IB Biology HL 2.2.8 Depolarization and repolarization Question Bank

Practise IB Biology HL 2.2.8 by applying depolarization and repolarization concepts to exam-style questions.

Exam points

identify the relevant biological structure, process or evidence
apply the correct biological mechanism to the question
evaluate the result using data, adaptation or ecological reasoning

[Maximum number: 2]

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.

Figure for Question C2.2.8 (HL)—Depolarization and repolarization question 1 — IB Biology HL

Outline how depolarization of the membrane of an axon occurs.

a. (local depolarization) causes ion / sodium / voltage gated channels to open /

b. altering membrane permeability to sodium ions/ $\mathrm{Na}^{+} /$ positive ions $/ \mathrm{Na}^{+}$ diffuses into the cytoplasm

c. membrane potential (of the axon) changes from negative to positive

d. a threshold potential is reached and an action potential is generated

Marking guidance:

Do not accept sodium pumps.

Mp b requires evidence that the student recognizes sodium is an ion.

Numerical values indicating change from -70 to +30 /+40 /+55 can be accepted.

2 max

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C2.2.8 (HL)—Depolarization and repolarization question 1