13. Photosynthesis
A section of Biology, 9700
Listing 10 of 183 questions
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 The natural hydrogen acceptor in chloroplasts that is replaced by DCPIP in the Hill reaction is NADP. Reduced NADP is then used in the light independent stage of photosynthesis. State the role of reduced NADP in the light independent stage. Predict and explain the effect on the concentration of RuBP in the chloroplasts if DCPIP becomes reduced instead of NADP. Explain the reasons for: the colour standard tube A covering the beaker containing the chloroplast-DCPIP mixture with foil. Table 2.1 shows the results of the experiment. Table 2.1 colour of filter wavelength of light / nm time taken to decolourise DCPIP / s rate of light dependent stage of photosynthesis / s–1 purple 27.0 blue 11.9 green 2.1 orange red 20.0 Complete Table 2.1 by calculating the rate of the light dependent stage of photosynthesis for the orange wavelength, using the formula: rate = 1000 t where t = time in seconds. With reference to Table 2.1, describe and explain the effect of light wavelength on the rate of the light dependent stage of photosynthesis.
9700_w17_qp_41
THEORY
2017
Paper 4, Variant 1
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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 The natural hydrogen acceptor in chloroplasts that is replaced by DCPIP in the Hill reaction is NADP. Reduced NADP is then used in the light independent stage of photosynthesis. State the role of reduced NADP in the light independent stage. Predict and explain the effect on the concentration of RuBP in the chloroplasts if DCPIP becomes reduced instead of NADP. Explain the reasons for: the colour standard tube A covering the beaker containing the chloroplast-DCPIP mixture with foil. Table 2.1 shows the results of the experiment. Table 2.1 colour of filter wavelength of light / nm time taken to decolourise DCPIP / s rate of light dependent stage of photosynthesis / s–1 purple 27.0 blue 11.9 green 2.1 orange red 20.0 Complete Table 2.1 by calculating the rate of the light dependent stage of photosynthesis for the orange wavelength, using the formula: rate = 1000 t where t = time in seconds. With reference to Table 2.1, describe and explain the effect of light wavelength on the rate of the light dependent stage of photosynthesis.
9700_w17_qp_43
THEORY
2017
Paper 4, Variant 3
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Non-cyclic photophosphorylation occurs in the light-dependent stage of photosynthesis. Outline the main features of non-cyclic photophosphorylation. Some Calvin cycle intermediates are used to produce other molecules that are not part of the Calvin cycle. Name two of these intermediates. For each intermediate, state one example of the type of molecule that is produced. intermediate molecule produced intermediate molecule produced shows how the rate of uptake of carbon dioxide by a plant varies with temperature, at an optimum intensity of light on a clear day. rate of uptake of carbon dioxide / arbitrary units temperature / °C Calculate the mean increase in rate of uptake of carbon dioxide as the temperature increases from 5 °C to 20 °C. Show your working. Give your answer to two decimal places. au °C–1 Suggest why the rate of carbon dioxide uptake levels off and then decreases after 20 °C. On , draw a curve to show the uptake of carbon dioxide on a cloudy day.
9700_w23_qp_42
THEORY
2023
Paper 4, Variant 2
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The effect of light intensity on the rate of photosynthesis can be investigated using a cut shoot of a pond plant. The apparatus used in the investigation is shown in . gas collects here test-tube water containing sodium hydrogencarbonate pond plant syringe air bubble in capillary tube scale in cm lamp X The light intensity can be changed by placing the lamp at different distances from the pond plant. Apparatus X, shown in , is a thin glass container filled with water. Explain the function of apparatus X. Before completing the assembly of the apparatus shown in , sodium hydrogencarbonate is added to the water surrounding the pond plant in the test-tube. Explain why sodium hydrogencarbonate is added to the water surrounding the pond plant in the test-tube. Name the gas collected in the test-tube. The investigation was carried out with the lamp at distances of 10, 20, 30, 40 and 50 cm from the pond plant. For each of these distances, the air bubble in the capillary tube was initially positioned at 0 cm on the scale and, after 5 minutes, the distance moved by the air bubble was measured. The rate of movement of the air bubble was then calculated. The results are shown in . rate of movement of air bubble / cm min–1 0.0 0.5 1.0 1.5 2.0 distance of lamp from pond plant / cm With reference to , describe the relationship between the rate of photosynthesis and light intensity. Further investigations showed that at distances of less than 10 cm, the rate of movement of the air bubble was the same as at 10 cm. Explain why there was no change in the rate of movement of the air bubble at distances less than 10 cm. Some of the light energy absorbed by the pond plant is used in cyclic photophosphorylation. Outline the process of cyclic photophosphorylation.
9700_m19_qp_42
THEORY
2019
Paper 4, Variant 2
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Describe the functions of the internal membranes of the chloroplast in photosynthesis. Rubisco activase (RA) is an enzyme that has an effect on the activity of rubisco. An investigation was carried out on the effect of RA on the activity of rubisco. • Solutions of rubisco and RuBP were added to two tubes, A and B. • RA was added to tube A. • Both tubes were incubated at 25 °C for 6 minutes. • The activity of rubisco was measured every 30 seconds. All conditions were kept the same, except for the addition of RA to tube A. The results are shown in . time / min rubisco activity / arbitrary units A B Describe the results shown in and suggest an explanation for the effect of RA on the activity of rubisco.
9700_m23_qp_42
THEORY
2023
Paper 4, Variant 2
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The light-dependent stage of photosynthesis occurs within chloroplasts. In this stage, electrons are emitted from the chlorophyll a molecules and passed to electron acceptors. If a redox indicator, such as DCPIP, is added to a suspension of illuminated chloroplasts, electrons will be transferred to DCPIP, causing the colour of the DCPIP to change from blue to colourless. A student investigated the effect of the wavelength of light (colour of light) on the rate of photosynthesis. • DCPIP was added to three colorimeter tubes, each containing a suspension of chloroplasts. The chloroplast suspensions were kept in the dark until required. • The colorimeter tubes were each exposed to light of a different colour: red, blue or green. The intensity of light was the same for all tubes, and each was exposed to light for four minutes. All other conditions were kept the same. • The absorbance of each chloroplast suspension was measured at one-minute intervals using a colorimeter. The results are shown in . 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 absorbance time / min green light blue light red light Explain why the chloroplast suspensions were kept in the dark until required. Describe the results shown in . With reference to the light-dependent stage of photosynthesis, explain the differences between the results shown in for red light and for green light. Changes in the atmospheric carbon dioxide concentration, light intensity and temperature can affect the rate of photosynthesis. These three factors directly affect different processes of photosynthesis. Complete Table 7.1 using a tick (3) to identify the processes that can be directly affected by each factor or a cross (7) to identify the processes that are not directly affected by each factor. Indirect effects where a change in the rate of one process affects the rate of a different process should not be considered. A tick or a cross must be placed in the final column of every row. Table 7.1 factor process 3 or 7 carbon dioxide concentration Calvin cycle photophosphorylation light intensity Calvin cycle photophosphorylation temperature Calvin cycle photophosphorylation
9700_m24_qp_42
THEORY
2024
Paper 4, Variant 2
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An absorption spectrum is a graph of the absorption of different wavelengths of light by a photosynthetic pigment. An action spectrum is a graph of the rate of photosynthesis at different wavelengths of light. shows the absorption spectra of chlorophyll a and chlorophyll b as well as an action spectrum. wavelength of light / nm rate of photosynthesis percentage light absorption action spectrum chlorophyll b chlorophyll a With reference to , compare the absorption spectra of chlorophyll a and chlorophyll b, explain the shape of the action spectrum, explain why plants appear green . is an electron micrograph showing a section through part of a chloroplast. On , draw label lines and use the letters W and Y to identify the following structures: • W where the light-independent reactions occur • Y where chlorophyll is found Explain why increasing the concentration of carbon dioxide may increase the rate of production of carbohydrates at high light intensities.
9700_s08_qp_4
THEORY
2008
Paper 4, Variant 0
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outlines the process of non-cyclic photophosphorylation in the chloroplast of a leaf mesophyll cell. light energy light energy process A H2O light energy photosystem II photosystem I NADP reductase NADP reduced NADP process B ATP 2e– 2e– 2e– 2e– 2e– 2e– 2e– 2H+ O2 electron carriers electron carriers State precisely where non-cyclic photophosphorylation occurs in the chloroplast. With reference to , name processes A and B. A B State what happens to the oxygen produced by process A. Name the primary pigment in photosystem I and photosystem II. Name two compounds shown in that are used in the conversion of glycerate-3-phosphate (GP) to triose phosphate (TP) in the Calvin cycle. Outline the uses of triose phosphate in the mesophyll cells of the leaf.
9700_s18_qp_41
THEORY
2018
Paper 4, Variant 1
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Questions Discovered
183