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A Level Biology > Paper 2 Exam Questions > Flashcards

Paper 2 Exam Questions Flashcards

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1
Q

Describe what happens during photoionisation in the light dependent reaction (2 marks)

A
  1. light excites electrons in chlorophyll
  2. chlorophyll becomes positively charged
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2
Q

why is the origin in chromatography marked in pencil instead of ink?

A

Ink and leaf pigments would mix

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3
Q

suggest and explain the advantage of having different coloured pigments and leaves. ( 1 mark)

A

absorb different wavelengths of light for photosynthesis

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4
Q

Where is RuBisCO found?

A

stroma of chloroplast

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5
Q

Heat stress decreases the light dependent reaction of photosynthesis.

Explain why this leads to a decrease in the light independent reaction
(2 marks)

A
  1. less ATP produced
  2. less reduced NADP
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6
Q

A decrease in the activity of the enzyme RuBisCO would limit the rate of photosynthesis. Explain why (2marks)

A

less CO2 reacts with RuBP
less GP

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7
Q

DCPIP is _____ when oxidised

A

blue

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8
Q

DCPIP is ____ when reduced

A

colourless

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9
Q

why is a control tube set up in the DCPIP practical?

2 marks

A
  1. to show light doesn’t affect DCPIP
  2. to show chloroplasts are required
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10
Q

name the the two products of the light dependent reaction that required for the light independent reaction

A

reduced NADP
ATP

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11
Q

What does cyclic phosphorylation produce?

A

ATP

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12
Q

describe how acteylcoenzyme A is formed in the link reaction

2 marks

A

1.hydrogen removed from pyruvate
2. and CO2 released

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13
Q

explain why converting pyruvate to lactate allows the continued production is ATP during anaerobic respiration

2 marks

A
  1. it regenerates ATP
  2. which is used in glycolysis
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14
Q

in muscles, some of the lactate is converted back to pyruvate when they are well supplied with oxygen. suggest one advantage of this

1 mark

A

lactic acid causes muscle fatigue

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15
Q

why is glucose not used as a respiratory substrate

2 marks

A

1.glucose is used during glycolysis
2. cannot cross mitochondrial membrane

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16
Q

describe the part played by the inner membrane of a mitochondrion in producing ATP

4 marks

A
  1. electrons transferred down ETC
  2. provide energy to take protons
  3. protons pass back through membrane
  4. energy used to combine ADP and phosphate
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17
Q

Describe the process of glycolysis

4 marks

A
  1. Phosphorylation of glucose using ATP
  2. oxidation of triose phosphate
  3. net gain of ATP
  4. NAD is reduced
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18
Q

Malonate inhibits a reaction in the Krebs Cycle. Explain why malonate would decrease the uptake of oxygen in a respiring cell

2 marks

A
  1. less reduced NAD
  2. oxygen is the final electron acceptor
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19
Q

Explain how resting potential is maintained across the axon membrane in a neurone.

3 marks

A
  1. Higher conc of NA+ outside and higher K+ inside.
  2. Membrane is more permeable to K+ leaving
  3. Na+ ions actively transported out
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20
Q

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

3 marks

A
  1. myelination provides electrical insulation
  2. in myelinated saltatory conduction
  3. in non-myelinated depolarisation occurs along whole axon
21
Q

Describe and explain how the PCR is used to amplify a DNA fragment

4 marks

A
  1. Requires DNA fragment, DNA polymerase, nucleotides and primers
  2. Heat to 95 to break H bonds
  3. Reduce temperature so primers can bind to DNA
  4. Increase temperature so DNA polymerase can join strands, REPEAT
22
Q

Explain how succession results in a wide variety of fish living on coral reefs

2 marks

A
  1. increase in diversity
  2. provides different habitats
23
Q

Describe a method that could be used to determine the mean percentage cover of algae on a coral reef

3 marks

A
  1. Use random no. generator to decide where to place quadrats
  2. Use a large sample of quadrats
  3. Divide total % by no. of quadrats
24
Q

Loss of nutrients into a lake has caused a decrease in some fish populations. Explain why

4 marks

A
  1. Algae grows and blocks light
  2. Reduces photosynthesis so plants die
  3. Saprobiotic organisms respire aerobically
  4. Less oxygen for fish to respire
25
Q

How does speciation occur to produce 2 different species of lemur from one original species?

5 marks

A
  1. geographical isolation
  2. reproductive isolation
  3. different selection pressures
  4. mutations
  5. different alleles will be selected
  6. no longer can interbreed to produce fertile offspring
26
Q

Describe the light-dependent reaction of photosynthesis.

6 marks

A
  1. CO2 combines with RuBP
  2. producing 2 GP using rubisco
  3. GP reduced to triose phosphate
  4. using reduced NADP
  5. using energy from ATP
  6. TP converted to glucose
27
Q

Nitrogenase catalyses the reduction of nitrogen during nitrogen fixation. The reaction requires 16 ATP for each molecule of nitrogen that is reduced. When ammonia inhibits nitrogenase activity, nitrogen-fixing bacteria may benefit. Explain how

2 marks

A
  1. less ATP is being used up for the nitrogen fixation as it is occuring less
  2. therefore the bacteria will have more energy for growth and respiration
28
Q

Scientists concluded that the obsereved frequencies of 4 phenotypes differed significantly from the expected. Use your knowledge of the Hardy-Weinberg principle to suggest 2 reasons why

2 marks

A

two from
1. selection
2. mutation
3. migration

29
Q

give two reasons why transmission across a cholinergic synapse is unidirectional

2 marks

A
  1. only receptors on the post synaptic neurone can recieve messages
  2. only the presynaptic nerone has neurotransmitter
30
Q

explain temporal summation

1 mark

A

there are several repeated impulses in a short time which provide enough neurotransmitter to reach threshold

31
Q

explain the role of reverse transcriptase in RT-PCR

1 mark

A

makes cDNA from mRNA

32
Q

explain the role of DNA polymerase in RT-PCR

1 mark

A

joins nucleotides to produce complementary strands of DNA

33
Q

Any DNA in a sample taken for PCR is hydrolysed by enzymes before the sample is added to the reaction mixtre. Explain why

2 marks

A
  1. to remove any DNA present
  2. because this DNA would be amplified
34
Q

suggest a reason why DNA replication stops in the polymerase chain reaction

1 mark

A

all of the free nucleotides have been used

35
Q

Scientists use the RT-PCR method to detect the presence of different RNA virsuses in patients suffering from respiratory diseases.

The scientists produced a variety of primers for this procedure. Explain why

2 marks

A
  1. base sequences of the viruses differ
  2. different primers will be complementary to each virus so will bind to that one
36
Q

Describe how you could estimate the size of a population of sundews in a small marsh

5 marks

A
  1. use a grid
  2. use a random no. generator to choose large no. of quadrats to sample
  3. count the no. of plant in each quadrat
  4. record a large sample and calculate mean
  5. multiply mean x no. of quadrats to stimate population
37
Q

suggest and explain how digesting insects helps a plant grow in soil with very low concentrations of some nutrients

2 marks

A
  1. digestion of proteins
  2. providing amino acids
38
Q

Succession occurs in a natural ecosystem. Describe and explain how succession occurs

4 marks

A
  1. colonisation by pioneer species
  2. pioneers change the conditions
  3. becomes less hostile for other species
  4. increase in biodiversity
  5. to climax community
39
Q

Explain how a single base subsitution causes a change in the structure of the polypeptide

3 marks

A
  1. change in amino acid sequence
  2. changes in H bonds
  3. alters tertiary structure
40
Q

What part of the plant produces IAA?

1 mark

A

the tip

41
Q

Explain how a decrease in the concentration of calcium ions within muscle cells could cause a decreased in the force of muscle contraction

3 marks

A
  1. less tropomyosin moved from the binding site
  2. fewer actinmyosin bridges formed
  3. myosin head does not move
42
Q

Explain how a decrease in the concentration of calcium ions within muscle tissues could cause a decrease in the force muscle contraction

3 marks

A
  1. less tropomyosin moved from the binding site
  2. fewer actinmyosin bridges formed
  3. mysoin head does not move
43
Q

Describe the role of glucagon in gluconeogenesis

2 marks

A
  1. activates enzymes
  2. glycerol into glucose
44
Q

Explain how increasing a cell’s sensitivity to insulin will lower the blood glucose concentration

2 marks

A
  1. more insulin binds to receptors
  2. stimulates uptake of glucose
45
Q

Explain how inhibiting adenylate cylase may help to lower the blood glucose concentration

3 marks

A
  1. less ATP converted to cAMP
  2. less kinase activated
  3. less glycogen converted to glucose
46
Q

Describe what happens during photoionisation in the light dependent reaction

2 marks

A
  1. chlorophyll absorbs light
  2. chlorophyll becomes positively charged
47
Q

What is a DNA probe?

2 marks

A
  1. (Short) single strand of DNA
  2. Bases complementary (with DNA/allele/gene)
48
Q

Describe how the DNA is broken into smaller fragments

2 marks

A
  1. cut by restriction endonucleases
  2. cuts at specific base sequences

A Level Biology (19 decks)

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