氧化磷酸化Oxidative phosphorylation

电子传递链由复合体 I（NADH 脱氢酶）、II（琥珀酸脱氢酶）、III（细胞色素 bc₁）和 IV（细胞色素 c 氧化酶）以及辅酶 Q、细胞色素 c 组成，电子按还原电势由低到高流动（NADH −0.32 V → O₂ +0.82 V）。复合体 I、III、IV 共泵出约 10 个 H⁺/NADH。ATP 合酶（复合体 V）的 F₀ 部分让质子通过并带动转子旋转，F₁ 部分按“结合变构”机制每转一圈合成 3 个 ATP。

The chain consists of complex I (NADH dehydrogenase), complex II (succinate dehydrogenase), complex III (cytochrome bc₁) and complex IV (cytochrome c oxidase), linked by coenzyme Q and cytochrome c; electrons flow from low to high reduction potential (NADH at −0.32 V to O₂ at +0.82 V). Complexes I, III and IV pump about 10 H⁺ per NADH. ATP synthase (complex V) lets protons through its F₀ part, turning a rotor, and its F₁ part makes three ATP per turn by the binding-change mechanism.

1961 年英国生化学家彼得·米切尔提出化学渗透学说：电子传递与 ATP 合成不是通过高能中间化合物偶联，而是通过跨膜质子电化学梯度（质子动力）偶联。这一学说起初饱受争议，后被雅根多夫的叶绿体酸碱跃变实验（1966 年）等证实，米切尔获 1978 年诺贝尔化学奖。博耶提出结合变构机制，沃克解析了 ATP 合酶结构，二人共获 1997 年诺贝尔化学奖。

In 1961 the British biochemist Peter Mitchell proposed the chemiosmotic theory: electron transport and ATP synthesis are coupled not by a high-energy chemical intermediate but by the transmembrane electrochemical proton gradient, the proton-motive force. Controversial at first, it was confirmed by experiments such as Jagendorf's acid–base transition in chloroplasts (1966), and Mitchell received the 1978 Nobel Prize in Chemistry. Boyer, who proposed the binding-change mechanism, and Walker, who solved the structure of ATP synthase, shared the 1997 Nobel Prize in Chemistry.

氰化物和一氧化碳与复合体 IV 结合，鱼藤酮抑制复合体 I，寡霉素抑制 ATP 合酶，因此这些物质剧毒。2,4-二硝基苯酚等解偶联剂使质子绕过 ATP 合酶回流，能量以热量散失。棕色脂肪组织中的解偶联蛋白 UCP1 利用同样的原理为新生儿和冬眠动物产热。

Cyanide and carbon monoxide bind complex IV, rotenone blocks complex I and oligomycin blocks ATP synthase, which is why they are so toxic. Uncouplers such as 2,4-dinitrophenol let protons bypass ATP synthase, so the energy is lost as heat. Uncoupling protein UCP1 in brown fat uses the same principle to keep newborns and hibernating animals warm.