Biochem 12.2 Electron Transport Chain Overview

Electron Transport Chain (ETC) is a series of protein complexes embedded within the inner mitochondrial membrane that utilize oxidation-reduction reactions to transfer electrons and generate energy.

The ETC begins with the oxidation of NADH or FADH2, generated by the citric acid cycle and other metabolic pathways.

The electron transport chain is a series of oxidation-reduction reactions, where electrons are passed from one molecule to another. The final electron acceptor is molecular oxygen (O2).

Each complex in the ETC, except Complex II, uses the energy released during the reactions to pump protons (H+) from the mitochondrial matrix into the intermembrane space.

Complex I is named NADH:ubiquinone oxidoreductase, which catalyzes the oxidation of NADH to NAD+ by removing hydride ions and transferring them to ubiquinone.

Ubiquinone (Q) is a hydrophobic molecule located within the inner mitochondrial membrane, while NADH is hydrophilic and found in the mitochondrial matrix.

The energy released by the oxidation of NADH by Complex I is used to pump protons (H+) from the mitochondrial matrix to the intermembrane space, contributing to the proton gradient.

The proton gradient generated by the ETC is essential for ATP synthesis by ATP synthase. This process is called oxidative phosphorylation.

The process of transferring electrons from ubiquinol to cytochrome c, a soluble protein in the intermembrane space.

A cyclical process within Complex III where ubiquinol transfers electrons to cytochrome c and ubiquinone, resulting in the reduction of two cytochrome c molecules.

A partially reduced form of ubiquinone with an unpaired electron, making it a radical.

Highly reactive molecules formed when semiquinone reacts with oxygen, leading to cellular damage.

A state of cellular imbalance caused by the presence of reactive oxygen species, leading to oxidative damage to cellular components.

A shuttle system that carries electrons produced from glycolysis in the cytoplasm to the electron transport chain in the mitochondria. It uses glycerol-3-phosphate dehydrogenase and ubiquinone as carriers.

A type of electron transport chain that uses a series of redox reactions to generate a proton gradient across the inner mitochondrial membrane. It is the primary mechanism for ATP generation in aerobic organisms.

The reduced form of ubiquinone, which carries high-energy electrons in the electron transport chain.

A process where cells undergo controlled self-destruction, often triggered by damage to cellular components.

A protein complex within the mitochondria involved in the electron transport chain. It receives electrons from reduced cytochrome c and uses them to reduce oxygen to water.

A cycle of chemical reactions within the mitochondria that breaks down glucose and produces high-energy electron carriers (NADH and FADH2).

The process of generating energy in the absence of oxygen. Typically involves fermentation and produces less energy than aerobic respiration.

The ratio of ubiquinone (oxidized form) to ubiquinol (reduced form) in the mitochondrial membrane. Provides an indication of the electron flow in the Electron Transport Chain.

Conditions that require the presence of oxygen for optimal cellular functioning. The ETC and Citric Acid Cycle are both aerobic processes.

A process that transfers electrons from cytosolic NADH to mitochondrial electron acceptors, regenerating NAD+ in the cytosol for glycolysis to continue.

A protein complex in the ETC that accepts electrons from FADH2, a reduced co-factor from the citric acid cycle.

A specific enzyme in the citric acid cycle that acts as a prosthetic group in Complex II, oxidizing succinate to fumarate and producing FADH2 in the process.

A coenzyme that carries electrons from the citric acid cycle and other metabolic pathways to the electron transport chain.

A transmembrane enzyme that carries electrons from glycerol-3-phosphate to FAD in the inner mitochondrial membrane.

An intermediate of glycolysis that acts as an electron acceptor in the glycerol-3-phosphate shuttle.

The final electron acceptor in both the malate-aspartate shuttle and the glycerol-3-phosphate shuttle.