dependent on fatty acid they contain
function (in seed):
- starch and triglycerides are insoluble and so osmotically inert
- starch’s helical/branched structure makes the molecule compact
- hydrolysis provides glucose readily
- required for respiration/produce ATP
- triglycerides also have a compact structure
- triglycerides have many high energy bonds / provide approx twice quantity of energy than starch
120
what is a polymer?
a chain of identical monomers
(so triglycerides arent)
121
explain how the shape of a protease is related to its function [2]
- (tertiary structure)
- shape is globular / specific 3D shape
- reference to active site being complementary to substrate
122
use your knowledge of the properties of water to explain:
pond skaters can live on the surface of the pond [2]
- hydrogen bonds (form between water molecules)
- stronger at surface / forms surface tension
123
use your knowledge of the properties of water to explain:
pondweed can grow underwater [2]
- water is transparent / light can penetrate for photosynthesis
- carbon dioxide / minerals can be absorbed for photosynthesis
124
why do cancer cells have a high demand for glucose for respiration?
as they divide continuously
125
apart from N, H, C, O what other element is found in some amino acids?
sulfur
126
explain why it is necessary to calculate the percentage change in mass [1]
- because the masses at the start were different
- to obtain comparable results
127
suggest and explain how mitochondria are able to self-replicate [3]
- mitochondria contain their own DNA
- have ribosomes and can synthesise their own proteins
- DNA can be replicated (so both new organelles have copy of DNA) / accept ref. to binary fission
128
name one structure in a flower where meiosis occurs [1]
ovary / anther
129
what are three differences between the DNA of a host cell and DNA of a virus?
- virus DNA circular, host cell DNA linear
- virus DNA smaller, only 8000 bases, host DNA has 6 billion bases
- virus only has 8 genes, host cell has many more (20,000)
130
explain why DNA cannot be replicated outside of the nucleus?
free DNA nucleotides not outside nucleus
131
lysozyme is an enzyme which catalyses the breakdown of glycosidic bonds in polysaccharides in bacterial cell walls. it works using the induced fit model of enzyme action.
- describe the three levels of protein structure in the lysozyme molecule.
- explain how the three levels of protein structure are maintained
- describe and explain the induced fit model of enzyme action as shown by lysozyme [9QER]
• levels of protein structure:
- primary - the SEQUENCE/ORDER of amino acids in a polypeptide
- secondary - folding of the primary structure - ALPHA-helix and BETA-pleated sheets formed
- tertiary - (FURTHER) folding of secondary structure a forms a GLOBULAR protein / SPECIFIC 3D shape
• how levels maintained:
- primary - PEPTIDE bonds between amino acids
- secondary - hydrogen bonds between -OH / polar R groups
- tertiary - hydrogen bonds “ “, ionic bonds between charged R groups, disulphide bonded between sulfur-containing R groups, hydrophobic interactions / hydrophobic R groups in centre (away from water), hydrophilic R groups on outside of protein
• enzyme action
- active site is complementary to only one substrate
- substrate binds to the enzyme’s active site
- active site changes shape slightly to fit more closely around substrate
- this puts strain on the bonds in the substrate
- less energy needed to break bond/ lowers activation energy
- products are released
132
why is inhalation an active process?
it involves muscle contraction
133
what happens to the lungs when we exhale strongly? e.g during intense exercise/blowing up a balloon
- internal intercostal muscles contract
- pulls ribs down and inwards
- forcing air out of lungs
- at the same time, the external intercostal muscles relax
- bc the internal intercostal muscles contract while the external intercostal muscles relax, describe them as antagonistic
134
why is the oxygen affinity of foetal haemoglobin only slightly greater than adult haemoglobin?
if foetal haemoglobin had a very high oxygen affinity, then that could prevent it from unloading oxygen in the foetal tissues
135
what enzyme catalyses the reaction from carbon dioxide and water to carbonic acid?
carbonic anhydrase
136
why is the left ventricle’s muscular wall thicker than the right ventricle?
because the left ventricle pumps blood around the whole body
(whereas the right ventricle only pump blood to the lungs)
137
why do the ventricles contract from the apex upwards?
to ensure that the maximum volume of blood is pumped out of the ventricles
138
describe what is meant by the terms mechanical digestion and chemical digestion [2]
- mechanical digestion (breaks food down into smaller pieces/increases its surface area)
(reject molecules)
- chemical digestion involves (hydrolysis / use of enzymes / larger into smaller MOLECULES / insoluble into soluble molecules)
139
what is the importance of lignin in the functioning of the xylem? [1]
- to prevent collapse of the xylem / provide (mechanical) support
ignore strength/waterproofing/rigidity
140
in an investigation into the mechanisms of transport, fluid filled micropipettes were inserted into xylem vessels and sieve tube elements.
use your knowledge of plant transport, explain the observations of:
- phloem sap oozes out of stem
- air is drawn into xylem [4]
- xylem contents under lower pressure (than air)
- contents pulled (upwards through xylem) due to (transpiration stream / cohesion-tension / adhesion / evaporation of water vapour from the leaves)
- phloem contents under higher pressure (than air)
- contents (pushed / forced) through phloem by (mass flow / active transport / hydrostatic pressure)
141
what are some variables that you would need to keep as similar as possible between two (e.g streams) in kick sampling?
- flow RATE/speed/current
- temperature
- oxygen CONCENTRATION
- light INTENSITY/EXPOSURE
- vegetation (on banks/in water)
- river width and depth
- same (stony) stream beds
142
when kick sampling, state two factors that need to be controlled to ensure standardisation of sampling [2]
- (same) sampling area
- (time spent/force/power/speed/amount) of KICKING / number of kicks
- net mesh size
- distance from bank/distance of kicking from the net
143
suggest two reasons why the values of species (number and variety) obtained might be an underestimate of the actual numbers of species at the kick sample sites [2]
- animals not caught by net / missed net / passed through net / net removed too soon
- animals not dislodged from stream bed / not kicked hard enough to dislodge them / organisms moved away from sample area
- not kicked entirely area / uneven kicking
- unable to identify animals / animals too small to identify
144
what does a bimodal distribution mean?
it has 2 peaks
145
explain the events occurring during: the P wave? [3]
- SAN generates (ELECTRICAL impulse / wave of excitation / ELECTRICAL signals)
- causes DEPOLARISATION of ATRIA
- contraction of ATRIA / ATRIAL systole
146
explain the events occurring during: the QRS compex? [3]
- AVN (transmits / relays / passes on) (ELECTRICAL impulse/electrical signals / wave of excitation)
- passes through (Bundle of His/Purkinje tissue/septum)
- depolarisation of VENTRICLES
- causes contraction of VENTRICLES / VENTRICULAR systole
147
explain the events occurring during: the T wave? [2]
- repolarisation of ventricles
- causes VENTRICULAR diastole / relaxation of ventricles
148
during exercise there is little change to the lengths of the P wave, QRS complex, or T wave.
describe and explain how the distance between consecutive P waves would differ in a person taking exercise [2]
- shorter / closer together
- due to shorter isoelectric line / flat part / PR segment / less time between (atrial systole and ventricular systole / ventricular systole and ventricular diastole / ventricular systole and atrial systole)
149
why is the symplast pathway fairly slow?
because the pathway for water in the cytoplasm is obstructed by the organelles
150
does a respiratory inhibitor stop root pressure?
yes - because it is an active process
- actively transports minerals into xylem (so lowers water potential gradient and water moves in)
151
what are the two pieces of evidence which support the cohesion-tension theory?
- if a plant stem is cut, then air is sucked into the xylem, suggesting that the xylem vessels are under tension. (however the air prevents cohesion between the water molecules, so water movement stops)
- if you measure the diameter of a tree trunk, we see that this reduces when transpiration is at its maximum. this supports the idea that transpiration pull is generating a negative pressure or tension in the xylem
