An experiment using radioactive carbon was carried out by scientists to investigate the Calvin Cycle. The algae Chlorella was exposed to radioactive carbon for different amounts of time. The algae was then analysed for radioactive compounds. The graph below shows the results.
Explain the changes in the amount of radioactive substances in the dark.
Melvin Calvin carried out similar experiments in the 1950s. At the time his approaches were novel and only possible because of advances in apparatus and techniques.
Describe the techniques, and their purpose, used by Calvin that allowed him to identify the compounds involved in the Calvin cycle.
When plants are exposed to extremely high or low temperatures for a continued period of time, they are put under a lot of stress. This stress greatly impacts the rate of photosynthesis, in particular the light-dependent reaction of photosynthesis.
Explain why extreme cold leads to a decrease in the light-independent reaction.
Plants can contain more than one type of chlorophyll, a and b. Scientists grew plants that contained a mutant version of chlorophyll a. They investigated the effect of this mutation on the rate of photosynthesis.
The scientists
Grew the mutant and normal plants in a range of light intensities
Isolated the chloroplasts from both types of plants
Measured the oxygen produced by the chloroplasts over a period of 20 minutes
Their results are shown in the graph below:
Explain why the scientists used the oxygen produced as a measure of the rate of photosynthesis.
Use the graph to calculate the difference in oxygen produced by the chloroplasts from normal plants compared to the mutant plants at a light intensity of 400 Watts/m².
