Really confused Question 3 (1 point) The enzyme ATP synthase is not part of the
ID: 201246 • Letter: R
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Really confused Question 3 (1 point) The enzyme ATP synthase is not part of the ETC (electron transport chain) of respiration, but is intimately related to it. Which of the following statements about this topic are correct? ATP synthase actively transports protons from the intermembrane space into the mitochondrial matrix and couples this to the synthesis of ATP ATP synthase harnesses the energy in the proton gradient that is built by the ETC, ATP synthase couples the passive flow of protons from the intermembrane space into the mitochondrial matrix to the synthesis of ATP ATP synthase harvests the electrons that pass through the ETCExplanation / Answer
Ans. Correct option- B. ATP synthase harness the energy of proton gradient that is built by the ETC.
ETC involves oxidation of NADH and FADH2 into NAD+ FAD respectively with donation of high energy to the complexes of ETC. When the high energy electrons are successively passed from complex I or II to III and then IV, there is establishment of proton gradient across the inner membrane as usual. The potential energy stored in proton gradient across the inner membrane is further harvested as ATP by ATP synthase- the process being called oxidative phosphorylation.
# Option A- Incorrect. Active transport is the process of transport of a chemical species from its lower to higher concertation on consumption of ATP. The transport of protons from intermembrane space (IMS) to mitochondrial matrix (MM) is NOT active transport because – I. No ATP consumption (input) is required for the transport, and II. H+ flows from its higher to lower concentration.
# Option C. Incorrect. Note that is the proton gradient, NOT the proton, which potential energy is harvest by ATP synthase in form of ATP. The proton gradient in the different in pH across the inner mitochondrial membrane (IMM), the pH intermembrane space (IMS) being more acidic that that of mitochondrial matrix (MM) by around 1 pH unit.
For example, if the pH gradient is low (say. 0.4 units), the flow of protons from IMS to MM, the energy is NOT sufficient to synthesize ATP.
# Option D. Incorrect. As explained in option #B, ATP synthase does not interact with electrons of ETC directly. It is the potential energy of proton gradient generated by electron flow through ETC which is harvested in form of ATP by ATP synthase.
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