Practise chloroplast adaptations, pigment spectra, light-dependent reactions and the Calvin cycle while analysing chromatography, limiting factors and rate investigations.
Photosynthesis is an energy transfer process that takes place in chloroplasts of plant cells.
Fig. 3.1 shows a diagram of a chloroplast.
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.
Explain how grana are adapted for their specific role in photosynthesis.
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
Discuss how the results in Fig. 3.2 support that chemiosmosis occurs during photophosphorylation.
Fig. 4.1 shows a diagram of a stoma, its guard cells and adjacent epidermal cells.
Fig. 4.1
The following experiment was carried out to investigate the effect of light intensity on the rate of photosynthesis of a water plant, Elodea.
- Elodea was cut into three pieces, each 10 cm long.
- Each piece of Elodea was placed in a glass tube, containing 0.5 % sodium hydrogen carbonate solution, which was then sealed with a bung.
- Tube A was placed 10 cm away from a lamp.
- Tube B was placed 5 cm away from a lamp.
- Tube C was placed in a dark room.
- An oxygen sensor was used to measure the percentage of oxygen in the solutions at the start of the experiment and again at 5,10 and 20 minutes.
The results are shown in Fig. 4.2.
Fig. 4.2
State why sodium hydrogencarbonate solution was used.
Suggest what factor, which may have an effect on the rate of photosynthesis, was not taken into account in this experiment.
Fig. 4.3 shows the relationship between the light dependent and light independent reactions in a chloroplast.
Fig. 4.3
Name substances X and Y in Fig. 4.3.
X
Y
Non-cyclic photophosphorylation occurs in the light-dependent stage of photosynthesis.
Outline the main features of non-cyclic photophosphorylation.
Some Calvin cycle intermediates are used to produce other molecules that are not part of the Calvin cycle.
Name two of these intermediates.
For each intermediate, state one example of the type of molecule that is produced.
intermediate
molecule produced
intermediate
molecule produced
Fig. 8.1 shows how the rate of uptake of carbon dioxide by a plant varies with temperature, at an optimum intensity of light on a clear day.
rate of uptake of carbon dioxide / arbitrary units (au)
Fig. 8.1
Suggest why the rate of carbon dioxide uptake levels off and then decreases after .
On Fig. 8.1, draw a curve to show the uptake of carbon dioxide on a cloudy day.
Fig. 7.1 outlines the process of non-cyclic photophosphorylation in the chloroplast of a leaf mesophyll cell.
Fig. 7.1
State precisely where non-cyclic photophosphorylation occurs in the chloroplast.
With reference to Fig. 7.1, name processes A and B.
A
B
State what happens to the oxygen produced by process A.
Name the primary pigment in photosystem I and photosystem II.
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.
Outline the uses of triose phosphate in the mesophyll cells of the leaf.