Which metabolic process is most closely associated with intracellular membranes?

Question

BlackTom AI · Accepted Answer

Oxidative phosphorylation is tightly linked to intracellular membranes because the electron transport chain (ETC) and ATP synthase are membrane proteins that create and use a proton gradient across a membrane.

1) Relevant knowledge points and concepts
- Oxidative phosphorylation: occurs when electrons from NADH/FADH2 pass through ETC complexes embedded in the mitochondrial inner membrane (or thylakoid membrane in chloroplasts), driving proton pumping and establishing an electrochemical gradient; ATP synthase uses proton flow back across the membrane to make ATP (chemiosmotic coupling).
- Substrate-level phosphorylation: direct enzymatic transfer of a phosphate to ADP (e.g., in glycolysis or the Krebs cycle) and does not require membrane-bound electron transport.
- Krebs cycle (citric acid cycle): takes place in the mitochondrial matrix (soluble enzymes), not primarily membrane-associated.
- Glycolysis: occurs in the cytosol, independent of intracellular membranes.

2) Step-by-step reasoning
- Electrons from metabolic NADH/FADH2 enter the ETC at membrane-bound complexes (Complex I, II, III, IV).
- As electrons move through these complexes, protons are pumped from the matrix into the intermembrane space across the inner mitochondrial membrane.
- This generates a proton-motive force (electrochemical gradient) across that membrane.
- Protons flow back through ATP synthase (a transmembrane enzyme), driving phosphorylation of ADP to ATP directly coupled to membrane proton flow.

3) Calculations
- Not applicable here because this is a conceptual/structural question rather than a numerical problem.

4) Why the correct answer is correct
- Oxidative phosphorylation requires membrane-embedded ETC complexes and ATP synthase; without the intracellular membrane to separate compartments and maintain a gradient, the process cannot operate.

5) Why the other choices are incorrect
- The Krebs cycle: occurs in the soluble mitochondrial matrix, not membrane-associated.
- Substrate-level phosphorylation: enzyme-mediated phosphate transfer within metabolic pathways (glycolysis/Krebs) and does not depend on membranes.
- Glycolysis: occurs in the cytosol and is not membrane-bound.

Conclusion: therefore the most closely associated process with intracellular membranes is c. Oxidative Phosphorylation, matching the provided answer.

Which metabolic process is most closely associated with intracellular membranes?单项选择题

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Question at position 1 The energy required to phosphorylate one molecule of ADP, producing ATP, is generated by:Uncoupling proteinsNADH or FADH2Electron gradient of the electron transport systemProton gradient between the inner and outer mitochondrial membranes