electron transport coupled proton transport

Definition

Target type: biologicalprocess

The transport of protons against an electrochemical gradient, using energy from electron transport. [GOC:mah]

Electron transport coupled proton transport is a fundamental process in cellular respiration, occurring within the mitochondrial inner membrane in eukaryotes and the plasma membrane in prokaryotes. This process harnesses the energy released from the oxidation of fuel molecules like glucose to establish a proton gradient across the membrane, ultimately driving the synthesis of ATP, the cell's energy currency.

The process begins with the transfer of electrons from electron donors, such as NADH and FADH2, to a series of electron carriers embedded within the membrane. These carriers, organized into four complexes (I-IV), each possess distinct redox potentials, facilitating a stepwise movement of electrons down an energy gradient.

As electrons flow through the electron transport chain, energy is released, which is used to pump protons (H+) from the mitochondrial matrix (or the cytoplasm in prokaryotes) across the inner membrane into the intermembrane space (or the periplasm). This active transport creates a proton gradient, where the concentration of protons is higher in the intermembrane space than in the matrix.

The proton motive force, driven by the electrochemical gradient, is then used by ATP synthase (Complex V), also embedded in the inner membrane, to synthesize ATP. ATP synthase utilizes the energy stored in the proton gradient to drive the phosphorylation of ADP to ATP, a reaction that releases the energy required for cellular functions.

The specific steps involved in electron transport and proton pumping include:

1. **Complex I (NADH dehydrogenase):** NADH delivers electrons to Complex I, which pumps protons across the membrane.
2. **Complex II (Succinate dehydrogenase):** FADH2 delivers electrons to Complex II, which does not directly contribute to proton pumping.
3. **Complex III (Cytochrome bc1 complex):** Electrons from Complex I or II are passed to Complex III, which also pumps protons across the membrane.
4. **Complex IV (Cytochrome c oxidase):** Electrons from Complex III are transferred to Complex IV, which ultimately uses oxygen as the final electron acceptor, reducing it to water.

This complex interplay of electron transport and proton pumping, coupled with ATP synthesis by ATP synthase, represents the core mechanism of oxidative phosphorylation, the major energy-producing pathway in most living organisms.'
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Proteins (5)

Compounds (7)