A-LevelBiologyPhotosynthesis9700/43 · May/June 2018 · Q710 Marks
Fig. 7.1 is a transmission electron micrograph of part of a chloroplast of a leaf cell from maize. [Figure 7.1] Table 7.1 shows some substrates and products involved in photosynthesis. Use letter A or letter B from [Fig. 7.1] to complete [Table 7.1] to show the location where the substrates or products are used or produced. | substrate or product | location | |:---------------------|:---------| | oxygen produced | | | carbon dioxide used | | | reduced NADP used | | | ATP produced | | | hexose produced | |
- (a)Use letter A or letter B from Fig. 7.1 to complete Table 7.1 to show the location where the substrates or products are used or produced.[3]
- (b)(i)Chloroplasts isolated from leaf palisade cells can still function if they are suspended in a buffer solution. The buffer solution has the same water potential as the chloroplasts. The dye DCPIP is a hydrogen acceptor that changes colour from blue to colourless when it becomes reduced. Three test tubes were set up as shown in Table 7.2 and left for 20 minutes to allow any colour change to occur. The results are also shown in Table 7.2. | test-tube | contents | conditions | colour change | |:----------|:--------------------------|:-----------|:--------------| | 1 | buffer solution + DCPIP | light | no | | 2 | chloroplast suspension + DCPIP | light | yes | | 3 | chloroplast suspension + DCPIP | dark | no | Explain the results for test-tube 2.[2]
- (b)(ii)Test-tube 1 is a control tube. Explain why test-tube 1 was included in the investigation.[1]
- (b)(iii)Suggest and explain what would happen to the chloroplasts if they were suspended in distilled water.[2]
- (c)The rate of photosynthesis in green plants can be limited by factors such as light intensity, temperature and carbon dioxide concentration. State which factor would have no effect on the reducing ability of a chloroplast suspension. Give a reason for your answer. factor ................................................................. reason ......................................................................................................................................................................................................................................................................................................................................................[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.
- 7(a)
- substrate or product | location
- oxygen produced | A
- carbon dioxide used | B
- reduced NADP used | B
- ATP produced | A
- hexose produced | B
- 5 correct = 3 marks
- 3 or 4 correct = 2 marks
- 1 or 2 correct = 1 mark
- 7(b)(i) two from:
- 1 light dependent reaction / photophosphorylation / photolysis occurred ;
- 2 hydrogen, produced / released ; R H+
- 3 DCPIP reduced;
- 7(b)(ii) one from:
- to show that any change in colour is, due to chloroplasts / not due to buffer ;
- to make (the experiment) valid / to act as reference point;
- 7(b)(iii) two from:
- 1 swell / burst / lyse / lysis;
- 2 higher water potential outside chloroplast; ora
- 3 water enters, by osmosis / down water potential gradient;
- 7(c) carbon dioxide concentration;
- not involved in, light dependent reaction / photophosphorylation / photolysis
- or
- only involved in light independent reaction / Calvin Cycle / ora;
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