When a suspension of algae is incubated in a flask in the presence of light and CO₂ and then transferred to the dark, the reduction of 3-phosphoglycerate to glyceraldehyde 3-phosphate slows and then stops.This happens because A) the reaction requires CO₂. B) the reaction is exergonic. C) the reaction requires ATP and NADPH. D) the reaction requires O₂. E) chlorophyll is not synthesized in the dark.

Question

Quizplus · Accepted Answer

The reduction of 3-phosphoglycerate to glyceraldehyde 3-phosphate is part of the Calvin cycle, which requires energy in the form of ATP and reducing power in the form of NADPH. In the presence of light and CO2, these energy and reducing molecules are generated by photosynthesis. However, in the dark, the supply of ATP and NADPH is depleted and the Calvin cycle slows down and eventually stops. This is the reason why the reduction of 3-phosphoglycerate to glyceraldehyde 3-phosphate slows and then stops when the algae are transferred to the dark.

When a Suspension of Algae Is Incubated in a Flask