13. Photosynthesis
A section of Biology, 9700
Listing 10 of 183 questions
Corals grow in shallow seawater. Corals consist of colonies of small animals called polyps. These polyps have photosynthetic protoctists called algae inside their cells, which is advantageous both to the coral polyps and to the algae. The algae that live within the cells of the polyps can also live independently as free-living algae. The rate of photosynthesis of algae that live within the cells of coral polyps is higher than that of free-living algae. Suggest and explain how living inside the cells of coral polyps increases the rate of photosynthesis in these algae compared to free-living algae. The relative abundance of five different chloroplast pigments in the algae of corals was determined. The results are shown in Table 2.1. Table 2.1 chloroplast pigment percentage of total chlorophyll a peridinin chlorophyll c2 dinoxanthin β-carotene Outline the method you would use to separate and identify the pigments present in an extract of these algae. Table 2.2 shows the light wavelengths at which each algal chloroplast pigment shows its two largest peaks of light absorption. Table 2.2 chloroplast pigment peak 1 wavelength / nm peak 2 wavelength / nm chlorophyll a peridinin chlorophyll c2 dinoxanthin β-carotene Corals kept in tanks are often illuminated by lamps radiating mostly violet and blue light with wavelengths in the range of 400–490 nm. With reference to Table 2.1 and Table 2.2, suggest why lamps radiating mostly violet and blue light are expected to increase coral growth.
9700_s17_qp_41
THEORY
2017
Paper 4, Variant 1
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Corals grow in shallow seawater. Corals consist of colonies of small animals called polyps. These polyps have photosynthetic protoctists called algae inside their cells, which is advantageous both to the coral polyps and to the algae. The algae that live within the cells of the polyps can also live independently as free-living algae. The rate of photosynthesis of algae that live within the cells of coral polyps is higher than that of free-living algae. Suggest and explain how living inside the cells of coral polyps increases the rate of photosynthesis in these algae compared to free-living algae. The relative abundance of five different chloroplast pigments in the algae of corals was determined. The results are shown in Table 2.1. Table 2.1 chloroplast pigment percentage of total chlorophyll a peridinin chlorophyll c2 dinoxanthin β-carotene Outline the method you would use to separate and identify the pigments present in an extract of these algae. Table 2.2 shows the light wavelengths at which each algal chloroplast pigment shows its two largest peaks of light absorption. Table 2.2 chloroplast pigment peak 1 wavelength / nm peak 2 wavelength / nm chlorophyll a peridinin chlorophyll c2 dinoxanthin β-carotene Corals kept in tanks are often illuminated by lamps radiating mostly violet and blue light with wavelengths in the range of 400–490 nm. With reference to Table 2.1 and Table 2.2, suggest why lamps radiating mostly violet and blue light are expected to increase coral growth.
9700_s17_qp_43
THEORY
2017
Paper 4, Variant 3
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Photosynthesis is a complex process involving the transfer of light energy into chemical energy. Describe the role of photosynthetic pigments. Name the precise location in a chloroplast of photosynthetic pigments. Name a practical technique to separate photosynthetic pigments. The rate of photosynthesis is affected by many environmental factors. A student carried out an experiment to investigate the relationship between the concentration of carbon dioxide available to an aquatic plant, Cabomba caroliniana, and its rate of photosynthesis. shows the experimental set-up for this investigation. sodium hydrogencarbonate (NaHCO3) solution 15 cm length of C. caroliniana sealed container LED lamp at fixed distance • Sodium hydrogencarbonate solution was used as a source of carbon dioxide. • The concentration of carbon dioxide was varied using six different concentrations of sodium hydrogencarbonate solution. • All C. caroliniana plants were kept in the dark before the light was switched on at the start of the experiment. • Five replicates were carried out at each concentration. • The rate of photosynthesis was obtained by calculating the percentage change in dissolved oxygen concentration in the solution over five minutes. shows the results of the investigation. percentage change in dissolved oxygen –15 –10 –5 0.25 0.00 0.50 0.75 1.00 1.25 concentration of sodium hydrogencarbonate solution / mol dm–3 With reference to , explain the pattern of results obtained between 0.25 mol dm–3 and 1.25 mol dm–3 of sodium hydrogencarbonate solution. The percentage change in dissolved oxygen for C. caroliniana at 0.00 mol dm–3 of sodium hydrogencarbonate solution is negative. Suggest reasons for this negative value. To minimise temperature changes, the student decided to use an LED lamp as a light source. LED lamps release very little heat energy. Explain the importance of minimising temperature changes in this experiment.
9700_s21_qp_41
THEORY
2021
Paper 4, Variant 1
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Use Wheat, maize and sorghum are three of the most important cereal crops in the world. shows the effect of temperature on the rate of photosynthesis of wheat plants. CO2 used per dm2 of leaf per hour / mg temperature / °C With reference to , describe the effect of temperature on the rate of photosynthesis of wheat plants. Suggest why temperature affects the rate of photosynthesis in the way you have described in . Examiner’s Use The conditions in which young plants of wheat and maize are grown affects their ability to photosynthesise at high and low temperatures when they are mature. Young maize and wheat plants were grown to maturity at high and low temperatures. When they were mature, their rate of photosynthesis was measured at different temperatures. The results are shown in . CO2 used per dm2 of leaf per hour / mg maize grown at high temperature wheat grown at low temperature wheat grown at high temperature maize grown at low temperature temperature / °C Examiner’s Use With reference to , compare the effect of temperature on the rate of photosynthesis of maize plants and wheat plants that were grown at a high temperature when they were young. Maize is a C4 plant. Explain how the structure of the leaves of maize plants enables them to photosynthesise more effectively at high temperatures than wheat plants. Low temperatures slow down the formation of the membranes inside chloroplasts in maize leaves, but not in wheat leaves. Use this information to explain the differences between the results for maize and wheat grown at low temperatures, shown in . Examiner’s Use Cereal crops frequently form the staple diet of human populations. Table 5.1 shows the oil and starch content of maize and sorghum grains. Table 5.1 percentage of dry mass maize sorghum oil 4.7 3.8 starch 62.2 70.1 Name the part of the maize grain in which oil and starch are stored. With reference to Table 5.1, compare the energy values of maize and sorghum grains when the oil and starch they contain are used as respiratory substrates.
9700_w07_qp_4
THEORY
2007
Paper 4, Variant 0
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In flowering plants, the light-dependent reactions are carried out by photosynthetic pigments which fall into two categories: primary pigments and accessory pigments. Outline the role played by accessory pigments in the light-dependent reactions. Photosynthetic pigments are arranged in photosystems. There are two photosystems, PS I and PS II. PS I takes part in cyclic photophosphorylation but PS II does not. Outline the differences between cyclic and non-cyclic photophosphorylation. The rate of photosynthesis is affected by several environmental factors. shows the effect of temperature on the rate of photosynthesis. temperature / °C rate of photosynthesis / arbitrary units Explain why the rate of photosynthesis levels out at 30 °C. On continue the curve to indicate what would happen to the rate of photosynthesis if the temperature was increased to 70 °C. Explain why you have continued the curve in this way. A palisade mesophyll cell is adapted to carry out photosynthesis. The table below lists some of the adaptations of a palisade mesophyll cell. Complete the table to show how these adaptations help the cell to carry out photosynthesis. adaptation how the adaptation helps photosynthesis thin cell wall cylindrical shape large vacuole chloroplasts can be moved within the cell
9700_w10_qp_41
THEORY
2010
Paper 4, Variant 1
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In flowering plants, the light-dependent reactions are carried out by photosynthetic pigments which fall into two categories: primary pigments and accessory pigments. Outline the role played by accessory pigments in the light-dependent reactions. Photosynthetic pigments are arranged in photosystems. There are two photosystems, PS I and PS II. PS I takes part in cyclic photophosphorylation but PS II does not. Outline the differences between cyclic and non-cyclic photophosphorylation. The rate of photosynthesis is affected by several environmental factors. shows the effect of temperature on the rate of photosynthesis. temperature / °C rate of photosynthesis / arbitrary units Explain why the rate of photosynthesis levels out at 30 °C. On continue the curve to indicate what would happen to the rate of photosynthesis if the temperature was increased to 70 °C. Explain why you have continued the curve in this way. A palisade mesophyll cell is adapted to carry out photosynthesis. The table below lists some of the adaptations of a palisade mesophyll cell. Complete the table to show how these adaptations help the cell to carry out photosynthesis. adaptation how the adaptation helps photosynthesis thin cell wall cylindrical shape large vacuole chloroplasts can be moved within the cell
9700_w10_qp_42
THEORY
2010
Paper 4, Variant 2
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is a transverse section through a leaf from the maize plant, Zea mays. Maize is a C4 plant. C On , use label lines and letters to show: A – a cell in the epidermal layer B – a cell that contains PEP carboxylase. Identify the cell type labelled C in . C Explain how the leaf anatomy shown in adapts the C4 plant to maintain a high rate of photosynthesis at high temperatures. shows the results of an experiment comparing the rate of carbon dioxide uptake in a C3 plant (Chenopodium album) and a C4 plant (Amaranthus retroflexus) in high and low carbon dioxide (CO2) conditions. The rate of CO2 uptake is used to measure the rate of photosynthesis. temperature / °C rate of CO2 uptake / μmol m–2 s–1 Key C4 plant in high CO2 conditions C4 plant in low CO2 conditions C3 plant in high CO2 conditions C3 plant in low CO2 conditions Using , compare the rates of photosynthesis in high CO2 conditions in the C3 and C4 plants. Using , compare the rates of photosynthesis in low and high CO2 conditions in the C4 plant between 30 °C and 35 °C and suggest an explanation for this difference.
9700_w20_qp_41
THEORY
2020
Paper 4, Variant 1
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is a transverse section through a leaf from the maize plant, Zea mays. Maize is a C4 plant. C On , use label lines and letters to show: A – a cell in the epidermal layer B – a cell that contains PEP carboxylase. Identify the cell type labelled C in . C Explain how the leaf anatomy shown in adapts the C4 plant to maintain a high rate of photosynthesis at high temperatures. shows the results of an experiment comparing the rate of carbon dioxide uptake in a C3 plant (Chenopodium album) and a C4 plant (Amaranthus retroflexus) in high and low carbon dioxide (CO2) conditions. The rate of CO2 uptake is used to measure the rate of photosynthesis. temperature / °C rate of CO2 uptake / μmol m–2 s–1 Key C4 plant in high CO2 conditions C4 plant in low CO2 conditions C3 plant in high CO2 conditions C3 plant in low CO2 conditions Using , compare the rates of photosynthesis in high CO2 conditions in the C3 and C4 plants. Using , compare the rates of photosynthesis in low and high CO2 conditions in the C4 plant between 30 °C and 35 °C and suggest an explanation for this difference.
9700_w20_qp_43
THEORY
2020
Paper 4, Variant 3
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Photosynthesis is a process that results in the synthesis of complex organic molecules. Respiration is a process that involves the breakdown of complex organic molecules. The light dependent stage of photosynthesis involves cyclic and non‑cyclic photophosphorylation. Describe two differences between cyclic and non‑cyclic photophosphorylation. Biochemical processes involving carbon dioxide change the external environment of the aquatic plant, Elodea canadensis, and the pond snail, Lymnaea stagnalis. Carbon dioxide dissolves in water to form carbonic acid. A student set up 8 test‑tubes. Each test‑tube contained 30 cm3 of distilled water containing a pH indicator, bromothymol blue. shows the experimental set up for these 8 test‑tubes. The test‑tubes were left for 12 hours. high light intensity aquatic plant Key: pond snail dark shows how the colour of bromothymol blue changes with pH. blue green yellow increasing pH neutral pH decreasing pH All tubes were green at the start of the experiment. The results of the experiment are shown in Table 5.1. Table 5.1 test‑tube colour after 12 hours green blue yellow green green yellow‑green yellow yellow Explain the purpose of test‑tube 1 and test‑tube 5. Explain the results of test‑tubes 2, 3 and 4. test‑tube 2 test‑tube 3 test‑tube 4 Explain the colour change in test‑tube 6.
9700_s21_qp_43
THEORY
2021
Paper 4, Variant 3
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Photosynthesis is an energy transfer process that results in the production of carbohydrate. It has two stages: the light-dependent stage and the light-independent stage. Cyclic photophosphorylation and non-cyclic photophosphorylation are essential pathways in photosynthesis that occur in the light-dependent stage. Describe the similarities and differences between cyclic photophosphorylation and non-cyclic photophosphorylation. Explain why herbicides that prevent cyclic photophosphorylation and non-cyclic photophosphorylation stop carbohydrate being produced in the chloroplast. The rate of regeneration of RuBP in the Calvin cycle is known to limit the rate of photosynthesis. Sedoheptulose-1,7-bisphosphatase (SBPase) is an enzyme in the Calvin cycle that controls the rate of regeneration of RuBP. SBPase is coded for by the gene SBPase. In an experiment, wheat plants were genetically modified to make more SBPase by introducing the SBPase gene from another grass species, Brachypodium distachyon. The resulting GM wheat plants were named Sox4. • Wild type plants (not GM) and Sox4 plants were grown. • A leaf from the wild type plant was placed in a sealed glass vessel. • The carbon dioxide (CO2) concentration in the vessel was increased so that the intercellular air spaces also had an increase in CO2 concentration. • The other environmental conditions were kept constant. • The rate of fixation of CO2 was measured for the leaf. • The experiment was repeated with a leaf from a Sox4 plant. shows the rate of fixation of CO2 by the leaves of wild type plants and Sox4 plants when the intercellular air space CO2 concentration was increased. 800 1000 CO2 concentration / mg m–3 Sox4 wild type CO2 fixation rate / μmol CO2 m–2 s–1 1200 1400 1600 1800 2000 With reference to , describe and explain the results shown by the wild type plants. With reference to , describe and suggest explanations for the differences in the rate of fixation of CO2 between wild type plants and Sox4 plants.
9700_s22_qp_43
THEORY
2022
Paper 4, Variant 3
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Questions Discovered
183