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    NEET 2025 Cut Off for SC Category for MBBS Government Colleges

    Chemiosmosis and Oxidative Phosphorylation MCQ - Practice Questions with Answers

    Edited By admin | Updated on Sep 18, 2023 18:34 AM | #NEET

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    • 18 Questions around this concept.

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    The mechanism of oxidative phosphorylation was explained by

    Which of the following combinations is required for chemiosmosis?

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    Chemiosmosis and Oxidative Phosphorylation
    • In chemiosmosis, the free energy from the series of redox reactions just described is used to pump hydrogen ions (protons) across the membrane.
    • The uneven distribution of H+ ions across the membrane establishes both concentration and electrical gradients (thus, an electrochemical gradient), owing to the hydrogen ions’ positive charge and their aggregation on one side of the membrane.
    • Many ions cannot diffuse through the nonpolar regions of phospholipid membranes without the aid of ion channels. 
    • Similarly, hydrogen ions in the matrix space can only pass through the inner mitochondrial membrane through an integral membrane protein called ATP synthase.
    • This complex protein acts as a tiny generator, turned by the force of the hydrogen ions diffusing through it, down their electrochemical gradient.
    • The turning off parts of this molecular machine facilitates the addition of a phosphate to ADP, forming ATP, using the potential energy of the hydrogen ion gradient.
    • The number of ATP molecules synthesized depends on the nature of the electron donor.
    • Oxidation of one molecule of NADH gives rise to 3 molecules of ATP, while that of one molecule of FADH2 produces 2 molecules of ATP.
    • ATP synthase (complex V)  consists of two major components, F1 and F0.
    • The F1 headpiece is a peripheral membrane protein complex and contains the site for the synthesis of ATP from ADP and inorganic phosphate. 
    • F0 is an integral membrane protein complex that forms the channel through which protons are across the inner membrane. 
    • The passage of protons through the channel is coupled to the catalytic site of the F1 component for the production of ATP. 
    • For each ATP produced, 2H+ passes through F0  from the intermembrane space to the matrix down the electrochemical proton gradient.
    • Although the aerobic process of respiration takes place only in the presence of oxygen, the role of oxygen is limited to the terminal stage of the process.
    • Yet, the presence of oxygen is vital, since it drives the whole process by removing hydrogen from the system. 
    • Oxygen acts as the final hydrogen acceptor.
    • In respiration, it is the energy of oxidation-reduction utilized for the production of proton gradient required for phosphorylation.
    • It is for this reason that the process is called oxidative phosphorylation.

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