Photosynthesis is a ______ reaction that involves ______ reactions where ______.

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Multiple Choice

Photosynthesis is a ______ reaction that involves ______ reactions where ______.

Photosynthesis stores energy by using light to build sugars, so it is endergonic. It also involves redox chemistry: carbon dioxide is reduced to carbohydrate, while water is oxidized to oxygen. In the light-dependent reactions, water is split to release electrons and oxygen, and energy carriers like ATP and NADPH are produced. Those carriers provide the energy and electrons to reduce CO2 to sugar in the Calvin cycle. This combination of energy input and opposite redox changes—CO2 reduced to carbohydrate and water oxidized to O2—is the best description of what happens. The other statements mix up energetics or redox roles: photosynthesis is not exergonic, and oxygen is not formed by reducing water; CO2 is reduced, not oxidized, to form carbohydrate; and hydrolysis is not the driving mechanism of photosynthesis.

Photosynthesis stores energy by using light to build sugars, so it is endergonic. It also involves redox chemistry: carbon dioxide is reduced to carbohydrate, while water is oxidized to oxygen. In the light-dependent reactions, water is split to release electrons and oxygen, and energy carriers like ATP and NADPH are produced. Those carriers provide the energy and electrons to reduce CO2 to sugar in the Calvin cycle. This combination of energy input and opposite redox changes—CO2 reduced to carbohydrate and water oxidized to O2—is the best description of what happens.

The other statements mix up energetics or redox roles: photosynthesis is not exergonic, and oxygen is not formed by reducing water; CO2 is reduced, not oxidized, to form carbohydrate; and hydrolysis is not the driving mechanism of photosynthesis.

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