13.2. Investigation of limiting factors
A subsection of Biology, 9700, through 13. Photosynthesis
Listing 10 of 75 questions
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
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
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
View
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
View
is a transmission electron micrograph of part of a chloroplast of a leaf cell from maize. A B Table 7.1 shows some substrates and products involved in photosynthesis. Use letter A or letter B from to complete Table 7.1 to show the location where the substrates or products are used or produced. Table 7.1 substrate or product location oxygen produced ………… carbon dioxide used ………… reduced NADP used ………… ATP produced ………… hexose produced ………… Chloroplasts isolated from leaf palisade cells can still function if they are suspended in a buffer solution. The buffer solution has the same water potential as the chloroplasts. The dye DCPIP is a hydrogen acceptor that changes colour from blue to colourless when it becomes reduced. Three test tubes were set up as shown in Table 7.2 and left for 20 minutes to allow any colour change to occur. The results are also shown in Table 7.2. Table 7.2 test- tube contents conditions colour change buffer solution + DCPIP light no chloroplast suspension + DCPIP light yes chloroplast suspension + DCPIP dark no Explain the results for test-tube 2. Test-tube 1 is a control tube. Explain why test-tube 1 was included in the investigation. Suggest and explain what would happen to the chloroplasts if they were suspended in distilled water. The rate of photosynthesis in green plants can be limited by factors such as light intensity, temperature and carbon dioxide concentration. State which factor would have no effect on the reducing ability of a chloroplast suspension. Give a reason for your answer. factor reason
9700_s18_qp_43
THEORY
2018
Paper 4, Variant 3
View
Questions Discovered
75