Aerobic respiration, from which the term aerobic exercise borrows its name, is a metabolic process in many organisms that requires oxygen to generate energy. This process uses oxygen in low- to moderate-intensity tasks for long periods of time, preferably with the sugar glucose as fuel, which burns very readily as a source of energy. Other fuels may also be used, however. Much of this activity occurs within the Krebs cycle.
Metabolism
The Krebs cycle, also known as the citric acid cycle, is a key metabolic process common to many organisms. Like all metabolic pathways, it is needed to modify molecules into a form that the body can use to perform many of its basic functions. In the case of the Krebs cycle, the metabolic reaction is part of a larger process that creates the molecule ATP, which is used as a source of energy to power muscle movement and for many other important functions. This reaction occurs within tiny modules known as mitochondria, which are the powerhouses of the cell.
Chemical Reactions
The Krebs Cycle is a series of eight reactions that occur in the mitochondria. These reactions take a two carbon molecule known as acetate and produce carbon dioxide as a byproduct. This is why carbon dioxide, when exchanged for oxygen in the lungs, is exhaled out. Acetate is the molecule that enters the Krebs cycle, but in reality the entire process is used to breakdown sugars, amino acids and fats, the three main molecules in our diet from which energy is derived.
Electron Transfer
The Krebs cycle itself does not handle or use oxygen, but it is nevertheless an instrumental process found in just about all aerobic organisms. Its main purpose is to donate electrons from broken down acetate in order to generate chemical energy in the form of ATP. Electrons are the tiny negatively charged particles of atoms. The donated electrons enter a long chain known as an electron transport chain to perform work and generate new ATP molecules. In a sense, it is like a power plant.
Oxygen
Oxygen is needed at the very end of the chain to remove all used electrons from the system. Otherwise, the entire system will grind to a halt, causing the Krebs cycle to stop, too. Because it cannot run successfully without oxygen, the Krebs cycle is said to be aerobic. The last act of the process is the formation of water by the combination of oxygen, electrons and hydrogen.
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