WRONG Qs Paper 2

Question 1

Describe how stimulation of a pacinian corpuscle produces a generator potential (5 marks)

Answer 1

1. There are stretch mediated sodium channels in the membrane
2. Increased pressure deforms axon membrane
3. Sodium ion channels open
4. Sodium ions diffuse in
5. Depolarisation leads to a generator potential

Question 2

Explain how a resting potential is maintained across the axon membrane in a neurone (3 marks)

Answer 2

1. Higher concentration of sodium ions outside AND higher concentration of potassium ions inside the neurone
2. Membrane more permeable to potassium ions leaving than sodium ions entering
3. Sodium ions actively transported out and potassium ions in

Question 3

Explain why the speed of transmission of impulses is faster along a myelinated axon than a non-myelinated axon (3 marks)

Answer 3

1. Myelination= electrical insulation
2. In myelinated, saltatory conduction occurs
3. In non myelinated depolarisation occurs across the whole length of the axon

Question 4

Why would binding of a drug not lead to the production of an action potential? (2 marks)

Answer 4

1. Binding does not lead to opening of sodium channels
2. So no depolarisation

Question 5

What is meant by a non-coding base sequence? (1 mark)

Answer 5

Does not code for amino acids

Question 6

How do DNA probes work?

Answer 6

1. DNA probes single stranded
2. Complementary base sequence on specific spacer
3. Binding of single strands= glowing/ produces light

Question 7

How would geneticists insert a gene into a plasmid? (3 marks)

Answer 7

1. Cut plasmid with restriction endonuclease
2. So both have complementary sticky ends
3. Mix together and add ligand to join complementary sticky ends

Question 8

Why would scientists use a marker gene? (2 marks)

Answer 8

1. Shows which cells have successfully taken up plasmid
2. Glowing is easy to find

Question 9

Meaning of non-overlapping? (1 mark)

Answer 9

Each base is only part of one triplet/ codon

Question 10

Why can’t bacteria produce every human protein? (2 marks)

Answer 10

1. Cannot splice pre-mRNA so cannot remove introns
2. Do not have Golgi so cannot process/ modify proteins

Question 11

What is the purpose of a marker gene? (1 mark)

Answer 11

Allows detection of genetically modified cells/ organisms

Question 12

How would a mutation alter a transport protein? (5 marks)

Answer 12

1. Mutation changes base sequence of DNA
2. Changing amino acid sequence
3. Changes tertiary structure of protein/ transporter
4. Cocaine binding site changes so cocaine cannot bind
5. Dopamine can still bind and be transported

Question 13

Why would two strands of DNA be the same length? (1 mark)

Answer 13

Cut at same base sequence and same restriction enzyme used

Question 14

What is an antibody? (3 marks)

Answer 14

1. Protein
2. Specific to an antigen
3. Complementary shapes to one another

Question 15

How could a gene be introduced to offspring? (6 marks)

Answer 15

1. Antibody gene located using gene probe
2. Cut using restriction endonuclease
3. At specific base pairs
4. Leaving sticky ends
5. Cut maize/ DNA/ vector using same restriction enzyme
6. Join using DNA ligase
7. Introduce vector into crop/ maize

Question 16

How is the process of genetic fingerprinting carried out? (6 marks)

Answer 16

1. DNA is cut
2. Using a restriction enzyme
3. Gel electrophoresis occurs
4. Separates DNA according to length
5. DNA made single stranded
6. Transferred to membrane by SOuthern Blotting
7. Add/ apply DNA probe
8. Binds to complementary DNA and so turns flourescent
9. VNTRs
10. Pattern unique to every individual

Question 17

Why are two different primers required in PCR? (1 mark)

Answer 17

Sequences at ends of target sequence are different

Question 18

What is meant by a gene? (2 marks)

Answer 18

1. Length of DNA
2. Codes for a single protein/ polypeptide

Question 19

Hibernation adaptations (4):

Answer 19

1. Large fat stores= use in respiration
2. Gluconeogenesis
3. Low SA:V ratio reduces heat loss
4. Long loop of henle so less water lost

Question 20

Why does converting pyruvate to lactate allow the continuous production of ATP by anaerobic respiration? (2 marks)

Answer 20

1. Regenerates/ produces NAD
2. So glycolysis continues

Question 21

Explain how a resting potential is maintained across the axon membrane in a neurone. (3 marks)

Answer 21

1. Higher concentration of K+ ions inside AND higher concentration of Na+ ions outside the neurone
2. Membrane more permeable to K+ ions leaving than Na+ ions entering due to leaky potassium channels
3. 3 sodium ions actively transported out of axon membrane and 2 potassium ions actively transported into the axon membrane

Question 22

Why is the speed of transmission of impulses faster along a myelinated axon than a non-myelinated axon? (3 marks)

Answer 22

1. Myelin sheath provides electrical insulation which speeds up transmission of impulses
2. Myelinated neurone surrounded by Schwann cells and have nodes of Ranvier so saltatory conduction can occur
3. In non- myelinated, depolarisation occurs along the whole length of the axon

Question 23

GABA causes negatively charged chloride ions to enter postsynaptic neurones. Explain how this inhibits postsynaptic neurones. (3 marks)

Answer 23

1. Inside of neurone becomes more negative= hyperpolarisation
2. More sodium ions required to reach threshold
3. For depolarisation

Question 24

Descibr how ultrafiltration occurs in a glomerulus (3 marks)

Answer 24

1. High hydrostatic pressure
2. Small substances e.g. glucose and water pass out
3. Through small pores in the capillary endothelium
4. And through capillary basement membrane

Question 25

Describe the light independent reaction of photosynthesis (6 marks):

Answer 25

1. CO2 combines with 5 carbon molecules Ribulose Biphosphate (RuBP) to form unstable 6 carbon molecule 2. Splits to produce two molecules of glycerate 3 phosphate using enzyme rubisco 3. Glycerate 3 phosphate reduced to triose phosphate 4. Using reduced NADP 5. And using energy from ATP hydrolysis 6. Some TP converted back into RuBP and some converted into useful organic substances for the organism e.g. glucose

Question 26

What does a P value of P> 0.5 tell us? (2 marks)

Answer 26

1. The difference is not significant 2. There is a greater than 0.5 probability that this result is due to chance

Question 27

Explain how farming practices increase the productivity of agricultural crops (5 marks)

Answer 27

1. Fertilisers added to soil 2. Nitrogen for protein production 3. GM of crops 4. Ploughing decreases denitrification 5. Crop rotation= increased pest reduction and soil fertility