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Date November 2015 Marks available 4 Reference code 15N.3.SL.TZ0.9
Level Standard level Paper Paper 3 Time zone TZ0
Command term Explain Question number 9 Adapted from N/A

Question

Draw a labelled diagram showing the structure of a chloroplast.

[3]
a.

Explain how energy is released and used to make ATP by electron carriers in the electron transport chain during aerobic respiration.

[4]
b.

Markscheme

Award [1] for each of the following clearly drawn and correctly labelled.

a. outer and inner membranes;

b. stroma;

c. thylakoid;

d. granum;

e. (70S) ribosomes / (naked) DNA;

f. starch granules;

a.

a. electron carriers found on inner membrane/cristae of mitochondria;

b. H/H+/protons transported to electron carriers by NAD and FAD;

c. series of redox reactions in membrane;

d. electrons are passed down energy gradient;

e. establishes proton gradient / protons accumulate (in intermembrane space);

f. oxygen is the final electron acceptor;

g. generation of ATP through chemiosmosis;

Accept correct answers in an annotated diagram.

b.

Examiners report

There was a range of diagrams of the chloroplast with the many achieving all 3 marks.

a.

The electron transport chain was not well understood. Many candidates assumed it referred to the chloroplast from part (a).

b.

Syllabus sections

Additional higher level » Topic 8: Metabolism, cell respiration and photosynthesis » 8.2 Cell respiration
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