Biology 9700 · AS & A Level · Respiration

Respiration — practice question

Chemiosmosis is the name given to ATP synthesis that uses a proton gradient across a membrane in a mitochondrion or chloroplast. Peter Mitchell first showed this in 1961.
(a)[2]

In some of his experiments, Peter Mitchell worked with mitochondria that had been removed from cells. He stored the mitochondria in liquid, in glass dishes, and added ADP, Pi and other substances. Temperature, pH and water potential were kept unchanged. After some time, he looked for ATP. The contents of some of the dishes are shown in the table below. Complete the table using a tick (✓) if ATP was made and a cross (✗) if ATP was not made.

(b)[2]

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

(c)[1]

State the precise role of oxygen in the mitochondrion.

(d)[1]

Name the enzyme that makes ATP in chemiosmosis.

(e)[4]

Describe how the inner mitochondrial membrane (crista) functions 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 produced with oxygen and acetyl CoA present

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