13.1. Photosynthesis as an energy transfer process
A subsection of Biology, 9700, through 13. Photosynthesis
Listing 10 of 108 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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In eukaryotes, the cells of plants and photosynthetic protoctists contain chloroplasts. Describe the relationship between the function of a chloroplast and its structure. Outline the main features of cyclic photophosphorylation. Red algae are aquatic protoctists that are multicellular. The cells of red algae have chloroplasts containing photosynthetic pigments. Many red algae live in deep water. Two of the accessory pigments of red algae chloroplasts are: • phycoerythrin (appears red), often present in large concentrations • phycocyanin (appears blue). The first few metres of water nearest the surface absorb the red wavelengths of light. If the water also contains particles of organic material it absorbs blue wavelengths. shows absorption spectra of some pigments in red algae chloroplasts. chlorophyll a Key phycoerythrin phycocyanin percentage light absorption red yellow green blue violet wavelength of light / nm
9700_s22_qp_41
THEORY
2022
Paper 4, Variant 1
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Questions Discovered
108