Question

What is meant by oxidative phosphorylation?

Short answer

Oxidative phosphorylation is the process of ATP production using the electron transport chain and chemiosmosis during cellular respiration.

Step-by-step solution

Define Oxidative Phosphorylation

Oxidative phosphorylation is a metabolic process by which cells produce ATP, the main energy currency, through the electron transport chain and chemiosmosis.

Explain the Electron Transport Chain

The electron transport chain is a series of protein complexes and other molecules embedded in the inner mitochondrial membrane. Electrons are transferred through these complexes, releasing energy used to pump protons across the membrane, creating a proton gradient.

Define Chemiosmosis

Chemiosmosis is the movement of protons down their gradient through the enzyme ATP synthase. This movement drives the synthesis of ATP from ADP and inorganic phosphate.

Link the Process to Cell Respiration

Oxidative phosphorylation is the final stage of cellular respiration, following glycolysis and the Krebs cycle, and it produces the majority of ATP for cellular activities.

Key concepts

Electron Transport Chain

The electron transport chain (ETC) is a crucial step in cellular respiration. It consists of a series of protein complexes and molecules located in the inner mitochondrial membrane. These proteins act like a relay race for electrons.
Generators of electrons, called NADH and FADH2, donate electrons to the ETC. As electrons pass through the protein complexes, energy is released. This energy is used to pump protons (H+) from the mitochondrial matrix to the intermembrane space, creating an electrochemical gradient.
The process culminates with electrons being transferred to molecular oxygen (O2), which combines with protons to form water (H2O). The ETC is vital because it sets up the proton gradient needed for the next step, chemiosmosis.

Chemiosmosis

Chemiosmosis is the process of using the proton gradient, established by the electron transport chain, to drive the synthesis of ATP. This occurs across the inner mitochondrial membrane and involves the enzyme ATP synthase.
The high concentration of protons in the intermembrane space creates a proton motive force, due to both the chemical concentration and electrical charge differences. Protons flow back into the mitochondrial matrix through ATP synthase, a process that can be likened to water flowing through a dam.
This flow of protons turns ATP synthase into a molecular turbine, facilitating the binding of ADP and inorganic phosphate to form ATP. Chemiosmosis is the bridge between the electron transport chain and the generation of ATP, the energy currency of the cell.

Cellular Respiration

Cellular respiration is the metabolic process by which cells convert nutrients into energy in the form of ATP. It consists of three main stages: glycolysis, the Krebs cycle, and oxidative phosphorylation.
Glycolysis occurs in the cytoplasm and breaks down one molecule of glucose into two molecules of pyruvate, producing small amounts of ATP and NADH. The pyruvate then enters the mitochondria and is converted into Acetyl-CoA to enter the Krebs cycle (also known as the Citric Acid Cycle).
The Krebs cycle occurs in the mitochondrial matrix and generates high-energy electron carriers, NADH and FADH2. These carriers enter the electron transport chain, where their stored energy is used to create a proton gradient.
Finally, oxidative phosphorylation uses the proton gradient established by the electron transport chain in chemiosmosis to produce ATP. This final stage produces the majority of ATP during cellular respiration, making it essential for meeting the energy demands of the cell.