Which molecule donates electrons to Complex IV?

Complex IV, also known as cytochrome c oxidase, is a crucial component of the electron transport chain in cellular respiration. It catalyzes the transfer of electrons from cytochrome c to molecular oxygen, resulting in the reduction of oxygen to water.

Cytochrome c is a small heme protein that acts as an electron carrier in this process. It is located in the intermembrane space of the mitochondria and receives electrons from Complex III (ubiquinone-cytochrome c reductase). Once reduced, cytochrome c carries those electrons to Complex IV, where it donates them, allowing the complex to facilitate the reduction of oxygen.

By donating its electrons to Complex IV, cytochrome c plays a pivotal role in the final stages of oxidative phosphorylation, which is essential for ATP production in aerobic organisms. This specific transfer of electrons is critical for maintaining the flow of electrons through the electron transport chain and for sustaining the proton gradient necessary for ATP synthesis.