What Is Respiration?
Respiration can refer to many different cellular and physiological processes that occur in living things and are related to the generation of energy. One example of such a process is breathing, by which oxygen is taken into the body and carbon dioxide is removed. A similar process also occurs in aquatic creatures as they extract dissolved oxygen from the water using their gills or similar organs. Oxygen is necessary for the process of cellular respiration, by which cells produce useful energy. Another common example occurs in the roots of plants as the plants exchange various gases with the atmosphere.
There are four primary stages to respiration in humans and in other similar air-breathing animals; these stages plot the progress of oxygen from inhalation into the lungs to absorption by internal organs. The process starts with ventilation, when air is simply moved in and out of the lungs. When it is moved into the lungs, oxygen is extracted from the air; when it moves out, carbon dioxide is released back into the air. After ventilation comes pulmonary gas exchange, in which the oxygen from the lungs enters the circulatory system through the pulmonary capillaries.
Once the oxygen enters the pulmonary capillaries, the process of gas transport begins. In gas transport, oxygen circulates throughout the circulatory system and eventually enters capillaries that are attached to major organs that need a constant supply of oxygen to function properly. Other unneeded gases, such as carbon dioxide, continue along the circulatory channels and are released from the lungs during exhalation. This leads to the final stage: peripheral gas exchange. In peripheral gas exchange, oxygen moves from the capillaries into the tissues and organs that need it to function properly.
The oxygen that is brought to the tissues through respiration is specifically needed for the microscopic process of cellular respiration. Cellular respiration, which is also referred to as oxidative metabolism, involves a set of chemical reactions, many involving oxygen, that allow the body to convert substances into usable energy. Specifically, the reactions that occur within the cells work to convert sugar into adenosine triphosphate, or ATP.
Oxygen is needed for cellular respiration because many oxidation-reduction, or redox, reactions occur throughout the respiration process. Oxygen is a powerful oxidizing agent; it can give up electrons in reaction fairly readily. These released electrons go to the production of the energy-rich ATP molecules, which are later broken down and used for energy when needed.
Written by Daniel Liden
