Beyond Gylcolysis - Cellular Respiration

In cellular respiration, several different steps and pathways provide the means to produce the needed energy (ATP) required for the cell, and the body, to function. After the breakdown of glucose and the production of pyruvate, three different steps are encountered during aerobic cellular respiration.

First is the pyruvate decarboxylation, in which the pyruvate molecule loses a carbon dioxide group, becoming simply an acetyl group, and then forms acetyl CoA as the final product.

Next in the list of processes comes the Citric Acid cycle, sometimes called the Krebs cycle, or the TCA cycle. It's basically a large process that goes in a circle of chemical reactions, with the Acetyl group from acetyl CoA entering the circle, CO2 is lost, 1 ATP is produced from each turn of the circle, and electrons are moved from the carrier NAD+ and FAD molecules, reducing them to NADH and FADH2.

Finally, the Electron Transport Chain is reached. While the Citric Acid cycle occurs in the inner matrix of the mitochondria, the Electron Transport Chain occurs in the inner membrane of the Mitochondria. In the Electron Transport Chain, or ETC for short, the carrier molecules with the electrons from the Citric Acid Cycle transfer their electrons to oxygen through a series of complicated reactions with carrier molecules. This process is known as oxidative phosphorylation, and ends up producing ATP as a product. Three types of electron carrier molecules are present in this system, these being NADH dehydrogenase, b-c1 complex, and cytochrome oxidase. Electrons are moved from the carrier molecules to the next carrier molecule, generating ATP as it is moved by the release of energy between carriers. A proton gradient is used to produce and power the production of the ATP through this process, with a proton-motive force that sends H+ ions across the mitochondria membrane, thereby sending them into the matrix, with the help of the channels made by the ATP synthesase enzymes. Energy is given off when these ions move through the channels, allow for the oxidation of ADP to ATP, hence the process called oxidative phosphorylation.