6.1. Photosynthesis
A subsection of Biology, 0610, through 6. Plant nutrition
Listing 10 of 307 questions
shows a diagram of a leaf. H G • The part of the leaf labelled G contains no chlorophyll and is a white colour. • The part of the leaf labelled H contains chlorophyll and is a green colour. Glucose produced during photosynthesis is stored in the leaf as starch. The leaf was boiled in ethanol to remove the chlorophyll. The leaf was then tested for the presence of starch with iodine solution. Predict the colour of the part of the leaf labelled G after iodine solution has been added. Predict the colour of the part of the leaf labelled H after iodine solution has been added. State a conclusion about chlorophyll from this investigation. A similar leaf was kept in the dark for 24 hours and then tested for the presence of starch. The leaf contained no starch. Explain why the leaf contained no starch. Water is required for the process of photosynthesis. Describe where and how water enters a plant. Describe one function of water in a plant other than for photosynthesis. State the name of the tissue in a plant that transports water. State the name of the part of a leaf through which water vapour is lost from the plant.
0610_s18_qp_32
THEORY
2018
Paper 3, Variant 2
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shows part of the carbon cycle. carbon dioxide in the atmosphere carbon dioxide in the atmosphere carbon compounds in animals B C C A carbon compounds in limestone rock carbon compounds in plants carbon compounds in coal Identify the processes shown by arrows A, B and C on . Choose words from the list. combustion decomposition excretion feeding fossilisation process A process B process C On draw one arrow to represent photosynthesis. Label this arrow with a letter D. On draw one arrow to represent respiration. Label this arrow with a letter E. The concentration of carbon dioxide in the atmosphere is increasing. Describe two possible causes of the increased carbon dioxide concentration in the atmosphere. State two adverse effects of the increase in carbon dioxide concentration in the atmosphere. Carbon dioxide is a greenhouse gas. State the name of one other greenhouse gas.
0610_s18_qp_33
THEORY
2018
Paper 3, Variant 3
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The rate of photosynthesis of terrestrial plants can be determined by measuring the uptake of carbon dioxide. Explain why plants take up carbon dioxide during photosynthesis. The rate of photosynthesis of parts of individual leaves can be measured using a hand-held device as shown in . transparent chamber This apparatus allows air to flow through the transparent chamber that encloses part of the leaf. The apparatus measures the carbon dioxide concentration of the air entering and leaving the chamber. Explain how the results from the apparatus can be used to calculate the rate of photosynthesis. A student used the apparatus shown in to investigate the effect of temperature on the rate of photosynthesis of the leaves of Chinese plantain, Plantago asiatica, at two different concentrations of carbon dioxide, A and B. shows the results of the investigation. rate of photosynthesis / μmol per m2 per s temperature of leaves / °C B A 370 ppm CO2 1000 ppm CO2 370 ppm CO2 1000 ppm CO2 B A State one environmental factor that should have been kept constant in this investigation. Describe the effect of temperature on the rate of photosynthesis when carbon dioxide concentration A was supplied. Use the data from in your answer. Calculate the percentage increase in the rate of photosynthesis at 30 °C when the carbon dioxide concentration was increased from A to B as shown in . Show your working and give your answer to the nearest whole number. % Explain the effect of increasing temperature on the rate of photosynthesis for carbon dioxide concentration B. Use the term limiting factor in your answer. The student concluded that carbon dioxide concentration is the factor limiting the rate of photosynthesis between 30 °C and 35 °C for the results shown for A in . State the evidence for this conclusion. A similar investigation was carried out on Arizona honeysweet, Tidestromia oblongifolia, that grows in Death Valley in California where the highest temperatures may be greater than 45 °C. The results are shown in . rate of photosynthesis / μmol per m2 per s temperature of leaves / °C Predict and explain what would happen to the rate of photosynthesis if the investigation is continued at temperatures higher than 45 °C.
0610_s19_qp_41
THEORY
2019
Paper 4, Variant 1
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The concentration of atmospheric carbon dioxide has increased considerably in recent years. Describe the possible causes of increased atmospheric carbon dioxide. Soybean plants, Glycine max, were grown in two separate plots. Each plot used a carbon dioxide enrichment system to control the atmospheric carbon dioxide concentration. The atmospheric carbon dioxide concentrations in the two plots were kept at: • 370 ppm, which is similar to the current atmospheric carbon dioxide concentration • 550 ppm, which is a possible future atmospheric carbon dioxide concentration. When the soybean plants were fully grown, scientists calculated the average rates of photosynthesis at regular intervals from 04:00 to 22:00 for both plots. The results are shown in . average rates of photosynthesis / μmol per m2 per s 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 time of day 550 ppm CO2 370 ppm CO2 550 ppm CO2 370 ppm CO2 The scientists also made observations of the leaf structure of the soybean plants. Epidermis and mesophyll tissues are adapted for photosynthesis. Complete Table 2.1 by stating two structural features of each of these tissues and explain how each feature is an adaptation for photosynthesis. Table 2.1 tissue feature how the feature is an adaptation for photosynthesis epidermis mesophyll When the scientists were working in the plot with a carbon dioxide concentration of 550 ppm, their breathing rates were higher than when they worked in the other plot. Suggest why their breathing rates were higher.
0610_s19_qp_42
THEORY
2019
Paper 4, Variant 2
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Scientists measured the rate of photosynthesis in the leaves of a sunflower plant, Helianthus annuus. The scientists used the apparatus shown in to measure the rate of photosynthesis. temperature 20 °C air flow regulator chamber 1 chamber 2 chamber 3 direction of air flow timer 00:00 CO2 400 ppm CO2 360 ppm The apparatus in maintains a constant temperature and a constant humidity. Explain why temperature has an effect on the rate of photosynthesis. Explain why the rate of photosynthesis will decrease if the humidity in the apparatus becomes very low. The apparatus was left for 15 minutes. Explain how the scientists would use the readings for the concentration of carbon dioxide in chambers 1 and 3 to calculate the rate of photosynthesis. The scientists carried out another investigation using the same apparatus at different temperatures. They measured the rate of uptake of carbon dioxide in the light and then they measured the rate of release of carbon dioxide in the dark. The results are shown in . temperature / °C rate of carbon dioxide uptake and release / μg per hour per cm2 of leaf CO2 release in the dark CO2 uptake in the light Use the information in to complete Table 3.1. Table 3.1 temperature / °C rate of uptake of carbon dioxide in the light / μg per hour per cm2 of leaf rate of release of carbon dioxide in the dark / μg per hour per cm2 of leaf The scientists determined that photosynthesis in the leaves at 35 °C used carbon dioxide at a rate of 135 μg per hour per cm2 of leaf. shows that the rate of carbon dioxide uptake at 35 °C was 90 μg per hour per cm2 of leaf. Explain why the rate at which carbon dioxide is used in photosynthesis is greater than the rate of carbon dioxide uptake. Explain why the results in Table 3.1 are expressed as ‘per cm2 of leaf’ rather than ‘per leaf’. Some crops are grown in controlled environments. Glasshouses are an example of a controlled environment. shows a glasshouse where lettuces are growing. Discuss the advantages of growing crops in glasshouses.
0610_s21_qp_43
THEORY
2021
Paper 4, Variant 3
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Glasshouses are designed to maximise crop plant yield. Explain why carbon dioxide enrichment is used in many glasshouses to increase crop plant yield. Suggest how the carbon dioxide concentration in a glasshouse can be enriched. Outline how carbon dioxide in a glasshouse moves into leaves. Additional lighting is often installed in glasshouses in countries with temperate climates. Table 5.1 summarises some of the factors that are considered by plant growers when choosing the type of lamps to install in a glasshouse. Table 5.1 type of lamp electrical energy used by the lamp / J per s light intensity output / arbitrary units notes sodium • releases lots of heat • best when used in addition to sunlight LED • releases very little heat • can be used as an alternative to sunlight metal halide • releases some heat • can be used as an alternative to sunlight fluorescent • releases some heat • best when used in addition to sunlight Calculate the percentage increase in the energy used by the metal halide lamp compared to the energy used by the fluorescent lamp. Give your answer to two significant figures. Space for working. % State which type of lamp has the highest light intensity output per unit of electrical energy used. Some types of lamp release a lot of heat. Explain the possible effects of excessive heat on the plants in a glasshouse.
0610_s22_qp_43
THEORY
2022
Paper 4, Variant 3
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Questions Discovered
307