Paper 3 Biology (ALL THE CONTENT) Flashcards

Question

What are amino acid structures?

Answer 1

- Same R group - Different carboxyl group - Different amine group

Answer 2

- Peptide bonds

Answer 3

Sequence of amino acids

Answer 4

- Hydrogen bonds form between the amino acids in the chain such as alpha helix and beta pleated sheet

Answer 5

- Further folding of alpha helix and beta pleated sheet including hydrogen bonds, ionic bonds and disulphide bridges.

Answer 6

- A number of polypeptide chains joined together ( 2 or more)

Answer 7

Blue to purple

Answer 8

- Proteins that act as biological catalysts by lowering the activation energy, minimum amoutn of energy for reaction to happen.

Answer 9

- When the lock and key happens, the enzyme and substrate alter their shape slightly - Weakens specific bonds in the substrate needing to be broken, which lowers the activation energy required for the reaction to happen, increasing rate of reaction.

Answer 10

(temperature, ph, substrate concentration)

Answer 11

- Molecules with similar shape to the substrate that fit into the enzyme's active site to form an enzyme-inhibitor complex, preventing the substrate from binding.

Answer 12

- Work by binding to enzyme in a place other than the active site. - Changes tertiary structure of the adctive site meaning no complementary binding. - Can't be reversed - No competition happens

Answer 13

- DNA holds genetic information in all living cells - RNA transfers genetic information from DNA to ribosomes.

Answer 14

- Phosphate - Pentose (Deoxyribose) - Base

Answer 15

- Phosphate - Ribose - Either A,U,C,G

Answer 16

- Nucleotides join by a condensation reaction between the phopshate group of one nucleotide and pentose sugar of another - Forms a phosphodiester bond between two nucelotides

Answer 17

- antiparallel

Answer 18

- Some argued that DNA was too simple to carry the genetic code. - Some argued that genetic information must be carried by proteins, which are more chemically varied. - 1953 experiments showed that DNA was the true carrier of genetic code after Watson and Circk determined the sturtcure of DNA.

Answer 19

- Two DNA polynucleotide strands are only joined together by weak H bonds, meaning that strands can separate during DNA replication - Base pairs are protected by sugar-phosphate backbone - Large molecule so carries losts of genetic information

Answer 20

- Much shorter than DNA - mRNA - Genetic info from DNA to ribosomes - tRNA: involved in protein synthesis - rRNA: makes up part of the ribosome structure

Answer 21

- To ensure all the daughter cells produced have the genetic information to produce all the enzymes and other proteins they need.

Answer 22

- Each of the two new DNA molecules has 1 strand from the original molecule and 1 strand of new material.

Answer 23

1) DNA helicase breaks hydrogen bonds between bases on the two strands of DNA. The DNA double helix begins to unwind. 2) Original strands act as template for a new strand. Free DNA nucleotides are attracted to complementary bases. 3) DNA polymerase catalyses condensation reaction which join the nucleotides of the new strands together by phosphodiester bonds.

Answer 24

- Through the Meselson and Stahl Experiment. - This was where bacteria were grown on a medium containing heavy 15N nitrogen and the bacteria incorporated nitrogen from the medium into their DNA and is ultracentrifuged to obtain a heavy band of DNA. - Bacteria is transferred to a medium containing lighter 14N nitrogen and are allowed to replicate once and are ultracentrifuged, obtaining an intermediate density band of DNA - Bacteria replicates once more in the lighter 14N medium and the DNA is ultracentrifuged, obtaining both light and intermediate density DNA.

Answer 25

- Conservative (New material would consist of only old DNA) - Dispersive (Original DNA would be cut up into sections leaving you with new DNA molecules with new and original material) (Can't just have intermediate density DNA)

Answer 26

Adenosine triphosphate

Answer 27

- Low activation energy so little energy needed to be put in to break these bonds and are easily broken/ - Lots of energy released when these bonds are broken.

Answer 28

- ATP synthase

Answer 29

- ATP diffuses to the part of the cell that requires energy and is hydrolysed into ADP and Pi

Answer 30

- ATP hydrolase

Answer 31

- ATP is an immediate source of energy - ATP releases energy is smaller, more manageable quantities

Answer 32

- Because many metabolic reactions are either condensation or hydrolysis reactions involving water

Answer 33

- Water is a polar molecule so can therefore interact with charged ions or polar molecules.

Answer 34

- Due to hydrogen bonding, it takes a lot of energy to change the temperature of water

Answer 35

- It takes a lot of energy to break hydrogen bonds and change liquid water into a gas

Answer 36

Water forming hydrogen bonds with itself

Answer 37

Water forms hydrogen bonds with other materials

Answer 38

- Ions that don't contain carbon

Answer 39

- Concentration of H ions determines pH - Higher = lower pH - pH affects enzymes

Answer 40

- Haemoglobin contains Fe2+ at its centre which binds to oxygen to temporarily become Fe3+

Answer 41

- Co transporter across cell membranes (sodium-glucose) - Active transport (sodium potassium pump) - Nerve impulse transmission

Answer 42

- Bonds between phosphate groups store energy in ATP - Phosphate allows DNA and RNA nucleotides to join to form polynucleotides

Answer 43

- Non specific (Immediate responses and the same for all pathogens E.G. physical barriers and phagocytosis) - Specific (slower responses, specific to each pathogen involving lympocytes)

Answer 44

- Each type of cell has specific molecules on its surface that identify it. - However it is by the proteins on the surface which the immune system can recongnise if the cell is self or foreign.

Answer 45

- A molecule/protein that triggers an immune response by lymphocytes

Answer 46

- A type of white blood cell which carries out phagocytosis

Answer 47

- The mechanism by which cells engluf particles to form vesicles that eventually destroy pathogens.

Answer 48

1) Phagocyte is attracted to the pathogen 2) phagocyte attaches to chemicals on the surface of the pathogen by specific receptors 3) Phagocyte englufs pathogen and forms a phagosome 4) lysosome fuses with phagosome forming phagolysosome 5) Hydrolysis of the pathogen 6) Phagocyte presents its antigens on its cell surface membrane (APC)

Answer 49

- Bone marrow - Mature in the Thymus gland - Associated with the cellular response (cell-mediated)

Answer 50

- Made in bone marrow like T - Mature in the bone marrow - Associated with the humoural response

Answer 51

- Immunity involving body cells that have antigens presented on their surface

Answer 52

- Involves antibodies that are present in body fluids

Answer 53

- Pathogen invades body cell or are taken in by phagocytosis - Invaded cell presents antigen on its surface membrane - T helper cell binds to the antigen via a specific T-cell receptor - This activates the T helper cell to rapidly divide by mitosis and form clones of this specific T helper cell (clonal selection)

Answer 54

- Can develop into memory cells that enable rapid response to future infections by the same pathogen - Stimulate phagocytes to engulf pathogens by phagocytosis - Stimulation of B cells to divide and secrete antibodies - Activation of cytotoxic T cells.

Answer 55

- Cells that kill abnormal cells and body cells that are infected by pathogens - Produce perforin, a type of protein, which makes holes in the cell membrane causing the cell to die as any substances enter it.

Answer 56

- proteins produced by b lymphocytes in response to an antigen.

Answer 57

- On the surface of pathogens to form an antibody-antigen complex.

Answer 58

- B cell takes in antigens of a pathogen by endocytosis - B cell processes antigens and presents them on its surface - T helper cells attach to the processed antigens on the B cells and activate it. - B cell divides by mitosis to provide a clone to form plasma cells - Plasma cells produce and secrete the antibodies specific to the antigen on the pathogen's surface. - Antibodies attach to antigens on the surface of pathogens causing them to agglutinate, making it easier for phagocytes to locate and engulf them - B cells develop into memory cells which can divide rapidly into plasma cells.

Answer 59

- Secrete antibodies, usually in blood plasma and are involved in the primary immune response

Answer 60

- Involved in the secondary immune response

Answer 61

- Secondary response is quicker than primary response - Memory B cells are able to divide rapidly into plasma cells.

Answer 62

- The introduction of dead/inactive pathogen to stimulate an immune response. - Vaccine stimulate the production of memory cells to an antigen without producing harsh symptoms. - So if the body is exposed to the same antigen, antiboides are produced rapidly.

Answer 63

- When a large population is immune to a disease, then the spread of that pathogen is significantly reduced.

Answer 64

- Where the tertiary structure of antigens changes so the vaccine can no longer be effective against a particular disease. - Pathogens mutate to have different antigens so it is no longer recognised by the immune system.

Answer 65

- Active immunity is the triggering of immune system by exposure to antigens - Passive immunity is the introduction of antibodies from an outside source

Answer 66

- Infection and recovery

Answer 67

- Antibodies recieved from mother via breast milk or placenta

Answer 68

- Vaccination by a jab

Answer 69

- Injection of antiserum containing antibodies

Answer 70

- Active provides long term immunity but passive is short term immunity - Active produces memory B cells but passive doesn't - Passive is quicker

Answer 71

- An enzyme that catalyses the production of DNA from RNA.

Answer 72

1) HIV binds to host T helper cell receptor via the attachment protein 2) Viral capsid and host cell membrane fuse and RNA and reverse transcriptase enters. 3) Reverse transcriptase makes DNA 4) Double stranded DNA is mad and inserted into host cell's DNA 5) Transcription into mRNA, making new proteins that are viral and then these are released and infect other areas.

Answer 73

- Kills T helper cells leading to insufficient T helper cells - Less T helper cells means less B cells can bind to their antigens to produce antibodies - Memory cells are infected and destroyed

Answer 74

- Antibiotics target bacterial enzymes however viruses use human enzymes which are a different structure - Viruses do not have sites where antibiotics can work

Answer 75

- Antibodies produced from a single group of genetically identical B cells

Answer 76

- They have binding sites that are only complementary to one antigen

Answer 77

E.G cancer cells 1) Monoclonal antibodies are produced which are specific to receptors on cancer cells 2) Antibodies attach to the surface of cancer cells and block chemical signals that stimulate uncontrolled growth. (direct monoclonal antibody therapy)

Answer 78

- Specific to one type of cell - Not toxic - Fewer side effects as there doesn;t need to be used in large doses

Answer 79

- Animals are used and may suffer - Vaccines may not be fairly distributed to people - Cancer is deliberately induced in the animals

Answer 80

- We can measure the presence and quantity of a protein in a sample.

Answer 81

- Infections - Allergies - Levels of a drug

Answer 82

1) Antigen is bound to the surface of a well. 2) Antibody specific to the antigen is added and will bind if present (enzyme linked, enzyme attached) 3) rinse the well to remove unbound antibodies 4) Substrate solution is added, substrate binds to enzymes 5) Causes a colour change 6) colourimeter detects the amount of colour change which correlates to the the amount of antigen present.

Answer 83

- Act as barriers between cells and their environment as well as between the cytoplasm and the organelle

Answer 84

- The structure of all cell membranes is the same being made of lipids, proteins and carbohydrates - It is fluid as phospholipids are constantly moving and mosaic because it is packed full of proteins.

Answer 85

- Span the two sides of the membrane

Answer 86

- Water filled tubes which allow water soluble molecules to pass through

Answer 87

- Proteins that bind to molecules or ions and change their shape to move them across.

Answer 88

- Mechanical support for the membrane, acting as cell receptors for molecules such as hormone and act as receptors to identify other cells

Answer 89

- Proteins with carbohydrates attached - They act as receptors for molecules such as hormones and neurotransmitters. - Allows cell adhesion - Allow cell recognition

Answer 90

- Lipids with carbohydrates attached - Act as recognition sites - Help stability of the membrance - Cell adhesion

Answer 91

- A type of lipid - Restricts the movement of other molecules in the membrane which causes rigidness - They can bind to phosopholipid fatty acid tails to pack closely together.

Answer 92

- The centre of the bilayer is hydrophobic so no water soluble substances pass through such as ions

Answer 93

- Diffusion - Facilitated diffusion - Active transport - Osmosis - Co-transport

Answer 94

- Concentration gradient - Surface area - Temperature - Diffusion distance - Size of particle - Number of channel/carrier proteins

Answer 95

- The pressure created by water molecules - The likelihood of water molecules to move in or out

Answer 96

- Hypertonic the movement of water into a cell causing bursting - Hypotonic is the movement of water out of a cell (remember hyper movement into not out)

Answer 97

- The movement of molecules or ions from a region where they are in low concentration to one where their concentration is higher, against a concentration gradient.

Answer 98

- Takes place in the ileum where concentration is too low for diffusion to occur.

Answer 99

1) Sodium ions are actively transported out of the epithelial cells into the blood via a sodium potassium pump in exchange for a potassium ion (carrier protein) 2) Low conc of sodium ions creating diffusion gradient of sodium from the lumen 3) Sodium ions diffuse into epithelial cells via a sodium-glucose co transporter protein and as it does this is couple with a glucose molecule to take more glucose into the epithelial cell too. 4) Concentration of glucose inside cell increases too. 5) Glucose diffuses into the blood via facilitated diffusion

Answer 100

- They have the same organelles as well as a cell wall and chloroplast

Answer 101

- Cell walls are made of chitin, not cellulose - Fungal cell don't have chloroplasts

Answer 102

- Group of fluid-filled, membrane bound flattened sacs - Vesicles are often seen at the edges of the sacs

Answer 103

- Processes and packages new lipids and proteins - Also makes lysosomes

Answer 104

- Small, fluid filled sac found in cytoplasm which is surrounded by a membrane and produced by golgi apparatus

Answer 105

- Store lipids and proteins produced by the golgi apparatus and transport them out of the cell via exocytosis

Answer 106

- Round organelle surrounded by a membrane with no clear internal structure

Answer 107

- Contains enzymes that hydrolyse invading cells or worn out components

Answer 108

- Small organelle - Made of protein and rRNA

Answer 109

- System of membranes enclosing a fluid filled space - Consistent with the nuclear envelope and covered with ribosomes

Answer 110

- Process and packages proteins made at the ribosome.

Answer 111

- Similar structure to the rough ER but no ribosomes

Answer 112

- Synthesise and processes proteins and lipids

Answer 113

- The cytoplasm has no mmebrane bound organelles - Ribosomes are much smaller than in eukaryotic cells (70s only) - Single ciruclar DNA molecule that is free in the cytoplasm and isn't associated with proteins - Cell wall supports the cell and prevents change in shape made of muerin (peptidoglycan)

Answer 114

- One or more plasmids (small loops od DNA which contain genes for things such as antibiotic resistance and are used to transfer genetic material between bacterium) - Slime capsule helps protect bacteria from attack by other cells and helps bacteria group together for further protection - Flagella allow the bacteria to move

Answer 115

- Prokaryotic have no nucleus but eukaryotic do - Prokaryotic have plasmid but eukaryotic don't - Prokaryotic have smaller ribosomes than eukaryotic cells - Prokaryotic cells have a peptidoglycan cell wall but eukaryotic have a cellulose cell wall in plants

Answer 116

- Acellular and non-living - Genetic material - Capsid - Attachment proteins

Answer 117

- Bind to complementary receptor proteins using attachment proteins - Inject genetic material into the cell - Host cell's enzymes and ribosomes are used to make new viral proteins that assemble into viruses which are released from the host and go on to hijack other cells.

Answer 118

Light: Uses a beam of light Electron: Uses a beam of electrons Light: Max magnification of x1500 Electron: Max magnification of x1,500,000 Light: Max resolution (0.2 micrometres) Electron: Max resolution (0.002 micro metres) Light: Live specimen yes Electron: Live specimen no because speciments have to be contained in a vacuum as the air particles would absorb electrons and interfere with results.

Answer 119

- Cannot see ribosomes, endoplasmic reticulums and lysosomes as theyre too small for the 0.2 micrometre resolution

Answer 120

- Electrons are transmitted through the speciment - Show you the internal structure of organelles - Higher resolution - Can only be used for thin speciments - 2D images

Answer 121

- Scan a beam of electrons across the speciment - Only show the specimen's surface - Lower resolution - Can be used for thick speciments - 3D

Answer 122

- Process by which cells are broken up and their organelles are separated out

Answer 123

- Breaking up cells using a homogeniser or by vibrating them

Answer 124

Cold - reduces enzyme activity which may hydrolyse organelles Isotonic - To prevent the movement of osmis which may burst or shrink the cell Buffered - To maintain pH and prevent ay damage to organells or enzymes

Answer 125

- Resultant fluid is filtered to remove any unbroken cells or cell debris

Answer 126

- Different organelles in the filtered solution are separated out in a centrifuge - Centrifuge spun at low speed forming pellet (individual organelle) and supernatent (remaining liquid) - Spun at higher speed

Answer 127

Nucleus, mitochondria, lysosomes, ER, ribosomes

Answer 128

- mitosis, meiosis

Answer 129

- Produces 2 genetically identical daughter cells

Answer 130

- Growth - Repair

Answer 131

- Chromosomes condense, get shorter and fatter - Nucleolus disappears - Nuclear envelope breaks down - Centrioles move to opposite poles

Answer 132

- Spindle fibres pull chromsomes to the equator of the cell

Answer 133

- Centromeres divide separating each pair of sister chromatids - Spindle fibres shorten and pull each chromatid to opposite poles where they are referred to as chromsomes

Answer 134

- Chromsomes lengthen again - Spindle fibres disintegrate - Cytoplasm divides to form two sepearate cells.

Answer 135

- Part of the cell cycle - Period of cell growth and DNA replication

Answer 136

- Cell grows and increases in volume when new organelles are made

Answer 137

- Cell replicates its DNA

Answer 138

- Cell continues growing and synthesises enzymes and structures needed for mitosis

Answer 139

Number of cell in phase/total number undergoing mitosis x time taken for one cell cycle

Answer 140

Number of cells undergoing mitosis/Total number of cells x100

Answer 141

- Uncontrolled cell division by mitosis

Answer 142

- Binary fision 1) Replication of DNA and plasmids 2) circular DNA strands move to opposite poles 3) Cytoplasm divides and new cell walls grow to divide the original cell into 2 identical daughter cells, each with 1 copy of the ciruclar DNA and a variable number of plasmids.

Answer 143

- As organisms increase in size, its volume increases faster than its surface area so the SA:V ratio decreases

Answer 144

- Large surface area to volume ratio - Rely on solely diffusion - Diffusion is fast because substances only travel small distances.

Answer 145

- Small surface area:volume ratio - Cannot rely on diffusion of substances through its surface to meet needs of the organism.

Answer 146

- Large surface area - Good blood supply - Thin membranes

Answer 147

- The Tracheal System

Answer 148

- Oxygen diffuses down a concentration gradient towards the cells. - Tracheae branch off into tracheoles, which have thin, permeable walls that border respiring cells. - Oxygen diffuses from branches directly to respiring cells - CO2 diffuses from cells towards spiracles, to be released into the atmosphere.

Answer 149

- Much lower concentration of O2 in water than in air - Diffusion of O2 and Co2 is slower in water.

Answer 150

- Fish have gills which are gas exchange organ, adapted to overcoming these problems

Answer 151

- Fish open their mouths and allow the water to flow through the gills, and out via the operculum (gill cover)

Answer 152

- Each gill is made of filaments providing a large surface area -Lots of lamellae - One cell thick provides a short diffusion pathway - Good blood supply - Maintains a favourable concentration gradient.

Answer 153

- Blood flows through the llamellae in the opposite direction to the flow of water.

Answer 154

- Maintanance of a favourable O2 concentration gradient between water and blood across the entire length of the gill lamellae.

Answer 155

- Palisade mesophyll cells contain lots of chloroplasts.

Answer 156

- Protects internal tissues from mechanical damage or the invasion of bacteria

Answer 157

- Stomata allow the diffusion of gases in and out of the leaf. - Many stomata means a short diffusion distance - Air spaces allow for diffusion of gases - Large surface area means greater rate of diffusion.

Answer 158

- By regulating the opening and closing of stomata by guard cells - This is affected by light intensity, water avaliability and carbon dioxide concentration

Answer 159

- Stomata closes as the cell can't photosynthesise so there is no need for CO2 and O2 to diffuse in and out of the leaf so closing the stomata helps prevent unneccesary water loss.

Answer 160

1) As you breathe in, air enters the trachea 2) Splits into 2 bronchi 3) Split into bronchioles 4) Lead to alveoli 5) Uuse diaphgram, internal and external intercostal muscles work together to allow ventilation

Answer 161

- O2 diffuses out of the alveoli across the alveolar epithelium + capillary endothelium, into haemoglobin in the blood - CO2 diffuses into the alveoli from deoxygenated blood and is breathed out

Answer 162

- They are pressed against the capillary wall which : - allows time for diffusion of gases - increases the surfaces area avaliable of red blood cells exposed - Minimises the diffusion distance

Answer 163

1) External intercostal muscles contract 2) Internal intercostal muscles relax 3) Diaphgram contracts 4) Volume of cavity increases 5) Pressure of thoracic cavity decreases 6) Air flows from of an area of high pressure to an area of low pressure down a concentration gradient

Answer 164

- Active process becuase it involves the contraction of muscles

Answer 165

- External intercostal muscles relax - Internal intercostal muscles contract - Diaphgram relaxes - Pressure increases - Volume decreases - Air moves out of the lungs

Answer 166

- Alveolar epithelium is only 1 cell thick which shortens the diffusion distance - Large surface area for gas exchange - Rich blood supply (Maintains the conc gradient) - Ventilation

Answer 167

- Hydrolysis of large biological molecules into smaller biological molecules that can be absorbed

Answer 168

- The hydrolysis of glycosidic bonds

Answer 169

- Amylose hydrolyses starch into maltos, which then is hydrolysed by the disacchardie maltase

Answer 170

- Salivary glands - Small intestine (Note: Pancrease releases enzymes which are then released into the small intestine)

Answer 171

- Enzymes attached to the cell-surface membranes of epithelial cells lining the ileum

Answer 172

- By the process of active transport via a co-transporter protein

Answer 173

- Fructose is absorbed via facilitated diffusion through a different transporter protein

Answer 174

- Through the hydrolysis of ester bonds

Answer 175

- Lipase enzymes are produced by the pancreas and secreted into the small intestine

Answer 176

- Reduce the surface tension between lipids and water which splits the larger drops of lipid into smaller ones (emulsification) - This in turn increases the surface area for lipase enzymes to act upon

Answer 177

- When the bile salts and fatty acids and glycerol stick together - This moves the products to the epithelial cells.

Answer 178

- By protease enzymes hydrolysing peptide bonds to form amino acids.

Answer 179

- Endopeptidases (Found within peptide bonds) - Exopeptidases (Found on the outside of peptide bonds) - Dipeptidases (Found in between 2 peptides)

Answer 180

- Via co-transport, in a similar way to glucose and galactose - Via sodium ions with a co-transporter protein

Answer 181

- Ileum is very long which allows time for diffusion and active transport of products of digestion - Lining is folded into millions of villi which increase the surface area for diffusion - Cells are one cell thick to decrease the diffusion distance - Rich blood supply in the villi which maintains a concentration gradient

Answer 182

- Quaternary structure

Answer 183

- 4 O2 molecules

Answer 184

- Measure of the concentration

Answer 185

high at the lungs lower at respiring tissues

Answer 186

- affinity means that the level of binding

Answer 187

- Loads onto Hb when there is a high partial pressure of oxygen (lungs)

Answer 188

- When there is a low pO2 (respiring tissue)

Answer 189

- How muich oxygen is being carried by haemoglobin

Answer 190

- The joining of the first oxygen molecule is slow but once it has happened, Hb changes shape, making it easier for other O2 molecules to bind.

Answer 191

- High pCO2 lowers Hb's affinity for oxygen as oxygen unloads (lowers blood pH) - Faster rate of respiration leads to more O2 being unloaded for a given pO2.

Answer 192

- Depends on activeness - Depends on metabolic rate - Depends on altitude (E.G. organisms living at altitude have higher affinities for O2 so it loads more readily)

Answer 193

- Double Closed Circulatory System (goes through the heart twice) - Arteries carry blood away from the heart - Veins carry blood to the heart

Answer 194

- Transport of blood to the lungs

Answer 195

- Transport of blood to the rest of the body

Answer 196

- Vena Cava

Answer 197

- Pulmonary artery

Answer 198

- Pulmonary vein

Answer 199

- Its function is to transport blood to the rest of the body so had thicker and more muscular walls than the right ventricle because it needs to contract more powerfully and generate higher pressures

Answer 200

- Thicker walls as they have to force blood out of the heart wheras atria only have to push the blood small distances

Answer 201

- When pressure is higher behind the valve it opens

Answer 202

- When pressure is higher in front of the valve

Answer 203

- They prevent any backflow of blood which means blood only travels one direction

Answer 204

- It can contract on its own without nerve impulses

Answer 205

- In the sinoatrialnode within the right atrium - Signals are then delayed at the AVN - Signal passes to the heart apex - Signals are spread throughout the ventricles

Answer 206

- Volume of blood decreases - Pressure of blood increases - Blood is forced into the ventricles

Answer 207

- Volume of ventricles decreases - Pressure of ventricles increases - Atrioventricular valves shut - Semi-lunar valves open

Answer 208

- Carry blood away from heart to tissues

Answer 209

- Thick walls, small lumens, folded endothelium allows the arteries to stretch - Muscular fibres can constrict and dilate to change the level of blood flow.

Answer 210

- Allow the exchange of materials between the blood and cells via tissue fluid

Answer 211

- One cell thick - Form a capillary bed so a large SA - Found near cells at exchange surfaces so a short diffusion distance

Answer 212

- Carry blood from tissues to the heart

Answer 213

- Large lumen - Thin muscular walls

Answer 214

- Fluid that surrounds cells in tissues

Answer 215

- Move out of the capillaries and into tissue fluid by pressure filtration

Answer 216

Make up: - Oxygen - Carbon dioxide - Water - Glucose - Nutrients - Hormones Don't make up: - LArge proteins - Red blood cells

Answer 217

- At the arteria end, hydrostatic pressure is greater than hydrostatic pressure in tissue fluid, so fluid is forced out the blood

Answer 218

- Venule end of the capillary experiences a decrease in water potential due to smaller volume and an increase in concentration of large proteins which were too large to leave the blood. - As a result, water enters capillaries by osmosis

Answer 219

- Lymph vessel transport the tissue fluid back into the blood

Answer 220

- Tissue that transports water and dissolved mineral ions from the roots, up the stem and to the leaves.

Answer 221

- Tissue that carries organic substances from the source to the sink in plants

Answer 222

- Long, hollow tubes - Formed from dead cells, joined together - One way only - No end walls between cells - Walls contain lignin for strength which helps provide structural support for the plant

Answer 223

- Water molecules being attracted to other water molecules by hydrogen bonding

Answer 224

- Movement of water through xylem from roots to leaves

Answer 225

1) Water transpires from leaves and reduces the water potential in leaf cells so water is drawn out of the xylem by osmosis 2) Creates tension as more water needs to be drawn up through the xylem 3) Therefore more water enters the roots by osmosis as the WP in root cells decreases.

Answer 226

- humidity - temp - wind - light intensity

Answer 227

- Using a potometer - Shoot draws up water from potometer - Measure how far the water bubble moves towards the plant so we can caluclate how much water is drawn up - Reservoir adds water to move the air bubble back and fourth.

Answer 228

- Where sucrose is formed

Answer 229

- Where sucrose is needed

Answer 230

- Sieve tube elements (end to end to form long tubes so that dissolved substances can pass) - no nucleus and no organelles - Companion cells provide ATP for the transport of sucrose

Answer 231

- By enzymes which monitor the amount of solute at sinks and hydrolyse when necessary.

Answer 232

- Sucrose is actively transported from cells in the source into the phloem sieve elements (done by companion cells, which have mitochondria) - This lowers WP of the phloem, causing water to enter by osmosis. (increased hydrostatic pressure) - At the sink end, sucrose is actively transported out of the phloem into sink cells - WP of phloem increases so water goes back into the xylem (decreased hydrostatic pressure) - Creates a pressure gradeint that pushes solutes towards the sink

Answer 233

FOR: - Pholem is removed and a bulge forms due to pressure, the concentration of sucrose is higher above the bluge rather than below bulge suggesting the sucrose moves down the bulge. - Radioactive tracers incorportate into glucose which is converted into sucrose, sucrose moves by translocation and the movement is tracked by radiocative tracers. AGAINST: - Sucrose moves at a standard speed that doesn't appear to change due to the concentration gradient .

Answer 234

Short vs long Circular vs Linear Not associated with proteins vs Associated with histones

Answer 235

- Contain 70S ribosomes - Circular DNA - Not associated with histones

Answer 236

- Short section of DNA that codes for the amino acid sequence of a polypeptide or a functional RNA

Answer 237

- Poisition of a gene

Answer 238

- Full set of genes in a cell

Answer 239

- Full range of proteins a cell is able to produce

Answer 240

- Same codons in DNA/RNA code for the same amino acid in almost every organism.

Answer 241

- Codons are read one at a time so each base is read just once

Answer 242

- More than one codon codes for each amino acid

Answer 243

- Sections of genes that don't code for anything and are non-coding sequences.

Answer 244

- The same bases repeated for a long time

Answer 245

- Transfers genetic information from the DNA to ribosomes, where it acts as a template for protein synthesis

Answer 246

- Very long, single polynucleotide strand - Polymer of RNA nucleotides - Possesses information in the form of codons - determines the amino acid sequence of a polypeptide

Answer 247

- Transfers amino acids that are used to make proteins to ribosomes

Answer 248

- Shorter, single polynucleotide strand - Hydrogen bonds between specific base pairs so the tRNA molecule folds into a cloverleaf shape - One end (specific sequence of three bases (anticodon) - Other is the amino acid binding site.

Answer 249

- Production of mRNA from DNA

Answer 250

1) RNA polymerase (with a DNA helicase attached to it) binds to the start of the gene and begins to unwind the DNA, exposing some of the bases (breaks the hydrogen bonds) 2) Free RNA nucleotides bind by hydrogen bonding to their complementary bases, RNA polymerase adds each nucleotide to the mRNA polynucleotide chain by forming a phosphodiester bond. 3) recoiled into a double helix and when RNA polymerase reaches stop triplet code, it detaches from DNA and the production of mRNA is complete

Answer 251

- The production of polypeptides from the sequence of codons carried by mRNA

Answer 252

1) A ribosome becomes attached to the start codon at one end of the mRNA 2) tRNA molecule with an anticodon complementary to the first codon on the mRNA attaches itself to mRNA by complementary base pairing 3) Second tRNA molecule attaches itself to the next codon in the same way 4) 2 amino acids attached to the tRNA molecules joined by peptide bond (enzyme+ATP, which is hydrolysed to provide energy) 5) Ribosome moves along the mRNA and another codon becomes available for the next tRNA to bind, carrying a third amino acid. 6) tRNA disccoicates, leaving its amino acid behind. 7) process repeats until polypeptide is created and the ribosome reaches a stop codon

Answer 253

- The change in the DNA base sequence of chromosomes

Answer 254

- Removal of a base - Substituting different bases

Answer 255

- Deletions cause frame shifts that change the whole amino acid sequence leading to a potentially dysfunctional polypeptide

Answer 256

- BEcause of the genetic code being degenerate, not all base substitutions cause a change in the sequence of encoded amino acids, as the new codon may code for the same amino acid

Answer 257

- Agents that increase the rate of mutations - UV - X-rays - Viruses/Bacteria - Some chemicals such as methyl groups

Answer 258

- 1 cell divides to produce 4 haploid daughter cells - Each daughter cell is genetically different and has half the number of chromosomes of the parent cell

Answer 259

- Single cell formed which contains half the chromosomes from the father and half from the mother.

Answer 260

- Same gene and same loci but may have different alleles

Answer 261

- a single chromosome is present before replication but becomes double armed after replication when they are formed from 2 sister chromatids.

Answer 262

- Because it produces daughter cells with half the number of chromosomes of the parent cell.

Answer 263

- Before meiosis, the DNA unravels and replicates so there are two copies of each chromosome, called chromatids - DNA condenses to form double armed chromosomes, each made from two sister chromatids, joined by a centromere. - Meoisis 1 and 2 condenses the chromatids

Answer 264

- Independent assortment - Each homologous pairs is made up of chromosome from mother and father, during meiosis 1, it is random which chromosome from each pair ends up in which daughter cell - Crossing Over - Homologous pairs of chromosomes come together and pair up with chromatids twisting around each other and bits of chromatid crossing over - Crossing over means that the four daughter cells produced certain chromatids with a different combination of alleles (variation)

Answer 265

- Mutation which causes an addition or deletion of chromosomes, leading to an uneven distribution of chromosomes.

Answer 266

- Aneuploidy involves having abnormal numbers of chromosomes involving the loss or gain of one or a few chromosomes. - Polyploidy involves having multiple complete sets of chromosomes, often more than two.

Answer 267

- The number of different alleles of genes in a population

Answer 268

- The increased likelihood that organisms with certain alleles will survive longer than organisms without that allele.

Answer 269

- Genetic mutations lead to new alleles - New alleles being introduced into a population - Meiosis - Random fertilisation

Answer 270

1) A mutation happens in the population causing new alleles 2) Mutations are harmful causing organisms to die out however, an allele sometimes gives an advantage, leading to the increased chance of survival and reproductive success. 3) These individuals then pass on their advantageous alleles to the next generation 4) Over many generations, the new allele increases in frequency in the population

Answer 271

Directional: Extreme alleles are more likely to survive and reproduce (E.G antibiotic resistance in bacteria) Stabilising: The more common allele is more likely to survive and repoduce (E.G human birth weight)

Answer 272

- Behavioural adaptations: The way an organism acts that increases its chance of survival - Physiological: Processes inside the body that increase chances of survival - Anatomical: Features of an organism's body that increase its chances of survival

Answer 273

- A group of organisms that can interbreed to produce fertile offspring

Answer 274

- A necessary precursor to successful mating - This is because it allows individuals to recognise and reproduce with individuals of their own species, making reproduction much more successful. - Visual, auditory, chemical, tactile (species specific) (classifiy orrganisms using courtship behaviour as the more closely related a species is, the more similar their courtship behaviour is)

Answer 275

- Smaller groups are placed within larger groups, with no overlap between groups

Answer 276

- The variety/frequency of different species within a habitat

Answer 277

- Species richness is a measure of the number of different species in a community - Index of diversity puts a figure to biodiversity so we can numerically compare

Answer 278

N(N-1)/Sum of n(n-1)

Answer 279

- Deforestation removes vegetation - Overgrazing (removing hedgerows which removes trees and species) - Pesticides and herbicides - kills pests and weeds which would compete with crops - Overcultivation of monocultures means it is more efficient to grow just one crop which directly reduces diversity.

Answer 280

- Looking at the frequency of measurable or observable characteristics

Answer 281

- The direct study of base sequences of DNA - mRNA - Amino acid sequences

Answer 282

- Same genes but different alleles meaning most variation is a combination of both genetic and environmental factors

Answer 283

- By the amount of differents in DNA, mRNA, amino acid bases

Answer 284

- Degenerate code means that there will be differences in codons but the same amino acid can be formed - Mutations can be subtle as larger changes would change the teritary structure meaning a dysfunctional protein. - You have to find a common protein - Single gene codes a single protein which gives us a small insight

Answer 285

- Take random samples of a population - Collect data (size of tree e.g) - Calculate the mean - Calculate standard deviation of that mean (spread of values about the mean)

Answer 286

- Internal/external changes to the environment

Answer 287

- Tropisms - Taxes and Kineses - Simple reflexes

Answer 288

- Growth response of a plant to a stimulus

Answer 289

- Growth factors such as hormones

Answer 290

- Produced in growing regions and move to other tissues, where they regulate growth in response to a direcitonal stimulus

Answer 291

Phototropism Shoots - IAA causes cell elongation Roots - IAA inhibits cell elongation - Light is detected by receptors in the shoot Positve phototropism: - IAA diffuses to the darker side - Concentration of IAA increases on this side - IAA causes cells on the darker side to elongate so the shoot bends towards the light Negative phototrpoism: - In roots, IAA does the opposite - IAA diffuses to the darker side (underside) - Cell elongation is inhibited, root bends downwards. Negative Gravitropism - IAA diffuses to lower side of the shoot - Concentration of IAA increases on the lower side - IAA causes elongation directly upwards Positive Gravitropism - IAA diffuses to lower side of the root - Inhibits cell elongation and root bends downwards.

Answer 292

- Responses that maintain a mobile organism in a favourable environment Taxis - Organism moves towards/away from a directional stimulus Kinesis - Organism's movement affected by a non-directional stimulus such as humidity - Cause rate of turning to increase or decrease to move the organism away from the stimulus

Answer 293

- Receptor detects stimulus - Sensory neurone carries impulse from receptor to relay neurone - CNS processes response - Relay neurone carries impulse to the motor neurone - Motor neurone carries impulse from relay neurone to effector - Effector carries out response (muscle or gland)

Answer 294

- FAST (Does not involve concious part of the braint because the impulse is carried directly from a sensory neurone to a motor neurone via a relay neurone. - LOCALISED - Target cells, stimulus produce same response - SHORT LIVED - Re uptake of neurotransmitter is rapid - Response is involuntary where the body cannot override it. (Aid survival by protecting the body from tissue damage and escape from predators)

Answer 295

Baroreceptors (pressure) Chemoreceptors (chemical) Photoreceptors (light)

Answer 296

- Detect pressure/vibrations - Contain sensory neurone endings wrapped in tissues of lamella - Found in fingertips, soles, joints 1) Pressure cause lamellae to be deformed 2) Increase in pressure deforms stretch mediated sodium ion channels 3) Sodium ion channels open and sodium ions diffuse into the sensory neurone ending 4) Depolarises the membrane creating generator potential 5) AP triggered when threshold reached

Answer 297

- Potential difference between inside and outside - Resting potential is -70mV when cell is at rest - When stimulus is detected, the membrane becomes more permeable so ions diffuse across it and the potential difference increases - Change in potential difference is called the generator potential - If the change is large enough and exceeds the threshold value, then an action potential is triggered.

Answer 298

- Light is detected by photoreceptors - Light is absorbed by optical pigments - Light bleaches the pigments, altering the membrane permeability to sodium ions - Generator potential is created and if large enough and over threshold, causes an action potential - Bipolar neurone connects to the optic nerve, taking the impulses to the brain

Answer 299

- Rods have high sensitivity because many rods connect to 1 bipolar neurone so many weak generator potentials combine to reach threshold - Cones have low sensitivity to light as 1 cone connects to a bipolar neurone meaning it takes more light to reach the threshold and generate an action potential - Rods have low sensitivity to colour as they are ponly sensitive to light levels - Cones have high sensitivity to colour as there are 3 different types of cones representative of different colours - Rods have low visual acuity (how clearly you can see objects at a distance) because many rods connect to 1 bipolar neurone so light from 2 points close together can't be distinguished. - Cones have 1 cone connected to 1 bipolar neurone so separate impulses are sent, many action potentials triggered so the brain receives many impulses.

Answer 300

- Muscle initiates contraction without nerves

Answer 301

- SAN in right atrium sets the frequency at which the cardiac muscle cells contract, sending out regular electrical impulses to the atrial wall, causing atria to also contract. - impulse spreads from SAN across both atria, causing contraction simultaneously - Septum prevents impulses crossing - Impulses reaches AVN - AVN passes impulse to the Bundle of His fibres, which conduct the impulse down the Purkyne fibres - Impulse reaches the heart apex causing them both to contract simultaneously, from bottom up.

Answer 302

- To allow all the blood to empty from the atria before ventricles contract.

Answer 303

- Done by the autonomic nervous system - Controlled by the medulla - Heart rate is changed in response to internal stimuli (blood pressure (barocreceptors) , chemicals in the blood (chemoreceptors) E>G carbon dioxide) - Sends electrical impulses to the medulla via sensory neurones which processes the info and sends the impusle to the SAN down the autonomic nervous system (sympathetic - increase heart rate (noradrenaline), parasympatheitc - decreases heart rate via acetylcholine (less frequent heart contractions)) Antagonistic

Answer 304

- Cell body - Dendrites (recieves electrical impulses) - Nucleus - Axon (transfers electrical impulses to synapse) - Myelin sheath (electrical insulation made of schwann cells) - Synapses

Answer 305

- 3 sodium ions actively transported out - 2 potassium ions actively transported in via sodium-potassium pump - outside of axon is more positive than inside of axon - resting potential is -70mV

Answer 306

- Depolarisation involves stimulus exciting membrane so the cell membrane becomes more permeable to sodium ions - Sodium ion channels open allowing diffusion of sodium ions - Inside becomes more positive as potassium ion channels stay closed. - Repolarisation involves sodium ion channels closing and potassium ion channels opening so potassium ions diffuse out of the neurone. - Inside of neurone becomes more negaitve and voltage decreases back to normal level. - Hyperpolarisation involves potassium ion channels remaining open for a short time and too many potassium ions diffuse out of neurone - Resting potential is re established

Answer 307

Refractory period is the time delay which prevents ion channels from opening - Keeps action potential unidirectional - No overalp - Time limit to action potential frequency

Answer 308

- Myelination sees regular breaks in insulation (nodes of ranvier) - APs only occur at nodes of ranvier - APs jump via saltatory conduction between nodes of ranvier - Quicker nerve transmission, so less energy is needed from the sodium potassium pump

Answer 309

- Action potential only happens if stimulus reaches threshold - Action potential is always the same size - Size of stimulus from frequency of impulses and neurones with a different threshold value

Answer 310

- Myelination - Axon diameter - less resistance to the flows of ions - Temperature - more kinetic energy

Answer 311

- Junction between neurones or neurones and a muscle - Found at the ends of axons - Most use cholinergic synapses or neuromuscular junctions

Answer 312

- Action potential arrives at synpatic knob of presynaptic neurone - Stimulates calcium ion channels to open allowing diffusion and influx of calcium ions, triggering vesicles to move to the membrane, releasing acetylcholine into the synpatic cleft - Acetylcholine diffuses across celft and binds to receptors on the post synpatic membrane so sodium ions diffuse into post synpatic neurone when sodium ion channels open. - If threshold reached, another AP is triggered.

Answer 313

- Synapses only travel in one direction because receptors are only found on the post synaptic membrane - Neurotransmitter is only made and released from pre synaptic neurone's side.

Answer 314

- Low frequency action potentials cause insufficient amounts of neurotransmitter to be released to trigger a new action potential. Temporal - Presynaptic neurone connect to single postsynaptic neurones and releases neurotransmitter in timed intervals. - Spatial summation is when lots of pre synaptic neurone bind to the post synaptic neurone and exceed the threshold value, triggering an action potential.

Answer 315

- When some synapses make it less likely for a new action potential to be triggered in the post synaptic neurone. - Neurotransmitters may bind to chloride ions causing them to open and negative ions influx the post synaptic neurone - May cause K+ channels to open so K+ diffuses out which lowers resting potential more negative

Answer 316

- Synpase between motor neurone and muscle fibre. - Many neuromuscular junction along a muscle - Acetylcholine used

Answer 317

Cholinergic: - Neurone to neurone - Motor sensory or relay - Excitatory or inhibitory - New AP is triggered - Ach binds to receptors on post synaptic neurone - Less receptors Neuromuscular junction: - Neurone to muscle - Motor neurones only - Excitatory only - AP ends here - Ach binds to the receptors on muscle fibres

Answer 318

- Some may have similar shapes to neurotransmitters which bind to receptors and cause more action potentials - Act as blockers to prevent neurotransmitters from binding so fewer sodium ion channels open and fewer action potentials are triggered - Inhibit enzyme breakdown and prevent neurotransmitters from being broken down. b

Answer 319

- Smooth - Cardiac - Skeletal

Answer 320

- When one contracts, other relaxes

Answer 321

- Muscle made of muscle fibres - Muscle fibres are made up of organelles called myofibtrils - Cytoplasm is called sarcoplasm - Sarcolemma has folds called T-tubules which help spread electrical impulse - Mitochondria - Sarcoplasmic reticulum stores calcium ions needed for contraction.

Answer 322

- Bundles of thick and thin myofilaments that move past each other to make muscles contract - Myofilaments are Myosin (thick) and Actin (thin)

Answer 323

- A single contractile unit

Answer 324

- Ends of the sarcomere

Answer 325

- A bands are the length of the myosin - I band contains actin only - H zone contains myosin only - M line is the middle of myosin

Answer 326

- I band shortens when the thick filaments shortens as the thick and thin filaments slide past - H zone shortens - A band stay the same because the myosin filaments themselves do not shorten - Myofilaments stay the same length because they themselves don't shorten.

Answer 327

- Tropomyosin blocks myosin head from binding to the actin-myosin binding site so the myosin can't bind and myofilmanets can't slide past each other. - Action potential reaches neuromuscular junction - Acetylcholine diffuses over to the postsynaptic membrane and binds to receptors - Depolarisation of the sarcolemma - Wave of depolarisation spreads along T-tubules and sarcoplasmic reticulum. - Calcium ions bind to troponin, causing it to change shape which pulls tropomyosin out of the actin myosin binding site. - Myosin head binds to actin myosin binding site. (actinmyosin bridge) - Calcium ions activate ATP hydrolase which hydrolyses an ATP that is bound to the myosin head - Energy released causes the myosin head to bend which pulls actin filament along. - ATP attaches to myosin head and hydrolyses to break the bridge and then another myosin heads binds to a different actin myosin binding site further along.

Answer 328

- Aerobic respiration - Anaerobic respiration (slower ATP production) - ATP-Pcr system (Phosphocreatine provides an extra phosphate molecule for ATP synthesis) - ADP+PCr - > ATP + Creatine

Answer 329

- Small amounts so is used as short term energy.

Answer 330

Slow: - Works for long times without getting tired - Long periods of low intensity - Aerobic - Thin in diameter, red in colour - More widespread Fast: - Short periods of high intensity - Anaerobic - Thick in diameter but pale.

Answer 331

- The use of physiological control systems that maintain the internal environment within restricted limits. - Core temperature, blood glucose and blood pH are controlled. - Enzymes are important in regulating and increasing the rate of metabolic reactions so need to be controlled.

Answer 332

- Restores systems to their original level - Stimulus is a change to the internal environment - Passed onto a receptor or coordinater - Nerve impulses or hormones are sent out leading to the reversal of the change

Answer 333

- By having different negative feedback mechanisms meaning that can reverse the change in multiple directions from the norm. # - More control due to quicker responses.

Answer 334

- Increasing amplification from the norm - Blood clotting platelets releasing chemicals to activate more platelets.

Answer 335

- Food intake, exercise and metabolic rate (glucose) (Exercise causes higher demand so does metabolism)

Answer 336

- Glycogenesis - glucose converted into glycogen (insulin) - Glycogenolysis - hydrolysis of glycogen into glucose (glucagon/adrenaline) - Gluconeogenesis - conversion of non-carbohydrates into glucose

Answer 337

- Alpha (secrete glucagon by detecting low glucose) - Beta cells (secrete insulin by detecting high levels of glucose)

Answer 338

- Insulin binds to specific receptors on CSM of target cells - Glucose channel proteins change shape and open allowing more glucose to enter cells from the blood - Triggers the fusion of channel-containing vesicles with the CSM of target cells, increasing number of glucose channel proteins in the membrane. - Activation of enzymes involved in the formation of glycogen (glycogenesis) LOW: - Glucagon binds to specific receptors on the CSM of target cells - Activates enzymes that convert glycogen into glucose (glycogenolysis) - Activates enzymes that convert glycerol and amino acids into glucose (gluconeogenesis)

Answer 339

- Glucagon/Adrenaline bind to receptors on CSM - This activates Adenylate Cyclase enzyme which catalyses cAMP from ATP - Protein kinase enzyme activates a chain of reaction (cascade effect) leading to glycogenolysis. (amplifies the effects)

Answer 340

Type 1: - Pancrease doesn't produce enough insulin - Caused by an autoimmune disease that destroys b cells that produce insulin - Thirst is a symptom - So is excessive urination - Weight loss as you respire lipids - Treatment could be regular insulin injections. Type 2: - Pancreas stops responding to glucose - Glycoprotein receptors on the CSM of target cells are less responsive to insluin - Obesity - Management of diet and exercise and losing weight are ways to treat type 2.

Answer 341

- Control of the water potential of the blood

Answer 342

- Ultrafiltration - formation of glomerular filtrate - Selective reabsorption - reabsorption of useful substances, such as glucose, amino acids, and ions - Osmoregulation

Answer 343

- Happens at glomerulus and bowman's capsule. - Efferent arteriole's are smaller in diameter than the afferent arteriole so the hydrostatic pressure in the glomerular capillaries increases and small molecules are forced through a 3 layer filter into the bowman's capsule. - 3 layer filter is made of collagen, endothelium, basement membrane and podocytes. - RBCs don't pass through - Glucose, water, amino acids, excess vitamins, urea pass through.

Answer 344

- Useful substances such as glucose, amino acids and ions return. - Pass back into blood capillaries wrapped around the PCT. - Done by co-transport.

Answer 345

- At the loop of henle, medulla sees a loweringof water potential, so that water can be reabsorbed at the descending limb, the Distal Convoluted Tubule and collecting duct by osmosis. - Top of the ascending limb, sodium ions pumped into medulla by active transport, the ascending limbs is impermeable to water so water remains in the tubule which lowers the WP of the medulla. - Water moves out of the descending limb which is permeable to water by osmosis. - Descending limb is not permeable to ions so the filtrate becomes more concentrated. - Bottom of ascending limb - Sodium ions move into the medulla lowering WP of medulla even more. - Water is reabsorbed by capillary system.

Answer 346

Low water potential in blood: - Detected by osmoreceptors in hypothalamus - Posterior pituitary gland stimulated to release more ADH into the blood. - ADH binds to receptors on the cell membrane lining the distal convoluting tube and collecting duct. - Triggers vesicles containing aquaporins to fuse with the cell surface membrane so more aquaporins are incorporated into the cell surface membrane of cells lining the DCT and collecting duct. - More water leaves by osmosis - Less water lost, urine concentrated.

Answer 347

- High water potential is detected by osmoreceptors in hypothalamus - Posterior pituitary gland releases less ADH into blood - Less ADH molecules bind to receptors in cell surface membrane of cells lining the DCT and collecting ducts so less aquaporins are incorporated into the cell surface membrane of cells lining these tubules. - DCT and collecting duct less permeable to water so there are fewer places for water to leave by osmosis - More water lost - urine more dilute with water.

Answer 348

- Genotype is the genetic constitution of an organism - Phenotype is the expression of this genetic constitution and its interaction with the environment.

Answer 349

- Different forms of the same gene

Answer 350

- Dominant allele needs one allele present to be expressed in the phenotype - Recessive alleles need 2 copies present to appear in the phenotype - Co-dominant alleles are alleles that are both expressed in the phenotype.

Answer 351

- Inheritance of one single character, controlled by a single gene.

Answer 352

- Inheritance of 2 characteristics, controlled by 2 genes - Involves 2 genes on 2 different chromosomes

Answer 353

- Both alleles will be expressed in the phenotype

Answer 354

1) Heterozygous of both alleles 2) Homozygous of one allele 3) Homozygous of another allele

Answer 355

- Where some genes have more than 2 alleles, for example bloody type, where type a and b are codominant over allele iO.

Answer 356

- A gene that is found on a sex chromosome is said to be 'sex-linked' - Most genes on sex chromosomes are carried by the X chromosome so males are much more likely to show recessive phenotypes for sex linked genes as they only have one X chromsome .

Answer 357

- Their dominant allele on their X chromsome may cancel out the recessive allele on the Y chromosome.

Answer 358

- Autosomal Genes that aren't found on sex chromosomes. - Genes found on the same autosome are said to be 'linked' - They will stay on the same chromosome during independent segregation in meiosis 1 and offspring will inherit these alleles together. - The more closely two genes are together on the same chromosome, the less liekly they'll be split by crossing over.

Answer 359

- Because the 2 linked alleles are inherited together.

Answer 360

- The effect of one gene upon another. - 2 genes interact, so that one may be masked (prevented from being expressed) by another.

Answer 361

- If the effect of one locus is altered by the effect at another locus, power to detect the first locus is reduced.

Answer 362

- Used to compare the goodness of fit of observed phenotypic ratios with expected ratios - Can use to see if there is a dihybrid cross with linkage or no linkage

Answer 363

- Random fertilisation of gametes - Epistasis - Small sample size

Answer 364

- A group of organisms of the same species occupying a particular space at a particular time that can interbreed.

Answer 365

- The complete range of alleles present in a population.

Answer 366

- How often an allele occurs in a population.

Answer 367

- Mathematical model which predicts that allele frequencies will not change from generation to generation.

Answer 368

P+Q=1 (allele frequencies) p^2+2pq+q^2=1 (frequency of individuals) P - frequency of dominant alleles Q - frequency of recessive alleles 2pq - Homozygous

Answer 369

- To see whether the frequency of alleles is changing (if there is a selection pressure) - We know this as we can measure the frequency of individuals in a population

Answer 370

1) No natural selection meaning equal chance of survival and reproduction 2) Assumes there is no gene flow, introducing new genes or altering existing genes. 3) Assumes the population is large and isn't affected by genetic drift 4) Assumes that there are no mutations as allele frequencies don't get altered.

Answer 371

- When two extreme genotypes at both ends of the range are the most common and likely to survive and reproduce.

Answer 372

- The change in allele frequencies in a population

Answer 373

- When new species develop from a common ancestor

Answer 374

1) Geographic isolation by a natural barrier so reproductively isolated 2) Each population finds itself in a different environment, so experiences different selection pressures 3) Natural selection occurs and different alleles are of an advantage in the different populations. 4) Allele frequencies change in the two gene pools 5) Two populations are so genetically different that they no longer interbreed to produce fertile offspring.

Answer 375

Allopatric - physical reproductive isolation via a river or moutanin range Sympatric - Populations don't become physically separated but there are other reasons for reproductive isolation. (change in genetics, behavioural changes)

Answer 376

- When allele frequencies change due to chance - Not every individual will become a parent - Not the same offsprint when they do have kids. (as a result, chance rather than selection pressures dictates the likelihood of reproduction)

Answer 377

- Because more individuals make up a larger proportion of the population.

Answer 378

- Work alongside each other in evolution but ultimately one may drive evolution more, depending on the size of the population. - Unlike natural selection, genetic drift doesn't cause better adaptation to the environment.

Answer 379

- Populations of different species in a habitat

Answer 380

- Community and the non-living components of its environment

Answer 381

- A species' role within an ecosystem

Answer 382

- They will compete with each other.

Answer 383

- The maximum stable population size of a species that an ecosystem can support.

Answer 384

- The effect of abiotic factors such as light intensity, water availability, food availability, soil pH and temperature - Interactions between organisms such as inter and intraspecific competition - Predation

Answer 385

- Interspecific competition is when organisms of different species compete for resources. - Interspecific competition results in decreasing food availability for both species - So population size decreases as survival and reproduction is less likely. Intraspecific competition is when organisms of the same species compete with each other for resources

Answer 386

- Happens when one organism eats another. - As population size increase, predator population increases but as predators eat prey, their population will also decrease when food becomes scarce.

Answer 387

Measure on slow moving organisms 1) Randomly place quadrats, being random to avoid bias. 2) Plot coordinates and use a radnom number generator to generate coordinates. 3) Place a 1mx1m quadrat and count the number of individuals, repeating many times. 4) Calculate the mean 5) Multiple mean x area.

Answer 388

- To measure gradual changes in population size across an area. - By taking samples at regular intervals along a transect. - More samples means more reliability.

Answer 389

- Mark-release-recapture 1) Capture a sample of individuals from the population by using E.g pitfall traps for insects. 2) Count the number of individuals and mark them in a harmless way 3) Return them to mix with the population 4) Capture second sample and count the number of individuals caught and number of those marked. 5) S1 x S2 divided by the number marked in S2

Answer 390

- Marking doesn't affect survival by making them more visible to predators. - We also assume that marked individuals mix randomly and evenly with the population. - We assume no change in population size

Answer 391

- Takes place on land that is newly formed or has been exposed 1) Pioneer species are those that live in extreme abiotic conditions that are hostile with little nutrients or water. 2) Adaptations allow them to live in these conditions such as asexual reproduction. Or the ability to fix nitrogen and tolerant to salt. 3) Pioneer species change the environemnt to make abiotic conditions less hostile such as eroding the rock and releasing minerals or adding more humus. 4) New species makes the environment more hostile for the previous species. 5) Over time conditions become less hostile and organisms becoming better adapted and outcompete older species. 6) Climax community is formed meaning the same species is stable and has been present over a long period of time.

Answer 392

1) Climax community is cleared in some way 2) Succession occurs quicker due to soil that contains seeds and nutrients to start a new community. 3) Pioneer species are larger plants therefore climax community reaches much quicker due to the lack of hostile conditions.

Answer 393

- We prevent succession from continuing to preserve an ecosystem in its current stage of succession. - If another species arrived and dominated, existing species would be outcompeted and die out.

Answer 394

- Grazing and mowing to remove growing tips so no climax community is reached. - Managed fires so all species are wiped out and secondary succession will occur. Small species are pioneer species and grow more quickly than larger trees and shrubs.

Answer 395

- Light dependent - Light independent

Answer 396

- Double membrane - Stroma - Thylakoid membrane - Granum - Linked by lamellae

Answer 397

- Large surface area for the attachment of: Chlorophyll Electron carriers Enzymes - Permeable membrane for gas diffusion - Fluid in the strom contains all enzymes required to make carbohydrates for the light indepedent reaction.

Answer 398

- Photoionisation - Chlrophyll absorbs lightt, electrons are excited and are donated to an electron carrier that moves the electrons down the chain. -Photolysis - Electrons are replaced by the splitting of water into hydrogen, oxygen and electrons. Chemiosmosis - Excited electrons lose energy as they move down the ETC. - This energy is used to pump Hydrogen ions into the thylakoid space via a proton pump. - Creates a favourable concentration gradient for the diffusion of H+ ions into the stroma via ATP synthase, which catalyses ADP+Pi to form ATP. Formation of NADPH - Electrons from ETC and H+ ions that have diffused through ATP synthase are used to form Reduced NADP.

Answer 399

- occurs in the stroma - Rubisco catalyses reaction of RuBP and CO2 to temporarily give an unstable 6-carbon compound which breaks down into 2 GP molecules. - GP is reduced to TP using NADPH, using energy from ATP hydrolysis. - TP is converted into useful organic compounds such as glucose and amino acids - In one cycle 10 TP molecules are converted into RuBP but only 2 TPs are converted into useful compounds.

Answer 400

- Temperature (Involve enzymes which require optimum temperatures) - CO2 concentration as the light independent reaction requires a source of carbon so fixation is slowed. - Light intensity as energy from sunlight is needed to excite electrons in chlorophyll

Answer 401

- Conversion of glucose into pyruvate 1) Occurs in the cytoplasm 2) Glucose is converted in glucose phosphate via ATP hydrolysis 3) 2xTP molecules are formed 4) 2 TP molecules are converted into 2 pyruvate molecules via redox reactions where ATP is oxidised and NAD is reduced - 2 ATP net gain - 2 NADH - 4 ATP molecules

Answer 402

Animals - Pyruvate is converted to lactate during redox with NADH - Lactate regenerates NAD which is fed back into glycolysis, meaning ATP is still produced. Plants Pyruvate is converted to ethanal, producing CO2 in the process, then ethanal is converted to ethanol during a redox reaction that converts NADH to NAD.

Answer 403

- Link reaction happens in the mitochondrial matrix - Pyruvate loses carbon as CO2 and is converted to a 2C Acetate via a redox reaction of NAD. - Acetate reacts with coA to form Acetyl coA. - Link reaction would happen twice per glycolysis.

Answer 404

- Mitochondrial matrix - Acetyl coA reacts with 4C compound to produce 6C citrate - Series of redox reactions produces 2 CO2 molecules, 3 NADH molecules, 1 FADH2 molecules and 1 ATP molecule. - coA is regenerated

Answer 405

1) H atoms released from NADH and FADH2 2) Hydrogen atoms split into hydrogen ions and electrons. 3) Electrons move down the ETC 4) Energy lost by electrons at each carrier are used to pump hydrogen ions into the intermembrane space via a proton pump creating a favourable concentration gradient for diffusion of hydrogen ions into the matrix via ATP synthase causing it to spin. - Catalysed ADP+Pi -> ATP. - O2 combines with hydrogen ions and electrons to form water.

Answer 406

- Oxygen accepts H+ ions and electrons to form water - ETC would stop and no pumping of hydrogen ions, no gradient for the diffusion of hydrogen ions so no ATP molecules produced.

Answer 407

- The mass of carbon or dry mass of tissue per given area.

Answer 408

1) Dry the sample, burn the sample 2) Use this to heat a known volume of water 3) Measure temperature change and use this to calculate the chemical energy that was stored in the dry biomass.

Answer 409

- The chemical energy store in plant biomass, in a given area or volume.

Answer 410

- The chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.

Answer 411

- Available for plant growth and reproduction. It is also available for other trophic levels in the ecosystem.

Answer 412

N=I - (F+R) N - Net production of consumers I = Chemical energy store F = Energy lost in faeces and urine R = Respiratory losses in the environemtn

Answer 413

- In plants, some light energy is reflected or transmitted through loveaves or not of the right wavelength so the efficiency of photosynthesis is very low. - Energy is lost to the surrounding as heat from respiration. - Energy lost in faeces or urine. - Some parts of the organism are not eaten, so some energy is not transferred to the next trophic level.

Answer 414

- Energy is lost at each trophic level so the efficiency of energy transfer is very low. - Total biomass is less at higher trophic levels - Insufficient energy available to support a large enough breeding population.

Answer 415

- Simplify food webs by using pesticides so that energy isn't lost. - Reduce respiratory losses within a human food chain such as controlling the conditions livestock are kept in such as restricting their movement or keeping them warm (unethical) . - More biomass so greater chemical energy store so more biomass and a higher chemical energy store so more NPP and efficiency of transfer.

Answer 416

- The rate of primary and secondary production respectively - kJ per hectare per year

Answer 417

- Break down organic molecules into simple inorganic molecules and ions, that plants can make use of. - Saprobionts feed by extracellular digestion by secreting digestive enzymes and absorb the soluble nutrients released. - Converts organic into inorganic compounds - DNA, RNA and amino acids into phosphates and nitrates

Answer 418

- Break larger leaves into smaller leaves, increasing the surface area for saprobionts to act upon.

Answer 419

- DNA, protein, RNA.

Answer 420

- Decomposition of DNA, RNA, protein - Produced ammonium ions (ammonification)

Answer 421

- Undergo nitrification which involves ammonium ions being converted to nitrite ions and nitrate in aerboic conditions by nitrifying bacteria as these bacteria need oxygen to function.

Answer 422

- Taken in by active transport during Assimilation

Answer 423

- Conversion of the nitrate ions into nitrogen gas. - Done by denitrifying bacteria and is done in anaerobic conditions.

Answer 424

- Conversion of nitrogen gas into bacteria.

Answer 425

- Animals and plants store nitrogen through DNA, RNA, proteins - When animals die, sacrobionts decompose this into ammonium ions. - Ammonification converts ammonium into nitrite ions and then nitrate ions via nitrification. - Nitrate ions move via active transport during assimilation into root hair cells or are converted into a gas during denitrification. - Nitrogen fixation is the take up of nitrogen gas from the atmosphere.

Answer 426

- Process of weathering

Answer 427

- Phosphate ions move by seas and rivers and are stored in sedimentary rocks. - Tectonic plate movements pushes phosphate ions into higher regions again. - The phosphate is then recycled again through rivers and seas. - Phopshate ions can enter roots by active transport/assmiliation - Plants can feed on the phosphate ions and incorperate it into its DNA.

Answer 428

- Fungi that associate with the roots of plants - They grow in and around the root system, increasing the surface area for absorption of water and mineral ions.

Answer 429

- Where both species benefit from the interaction. - Micorrhizae recieve sugars from the plant for growing in and around the root.

Answer 430

- Crops taking in mineral ions from the soil to build their own tissues. - When they are harvested, this means no mineral ions are returned to the soil as the crops don't die and decompose there. - So we need fertilisers to replace lost minerals.

Answer 431

- Organic matter is an example of a natural fertiliser - Artificial fertilisers are pure inorganic ions blended together to give the appropritate balance of mineral ions for a particular crop.

Answer 432

Nitrate ions (protein synthesis, ATP synthesis, nucleic acids) Phosphate ions (ATP synthesis) Potassium ions (stomatal regulation) Sulphur ions (sulfur containing R-groups)

Answer 433

- The blending of nitrogen, potassium and phosphate ions.

Answer 434

-Loss of soluble susbtances from the top layer of the soil when water drains through. - Occurs when fertilisers are applied before rainfall events because there has not been enough time for ions to be taken up by plants and free mineral ions in the soil are washed away.

Answer 435

- Leaching of excess mineral ions from fertilisers into waterways. - Algal boom is the rapid growth of algae in ponds and rivers which happens after the increase of mineral ions. - Algae grow rapidly and block sunlight from reaching the plants below. - The plants do not photosynthesise so they die. - Bacteria feed on dead remains and decompose it so oxygen levels decrease. - Fish and other organisms die because not enough oxygen is available. - Leads to oxygen depletion so the ecosystem dies out.

Paper 3 Biology (ALL THE CONTENT) Flashcards

(470 cards)