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Date	May 2017	Marks available	2	Reference code	17M.2.HL.TZ2.2
Level	Higher level	Paper	Paper 2	Time zone	Time zone 2
Command term	Explain	Question number	2	Adapted from	N/A

Question

The enzyme ATP synthase has an essential role in aerobic cell respiration.

The sketch shows the relationship between the reaction rate and substrate concentration in the presence and the absence of a competitive inhibitor.

Explain the effect of the competitive inhibitor on the reaction rate.

[2]

Describe its location.

[1]

b.i.

Describe its function.

[2]

b.ii.

Markscheme

a. competitive inhibitor «slows the reaction rate as it» competes for the active site
OR
competitor has similar shape/structure/composition to substrate «and slows the reaction rate»

b. binding of competitor is reversible

c. «as the substrate concentration increases» more substrate binds to the active site than the competitor «and reaction rate increases»

d. «as the substrate concentration increases» the reaction rate reaches the maximum plateau «same as with no inhibitor»

the inner mitochondrial membrane critstae/thylakoid membrane

b.i.

a. protons build up in the intermembrane space due to electron transport chain OWTTE

b. protons move through ATP synthase down the concentration gradient
Accept H⁺ ions in place of protons

c. catalyses formation of ATP OWTTE

b.ii.

Examiners report

[N/A]

b.i.

[N/A]

b.ii.

Syllabus sections

Additional higher level » Topic 8: Metabolism, cell respiration and photosynthesis » 8.1 Metabolism

Additional higher level » Topic 8: Metabolism, cell respiration and photosynthesis

Additional higher level

Question

Markscheme

Examiners report

Syllabus sections

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