Question

In the electron-transport chain in chloroplasts, ________-energy electrons are taken from

__________.
(a) high; H2O.
(b) low; H2O.
(c) high; NADPH.
(d) low; NADPH.

Answer 1

The initial source of high-energy electrons for the chloroplast electron transport chain is water (H2O), which is split by photosystem II during the light-dependent reactions of photosynthesis to produce NADPH. Hence the correct answer is option A

Step-by-step explanation:

In the electron-transport chain in chloroplasts, high-energy electrons are taken from H2O. During photosynthesis, specifically in the light-dependent reactions, these high-energy electrons are initially extracted from water molecules by photosystem II (PSII), after which they travel through the chloroplast electron transport chain and finally reach photosystem I (PSI). PSI then reduces NADP+ to form NADPH, which is an energy-rich molecule used in the Calvin cycle for synthesizing sugars.

Hence the correct answer is option A