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Date	May 2021	Marks available	1	Reference code	21M.2.SL.TZ1.2
Level	Standard level	Paper	Paper 2	Time zone	Time zone 1
Command term	Identify	Question number	2	Adapted from	N/A

Question

The diagram shows some of the metabolic processes taking place in a plant cell.

Identify the process Y and state the name of the organelle where it takes place in a plant cell.

Process Y:

Name of the organelle:

[1]

a.i.

Identify the molecule Z.

[1]

a.ii.

State the type of reaction which converts excess monosaccharides to polysaccharides.

[1]

b.

The process X uses oxygen and produces ATP. Identify the process X.

[1]

c.

Outline the uses of ATP in plant cells.

[2]

d.

With reference to the diagram, identify one example of catabolism.

[1]

e.

Markscheme

process Y: photosynthesis ✔

organelle: chloroplast ✔

Both needed.

a.i.

glycerol /glycerin ✔

a.ii.

condensation/dehydration/synthesis/anabolic/anabolism ✔

b.

aerobic respiration ✔

c.

a. used as an energy source ✔

b. supplies/releases energy for biochemical reactions ✔

c. photosynthesis/active transport/other verifiable example of reaction or process ✔

d.

a. (letter X) breakdown of monosaccharides/respiration ✔

b. (letter Y) hydrolysis/photolysis in photosynthesis/oxidation of water ✔

Answer must come from the diagram.

e.

Examiners report

The diagram was generally confusing to candidates.

This was generally answered correctly.

a.i.

The diagram was generally confusing to candidates.

This was generally missed.

a.ii.

The diagram was generally confusing to candidates.

This was often answered correctly.

b.

The diagram was generally confusing to candidates.

Although many answered cell respiration, aerobic respiration was expected since the question defined aerobic respiration.

c.

The diagram was generally confusing to candidates.

Expressing the nature of ATP in an outline of its use to plants was problematic for many students. Rather than a source of energy it was thought to be energy itself. Many processes use ATP in one part of the pathway or another, so a wide variety of seemingly contradictory answers received credit. For example, ATP is used in cell respiration during glycolysis. Credit was given for glycolysis as well as for respiration.

d.

The diagram was generally confusing to candidates.

Too often candidates did not make reference to the diagram when giving an example of catabolism. Some thought that ADP changing to ATP was catabolism. This probably comes from a failure to understand paired reactions.

e.

Syllabus sections

Core » Topic 2: Molecular biology » 2.9 Photosynthesis

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