During cyclic photophosphorylation, ATP is generated by the:
Correct answer: C. ETC
- A. Photosystem I
- B. Photosystem II
- C. ETC
- D. Calvin cycle
Explanation
ATP in photophosphorylation is generated through the electron transport chain, making it the correct option. During cyclic photophosphorylation, electrons from Photosystem I travel through the electron transport chain and return to the same photosystem, releasing energy to pump protons and create a proton gradient. In non-cyclic photophosphorylation, electrons from Photosystem II pass through the chain to Photosystem I, and the energy released is used to produce ATP. Photosystem I and Photosystem II are involved in capturing light energy and exciting electrons, but they do not directly produce ATP. The Calvin cycle does not generate ATP at all; it uses ATP produced in the light reactions to fix carbon dioxide into sugars. This is why only the electron transport chain is responsible for ATP synthesis in photophosphorylation.
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Cellular respiration explains how cells release energy from glucose through glycolysis, the link reaction, Krebs cycle and electron transport chain. It includes ATP production, substrate-level and oxidative phosphorylation, aerobic versus anaerobic respiration, and the roles of mitochondria, oxygen and fermentation in energy transfer.
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