Glycolysis is a series of chemical reactions that convert sugars (primarily glucose) to pyruvate (also known as pyruvic acid). Glycolysis uses and generates chemical energy. It also produces electron carrier molecules. This chemical pathway is found in nearly all living cells.
Oxidative Phosphorylation
In the inner mitochondrial membrane, the energy released through the electron transport chain is used to generate chemical energy in the form of ATP.
Acetyl CoA Production
Acetyl CoA is the major input into the citric acid cycle. The breakdown of sugars is a major source of acetyl CoA formation. The metabolic breakdown of both proteins and fats can also produce this important molecule.
Citric Acid Cycle
The citric acid cycle is also known as the Krebs cycle and the tricarboxylic acid (or TCA) cycle. This cycle occurs in aerobic organisms. It generates electron carrier molecules that are used in the electron transport chain.
2 ATP to perform work
2 NADH that travel to the electron transport chain in the mitochondria
2 pyruvate that can move onto the mitochondria or be used in fermentation
Energy released through the passing of electrons is used to transport protons across the membrane. Protons (H+) pass through ATP synthase, generating an additional 25 ATP molecules for each glucose molecule that entered glycolysis.
Limited oxygen
Arsenic
DNP (diet pill)
When oxygen is low, the electron carriers necessary for glycolysis can be replenished through fermentation. Each pyruvate is converted to a lactate molecule. During this process, an NAD+ molecule is produced which can return to glycolysis.
Oxygen is no longer the final electron acceptor molecule in the electron transport chain, stalling the flow of electrons through the complexes of the electron transport chain. This disables oxidative phosphorylation and ATP synthesis in the mitochondrion.
The pyruvate coming from glycolysis can no longer be converted to acetyl CoA, so there is no acetyl CoA to enter the citric acid cycle. The few ATP molecules produced in the cell are generated through glycolysis.