13. Photosynthesis
A section of Biology, 9700
Listing 10 of 183 questions
is an electron micrograph of a chloroplast from a maize leaf cell. X Y Z Indicate below which of X, Y or Z contains: transport proteins pigments A chloroplast also contains DNA. Suggest the functions of DNA in this organelle. Changes in the atmospheric carbon dioxide concentration, light intensity and temperature alter the rate of photosynthesis. These three factors directly affect different stages of photosynthesis. Complete the table below using a tick (✓) if the factor directly affects the stage or a cross (✗) if it does not affect the stage. factor stage ✓ or ✗ carbon dioxide concentration Calvin cycle photolysis light intensity Calvin cycle photolysis temperature Calvin cycle photolysis
9700_s14_qp_42
THEORY
2014
Paper 4, Variant 2
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shows an electronmicrograph of a chloroplast. On , use label lines and letters to label one place where: L – the light-dependent stage takes place R – the enzyme rubisco is found. Chloroplasts can move within palisade cells. Suggest two advantages of chloroplast movement within palisade cells. Complete the following paragraph by naming the most suitable compounds to fill in the gaps. Rubisco is involved in the fixation of by RuBP (ribulose bisphosphate) in the Calvin cycle. The resulting six carbon compound immediately splits to give two molecules of glycerate-3-phosphate (GP). GP is converted to triose phosphate (TP) using and produced in the light-dependent stage. Some of the TP produced is used to regenerate ribulose bisphosphate so that the Calvin cycle can continue. The remaining TP may be used to synthesise other compounds including which can directly enter the Krebs cycle.
9700_s15_qp_42
THEORY
2015
Paper 4, Variant 2
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Chloroplasts belong to a group of organelles called plastids. Although different types of plastid have different structures and functions, one type of plastid can change into another type of plastid in response to environmental or developmental signals. • Example 1: plants grown in the dark have plastids called etioplasts which lack chlorophyll. If these plants are exposed to light, the etioplasts quickly change into chloroplasts. • Example 2: chloroplasts in surface tissues of tomato fruits change into plastids called chromoplasts as the fruits ripen. Thylakoid membranes break down and chlorophyll synthesis stops. Chromoplasts synthesise and accumulate red lycopene and orange β-carotene pigments. For each of these examples, explain the effect on the rate of photosynthesis of one type of plastid changing into another type of plastid. Example 1 Example 2 Outline the method you would use to separate and identify the pigments in an extract of tomato chromoplasts. Cyanobacteria are prokaryotic organisms. Plastids are thought to have evolved from cyanobacteria that became incorporated into larger cells. Experiments show that free-living cyanobacteria can adapt to environmental signals in the same way as plastids. shows the absorption spectra of cyanobacteria grown under two different lighting conditions. One group was grown under fluorescent light and the other group was grown under red light. The range of light wavelengths absorbed by each group of cyanobacteria was then measured under identical lighting conditions. 0.0 0.2 0.4 0.6 0.8 absorbance 1.0 light wavelength / nm fluorescent light Key: red light With reference to and the information given on pages 4 and 5, explain the effect of different lighting conditions on the absorption spectra of the two groups of cyanobacteria.
9700_s17_qp_42
THEORY
2017
Paper 4, Variant 2
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is a transmission electron micrograph of part of a chloroplast of a leaf cell from maize. A B Table 7.1 shows some substrates and products involved in photosynthesis. Use letter A or letter B from to complete Table 7.1 to show the location where the substrates or products are used or produced. Table 7.1 substrate or product location oxygen produced ………… carbon dioxide used ………… reduced NADP used ………… ATP produced ………… hexose produced ………… 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. Table 7.2 test- tube contents conditions colour change buffer solution + DCPIP light no chloroplast suspension + DCPIP light yes chloroplast suspension + DCPIP dark no Explain the results for test-tube 2. Test-tube 1 is a control tube. Explain why test-tube 1 was included in the investigation. Suggest and explain what would happen to the chloroplasts if they were suspended in distilled water. 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
9700_s18_qp_43
THEORY
2018
Paper 4, Variant 3
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Questions Discovered
183