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CAIE A-Level Biology A2 13.1 Photosynthesis As Energy Transfer Process Questions

Practise photosynthesis energy-transfer questions by linking chloroplast structure, pigments, spectra and photophosphorylation to Calvin-cycle products.

Syllabus
2028–2030
Course
Biology 9700
Level
A2

Exam points

  • link thylakoids, grana, stroma, pigments and ATP synthase to photosynthesis stages
  • interpret absorption spectra, action spectra and pigment chromatography with Rf values
  • compare cyclic and non-cyclic photophosphorylation, photolysis and reduced NADP formation

Covered syllabus points

13.1.1—Chloroplast structure-function relationship13.1.2—ATP and reduced NADP in Calvin cycle13.1.3—Sites within chloroplast13.1.4—Chloroplast pigments in light absorption13.1.5—Absorption and action spectra13.1.6—Pigment chromatography13.1.7—Light-dependent stage13.1.8—Cyclic photophosphorylation13.1.9—Non-cyclic photophosphorylation13.1.10—During photophosphorylation13.1.11—Calvin cycle three main stages13.1.12—Calvin cycle intermediates

Question 1

[Maximum number: 9]

Question (a)

(a)

Photosynthesis is an energy transfer process that takes place in chloroplasts of plant cells.

[ 6 ]

Question (i)

(i)

Fig. 3.1 shows a diagram of a chloroplast.

Fig. 3.1

Fig. 3.1

Using the letters A, B, C or D, identify the structure that:
- contains genes that code for some of the enzymes used in photosynthesis
- is the site of synthesis of some of the enzymes used in photosynthesis.

[ 2 ]

Question (ii)

(ii)

Explain how grana are adapted for their specific role in photosynthesis.

[ 4 ]

Question (b)

(b)

An experiment was carried out to investigate the effect of changing light conditions on the pH of the chloroplast stroma. Scientists followed pH changes in chloroplast stroma using fluorescent chemicals that can be used as pH indicators.
- Chloroplasts were isolated from cells.
- A suspension of chloroplasts was prepared and kept in the dark for 180 seconds.
- The chloroplasts were exposed to a period of light of fixed intensity for 240 seconds, then returned to dark conditions.
- The pH of chloroplast stroma was continuously measured and recorded.

Fig. 3.2 shows the results of this experiment.

Fig. 3.2

Fig. 3.2

[ 3 ]

Question (i)

(i)

Discuss how the results in Fig. 3.2 support that chemiosmosis occurs during photophosphorylation.

[ 3 ]

Question 2

[Maximum number: 2]

Fig. 4.1 shows a diagram of a stoma, its guard cells and adjacent epidermal cells.

Fig. 4.1

Fig. 4.1

Fig. 4.3 shows the relationship between the light dependent and light independent reactions in a chloroplast.

Fig. 4.3

Fig. 4.3

Name substances X and Y in Fig. 4.3.
X
Y

Question 3

[Maximum number: 9]

Question (a)

(a)

Fig. 7.1 outlines the process of non-cyclic photophosphorylation in the chloroplast of a leaf mesophyll cell.

Fig. 7.1

Fig. 7.1

[ 6 ]

Question (i)

(i)

State precisely where non-cyclic photophosphorylation occurs in the chloroplast.

[ 1 ]

Question (ii)

(ii)

With reference to Fig. 7.1, name processes A and B.

A

B

[ 2 ]

Question (iii)

(iii)

State what happens to the oxygen produced by process A.

[ 1 ]

Question (iv)

(iv)

Name the primary pigment in photosystem I and photosystem II.

[ 1 ]

Question (v)

(v)

Name two compounds shown in Fig. 7.1 that are used in the conversion of glycerate-3-phosphate (GP) to triose phosphate (TP) in the Calvin cycle.

[ 1 ]

Question (b)

(b)

Outline the uses of triose phosphate in the mesophyll cells of the leaf.

[ 3 ]
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