Paper 2 Exam Questions Flashcards by Jess Sails

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

light excites electrons in chlorophyll
chlorophyll becomes positively charged

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

Ink and leaf pigments would mix

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

absorb different wavelengths of light for photosynthesis

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Where is RuBisCO found?

stroma of chloroplast

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Heat stress decreases the light dependent reaction of photosynthesis.

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

less ATP produced
less reduced NADP

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

less CO2 reacts with RuBP
less GP

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DCPIP is _____ when oxidised

blue

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DCPIP is ____ when reduced

colourless

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

2 marks

to show light doesn’t affect DCPIP
to show chloroplasts are required

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

reduced NADP
ATP

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What does cyclic phosphorylation produce?

ATP

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describe how acteylcoenzyme A is formed in the link reaction

2 marks

1.hydrogen removed from pyruvate
2. and CO2 released

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

2 marks

it regenerates ATP
which is used in glycolysis

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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

lactic acid causes muscle fatigue

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why is glucose not used as a respiratory substrate

2 marks

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

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

4 marks

electrons transferred down ETC
provide energy to take protons
protons pass back through membrane
energy used to combine ADP and phosphate

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Describe the process of glycolysis

4 marks

Phosphorylation of glucose using ATP
oxidation of triose phosphate
net gain of ATP
NAD is reduced

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

2 marks

less reduced NAD
oxygen is the final electron acceptor

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

3 marks

Higher conc of NA+ outside and higher K+ inside.
Membrane is more permeable to K+ leaving
Na+ ions actively transported out

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

3 marks

myelination provides electrical insulation
in myelinated saltatory conduction
in non-myelinated depolarisation occurs along whole axon

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

4 marks

Requires DNA fragment, DNA polymerase, nucleotides and primers
Heat to 95 to break H bonds
Reduce temperature so primers can bind to DNA
Increase temperature so DNA polymerase can join strands, REPEAT

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

2 marks

increase in diversity
provides different habitats

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

3 marks

Use random no. generator to decide where to place quadrats
Use a large sample of quadrats
Divide total % by no. of quadrats

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

4 marks

Algae grows and blocks light
Reduces photosynthesis so plants die
Saprobiotic organisms respire aerobically
Less oxygen for fish to respire

How does speciation occur to produce 2 different species of lemur from one original species? 5 marks

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

Describe the light-dependent reaction of photosynthesis. 6 marks

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

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

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

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

two from 1. selection 2. mutation 3. migration

give two reasons why transmission across a cholinergic synapse is unidirectional 2 marks

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

explain temporal summation 1 mark

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

explain the role of reverse transcriptase in RT-PCR 1 mark

makes cDNA from mRNA

explain the role of DNA polymerase in RT-PCR 1 mark

joins nucleotides to produce complementary strands of DNA

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

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

suggest a reason why DNA replication stops in the polymerase chain reaction 1 mark

all of the free nucleotides have been used

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

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

Describe how you could estimate the size of a population of sundews in a small marsh 5 marks

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

suggest and explain how digesting insects helps a plant grow in soil with very low concentrations of some nutrients 2 marks

1. digestion of proteins 2. providing amino acids

Succession occurs in a natural ecosystem. Describe and explain how succession occurs 4 marks

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

Explain how a single base subsitution causes a change in the structure of the polypeptide 3 marks

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

What part of the plant produces IAA? 1 mark

the tip

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

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

Explain how a decrease in the concentration of calcium ions within muscle tissues could cause a decrease in the force muscle contraction 3 marks

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

Describe the role of glucagon in gluconeogenesis 2 marks

1. activates enzymes 2. glycerol into glucose

Explain how increasing a cell's sensitivity to insulin will lower the blood glucose concentration 2 marks

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

Explain how inhibiting adenylate cylase may help to lower the blood glucose concentration 3 marks

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

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

1. chlorophyll absorbs light 2. chlorophyll becomes positively charged

What is a DNA probe? 2 marks

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

Describe how the DNA is broken into smaller fragments 2 marks

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