mitochondrial electron transport, NADH to ubiquinone

Definition

Target type: biologicalprocess

The transfer of electrons from NADH to ubiquinone that occurs during oxidative phosphorylation. [ISBN:0716731363]

Mitochondrial electron transport is a fundamental process that powers cellular respiration, converting energy from food molecules into a usable form called ATP. The NADH to ubiquinone segment of this process involves the transfer of electrons from NADH, a reduced electron carrier, to ubiquinone (Q), a mobile electron carrier in the mitochondrial inner membrane. This process occurs through a series of protein complexes embedded in the membrane, known as Complexes I, II, and III.

Complex I, also known as NADH dehydrogenase, is the primary entry point for electrons from NADH. It binds NADH and uses the energy released during its oxidation to pump protons across the inner mitochondrial membrane, contributing to the proton gradient that drives ATP synthesis. These electrons are then transferred to ubiquinone (Q), reducing it to ubiquinol (QH2).

Complex II, also known as succinate dehydrogenase, is another entry point for electrons, specifically from succinate, a molecule involved in the citric acid cycle. Unlike Complex I, Complex II does not pump protons across the membrane. The electrons from succinate are transferred to ubiquinone, reducing it to ubiquinol.

Ubiquinol, now carrying the electrons from both Complex I and Complex II, moves freely within the membrane. It encounters Complex III, also known as cytochrome bc1 complex. Complex III accepts the electrons from ubiquinol, transferring them to cytochrome c, another mobile electron carrier. During this transfer, Complex III also pumps protons across the membrane, further contributing to the proton gradient.

The overall process of NADH to ubiquinone electron transfer is a key step in mitochondrial respiration. It involves a series of redox reactions, where electrons are transferred from one molecule to another, releasing energy that is used to pump protons across the membrane. This proton gradient is essential for ATP synthesis, the primary energy currency of cells.

The transfer of electrons from NADH to ubiquinone is tightly regulated and is subject to various factors such as the availability of oxygen, the levels of NADH and ubiquinone, and the activity of enzymes involved in the process.

This intricate series of events demonstrates the complexity and precision of cellular respiration, highlighting the crucial role of electron transport in maintaining cellular function and energy production.'
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Proteins (44)

Compounds (8)