Respiration

Respiration refers to the absorption of oxygen by cells, which releases energy. This process is essential for the existence of higher organisms, making it possible to maintain complex and adaptive structures, containing appropriately differentiated cells 6.

The structure inside the cell in which energy is produced by respiration is called the mitochondrion. Oxidation refers to the combination of a substance with oxygen, which can be beneficial, as in normal respiration that produces energy, or harmful, as in rancidity, irradiation, or stress reactions 2.

Respiring cells are always producing some water, by transferring hydrogen from fuel molecules to oxygen. Respiration also produces carbon dioxide, which in itself is a Lewis acid, that associates with cellular proteins, acidifying them in the process 4.

Antioxidants, such as vitamin E and vitamin C, stop the harmful free-radical chain reactions which often involve oxygen, but they do not inhibit normal oxidation processes in cells 2.

The relationship between respiration and carbon dioxide is complex, with carbon dioxide being produced during respiration and also playing a role in the acidification of cellular proteins 4.

In certain conditions, such as intravenous infusion of free fatty acid, respiration can be disrupted, leading to pulmonary edema, hypoxemia, and hypocapnia 8.