13. Photosynthesis
A section of Biology, 9700
Listing 10 of 183 questions
shows part of a section through the leaf of a C4 plant such as maize. The letters A, B and C show three types of cell found in the leaf. stoma A B C Complete Table 7.1 by using the letters A, B or C from to show the location of several compounds associated with photosynthesis in C4 plants. You may use A, B and C once, more than once, or not at all. Table 7.1 compound location PEP carboxylase RuBP rubisco Explain why the cells in C form a tight ring around the cells in B. Several enzymes have a role in the light independent stage of photosynthesis. shows the activity of one of these enzymes at different temperatures for a C3 plant, Pisum sativum, and a C4 plant, Amaranthus hypochondriacus. temperature / °C percentage of enzyme activity Amaranthus hypochondriacus C4 Pisum sativum C3 Describe the differences between the two curves and suggest explanations for these differences.
9700_s18_qp_42
THEORY
2018
Paper 4, Variant 2
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Structures, processes and compounds involved in photosynthesis in C4 plants include: A – carbon dioxide H – mesophyll cells B – phosphorylation I – guard cells C – palisade cells J – photorespiration D – PEP carboxylase K – photolysis E – rubisco L – oxaloacetate F – malate M – ATP synthase G – RuBP N – chlorophyll Complete Table 7.1 by matching each description with one letter chosen from A to N to show the correct structure, process or compound. You may use each number once, more than once or not at all. Table 7.1 description letter enzyme with a high optimum temperature enzyme in bundle sheath cells process that slows down the rate of photosynthesis compound that releases carbon dioxide into bundle sheath cells cells that stop oxygen reaching bundle sheath cells Some plants, such as rice, are adapted to grow when partially submerged in water. Describe and explain the adaptations that allow rice plants to survive in waterlogged fields.
9700_s20_qp_41
THEORY
2020
Paper 4, Variant 1
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Photosynthesis is a complex process involving a light dependent stage and a light independent stage. Name the products of the light dependent stage that are needed in the light independent stage. Describe the role of chlorophyll b in photosynthesis. A student carried out an experiment to investigate the effect of light intensity and light wavelength on the rate of photosynthesis. • An aquatic plant, Elodea canadensis, was put into a beaker containing sodium hydrogencarbonate solution as a source of carbon dioxide. • To minimise changes in temperature, an LED lamp was used as a source of light. • The lamp was switched on and the number of bubbles released by the aquatic plant in 1 minute was counted. • The lamp was placed at seven different distances from the beaker to change light intensity. • Five replicates were carried out at each lamp distance. • All other variables were controlled. The student calculated the light intensity for each distance using 1 d 2. Table 5.1 shows the calculated light intensities for each distance. Table 5.1 distance between plant and lamp / m light intensity / 1 d 2 0.025 0.050 0.100 0.150 0.200 0.250 0.300 Complete Table 5.1 by calculating the light intensity for distance 0.100 m. At each distance from the lamp, the experiment was repeated using a red filter in front of the lamp to give a different wavelength of light. The experiment was repeated using a blue filter and then using a green filter. Each filter transmitted the same light intensity. The student calculated the mean rate of bubble production as a measure of the rate of photosynthesis. shows a graph of the results. 800 1000 1200 1400 1600 rate of photosynthesis / bubbles min–1 light intensity green light blue light red light white light Key: With reference to : • state the range over which light intensity is the limiting factor • explain why light intensity above this range is not limiting the rate of photosynthesis. At a light intensity of 1600, explain why different colour filters result in different rates of photosynthesis.
9700_s21_qp_42
THEORY
2021
Paper 4, Variant 2
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is a diagram of a chloroplast. N M L K Using the letters K–N, complete Table 8.1. Each letter may be used once, more than once, or not at all. Table 8.1 letter high concentration of protons location of photosynthetic pigments site of light-independent stage site of light-dependent stage Chlorophyll a is the main photosynthetic pigment in plants. Describe the role of other photosynthetic pigments found in plant chloroplasts. The absorption of different wavelengths of light by chloroplast pigments can be represented by an absorption spectrum. is an absorption spectrum of an extract of chloroplast pigments and an absorption spectrum of whole chloroplasts. wavelength / nm absorbance / arbitrary units pigment extract whole chloroplasts With reference to , describe the differences between the two spectra and suggest explanations for the differences.
9700_s23_qp_43
THEORY
2023
Paper 4, Variant 3
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Use In the majority of plants the leaf is the main photosynthetic organ. List four ways in which the structure of a dicotyledonous leaf is adapted for gas exchange. In an experiment to investigate the effect of light intensity on the rate of photosynthesis, the following procedure was carried out. ● Discs were cut, using a cork borer, from the photosynthetic tissue of the brown alga, Fucus serratus, a common seaweed of rocky shores. ● Ten discs were placed in each of four beakers containing 50 cm3 of sea water. The discs are denser than sea water and therefore initially sink to the bottom of the beaker. ● Each beaker was illuminated with a bench lamp placed at different distances, d, from the beaker. ● With time the discs began to rise to the surface of the water. ● The time, t, in minutes, at which the fifth disc from each batch reached the surface was recorded. ● The rate of photosynthesis was determined by calculating 1000 / t. A student’s set of results is shown in Table 8.1. Table 8.1 distance of beaker from lamp, d / cm light intensity 1 / d 2 time for fifth disc to reach the surface t / min rate of photosynthesis 1000 / t 0.04 43.5 0.01 27.8 0.004 19.2 11.4 Examiner’s Use Calculate the value for light intensity when the distance between beaker and lamp was 20 cm. Record the value in the space in Table 8.1. Explain why the discs rise to the surface after being illuminated for a length of time. Using the data in Table 8.1, describe the relationship between light intensity and the rate of photosynthesis. The student found that there was no increase in the rate of photosynthesis when two lamps were placed 5 cm from the beaker. Suggest why there was no increase in the rate of photosynthesis.
9700_w09_qp_42
THEORY
2009
Paper 4, Variant 2
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An experiment was carried out into the effect of light of different colours on photosynthesis. • 15 leaf discs from the same plant were obtained. • Five sealed test-tubes were set up, each containing three leaf discs in hydrogencarbonate indicator solution. • Hydrogencarbonate indicator solution changes colour at different pH values. • At the start of the experiment the indicator solution in all five test-tubes was orange- red. • Four of the test-tubes were illuminated by light of a specific colour. • The test-tubes were illuminated for the same length of time. • The fifth test-tube was covered in black paper and was a control. The results are recorded in Table 7.1. Table 7.1 colour of light final colour of hydrogencarbonate solution white purple blue purple green orange-yellow red purple control – no light yellow When the pH increases, the indicator becomes purple and when the pH decreases, the indicator turns yellow. Explain the results for the leaf discs illuminated by blue light. Explain why the indicator in the control went yellow. Cyclic and non-cyclic photophosphorylation take place in the light-dependent stage of photosynthesis. Describe the role of accessory pigments in photophosphorylation. Write a balanced equation that summarises photolysis. State precisely the location of photosynthetic pigments within a chloroplast.
9700_w13_qp_41
THEORY
2013
Paper 4, Variant 1
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An experiment was carried out into the effect of light of different colours on photosynthesis. • 15 leaf discs from the same plant were obtained. • Five sealed test-tubes were set up, each containing three leaf discs in hydrogencarbonate indicator solution. • Hydrogencarbonate indicator solution changes colour at different pH values. • At the start of the experiment the indicator solution in all five test-tubes was orange- red. • Four of the test-tubes were illuminated by light of a specific colour. • The test-tubes were illuminated for the same length of time. • The fifth test-tube was covered in black paper and was a control. The results are recorded in Table 7.1. Table 7.1 colour of light final colour of hydrogencarbonate solution white purple blue purple green orange-yellow red purple control – no light yellow When the pH increases, the indicator becomes purple and when the pH decreases, the indicator turns yellow. Explain the results for the leaf discs illuminated by blue light. Explain why the indicator in the control went yellow. Cyclic and non-cyclic photophosphorylation take place in the light-dependent stage of photosynthesis. Describe the role of accessory pigments in photophosphorylation. Write a balanced equation that summarises photolysis. State precisely the location of photosynthetic pigments within a chloroplast.
9700_w13_qp_42
THEORY
2013
Paper 4, Variant 2
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One way to estimate the rate of photosynthesis is to measure the rate of uptake of carbon dioxide. shows the relationship between light intensity and relative carbon dioxide uptake and production in a dicotyledonous plant. carbon dioxide uptake State two features of a dicotyledonous leaf that can affect the rate of photosynthesis. Explain the shape of the curve as light intensity increases from 0 to X. The uptake of radioactively-labelled carbon dioxide in chloroplasts was investigated. Three tubes, each containing different components of chloroplasts, were exposed to light. The results of the investigation are shown in Table 7.1. Table 7.1 tube contents uptake of radioactively- labelled carbon dioxide / counts per minute A stroma and grana 96 000 B stroma, ATP and reduced NADP 97 000 C stroma 4 000 Name the substance that combines with carbon dioxide in a chloroplast. Explain why the results in tube B are similar to those in tube A. Explain why the uptake in tube C was less than the uptake in tube B. Complete the following paragraph by using the most suitable words to fill in the gaps. In a photosystem, several hundred accessory pigment molecules surround a primary pigment molecule, called , in the membrane. The position of the primary pigment is also called the . Light energy is absorbed by the accessory pigments and passed on to the primary pigment. Electrons are excited to a higher energy level. They are emitted from the primary pigment and are captured by electron acceptors and eventually pass along the , producing ATP.
9700_w15_qp_41
THEORY
2015
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One way to estimate the rate of photosynthesis is to measure the rate of uptake of carbon dioxide. shows the relationship between light intensity and relative carbon dioxide uptake and production in a dicotyledonous plant. carbon dioxide uptake State two features of a dicotyledonous leaf that can affect the rate of photosynthesis. Explain the shape of the curve as light intensity increases from 0 to X. The uptake of radioactively-labelled carbon dioxide in chloroplasts was investigated. Three tubes, each containing different components of chloroplasts, were exposed to light. The results of the investigation are shown in Table 7.1. Table 7.1 tube contents uptake of radioactively- labelled carbon dioxide / counts per minute A stroma and grana 96 000 B stroma, ATP and reduced NADP 97 000 C stroma 4 000 Name the substance that combines with carbon dioxide in a chloroplast. Explain why the results in tube B are similar to those in tube A. Explain why the uptake in tube C was less than the uptake in tube B. Complete the following paragraph by using the most suitable words to fill in the gaps. In a photosystem, several hundred accessory pigment molecules surround a primary pigment molecule, called , in the membrane. The position of the primary pigment is also called the . Light energy is absorbed by the accessory pigments and passed on to the primary pigment. Electrons are excited to a higher energy level. They are emitted from the primary pigment and are captured by electron acceptors and eventually pass along the , producing ATP.
9700_w15_qp_42
THEORY
2015
Paper 4, Variant 2
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The light dependent stage of photosynthesis in a suspension of isolated chloroplasts can be investigated using the Hill reaction. Dichlorophenolindophenol (DCPIP) can be used to follow the process. DCPIP is a blue dye which turns colourless when it is reduced by accepting hydrogen and electrons. oxidised DCPIP reduced DCPIP blue colourless DCPIP is an artificial hydrogen acceptor that can be used in the Hill reaction. Name the natural hydrogen acceptor found in chloroplasts that is replaced by DCPIP in the Hill reaction. Outline the way in which hydrogen is made available to reduce the hydrogen acceptor in the light dependent stage of photosynthesis. A suspension of isolated chloroplasts for measuring the rate of the Hill reaction can be prepared by carrying out the following steps: • prepare buffer solution with the same water potential as the stroma of chloroplasts • liquidise spinach leaves in ice cold buffer solution • filter the liquid and obtain the filtrate • centrifuge the filtrate to obtain a pellet of chloroplasts • add the chloroplast pellet to fresh buffer solution in a beaker and mix to obtain a suspension. Explain the reason for: keeping the temperature very low using a buffer solution using a solution of the same water potential as the stroma of chloroplasts. An experiment was carried out to measure the time taken for decolourisation of DCPIP mixed with a suspension of chloroplasts. The results are shown in Table 2.1. Table 2.1 replicate time taken for DCPIP to decolourise / s rate / s–1 mean Complete Table 2.1 by calculating: for the three replicates, the mean time taken for the DCPIP to decolourise the mean rate using the formula: rate = 1000 t where t = time in seconds. The time taken to decolourise DCPIP was measured at a range of light intensities. State and explain the expected relationship between light intensity and time taken to decolourise DCPIP. expected relationship explanation
9700_w17_qp_42
THEORY
2017
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Questions Discovered
183