What is photophosphorylation?

Photophosphorylation refers to the process of generating ATP from ADP in the presence of light energy. This process occurs primarily during the light-dependent reactions of photosynthesis and involves the absorption of light by chlorophyll, which activates the electron transport chain. As electrons are transferred along this chain, they create a proton gradient across the thylakoid membrane. This gradient drives ATP synthase, an enzyme that catalyzes the phosphorylation of ADP to form ATP.

This process is distinct from other processes mentioned in the options. The conversion of light energy into chemical energy, while related, describes a broader concept that includes both ATP formation and the reduction of NADP+ to NADPH. The breakdown of glucose into pyruvate is part of cellular respiration, not photosynthesis, and the synthesis of glucose from carbon dioxide describes the Calvin cycle, which occurs after photophosphorylation and does not directly involve light energy. Therefore, the definition of photophosphorylation specifically aligns with the generation of ATP from ADP using light energy, making it the correct choice.