Question:
Which one of the following is not a component of thylakoid integral membrane protein?
Which one of the following is not a component of thylakoid integral membrane protein?
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AOX acts as an alternative pathway in plant mitochondria, releasing energy as heat instead of ATP. It is associated with thermogenesis and stress responses, particularly in arum lilies.
Updated On: Jul 13, 2026
- Light Harvesting Complex (LHC)
- ATP synthase
- Alternative oxidase (AOX)
- $\text{O}_2$-Evolving complex (OEC)
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The Correct Option is C
Solution and Explanation
Step 1: Understanding the Concept:
The thylakoid membrane inside chloroplasts contains lipid-embedded proteins that facilitate light absorption, electron transport, and ATP synthesis during the light reactions of photosynthesis.
Step 2: Detailed Explanation:
Let us analyze the localization of each of these proteins:
- Light Harvesting Complex (LHC) (1): An integral membrane protein complex that binds chlorophylls and carotenoids, capturing light energy and transferring it to the reaction centers of Photosystem II and I.
- ATP Synthase (2): An integral membrane complex ($\text{CF}_0\text{-CF}_1$) embedded in the thylakoid membrane that uses the proton motive force to synthesize ATP.
- Oxygen-Evolving Complex (OEC) (4): Associated with the lumenal side of Photosystem II, this complex binds water and facilitates photolysis, releasing oxygen.
- Alternative Oxidase (AOX) (3): This is not a chloroplast thylakoid protein. AOX is an integral membrane protein located in the inner mitochondrial membrane. It functions as an alternative terminal electron acceptor in the mitochondrial respiratory chain, bypassing Complexes III and IV to prevent over-reduction of the electron transport chain.
Step 3: Final Answer:
The protein that is not a component of the thylakoid membrane is Alternative oxidase (AOX).
The thylakoid membrane inside chloroplasts contains lipid-embedded proteins that facilitate light absorption, electron transport, and ATP synthesis during the light reactions of photosynthesis.
Step 2: Detailed Explanation:
Let us analyze the localization of each of these proteins:
- Light Harvesting Complex (LHC) (1): An integral membrane protein complex that binds chlorophylls and carotenoids, capturing light energy and transferring it to the reaction centers of Photosystem II and I.
- ATP Synthase (2): An integral membrane complex ($\text{CF}_0\text{-CF}_1$) embedded in the thylakoid membrane that uses the proton motive force to synthesize ATP.
- Oxygen-Evolving Complex (OEC) (4): Associated with the lumenal side of Photosystem II, this complex binds water and facilitates photolysis, releasing oxygen.
- Alternative Oxidase (AOX) (3): This is not a chloroplast thylakoid protein. AOX is an integral membrane protein located in the inner mitochondrial membrane. It functions as an alternative terminal electron acceptor in the mitochondrial respiratory chain, bypassing Complexes III and IV to prevent over-reduction of the electron transport chain.
Step 3: Final Answer:
The protein that is not a component of the thylakoid membrane is Alternative oxidase (AOX).
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