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Question 1

advantages of atp

Answer 1

• releases energy instantaneously

- releases relatively small amount of energy

Question 2

calcium ions and atp role in muscle contraction

Answer 2

1. Calcium ions diffuse into myofibrils from
   (sarcoplasmic) reticulum;
2. (Calcium ions) cause movement of tropomyosin
   (on actin);
3. (This movement causes) exposure of the
   binding sites on the actin;
4. Myosin heads attach to binding sites on actin;
5. Hydrolysis of ATP (on myosin heads) causes
   myosin heads to bend;
6. (Bending) pulling actin molecules;
7. Attachment of a new ATP molecule to each
   myosin head causes myosin heads to detach
   (from actin sites)

Question 3

Explain how the resting potential of –70 mV is maintained in the sensory neurone when no pressure is applied

Answer 3

1. Membrane more permeable to potassium ions
   and less permeable to sodium ions;
2. Sodium ions actively transported/pumped out
   and potassium ions in;

Question 4

Explain how applying pressure to the Pacinian corpuscle produces the changes in membrane potential recorded by microelectrode P.

Answer 4

1. (Pressure causes) membrane/lamellae to
   become deformed/stretched;
2. Sodium ion channels in membrane open and
   sodium ions move in;
3. Greater pressure more channels open/sodium
   ions enter;

Question 5

The membrane potential at Q was the same whether medium or heavy pressure
was applied to the finger tip. Explain why.

Answer 5

1. Threshold has been reached;
2. (Threshold or above) causes maximal response
   / all or nothing principle;

Question 6

Multiple sclerosis is a disease in which parts of the myelin sheaths surrounding neurones are destroyed. Explain how this results in slower responses to stimuli.

Answer 6

1. Less/no saltatory conduction / action
   potential/impulse unable to ‘jump’ from node to node;
2. More depolarisation over length/area of
   membranes;

Question 7

Suggest why the plasmids were injected into the eggs of silkworms, rather than into the silkworms.

Answer 7

1. (If injected into egg), gene gets into all/most of
   cells of silkworm;
2. So gets into cells that make silk;

Question 8

Suggest why the scientists used a marker gene and why they used the EGFP gene

Answer 8

1. Not all eggs will successfully take up the
   plasmid;
2. Silkworms that have taken up gene will glow;

Question 9

What would the scientists have inserted into the plasmid along with the spider gene to ensure that the spider gene was only expressed in the silk glands of the silkworms?

Answer 9

Promoter (region/gene);

Question 10

Suggest two reasons why it was important that the spider gene was expressed only in the silk glands of the silkworms.

Answer 10

1. So that protein can be harvested;

2. Fibres in other cells might cause harm;

Question 11

Explain why the scientists measured the rate of production of oxygen in this investigation.

Answer 11

1. Oxygen produced in light-dependent reaction;
2. The faster (oxygen) is produced, the faster the
   light-dependent reaction;

Question 12

The scientists suggested that mutant plants producing more chlorophyll b would grow faster than normal plants in all light intensities.
Explain how these data support this suggestion

Answer 12

At all light intensities, chloroplasts from mutant
plants:
1. Have faster production of ATP and reduced
NADP;
2. (So) have faster/more light-independent
reaction;
3. (So) produce more sugars that can be used in
respiration;
4. (So) have more energy for growth;
5. Have faster/more synthesis of new organic
materials;

Question 13

what causes muscle fatigue

Answer 13

lactate from anaerobic respiration

Question 14

Explain why the student set up Tube 1.

Answer 14

1. To show light does not affect DCPIP;

2. To show chloroplasts are required;

Question 15

Explain the advantage of the student using the IC50 in this investigation.

Answer 15

Can compare different chemicals/weedkillers

Question 16

Explain how chemicals which inhibit the decolourisation of DCPIP could slow the growth of weeds.

Answer 16

1. Less/no ATP produced;
2. Less/no reduced NADP produced;
3. Less/no GP reduced/converted to TP;

Question 17

Give two reasons why pancreas transplants are not used for the treatment of type II diabetes.

Answer 17

1. (Usually)Type II produce insulin;
2. Cells/receptors less sensitive/responsive (to insulin)
   OR
   Faulty (insulin) receptors;
3. (Treated/controlled by) diet/exercise;

Question 18

Explain how donepezil could improve communication between nerve cells

Answer 18

1. Less/no acetylcholine broken down;
2. Acetylcholine attaches to receptors;
3. (More) Na+ enter to reach threshold/for depolarisation/action potential/impulse;

Question 19

Suggest and explain two reasons why there is a high frequency of the E280A mutation in Yaramul

Answer 19

1. Isolated so inbreeding/low genetic
   diversity/small gene pool;
2. Allele inherited (through generations) from
   (common) ancestor;

Question 20

Explain why natural selection has not reduced the frequency of the E280A
mutation in the population

Answer 20

1. AD/symptoms develops late/at 49;

2. Have already reproduced;

Question 21

The age at which the E280A mutation is expressed to cause AD can vary
Suggest and explain one reason for this.

Answer 21

1. Epigenetics/environment/named factor e.g.
stress, alcohol, toxins, diet, exercise,
smoking;
2. methylation (of genes)
OR
acetylation (of histones);

Question 22

One scientific study which analysed chromosome 14 involved 102 individuals. The scientists recorded a sample size of 204. In this sample they detected 75 E280A mutations but only 74 potential AD cases
Suggest explanations for the figures the scientists recorded

Answer 22

1. One person was homozygous dominant/has

two dominant alleles

Question 23

Suggest why a DNA probe for the mutated triplet was not considered a suitable
method for detection of the E280A mutation

Answer 23

1. (GCA/triplet) is common/found in other
places;
2. Would not know if it was the
mutation/allele/gene
OR
Produces ‘false positives’;

Question 24

Explain why a log scale is used to record the number of cells.

Answer 24

Large range/difference/increase in numbers;

Question 25

What is meant by a genome?

Answer 25

1. (All) the DNA in a cell/organism;

Question 26

Explain why the antibody binds to the transcription factor.

Answer 26

1. (Transcriptional factor/antibody) has a specific/tertiary structure/shape; 2. Complementary (shape/structure);

Question 27

Use Figure 8 to explain what ‘precipitated DNA’ consists of

Answer 27

1. DNA, transcription factor and antibody;

Question 28

Suggest how single-stranded cDNA could prevent transcription of the P34 gene.

Answer 28

1. Binds to P34 gene/DNA/mRNA

Question 29

Describe the roles of two named types of enzymes used to insert DNA fragments into box plasmids.

Answer 29

1. Restriction (endonuclease/enzyme) to cut plasmid/vector; 2. Ligase joins gene/DNA to plasmid/vector;

Question 30

Suggest two features of the structure of different proteins that enable them to be separated by gel electrophoresis.

Answer 30

1. Mass/number of amino acids/polypeptides; 2. Charge; 3. R groups (differ);

Question 31

Why does substitution mutation change structure of a protein

Answer 31

- Substitution is one base swapped for another - This changes the base triplet that that base was part of, the triplet then coded for a different amino acid - Different amino acid changes primary structure of protein, which determines the tertiary structure of the protein - Tertiary structure of the protein is therefore changed

Question 32

Why decreased calcium ions inhibits muscle contraction

Answer 32

- calcium ions bind to a protein attached to tropomyosin, cause it to change shape, pull tropomyosin out of actin-myosin binding site exposing it - so that myosin heads can bind, forms actin myosin cross bridge, pull actin over myosin causing muscle to contract as sarcomere shortens - so if calcium ions are decreased, tropomyosin blocks binding sites, less contraction - calcium also activates ATP hydrolyse (ATP -> ADP + Pi), energy used for contraction, so if less calcium then less energy

Question 33

Why use pencil instead of ink in chromatography

Answer 33

- Ink would dissolve in solvent and pigments separate as solvent spreads up chromatogram

Question 34

Method to separate pigments

Answer 34

- Place chromatogram in beaker of solvent, solvent shouldn’t go above pencil line - Solvent moves up paper and carries different pigments at different rates

Question 35

Why is different coloured pigments in leaves advantageous?

Answer 35

- Can absorb different wavelengths of light

Question 36

Role of glucagon

Answer 36

- Produced in alpha cells in islets of Langerhans in pancreas - Activates glycogenolysis and gluconeogenesis, decreases rate of respiration in cells

Question 37

Role of insulin

Answer 37

- Increases permeability of membrane to glucose, more uptake | - Activates glycogenesis

Question 38

Why does inhibiting adenylate Cyclase reduce glucose concentration

Answer 38

cannot form cAMP from ATP, does not activate protein kinase a, does not convert glycogen to glucose, process inhibited glucose concentration remains low.

Question 39

photoionisation

Answer 39

Light hits chlorophyll, electrons become excited, leave chlorophyll and move to higher energy level, move down ETC

Question 40

What is a DNA probe

Answer 40

- single stranded base sequence complementary to desired gene with label attached

Question 41

How is DNA cut

Answer 41

- Restriction endonuclease, cuts DNA at specific palindromic recognition sequences (recognition sites)

Question 42

reason for lid on petri dish

Answer 42

so it wouldn't evaporate so IAA conc the same in each dish

Question 43

explain the banding pattern from muscle diagram

Answer 43

- The centre of the sarcomere appears darker due to the overlap of both actin and myosin filaments (A band) - The peripheries of the sarcomere appear lighter as only actin is present in this region (I band) - The dark A band also contains a slightly lighter central region where only the myosin is present (H zone)

Question 44

explain why converting pyruvate to lactate allows the continued production of atp by anaerobic respiration

Answer 44

Regenerates / produces NAD | (NAD used) in glycolysis.

Question 45

Explain how two features of the design of this investigation helped to ensure the validity of any conclusions obtained. (zebrafish)

Answer 45

large sample size therefore representative | and use of a control group for comparisons

Question 46

gluconeogenesis

Answer 46

the synthesis of glucose from non-carbohydrate sources

Question 47

more insulin =

Answer 47

more glut4 proteins, absorb more glucose by active transport, reduces glucose conc