Why can the light-independent reactions not run indefinitely in the dark, even though they do not use light as a reactant?
AThey need oxygen made by the light reactions
BThey need chlorophyll to bind carbon dioxide
CThey need the products of the light reactions
DThey need direct sunlight to warm the stroma
Answer & Solution
Correct answer: C. They need the products of the light reactions
1. The light-independent reactions do not use light as a reactant.
2. They do, however, require the products of the light-dependent reactions to function.
3. Those products are the energy carriers that arrive full and return empty for recharging.
4. Several enzymes of the light-independent reactions are also activated by light.
5. So the name means light is not consumed, not that light can be dispensed with.
6. Oxygen is released as a waste product and is not required to drive these reactions.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 8 "Photosynthesis", section 8.1 Overview of Photosynthesis_
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