Activity of the light reactions can be assayed using an artificial, reducible compound (e- acceptor) added to take the place of the natural electron acceptor. The artificiale- acceptor used is called DCPIP, a blue dye that turns colorless when it accepts electrons. The reaction is:H20 + DCPIPoxidized (blue) ->02 + DCPIPreduced (colorless)To detect changes in the color of the DCPIP, a spectrophotometer is used to measure light intensity as a function of wavelength. When light is passed through asolution, the solute may either absorb or scatter light resulting in different color and opacity of the solution. DCPIP absorbs light in its oxidized state but not in itsreduced state. Data below shows the results of an experiment using this assay to test the effects of an herbicide on photosynthesis.0.60.550.5No Chloroplasts0.45Chloroplasts in the0.4darkChloroplasts in thelight0.350.3101520Time (minutes)How would you interpret the above data? Results indicate that the herbicide:O a. interferes with the Calvin cycle and prevents electron transportO b.interferes with the light reactions and prevents electron transportOc had no effect on photosynthesisO d. increased the rate of photosynthesisO e. may have inhibited photosynthesis but the controls indicate the chloroplasts were not reducing DCPIP therefore the experiment was not able to test the effect of theherbicideAbsorbance

2H2O +2A ---->2AH2 + O2 This is called hill reaction where A is the artificial hydrogen acceptor…

Nó Chloroplasts 0.45 Chloroplasts in the 0.4 dark Chloroplasts in the light 0.35 0.3 10 15 Time (minutes) w would you interpret the above data? Results indicate that the herbicide: a. interferes with the Calvin cycle and prevents electron transport b. interferes with the light reactions and prevents electron transport c had no effect on photosynthesis d. increased the rate of photosynthesis e. may have inhibited photosynthesis but the controls indicate the chloroplasts were not reducing DCPIP therefore the experiment wa herbicide 20

Nó Chloroplasts 0.45 Chloroplasts in the 0.4 dark Chloroplasts in the light 0.35 0.3 10 15 Time (minutes) w would you interpret the above data? Results indicate that the herbicide: a. interferes with the Calvin cycle and prevents electron transport b. interferes with the light reactions and prevents electron transport c had no effect on photosynthesis d. increased the rate of photosynthesis e. may have inhibited photosynthesis but the controls indicate the chloroplasts were not reducing DCPIP therefore the experiment wa herbicide 20

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter18: Glycolysis

Section: Chapter Questions

Problem 18P: Distinguishing the Mechanisms of Class I and Class I Aldolases Fructose bisphosphate aldolase in...

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If a reaction has a ΔG°′ value of at least −30.5 kJ · mol−1, suffi -cient to drive the synthesis of ATP (ΔG°′ = 30.5 kJ · mol−1), can it still drive the synthesis of ATP in vivo when its ΔG is only −10 kJ · mol−1? Explain.
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