Why must a plant carry out respiration as well as photosynthesis?
ATo function in light and dark and interconvert metabolites
BTo make the oxygen its own chloroplasts require
CTo fix carbon dioxide when the stomata are shut
DTo rebuild the pigments bleached by bright light
Answer & Solution
Correct answer: A. To function in light and dark and interconvert metabolites
1. All living things access energy by breaking down carbohydrate molecules, plants included.
2. Plants need both photosynthesis and respiration to function in both the light and the dark.
3. They also need both in order to interconvert essential metabolites.
4. That is why plants contain both chloroplasts and mitochondria.
5. Oxygen for the leaf's own mitochondria comes from photosynthesis, so respiration does not exist to supply it.
6. Carbon fixation belongs to photosynthesis alone, so it cannot be a reason for respiring.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 8 "Photosynthesis", section 8.3 Using Light Energy to Make Organic Molecules_
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