According to the chemiosmotic theory (chemiosmotic coupling), the energy required to move protons from the mitochondrial matrix to the intermembrane space against a concentration gradient comes most directly from

Question

BlackTom AI · Accepted Answer

Electrons flowing along the electron transport chain provide the direct energy to pump protons from the mitochondrial matrix to the intermembrane space.

1) Relevant knowledge points and concepts
- Chemiosmotic theory: electron transport creates a proton electrochemical gradient (proton-motive force, PMF) across the inner mitochondrial membrane; ATP synthase uses that PMF to make ATP.
- Electron transport chain (ETC) complexes I, III, and IV are proton pumps that couple electron transfer to proton translocation. NADH and FADH2 donate electrons; oxygen is the terminal acceptor.
- Proton pumping generates both a membrane potential (Δψ) and a chemical gradient (ΔpH), together the PMF.

2) Step-by-step reasoning
- NADH and FADH2, produced by metabolic pathways, donate electrons to Complex I (NADH) or Complex II (FADH2).
- Electrons are transferred through a series of redox carriers (Complexes I → III → IV, ubiquinone, cytochrome c).
- The free energy released as electrons move to progressively more positive redox potentials is used by Complexes I, III, and IV to translocate H+ from matrix to intermembrane space.
- The resulting H+ gradient (high [H+] in intermembrane space, low in matrix) constitutes stored energy used by ATP synthase to synthesize ATP when protons flow back into the matrix.

3) Intermediate quantitative detail
- Approximately, per NADH oxidized ~10 H+ are pumped (Complex I: 4, Complex III: 4, Complex IV: 2). Per FADH2, fewer H+ are pumped (~6) because electrons enter at Complex II which does not pump protons.

4) Why the correct answer is correct
- The direct source of energy for proton pumping is the exergonic transfer of electrons through ETC complexes; this coupling is the central claim of the chemiosmotic theory.

5) Why other options are incorrect
- Photons of red/blue light: drive photophosphorylation in chloroplasts, not mitochondrial ETC.
- Breakdown of fatty acids: yields NADH/FADH2 (indirect source) but the immediate energy for pumping comes from electron transfer, not the beta-oxidation reaction itself.
- Substrate-level phosphorylation: directly forms ATP without creating a proton gradient; it does not power proton pumping.
- Hydrolysis of ATP: would consume ATP and, if anything, dissipate or reverse gradients rather than directly drive physiologic proton pumping.

6) Conclusion
This reasoning confirms the provided correct answer: electrons flowing along the electron transport chain.

According to the chemiosmotic theory (chemiosmotic coupling), the energy required to move protons from the mitochondrial matrix to the intermembrane space against a concentration gradient comes most directly from单项选择题

类似问题

Oxidative phosphorylation occurs in

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

Which metabolic process is most closely associated with intracellular membranes?

Which metabolic process is most closely associated with intracellular membranes?

Oxidative phosphorylation occurs in

Certain compounds are known as "uncouplers" and can adversely affect cellular metabolism. In oxidative phosphorylation, uncouplers can:

Oxidative phosphorylation occurs in

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单