Concept preview

What you will be able to do

1. 01Describe how the electron transport chain on the inner mitochondrial membrane uses electrons from NADH and FADH2.
2. 02Explain the role of oxygen as the final electron acceptor and how chemiosmosis drives ATP synthase.
3. 03State the approximate ATP yields: about 34 ATP from the chain and roughly 36–38 in total per glucose.
4. 04Describe anaerobic fermentation (lactic acid in muscle, alcoholic in yeast) and how it regenerates NAD+.

The link reaction and the Krebs cycle made surprisingly little ATP, but they filled the mitochondrial matrix with loaded electron carriers — a rich haul of NADH and FADH2. Those carriers are like charged batteries, and the final stage of aerobic respiration is where they are finally cashed in for a huge payoff. This stage is the electron transport chain (ETC), a series of protein complexes embedded in the folded inner mitochondrial membrane, the cristae. Here the electrons that NADH and FADH2 have been carrying are at last put to work, and the great majority of all the ATP produced from a glucose molecule is generated in this one remarkable process.