mitochondrial electron transport, cytochrome c to oxygen

Definition

Target type: biologicalprocess

The transfer of electrons from cytochrome c to oxygen that occurs during oxidative phosphorylation, mediated by the multisubunit enzyme known as complex IV. [ISBN:0716731363]

Mitochondrial electron transport from cytochrome c to oxygen is the final stage of cellular respiration, where electrons are transferred from cytochrome c to molecular oxygen, generating a proton gradient that drives ATP synthesis. This process occurs in the inner mitochondrial membrane, specifically within the electron transport chain (ETC).

The ETC consists of four major protein complexes: Complex III (cytochrome bc1 complex), Complex IV (cytochrome c oxidase), and two mobile electron carriers, cytochrome c and ubiquinone (CoQ).

1. Cytochrome c, a small, soluble protein, carries electrons from Complex III to Complex IV. Cytochrome c contains a heme group that can reversibly bind and release electrons.

2. Complex IV, also known as cytochrome c oxidase, is a large protein complex embedded in the inner mitochondrial membrane. It contains two heme groups (a and a3) and two copper ions (CuA and CuB). Complex IV accepts electrons from cytochrome c and uses them to reduce molecular oxygen (O2) to water (H2O).

3. The reduction of oxygen to water is a four-electron process that occurs in a series of steps:

a. The first step involves the binding of oxygen to the heme a3 and CuB centers of Complex IV.

b. Electrons from cytochrome c are transferred to the heme a3 and CuB centers, reducing oxygen to a superoxide anion (O2-).

c. Two more electrons are transferred, reducing the superoxide anion to hydrogen peroxide (H2O2).

d. The final two electrons are transferred, reducing hydrogen peroxide to water.

4. During the electron transfer process, protons (H+) are pumped from the mitochondrial matrix across the inner mitochondrial membrane and into the intermembrane space. This creates a proton gradient, a difference in proton concentration between the two compartments.

5. The proton gradient represents a form of potential energy that can be used to generate ATP. ATP synthase, another protein complex embedded in the inner mitochondrial membrane, utilizes the proton gradient to drive the synthesis of ATP from ADP and inorganic phosphate (Pi).

The electron transport chain is a highly regulated process that is essential for life. It provides the energy needed for all cellular processes, including muscle contraction, nerve impulse transmission, and protein synthesis. Disruptions in electron transport can lead to a variety of diseases, including mitochondrial diseases, neurodegenerative diseases, and cancer.'
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Proteins (3)

Compounds (9)