Survival and response, Nerve impulses, Synaptic transmission, Receptors and Control of heart rate AQA A2 Biology - EXAM QUESTIONS

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Q1. This question should be written in continuous prose, where appropriate.
(a) Explain how a resting potential is maintained in a neurone.
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(4)
(b) In an investigation, an impulse was generated in a neurone using electrodes. During
transmission along the neurone, an action potential was recorded at one point on
the neurone. When the impulse reached the neuromuscular junction, it stimulated a
muscle cell to contract. The force generated by the contraction was measured. The
results are shown in the graph.
The distance between the point on the neurone where the action potential was
measured and the neuromuscular junction was exactly 18 mm.
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Use the graph to estimate the time between the maximum depolarisation and
the start of contraction by the muscle cell.
Time ................................ ms
(1)
(ii) Use your answer to part (i) to calculate the speed of transmission along this
neurone to the muscle cell. Give your answer in mm per second.
Show your working.
Speed ..................................…read more

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Use your knowledge of the processes occurring at a neuromuscular junction to
explain each of the following.
(i) The cobra is a very poisonous snake. The molecular structure of cobra toxin is
similar to the molecular structure of acetylcholine. The toxin permanently
prevents muscle contraction.
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(2)
(ii) The insecticide DFP combines with the active site of the enzyme acetyl
cholinesterase. The muscles stay contracted until the insecticide is lost from
the neuromuscular junction.
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Figure 1 Figure 2
(i) Explain why it takes time for the rod cells to recover their sensitivity to light after
moving into darkness.
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(2)
(ii) Use information in F igures 1 and 2
to explain the differences in sensitivity of rod
cells to red and green light.
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(2)
(iii) Suggest an explanation for the difference in sensitivity of rod cells to the white and
green spots after 30 minutes.
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Total 5 marks)
Q3. S In an investigation, the effects of caffeine on performance during exercise were
measured. One group of athletes (A ) was given a drink of decaffeinated coffee.
Another group (B) was given a drink of decaffeinated coffee with caffeine added.
One hour later the athletes started riding an exercise bike and continued until too
exhausted to carry on. Three days later the same athletes repeated the experiment,
with the drinks exchanged.
(a) (i) The researchers added caffeine to decaffeinated coffee.…read more

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Describe the effect of caffeine on exercise performance.
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(1)
(ii) Suggest one e xplanation for the higher glycerol and fatty acid concentrations
in the blood plasma of the athletes after they were given caffeine.
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(2)
(c) The researchers measured the volumes of carbon dioxide exhaled and oxygen
inhaled during the exercise. From the results they calculated the respiratory quotient
(RQ), using the formula
When a person is respiring carbohydrate only, RQ = 1.…read more

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The researchers found that, when the athletes were given the drink containing
caffeine, their mean RQ was 0.85. When given the drink without caffeine their
mean RQ was 0.92.
The researchers concluded that when the athletes had caffeine they used
glycogen more slowly than when they did not have caffeine, and that the store
of glycogen in their muscles was used up less quickly during the exercise.
Explain the evidence from the information above and from the table which
supports these conclusions.
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Explain what causes the conduction of impulses along a non-myelinated axon to be
slower than along a myelinated axon.
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(3)
(Total 5 marks)
Q5. S In an investigation by a student into the responses of maggots, the bottom of a
large box was marked with six coloured segments, as shown in the diagram.
30 maggots were placed on each segment in the box.…read more

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The experiment was repeated three more times. The total number of maggots in
each segment from the four experiments is shown in the table.
Colour of Intensity of reflected light /
Total number of maggots
segment arbitrary units
Black 4 154
Red 25 229
Blue 10 178
White 44 47
Green 25 48
Yellow 40 64
(a) Give one conclusion about the responses of maggots which is supported by these
results.
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Give the evidence from the table for your conclusion.
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Total 4 marks)
Q6. When a finger accidentally touches a hot object, a reflex action occurs. The biceps
muscle contracts, causing the arm to be flexed and the finger is pulled away. The diagram
shows the arrangement of the bones in the arm, the muscles used for flexing and
straightening the arm and the nervous pathways associated with the contraction of these
muscles.
(a) Explain the importance of reflex actions.
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