Oxidative Phosphorylation Overview

The matrix is the location within mitochondria where the citric acid cycle and parts of lipid and amino acid metabolism take place.

Electron-transport chain complexes contain different molecules that carry electrons, including flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), cytochromes, and iron-sulfur clusters.

Coenzyme Q, also known as ubiquinone, is a lipid-soluble electron carrier that transports electrons from complexes I and II to complex III.

Electron transfer in the electron transport chain is governed by reduction potentials; molecules with a higher tendency to accept electrons are reduced first.

Coenzymes are molecules associated with dehydrogenases and transfer hydride ions (H-) or hydrogen atoms (H) in redox reactions.

The process where energy from NADH and FADH2 is used to produce ATP.

Energy released from electron transport is used to pump protons against their gradient, creating a stored energy source to fuel ATP synthesis.

The process of creating ATP from ADP and inorganic phosphate (Pi).

The inner and outer membranes of mitochondria are critical for creating and maintaining a proton gradient needed for ATP production.

Protein complexes embedded in the inner mitochondrial membrane that facilitate the transfer of electrons and the pumping of protons.

Electron carriers like NADH and FADH2, which are formed during the breakdown of fuels.

The mitochondria has four sections (outer membrane, intermembrane space, inner membrane, and matrix) each with a specific function.

A difference in proton concentration across a membrane. This gradient stores energy that drives ATP synthesis.

One-electron carriers that use the Fe3+/Fe2+ redox system, with heme derivatives.

One-electron carriers using the Fe3+/Fe2+ redox system, coordinated by cysteines in proteins or in iron-sulfur clusters.

Electron transport in complexes creates a proton gradient (proton-motive force) used to drive ATP synthesis.

A concentration gradient of protons generated by electron transport in complexes, used to drive ATP production.

Enzyme complex I in the mitochondrial respiratory chain, involved in electron transfer.

Enzyme complex II in the mitochondrial respiratory chain, transferring electrons from succinate.

Enzyme complex III participating in the electron transfer chain between Fe-S and cytochrome c.

Enzyme complex IV, final electron acceptor in the electron transfer chain.

Cyanide blocks electron transfer in Complex IV (cytochrome oxidase), halting both respiration and ATP synthesis.

Mitochondria supplied with succinate respire and synthesize ATP only when ADP and Pi are present. Inhibiting ATP synthase blocks both processes.

DNP acts as an uncoupler, allowing respiration to continue without ATP synthesis. It disrupts the proton gradient.

Ionophores, like valinomycin, disrupt ion gradients across membranes, uncoupling electron transport and ATP synthesis.

Adding K+ artificially creates an electrochemical gradient that can drive ATP synthesis even without a substrate, proving the crucial role of proton gradients.

Thermogenin, found in brown fat, is an uncoupling protein that allows H+ flow, generating heat. Important for babies and hibernating animals.

This shuttle transports reducing equivalents (NADH) from the cytosol into the mitochondrial matrix, mainly in liver, kidneys, and heart.

This alternative shuttle moves reducing equivalents from cytosol to the mitochondrial matrix, prevalent in skeletal muscle and brain.

ADP, along with inorganic phosphate (Pi), serves as the primary acceptor of energy released from the electron transport chain in Oxidative Phosphorylation. The concentration of ADP reflects the cell's energy needs, regulating the rate of ATP production.

The Mass-Action Ratio ([ATP]/[ADP][Pi]) indicates the cell's energy state. A high ratio indicates high energy reserves, while a low ratio signals the need for ATP production.

High ATP levels act as an inhibitor at multiple points in the Oxidative Phosphorylation process, slowing down ATP production when energy demand is low. This ensures efficient energy utilization.

Inhibition of Oxidative Phosphorylation results in an accumulation of NADH, as the electron transport chain is stalled. This signifies a decrease in the overall energy production of the cell.

The rate of Oxidative Phosphorylation is primarily regulated by the availability of substrates, particularly NADH and ADP, which act as signals for energy demand.

Oxidative Phosphorylation is the process that fuels ATP synthesis. The energy released during electron transport is captured by the proton gradient, which then drives ATP synthesis.

The proton gradient, established across the mitochondrial membrane during electron transport, represents a stored energy source. This energy is released when protons flow back through ATP synthase, driving ATP production.

The electron transport chain, by moving electrons across the inner mitochondrial membrane, pumps protons against their concentration gradient. This proton gradient is used by ATP synthase to synthesize ATP.

A regulatory mechanism where high levels of ATP and citrate (a citric acid cycle intermediate) inhibit the enzyme phosphofructokinase-1 (PFK-1), the rate-limiting step in glycolysis.

Mitochondria play a critical role in programmed cell death by releasing cytochrome c into the cytosol, triggering the activation of caspases, a family of proteases that dismantle cellular components.

Mitochondrial DNA (mtDNA) is inherited maternally, meaning it is passed down from mother to offspring.

Mitochondria possess their own ribosomes for protein synthesis within the organelle, but most mitochondrial proteins are encoded by nuclear DNA, synthesized in the cytosol, and then imported into the mitochondria.

Defects in oxidative phosphorylation within mitochondria can lead to a rare form of diabetes because low ATP levels in the cell prevent insulin release.

This theory explains how energy from electron transport is used to create a proton gradient across the inner mitochondrial membrane, which is then used to drive ATP synthesis.

Oxidative phosphorylation uses electron carriers like NADH and FADH2, which transfer electrons through a series of protein complexes embedded in the inner mitochondrial membrane.

Electron flow and ATP production are tightly coupled, but uncouplers can disrupt this coupling, dissipating the proton gradient and reducing ATP synthesis.