Cellular respiration is the process living cells use to break down glucose and create energy in the form of ATP molecules.
Glycolysis steps for ATP production begin in the cell's cytoplasm, where glucose is split into two pyruvate molecules through a series of enzyme-controlled reactions. This process generates a small amount of ATP and NADH. During glycolysis, one glucose molecule is broken down into two pyruvate molecules, producing a net gain of 2 ATP molecules and 2 NADH molecules. This process doesn't require oxygen and is the first stage of both aerobic and anaerobic respiration.
The Krebs Cycle and Electron Transport Chain explained shows how cells generate most of their ATP through aerobic respiration. After glycolysis, if oxygen is present, the pyruvate molecules enter the mitochondria where they are converted into acetyl-CoA. The Krebs Cycle then uses these molecules to generate more NADH and FADH2, which carry electrons to the electron transport chain. The electron transport chain uses these electrons to pump hydrogen ions across the inner mitochondrial membrane, creating a gradient that drives ATP synthesis through a process called chemiosmosis. This aerobic process produces about 34-36 ATP molecules per glucose molecule.
The difference between Anaerobic vs aerobic respiration process is significant in terms of energy yield. When oxygen isn't available, cells must use anaerobic respiration or fermentation. In this process, after glycolysis, the pyruvate is converted to either lactic acid (in animals) or ethanol and carbon dioxide (in yeast). This process only yields 2 ATP molecules per glucose molecule, making it much less efficient than aerobic respiration. However, it allows organisms to survive in environments without oxygen or during periods of intense activity when oxygen demand exceeds supply. Understanding these processes helps explain why organisms need oxygen for optimal energy production and how they can adapt to different environmental conditions.
