Question:
Identify the first electron acceptor from an excited chlorophyll molecule of Photosystem-II:
Identify the first electron acceptor from an excited chlorophyll molecule of Photosystem-II:
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In PS-II, the first stable electron acceptor is always a quinone molecule (QA).
Updated On: Jun 20, 2026
- Cytochrome
- Ferredoxin
- Quinone
- Plastocyanin
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The Correct Option is C
Solution and Explanation
Step 1: Understanding Photosystem-II (PS-II).
In Photosystem-II, light energy excites chlorophyll molecules (P680), causing electrons to move to a higher energy level. These excited electrons must be transferred to a stable electron acceptor to continue the electron transport chain.
Step 2: Role of primary electron acceptor.
The first molecule that receives electrons from excited chlorophyll is called the primary electron acceptor. It stabilizes the electron and passes it further in the electron transport chain.
Step 3: Identification of the correct molecule.
In PS-II, the primary electron acceptor is a special quinone molecule (also called QA and QB), which accepts electrons directly from P680*.
Step 4: Analysis of options.
- Cytochrome: Functions later in the electron transport chain, not primary acceptor.
- Ferredoxin: Works in PSI, not PSII.
- Quinone: Acts as primary electron acceptor in PSII.
- Plastocyanin: Transfers electrons between cytochrome complex and PSI, not initial acceptor.
Step 5: Electron transport logic.
The electron flow in PS-II is: P680 → Quinone (QA/QB) → cytochrome complex, confirming quinone as first acceptor.
Step 6: Final conclusion.
Therefore, the first electron acceptor is quinone.
In Photosystem-II, light energy excites chlorophyll molecules (P680), causing electrons to move to a higher energy level. These excited electrons must be transferred to a stable electron acceptor to continue the electron transport chain.
Step 2: Role of primary electron acceptor.
The first molecule that receives electrons from excited chlorophyll is called the primary electron acceptor. It stabilizes the electron and passes it further in the electron transport chain.
Step 3: Identification of the correct molecule.
In PS-II, the primary electron acceptor is a special quinone molecule (also called QA and QB), which accepts electrons directly from P680*.
Step 4: Analysis of options.
- Cytochrome: Functions later in the electron transport chain, not primary acceptor.
- Ferredoxin: Works in PSI, not PSII.
- Quinone: Acts as primary electron acceptor in PSII.
- Plastocyanin: Transfers electrons between cytochrome complex and PSI, not initial acceptor.
Step 5: Electron transport logic.
The electron flow in PS-II is: P680 → Quinone (QA/QB) → cytochrome complex, confirming quinone as first acceptor.
Step 6: Final conclusion.
Therefore, the first electron acceptor is quinone.
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