DP Biology (last assessment 2024)

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Question 21M.2.HL.TZ2.2d.ii

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Date May 2021 Marks available [Maximum mark: 3] Reference code 21M.2.HL.TZ2.2d.ii
Level HL Paper 2 Time zone TZ2
Command term Explain Question number d.ii Adapted from N/A
d.ii.
[Maximum mark: 3]
21M.2.HL.TZ2.2d.ii

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.

(d.ii)

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

[3]

Markscheme

a. change in pH can cause a change in the tertiary structure of the enzyme
OR
enzyme denatured ✔

b. causing a change in the active site / substrate not able to bind ✔

c. the enzyme will not work as efficiently / decreased rate of reaction ✔

d. (may no longer be) the optimum/optimal pH for enzyme activity ✔

Allow answer in the form of a graph.

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