1 Look at the image on the photo support sheet, the micrograph shows a chloroplast.

Transcription

1 1 Look at the image on the photo support sheet, the micrograph shows a chloroplast. a Give the letter of the site of the light-dependent reactions of photosynthesis. b i ATP and reduced NADP are products of the light-dependent reactions. Describe the roles of these products in the light-independent reactions. ii Oxygen is another product of the light-dependent reactions. Describe how oxygen is produced. 2 Students investigated the effect of light intensity on the rate of photosynthesis. They set up a piece of aquatic plant in a test tube of sodium hydrogen carbonate as shown in the diagram. Light intensity was varied by moving the plant different distances away, between 5 and 30 cm, from a bench lamp. The plant was left for 5 minutes and then bubbles rising from the cut end of the stem were counted for 1 minute. This resource sheet may have been changed from the original 1

2 a The rate of bubbling can be used as a measure of the rate of photosynthesis. Explain why. b One of the students plotted a graph of the results. b i 1 Light intensity was calculated as 2 d where d is the distance from the lamp. Calculate the distance from the lamp when the light intensity is Show your working. ii Explain the shape of the curve between points A and B. This resource sheet may have been changed from the original 2

3 iii Explain the shape of the curve between points C and D. 3 A student carried out an experiment to separate the pigments found in spinach leaves by chromatography. The diagram below shows the resulting chromatogram. a The student was provided with the spinach leaves, chromatography paper and solvent. Describe how the student would use this equipment to produce the chromatogram shown. b Chromatography separates the different pigments. Explain how. c Scientists calculate Rf values to compare results on chromatograms. The Rf value is a ratio of the distance moved by the solute to the distance moved by the solvent. State the measurements the student would have made to calculate the Rf value of chlorophyll a? This resource sheet may have been changed from the original 3

4 4 Students at an agricultural college carried out an investigation into the effect of different types of artificial light on the growth of wheat plants. Once fully grown the total mass of the plants and the mass of the grain were measured. The table below shows their results. Type of lighting Total mass of plants/kg Mass of grain/kg Grain yield as a percentage of total biomass/% Low pressure sodium lamps High pressure sodium lamps Metal halide lamps a i The students calculated the grain yield as a percentage of total biomass. Explain why. ii Calculate the grain yield as a percentage of total biomass for the wheat grown under high pressure sodium lamps. Show your working. b Suggest two environmental factors that the students would need to consider to ensure their results were valid. Give reasons for your answers. Factor Reason Factor Reason This resource sheet may have been changed from the original 4

5 c The students concluded that the type of lighting had little effect on the growth of crops in artificial lighting. Evaluate this conclusion. d Wheat is not normally grown in glasshouses with artificial lighting. Suggest two reasons why. 5 Oxygen is produced in the light-dependent reaction of photosynthesis. A student conducted an investigation where light of different colours was shone on Elodea pondweed. The student counted the number of bubbles released in 1 minute in each colour of light. Colour of light Number of bubbles of oxygen released in one minute in each trial Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Trial 6 Mean Standard deviation Range White Blue Green Red a Describe how the student calculated the range. b The student decided it was better to use the mean and standard deviation rather than the range to describe variation in these results. Explain why. c After looking at the data the student decided to repeat the investigation with more trials for each colour of light. He did this so that he could carry out a statistical test. Suggest a suitable statistical test and give a reason for your choice. This resource sheet may have been changed from the original 5

6 d The results indicate that white light gave the fastest rate of photosynthesis. Suggest why. 6 The diagram shows part of the light-independent reactions of photosynthesis. a Two substances formed in the light-dependent reactions are necessary for the conversion of GP into triose phosphate. Name these two substances. Scientists supplied carbon dioxide containing the radioactive isotope 14 C to a culture of photosynthesising single-celled algae. The algae were kept in the light for 200 seconds, then in the dark for a further 1500 seconds, and were then returned to the light. The graph shows the amounts of radioactivity found in RuBP and in GP at different times throughout the investigation. This resource sheet may have been changed from the original 6

7 b Describe the evidence in the graph which supports each of the following statements. i The process by which RuBP is used to make GP is light-independent. ii RuBP is formed using GP only if substances formed in the light-dependent reactions are present. c The amount of radioactive GP falls between 250 and 1700 seconds. Suggest why. AQA Biology, 2009, Unit 5 (Question 3) This resource sheet may have been changed from the original 7