respiratory electron transport chain

Definition

Target type: biologicalprocess

A process in which a series of electron carriers operate together to transfer electrons from donors such as NADH and FADH2 to any of several different terminal electron acceptors to generate a transmembrane electrochemical gradient. [GOC:mtg_electron_transport, ISBN:0716720094]

The respiratory electron transport chain (ETC) is a series of protein complexes embedded in the inner mitochondrial membrane that plays a crucial role in cellular respiration. It functions by transferring electrons from electron donors, such as NADH and FADH2, to a final electron acceptor, which is typically oxygen. This process generates a proton gradient across the inner mitochondrial membrane, which drives the synthesis of ATP, the primary energy currency of the cell.

The ETC consists of four main protein complexes:

1. **Complex I (NADH dehydrogenase):** This complex accepts electrons from NADH and transfers them to ubiquinone (Q), also known as coenzyme Q. This process pumps protons from the mitochondrial matrix to the intermembrane space.

2. **Complex II (succinate dehydrogenase):** This complex receives electrons from FADH2 and transfers them to ubiquinone. Unlike Complex I, Complex II does not pump protons.

3. **Complex III (cytochrome bc1 complex):** This complex accepts electrons from ubiquinol (QH2), the reduced form of ubiquinone, and transfers them to cytochrome c. This process also pumps protons across the membrane.

4. **Complex IV (cytochrome c oxidase):** This complex receives electrons from cytochrome c and transfers them to molecular oxygen, the final electron acceptor. This process consumes oxygen and generates water.

The movement of electrons through the ETC is coupled to the pumping of protons from the mitochondrial matrix to the intermembrane space. This creates an electrochemical gradient, with a higher proton concentration in the intermembrane space. The energy stored in this gradient is used by ATP synthase, a complex that utilizes the proton flow to synthesize ATP from ADP and inorganic phosphate.

The ETC is essential for aerobic respiration, as it provides the energy needed for cellular processes, such as muscle contraction, nerve impulse transmission, and protein synthesis. Disruptions in the ETC can lead to various diseases, including mitochondrial disorders, cancer, and neurodegenerative diseases.'
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Proteins (4)

Compounds (207)