Aerobic cellular respiration refers to a process in which cells use oxygen to help convert stored food into energy. Without this energy transfer, cells cannot perform vital tasks needed for the survival of the organism. When oxygen is not available, some cells can perform anaerobic respiration; this type of respiration produces far less energy.
All cellular respiration begins with the process of glycolysis. In this process, glucose is broken down into two carbon-based molecules called pyruvate or pyruvic acid. During this process, two molecules of Adenosinse Tri-Phosphate (ATP) are generated. ATP is a nucleotide that provides cellular energy.
If oxygen is present, the pyruvate is further broken down into carbon dioxide, loose carbon and an electron transport molecule called NADH. If oxygen is not present, the pyruvate goes through a process called fermentation, which produces alcohol or lactic acid. This is the end of the anaerobic respiration cycle.
In aerobic respiration, the NADH and loose carbon go through a set of complex chemical reactions known as the Krebs cycle. The Krebs cycle generates eight more molecules of NADH and two molecules of another electron transport molecule called FADH2. The NADH and FADH2 carry electrons to the cells where they are used to generate ATP. Depleted electrons combine with hydrogen and oxygen to make water, which is eliminated from the body.
Purpose of Aerobic Cellular Respiration
The goal of aerobic cellular respiration is to generate ATP to fill cells' energy needs. Cells require energy to perform a variety of tasks in the body, including powering muscles, keeping vital organs working, and cell division and replication.
When Oxygen Is Not Available
If oxygen isn't available, some cells can perform anaerobic respiration for a limited amount of time. For example, when exercising sometimes oxygen is depleted faster than it can be restored. In this situation, muscle cells perform anaerobic respiration, which causes lactic acid to build in the muscles. The build-up of lactic acid causes muscle fatigue.
Oxygen depletion can eventually lead to unconsciousness and death. On a cellular level, oxygen is required to generate ATP; without ATP cells will not have energy to function. Important nerve signals such as the signals causing the heart to beat and the lungs to expand and contract cannot be sent down the spinal cord without ATP.
Aerobic Cellular Respiration in Plants
Many people wrongly believe that plants do not need oxygen. The difference between plants and animals is that plants make their own food through photosynthesis, which is then converted into energy via cellular respiration; animals get food by eating plants or other animals.
Plants perform both photosynthesis and aerobic respiration during the day. At night, photosynthesis ceases but aerobic respiration continues.
Oxygen deprivation leads to death in plants as well as in animals.