Question

In oxidative phosphorylation in mitochondria, high-energy electrons are transferred to the electron-transport chain from activated carriers like NADH. Stage 1 of photosynthesis also uses an electron-transport chain to pump protons and make ATP. In this case, where do the high-energy electrons come from? Choose one:

A. ADP
B. chlorophyll
C. FADH2
D. NADPH

Answer 1

In the stage 1 of photosynthesis, high-energy electrons that feed into the chloroplast electron transport chain are derived from water in the photosystem II, energized by sunlight.

Step-by-step explanation:

The initial source of high-energy electrons for the chloroplast electron transport chain during photosynthesis comes from water. This process occurs in the photosystem II (PSII) where energy from sunlight is used to extract electrons from water. As explained in the figures and text provided, these electrons then travel through the chloroplast electron transport chain to photosystem I (PSI), where they contribute to the reduction of NADP+ to NADPH, which along with ATP will then be used to fuel the Calvin cycle, the second stage of photosynthesis.