Biology 9700 · AS & A Level · Respiration

Respiration — practice question

Chemiosmosis refers to ATP synthesis driven by a proton gradient spanning a membrane in a mitochondrion or chloroplast. Peter Mitchell demonstrated this first in 1961.
(a)[2]

In some of his experiments, Peter Mitchell worked with mitochondria isolated from cells. He kept the mitochondria in liquid in glass dishes and added ADP, Pi and other substances. Temperature, pH and water potential were maintained at constant values. After a set time, he tested for ATP. The contents of some dishes are listed in the table below. Complete the table with a tick (✓) if ATP was made and a cross (✗) if it was not.

(b)[2]

Explain the consequences for a mitochondrion when the water potential of the liquid in the dishes is higher than the water potential of the mitochondrial matrix.

(c)[1]

State the exact role of oxygen in the mitochondrion.

(d)[1]

Name the enzyme that makes ATP in chemiosmosis.

(e)[4]

Describe the function of the inner mitochondrial membrane (crista) in chemiosmosis.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: ATP made with oxygen or high $[H^+]$

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