The electron transport chain takes place in the inner mitochondrial membrane and is the final step of aerobic cellular respiration. The proteins involved in the electron transport chain are outlined in Figure 1.

The electron transport chain consists of a series of redox reactions that transfer electrons from NADH and FADH2 through various intermediates to the final electron acceptor, oxygen (see detailed ETC steps). This process generates an electrochemical gradient that couples the oxidative reactions with the phosphorylation of ADP producing ATP in a process called oxidative phosphorylation.

A diagram of the structures involved in the electron transport chain. The structures are embedded in the inner membrane of the mitochondria, between the matrix and the inter membrane space. Four protein complexes, labelled 1, 2, ,3 and 4, sit in close proximity in the membrane. The complexes are clumps of many folded proteins. After complex 4, An ATP synthase pump is embedded in the membrane. These form the main structures involved in the electron transport chain. Between complex 1 and 2, and between complex 2 and 3, smaller transporting factors, labelled as coenzyme Q, transport electrons from complex to complex. Between complex 3 and 4, a transporting factor called cytochrome C, can be seen.

Figure 1. Proteins in the inner mitochondrial membrane involved in the electron transport chain: Complex I (I), Complex II (II), Complex III (III), Complex IV (IV), ubiquinone (Q), cytochrome c (Cyt C) and ATP synthase. In this image, the mitochondrial matrix is seen above and the intermembrane space is found below the inner mitochondrial membrane.