13. Photosynthesis
A section of Biology, 9700
Listing 10 of 183 questions
Paper chromatography is a technique that can be used to separate and identify different chloroplast pigments. Describe how the results of paper chromatography can be used to identify chloroplast pigments. Carotene and xanthophyll are chloroplast pigments. Describe the role played by these pigments in photosynthesis. The light‑dependent stage of photosynthesis produces ATP and reduced NADP, which are used in the light‑independent stage. Describe the light‑independent stage of photosynthesis.
9700_w24_qp_42
THEORY
2024
Paper 4, Variant 2
View
The rate of photosynthesis is affected by a number of environmental factors. shows the effect of light intensity on the rate of photosynthesis. rate of photosynthesis light intensity C A B State the limiting factor in region A of the graph. Explain what is meant by the term limiting factor. Explain why there is no further increase in the rate of photosynthesis beyond point C. For many plants living in temperate regions, the optimum temperature for photosynthesis is approximately 25 °C. Suggest reasons why the rate of photosynthesis decreases at temperatures above 25 °C.
9700_m16_qp_42
THEORY
2016
Paper 4, Variant 2
View
Red algae are multicellular photosynthetic protoctists that contain phycoerythrin. Phycoerythrin is a photosynthetic pigment. shows: • the absorption spectrum of phycoerythrin • the action spectrum of red algae. wavelength / nm absorption spectrum of phycoerythrin key percentage absorption of light rate of photosynthesis / arbitrary units action spectrum of red algae With reference to , state the wavelength of peak absorption by phycoerythrin. Explain how the data in show that phycoerythrin is not the only photosynthetic pigment in red algae. Phycoerythrin is not the primary pigment (reaction centre pigment) for photosynthesis in red algae. Suggest the role of phycoerythrin in photosynthesis in red algae. Phycoerythrin is rarely found in plants that have green leaves. State the name of a technique that can be used to separate and identify photosynthetic pigments. Explain how the results of this technique would be used to confirm that phycoerythrin is present in red algae and not present in a plant with green leaves.
9700_m21_qp_42
THEORY
2021
Paper 4, Variant 2
View
The eelgrass, Zostera, is a marine plant that forms dense vegetation in shallow coastal waters. The primary consumers in this ecosystem eat the eelgrass and the photosynthetic algae that grow on its surface. shows the flow of energy through an eelgrass ecosystem. The figures in circles represent the energy transfer in kJ m–2 yr–1. carnivorous birds invertebrate predators, e.g. crabs fish 2.5 detritus feeders, suspension feeders, grazers 1.05 x 106 eelgrass and photosynthetic algae sunlight dead plants and animals from other ecosystems Use [T Calculate the percentage of energy transferred from primary consumers to the secondary consumers in the ecosystem shown in . Show your working and express your answer to the nearest whole number. Answer …………………… Explain why little of the energy present in producers is transferred to the secondary consumers. Dead plants contain nitrogen in the form of proteins. These are decomposed by bacteria. Outline how bacteria convert nitrogen in these proteins to a form that may be taken up by living plants.
9700_s05_qp_2
THEORY
2005
Paper 2, Variant 0
View
Use shows the results of experiments investigating the effect of different light intensities on the rate of photosynthesis of cucumber plants measured as mm3 CO2 uptake per cm2 leaf area per hour. The experiments were carried out at two different temperatures and two different carbon dioxide concentrations. light intensity / arbitrary units rate of photosynthesis /mm3 cm-2 h-1 A B C key A 0.04% C02 20°C B 0.04% C02 30°C C 0.13% C02 30°C With reference to , describe the shape of curve A, Examiner’s Use explain the reasons for the difference between curves B and C. Suggest two ways in which a commercial grower of cucumbers may increase the yield of the growing crop.
9700_s06_qp_4
THEORY
2006
Paper 4, Variant 0
View
shows some feeding relationships in an Arctic ecosystem. glaucous gull little auk amphipods herbivorous copepods phytoplankton shrimps squid polar bear ringed seal Arctic fox Arctic cod eider duck bearded seal mussels and snails bottom-dwelling crustaceans decomposing organic matter Using the information shown in , name two organisms that are feeding as secondary consumers; explain why it is difficult to assign some organisms to trophic levels. The efficiency of energy transfer through a trophic level is calculated by comparing the energy available to that trophic level with the energy available to the next trophic level. It has been estimated that the efficiency of energy transfer by herbivorous copepods is about 17%. State two factors that are likely to influence the efficiency of energy transfer by herbivorous copepods.
9700_s08_qp_2
THEORY
2008
Paper 2, Variant 0
View
The unicellular green alga, Chlorella, a photosynthetic protoctist, was originally studied for its potential as a food source. Although large-scale production proved to be uneconomic, the many health benefits provided by Chlorella mean that it is now mass produced and harvested for use as a health food supplement. shows cells of Chlorella. Chlorella In one study into the productivity of Chlorella, carbon dioxide concentration was altered to investigate its effects on the light-independent stage of photosynthesis. • A cell suspension of Chlorella was illuminated using a bench lamp. • The suspension was supplied with carbon dioxide at a concentration of 1% for 200 seconds. • The concentration of carbon dioxide was then reduced to 0.03% for a further 200 seconds. • The concentrations of RuBP and GP (PGA) were measured at regular intervals. • Throughout the investigation the temperature of the suspension was maintained at 25 °C. The results are shown in . time / s concentration / arbitrary units 1 % CO2 0.03 % CO2 GP RuBP State precisely where in the chloroplast RuBP and GP are located. Explain why the concentration of RuBP changed between 200 and 275 seconds. Calculate the rate of decrease per second in the concentration of GP between 200 and 350 seconds. Show your working and give your answer to two decimal places. answer arbitrary units per second Explain how the decrease in the concentration of GP leads to a decreased harvest for commercial suppliers of Chlorella.
9700_s14_qp_41
THEORY
2014
Paper 4, Variant 1
View
The unicellular green alga, Chlorella, a photosynthetic protoctist, was originally studied for its potential as a food source. Although large-scale production proved to be uneconomic, the many health benefits provided by Chlorella mean that it is now mass produced and harvested for use as a health food supplement. shows cells of Chlorella. Chlorella In one study into the productivity of Chlorella, carbon dioxide concentration was altered to investigate its effects on the light-independent stage of photosynthesis. • A cell suspension of Chlorella was illuminated using a bench lamp. • The suspension was supplied with carbon dioxide at a concentration of 1% for 200 seconds. • The concentration of carbon dioxide was then reduced to 0.03% for a further 200 seconds. • The concentrations of RuBP and GP (PGA) were measured at regular intervals. • Throughout the investigation the temperature of the suspension was maintained at 25 °C. The results are shown in . time / s concentration / arbitrary units 1 % CO2 0.03 % CO2 GP RuBP State precisely where in the chloroplast RuBP and GP are located. Explain why the concentration of RuBP changed between 200 and 275 seconds. Calculate the rate of decrease per second in the concentration of GP between 200 and 350 seconds. Show your working and give your answer to two decimal places. answer arbitrary units per second Explain how the decrease in the concentration of GP leads to a decreased harvest for commercial suppliers of Chlorella.
9700_s14_qp_43
THEORY
2014
Paper 4, Variant 3
View
Sentences and are extracted from longer definitions of ecological terms. Each has one or more missing words. Complete and using the correct terms chosen from the list below. a population a community an ecosystem a niche a habitat trophic level producers organisms consumers ………………………………………………… is the particular location and type of local environment occupied by ………………………………………………… or organism, characterised by its physical features or by its dominant ………………………………………………… . ………………………………………………… is the functional role or place of a species of organism within ………………………………………………… . Only a small proportion of the light energy striking the leaves of producers becomes converted to chemical energy. The proportion that is converted is known as the photosynthetic efficiency (PE). Outline the possible reasons why a large proportion of light energy striking the leaves of plants is not converted into chemical energy. Most crops have a PE of 1% to 4%. Sugar cane, an important crop plant for food production and for the production of biofuel, has a PE of 7% to 8%. Suggest the advantages of growing crops with high PE for food production or for biofuel. Fertilisers containing nitrate are added to improve or maintain yield of crops such as sugar cane. Name two organic compounds containing nitrogen that are made by plants and state one function of each in plant growth. organic compound 1 function organic compound 2 function
9700_s15_qp_22
THEORY
2015
Paper 2, Variant 2
View
shows the effect of temperature on the rate of photosynthesis of a plant at low light intensity and at high light intensity. rate of photosynthesis high light intensity low light intensity temperature / °C With reference to , describe and explain the effect of temperature on the rate of photosynthesis. shows an absorption spectrum for chloroplast pigments and a photosynthetic action spectrum for the same plant. wavelength of light / nm action spectrum absorption spectrum absorbance or rate of photosynthesis Distinguish between an absorption spectrum and an action spectrum. absorption spectrum action spectrum Explain why the two curves shown in have similar shapes. Describe the role in photosynthesis of an accessory pigment, such as carotene.
9700_s16_qp_42
THEORY
2016
Paper 4, Variant 2
View
Questions Discovered
183