The Difference Between Breathing and Respiration
Humans, as well as all multi-cellular organisms on Earth, depend upon oxygen to produce the large quantities of energy necessary for life and intelligence. This oxygen must be transported from the atmosphere outside out bodies to the mitochondria, the cellular powerhouses which are the only cells within us that use oxygen. The gas is moved down a series of controlled gradients across diverse tissues before it reaches its destination within this unique structure.
The process of respiration is moving oxygen from the atmosphere to the mitochondria and carbon dioxide from the cells back to the atmosphere. Oxygen is used in the mitochondria to sweep up hydrogen protons to allow energy production to continue unabated. Carbon dioxide is produced during both anaerobic and aerobic metabolism and becomes the signal for increased breathing rate as its concentration within the lungs increases.
Breathing is a lay term that represents the first part of respiration, the moving of air into and out of the lungs. Breathing is called ventilation by physiologists. It is easy to remember that breathing is about moving air and not specific gases if you think of ventilating a room by opening a window to let air move in and out. Air contains mostly nitrogen along with oxygen and carbon dioxide, but it is only the final two components of air that actually move into and out of the lungs into the blood stream.
The initial step sees air move down its concentration gradient from the ambient atmosphere into the lungs because of the increased lung volume derived from contracting the diaphragm and the lifting of the rib cage. Air finds its way to the depths of the lungs and the alveoli which are the terminus of the pulmonary pathway.
Here the oxygen is pulled through the pulmonary membrane into the blood where it is bound to the iron component of hemoglobin within the red blood cells, in effect oxidizing or “rusting” the iron. The nearly non-existent blood pressure in the right atrium combined with the high pressure generated by the left ventricle force the blood throughout the circulatory system delivering the oxygen-rich hemoglobin to the 100 trillion cells of the body.
This delivery of oxygen from the atmosphere to the threshold of cell membranes is referred to as respiration. The act of breathing is a part of this whole process of respiration. What we usually think of as breathing, moving air into and out of the lungs, is referred to by physiologists as ventilation a component of respiration, differentiating it from diffusion across the pulmonary membrane and the final journey through the blood vessels called oxygen transport.
The term cellular respiration is not particularly relevant to this discussion. This internal respiration occurs within cells that results in the production of energy in the form of ATP. While this is significant for the maintenance of life, the confusion between the two terms breathing and respiration stops at the cell membrane.