alleryStart learning →Where does photosystem II obtain the electron that replaces the one it has given up?
AFrom a molecule of NADPH
BFrom a molecule of oxygen
CFrom a molecule of glucose
DFrom a molecule of water
Answer & Solution
Correct answer: D. From a molecule of water
1. The reaction centre of photosystem II loses an electron at every photoact.
2. Its missing electron is replaced by extracting a low-energy electron from water.
3. Water is therefore split and photosystem II is re-reduced after every photoact.
4. Oxygen is released as the waste product of that splitting, so it is an output rather than a source.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 8 "Photosynthesis", section 8.2 The Light-Dependent Reactions of Photosynthesis_
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