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Question 3

From Biology HL Paper 2 (May 2025, TZ2)

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  1. Voltage-gated ion channels are proteins that are embedded in the phospholipid bilayer of plasma membranes. They conduct ions at high rates, regulated by the voltage across the membrane. The diagram shows a typical voltage-gated potassium (K+) channel when it is closed and when it is open.
The diagram illustrates a voltage-gated potassium channel embedded in a phospholipid bilayer, showing its configuration when closed and when open, with labels for 'OUTSIDE', 'INSIDE', 'Phospholipid bilayer', and 'Cholesterol'.
The diagram illustrates a voltage-gated potassium channel embedded in a phospholipid bilayer, showing its configuration when closed and when open, with labels for 'OUTSIDE', 'INSIDE', 'Phospholipid bilayer', and 'Cholesterol'.

(a) Explain the action of the voltage-gated potassium channel during a nerve impulse. [3]

(b) State another type of gated ion channel. [1]

(c) Outline the amphipathic characteristic of phospholipid bilayers. [1]

(d) Outline the effect of cholesterol on the fluidity of membranes. [1]

(e) Outline the effect of fatty acids on the fluidity of membranes. [1]

Textbook topics in this question

Review the exact course sections assessed by each question part.

Mixed-topic question
3(a)7.2 Action Potentials and Impulse Conduction6.2 Neuronal Membranes and Saltatory Conduction
3(b)7.2 Synapses and Neural Integration7.2 Action Potentials and Impulse Conduction
3(c)6.1 Membrane Structure, Fluidity and Adhesion1.5 Lipids
3(d)6.1 Membrane Structure, Fluidity and Adhesion1.5 Lipids
3(e)6.1 Membrane Structure, Fluidity and Adhesion1.5 Lipids