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Date May 2018 Marks available 1 Reference code 18M.3.SL.TZ2.1
Level Standard level Paper Paper 3 Time zone Time zone 2
Command term Identify Question number 1 Adapted from N/A

Question

Chromatography is a technique used to separate the components of a mixture. The photosynthetic pigments from three organisms were separated by thin layer chromatography: spinach (Spinacia oleracea), a red alga (Porphyra) and a brown alga (Fucus).

Identify a pigment found in all three organisms.

[1]
a.

Compare and contrast absorption spectra and action spectra.

[2]
b.

Porphyra also contains phycoerythrin, which is a red pigment.

Suggest a reason for phycoerythrin being absent from the Porphyra chromatogram.

[1]
c.i.

Porphyra also contains phycoerythrin, which is a red pigment.

Predict one colour of light that will be absorbed efficiently by phycoerythrin.

[1]
c.ii.

Markscheme

chlorophyll a
OR
β carotene

a.

a. horizontal axis for both is wavelength/colour

OR

«for a chloroplast/cells/leaves/plants extract» they will have the same/similar shape 

Marking point a. may be shown with a diagram.

b. an action spectrum shows the rate of photosynthesis «in chloroplasts/cells/leaves/plants» and an absorption spectrum shows the absorption of light

b.

a. the pigment didn't dissolve / was insoluble when the pigments from the algae were extracted 

b. the pigment was not moved by / was insoluble in the solvent used to separate the pigments

c.i.

orange/yellow/green/blue/violet

c.ii.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.i.
[N/A]
c.ii.

Syllabus sections

Core » Topic 2: Molecular biology » 2.9 Photosynthesis
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