The aerobic respiration process is a series of chemical reactions that use oxygen to convert food nutrients into energy for a cell's use. It is the second stage within the cell metabolism process. The first stage doesn't require oxygen but provides the needed materials for aerobic processes to take place. The end result produces a material known as ATP. ATP is the fuel or energy source that enables cells to perform necessary functions.
For humans and animals, cell metabolism processes happen in three steps--glycolysis, the Krebs Cycle, and the electron transport chain. Aerobic respiration takes place within the Krebs Cycle and electron transport chain. The presence of oxygen enables cells to produce a greater amount of ATP than when no oxygen is available. The glycolysis step--which requires no oxygen--produces two molecules of ATP. By the end of the electron transport chain, 36 molecules of ATP are available for the cell's use.
Carbohydrates, fats, and proteins serve as the raw materials for cell metabolism processes. Glycolysis starts out with a glucose molecule--a sugar carbohydrate--and breaks it down into a chemical called pyruvate. If no oxygen is present, the cell can continue manufacturing ATP through glycolysis until oxygen becomes available. Under strenuous conditions, a muscle cell becomes depleted of oxygen and may start to burn and ache. This results from the buildup of pyruvate in the cells. Once aerobic respiration processes resume, pyruvate levels decrease, causing the burning sensations to subside.
Aerobic respiration processes use six molecules of oxygen for every one molecule of glucose that enters the glycolysis stage, according to InDepth Info. The Krebs Cycle works to manufacture citric acid molecules from the pyruvate created during glycolysis. When combined with oxygen, these citric acid molecules are broken down into NADH and FADH2. The electron transport chain works to release the energy contained inside NADH and FADH2 through a series of electron trade-offs. In effect, oxygen enables the oxidation of NADH and FADH2. The end products are ATP, carbon dioxide, and water.
Although most living organisms engage in aerobic respiration, individual processes may differ according to species. An example of this is how plant organisms use sunlight, carbon dioxide, and water to produce glucose and oxygen, according to Biology Online. Although they may differ, there is an interplay between human/animal and plant processes according to InDepth Info. Carbon dioxide by-products produced from human respiration provide an essential material for plant cell respiration to begin. Likewise, oxygen byproducts produced from plant respiration provide an essential material for the survival of humans and other animals.