Metabolic pathway
Respiratory chain
Carries the electrons from NADH down to oxygen along a staircase of carriers and uses each step to pump protons out of the matrix. The gradient that builds up is what drives ATP synthase.
- In
- 2 NADH + 2 Proton + Oxygen + 5 ADP + 5 Inorganic phosphate
- Out
- 2 NAD⁺ + 7 Water + 5 ATP
- Location
- Inner mitochondrial membrane
Fun facts
- Complex I · NADH:ubiquinone oxidoreductaseIt is the largest complex in the inner membrane: some forty-five subunits and a chain of eight to nine iron-sulfur clusters that conduct the electrons along almost ninety ångströms.
- Complex III · cytochrome bc1That split is called the Q cycle. One of the two electrons goes back to a quinone to half-reduce it and wait for the next one, so no electron is lost along the way.
- Complex IV · cytochrome c oxidaseReducing oxygen in one go with four electrons avoids releasing intermediates such as superoxide. The complex holds the molecule on an iron-copper center until the reduction is complete.
- ATP synthaseThe rotation is real and has been measured: the central subunit makes one full turn for every three molecules of ATP, and it works just as well in reverse, spending ATP to pump protons.
Reactions
| # | Enzyme | ΔG°′ |
|---|---|---|
| 1×2 | Complex I · NADH:ubiquinone oxidoreductaseEC 7.1.1.2 · irreversibleNADH + 5 Proton + Ubiquinone → NAD⁺ + Ubiquinol + 4 Proton (intermembrane space) | −70.4kJ/molexergonic |
| 2×2 | Complex III · cytochrome bc1EC 7.1.1.8 · irreversibleUbiquinol + 2 Oxidized cytochrome c + 2 Proton → Ubiquinone + 2 Reduced cytochrome c + 4 Proton (intermembrane space) | −40.3kJ/molexergonic |
| 3 | Complex IV · cytochrome c oxidaseEC 7.1.1.9 · irreversible4 Reduced cytochrome c + Oxygen + 8 Proton → 4 Oxidized cytochrome c + 2 Water + 4 Proton (intermembrane space) | −216.9kJ/molexergonic |
| 4×5 | ATP synthaseEC 7.1.2.2ADP + Inorganic phosphate + 4 Proton (intermembrane space) ⇌ ATP + Water + 4 Proton | 30.5kJ/molendergonic |
4 of 4 reactions with a documented ΔG.
Use Shift to select several
The data sheet includes the map. The logo goes at the bottom.
Sources
- Nelson, D. L. & Cox, M. M. (2021). Lehninger. Principios de bioquímica, 8.ª ed., ch. 19