Answer: Complex IV, also known as cytochrome c oxidase, oxidizes cytochrome c and transfers the electrons to oxygen, the final electron carrier in aerobic cellular respiration. The cytochrome proteins a and a3, in addition to heme and copper groups in complex IV transfer the donated electrons to the bound dioxygen species, converting it into molecules of water. The free energy from the electron transfer causes 4 protons to move into the intermembrane space contributing to the proton gradient. Oxygen reduces via the following reaction:
2 cytochrome c(red) + ½O2 + 4 H+(matrix) -> 2 cytochrome c(ox) + 1 H2O + 2 H+(intermembrane)
Explanation:
In the electron transport chain (ETC), the electrons go through a chain of proteins that increases its reduction potential and causes a release in energy. Most of this energy is dissipated as heat or utilized to pump hydrogen ions (H+) from the mitochondrial matrix to the intermembrane space and create a proton gradient. This gradient increases the acidity in the intermembrane space and creates an electrical difference with a positive charge outside and a negative charge inside. The ETC proteins in a general order are complex I, complex II, coenzyme Q, complex III, cytochrome C, and complex IV.
