CAIE A Level Biology 9700 · Control and coordination

Control and coordination: describe question

Describe5 marksChallenge

A cholinergic synapse connects a presynaptic neurone to a postsynaptic neurone. An action potential arrives at the presynaptic terminal.

Describe the role of calcium ions (Ca²⁺) in the transmission of the impulse across this synapse.

How this question is marked

5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.

Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.

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