EduNinja
Question rangeC2.2.7—Excitatory postsynaptic potential
[Maximum number: 14]

Mice (Mus musculus) have various defence systems against predators such as foxes (Vulpus vulpus) or stoats (Mustela erminea). The mice release specific alarm compounds when under threat that serve as danger signals for other mice. Predators also release scents that the mice can detect.

In one study, mice were exposed to paper soaked in compounds taken from other mice, foxes or stoats in a test chamber. The scientists then measured the reaction of three different groups of neurons used in smelling: G1, G2 and G3, as shown in the diagram.

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The percentage of G1, G2 and G3 neurons responding to the mouse, fox and stoat compounds, as well as a control compound, are shown in the chart.

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(a)

State the percentage of G2 neurons in the mice that respond to the fox scent.

[ 1 ]
(b)

Using evidence from the chart, identify, giving a reason, which group of neurons responded most to the chemicals.

The scientists recorded the neural traces (action and resting potentials) of six G1 neurons exposed to the compounds from the different animals. The horizontal bar beneath each trace corresponds to the time of exposure to the test compound.

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[ 1 ]
(c)

State the name of the instrument used to make these traces.

[ 1 ]
(d)

Distinguish between the effects of the mouse alarm compound and the effects of the control compound on the G1 neurons.

[ 1 ]
(e)

Compare and contrast the effects of the mouse alarm compound and stoat scent on the G1 neurons.

[ 2 ]
(f)

Deduce whether there is a correlation between the neural traces and the percentage of responding G1 neurons.

[ 2 ]
(g)

The molecular structures of the mouse alarm compound and fox scent are very similar.
Suggest an evolutionary advantage for this chemical similarity.

[ 1 ]
(h)

Another study was carried out on the defence systems in aphids (Myzus persicae) which feed on thale cress plants (Arabidopsis thaliana). Individual aphids release an alarm compound containing the chemical (E)- β\beta-farnesene (EBF) when attacked by a predator. Other aphids are repelled and leave the thale cress plant or hide.

The gene for EBF was inserted to produce transgenic (T) thale cress plants to test aphid reaction to EBF over several generations. Aphids were raised on wild type (W) thale cress and then allowed to feed for three generations on either W or T thale cress. Aphids were tested in each generation for their reaction when EBF was added to a choice chamber. The percentages of aphids attracted to or repelled by EBF and those which made no choice were recorded.

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Identify, with a reason, the aphids that were most strongly repelled by EBF.

[ 1 ]
(i)

Outline the conclusions that can be drawn from the data in the graph for the group of aphids fed for three generations on transgenic thale cress plants (T).

[ 2 ]
(j)

Discuss whether natural selection would favour the transgenic EBF-producing thale cress plants if they were released into the wild.

[ 2 ]
[Maximum number: 15]

Honeybees (Apis mellifera) are key pollinators in most ecosystems. The worldwide use of neonicotinoid pesticides has caused concern because they may be contributing to the decline of honeybee populations.

Scientists measured the concentration of five neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam) in honey samples from 198 different locations across the world. Each pie chart shows the relative frequency of neonicotinoids in honey samples from a continent.

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(a)

Identify in which continent the fewest types of neonicotinoid were detected in honey samples.

[ 1 ]
(b)

Using the data, outline the different use of thiamethoxam in North and South America.

The neonicotinoids can be used alone or together with other neonicotinoids. The percentage of honey samples with 0,1,2,3,4 or 5 different neonicotinoids in each continent are shown in the stacked bar chart.

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[ 1 ]
(c)

Identify the total percentage of honey samples contaminated with neonicotinoid pesticides in the continent with the lowest overall levels of contamination.
\%

In order to grow, honeybee larvae are fed royal jelly, a high energy food with very high acetylcholine concentrations.

In an experiment, larvae were bred artificially on a diet with reduced acetylcholine content in the royal jelly. The graph shows the mean survival rate of these larvae compared to control larvae fed on a normal diet.

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Key:
- Control
△ Reduced acetylcholine royal jelly

[ 1 ]
(d)

Deduce the conclusions that can be drawn from the data in the graph.

[ 2 ]
(e)

Suggest a reason for the effect of a diet reduced in acetylcholine on the larval survival rate.

[ 1 ]
(f)

The concentration of acetylcholine was measured in royal jelly produced by honeybees that had never been exposed to neonicotinoids (control) and honeybees that had been exposed for three weeks to two neonicotinoids; clothianidin and thiacloprid.

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Compare and contrast the effect of clothianidin and thiacloprid treatments on the concentration of acetylcholine in royal jelly.

[ 2 ]
(g)

Explain how neonicotinoids affect synaptic transmission in insects.
(h) Companies that manufacture neonicotinoid pesticides have argued that they do not

[ 3 ]
(h)

cause significant harm to honeybees. Construct an argument, based on the data in this question, for serious concern about the manufacture and use of neonicotinoid pesticides.

[ 4 ]
[Maximum number: 11]

Cholinergic synapses use acetylcholine as their neurotransmitter. They are widespread in the body, passing on signals to muscle cells. These synapses are affected by neonicotinoid pesticides.

The diagrams, which are not drawn to scale, show the synapse between two neurons and a detail of the synaptic cleft.

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(a)

On the diagrams, label:

[ 3 ]
(i)

with a letter H the hydrophilic end of a phospholipid

[ 1 ]
(ii)

with a letter E a vesicle involved in exocytosis

[ 1 ]
(iii)

with a letter P a location where a neonicotinoid pesticide could bind.

[ 1 ]
(b)

Outline how depolarization of the membrane of an axon occurs.

[ 2 ]
(c)

Explain how acetylcholine initiates an action potential in a postsynaptic membrane.

[ 2 ]
(d)
(i)

State the action of the enzyme acetylcholinesterase.

[ 1 ]
(ii)

Explain what happens to an enzyme if there is a change of pH .

[ 3 ]
(a)

The diagram shows the procedure used by Pavlov during his experiment on dogs.

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[ 2 ]
(i)

State the type of stimulus provided by the sight and smell of the food.

[ 1 ]
(ii)

State the function of the tube.

[ 1 ]
(b)

State two effects presynaptic neurons could have on postsynaptic transmission.
1.
2.

[ 1 ]
(c)

Describe one experiment that could be used to investigate taxis behaviour in a named invertebrate.

[ 3 ]
[Maximum number: 5]

The diagram shows a neuron.

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(a)

Identify the structure and function for the part of the neuron labelled X .

[ 2 ]
(b)

Describe how an excitatory postsynaptic potential is generated.

Answer one question. Up to one additional mark is available for the construction of your answer.

[ 3 ]
[Maximum number: 1]

What causes the formation of a nerve impulse on the post-synaptic membrane?

A

Ca2+\mathrm{Ca}^{2+} binding with a receptor site

B

K+\mathrm{K}^{+}leaking into the post-synaptic membrane

C

Neurotransmitter binding with receptor sites

D

Neurotransmitter being removed from the synapse

[Maximum number: 1]

What initiates an action potential along a neuron?

A

Potassium and sodium ions diffuse out of a neuron.

B

Potassium and sodium ions diffuse into a neuron.

C

Neurotransmitters cause depolarization of membrane.

D

Acetylcholinesterase breaks down acetylcholine.

(a)
(i)

Define stimulus.

[ 1 ]
(ii)

State two effects that presynaptic neurons can have on postsynaptic transmission.
1.
2.

[ 1 ]
(b)

Define the behaviour known as taxis.

[ 1 ]
(c)

Suggest causes of addiction to drugs.

[ 3 ]
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