Biochemistry : Other Light Reaction Concepts
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Example Questions
Example Question #2 : Carbohydrate Metabolism
In photosynthesis, if photosystem II absorbs 12 photons, how many molecules of would be produced?
Absorbing four photons by photosystem II creates one oxygen molecule, so absorbing 12 would produce 3 molecules of .
Example Question #2 : Light Reactions
During photosynthesis there is both a light phase and a dark phase. If the light phase were to continue unabated, but the dark phase came to a halt, which of the following is most likely to occur?
A proportional decrease in
Decrease in the level of
An increase in the production of carbohydrates
Decreased sensitivity of the chloroplast to incoming light
Increased sensitivity of the chloroplast to incoming light
Decrease in the level of
During photosynthesis, the dark phase follows the light phase. The light phase produces which, along with , is fed into the dark phase where it is consumed (becomes and ). If the light phase continues working, but the dark phase does not, the and created during the light phase will not be consumed. Thus, there will be a decrease in the level of and (the correct answer). The relative proportion of will actually increase.
Carbohydrate production is a result of the dark phase working properly, so their levels would decrease in this instance. The sensitivity of the chloroplast to light would not change.
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