0.22 Bis2a 06.2 oxidative phosphorylation v1.2  (Page 3/14)

The total difference in the reduction potential of the electron donor and the final electron acceptor can be thought of as the total energy available for the system. How that energy is released, in one big chunk or in small aliquots is dependent upon the number of red/ox complexes the electrons will travel through. Each complex (in general) can be thought of as a release valve, where the energy being generated by the various red/ox reactions can be captured by the translocation of a proton. NOTE, not all complexes can generate enough energy to translocate a proton. The number of protons being translocated is important because in general it takes 3 protons to enter the F ₁ F ₀ ATPase to generate 1 ATP molecule. The more protons translocated per 2 electrons that enter the chain, the more ATP that can be made.

How do etc complexes transfer electrons?

The electron and proton carriers

• Flavoproteins ( Fp ), these proteins contain an organic prosthetic group called a flavin , which is the actual moiety that undergoes the oxidation/reduction reaction. FADH ₂ is an example of a Fp.
• Quinones , are a family of lipids which means they are soluble within the membrane.
• It should also be noted that NADH and NADPH are considered electron (2e-) and proton (2 H ⁺ ) carriers.

Electon carriers

• Cytochromes are proteins that contain a heme prosthetic group. The Heme is capable of carrying a single electron.
• Iron-Sulfur proteins contain a non-heme iron-sulfur clusters that can carry an electron. The prosthetic group is often abbreviated as Fe-S

Aerobic versus anaerobic respiration