You've probably heard that respiration is an important part of human metabolism, which may be confusing given that in common usage, "respiration" refers to the process of breathing. Actually, breathing itself is essential to metabolism, but that aside, the word "respiration" actually refers to the process of burning nutrient molecules to release energy that your cells require.
Metabolism
Human metabolism is defined as the sum of all chemical reactions that take place in your body. Your body engages in a huge variety of chemical reactions to maintain itself. Some metabolic reactions break down large molecules into smaller ones, generally releasing energy in the process; these are known as catabolic reactions. Other metabolic reactions build larger molecules from smaller ones, and are called anabolic reactions, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry."
Respiration
Specifically, respiration is the subset of metabolic reactions whereby the breakdown products of food digestion are burned in the presence of oxygen to release energy. The cells then store this released energy in the form of molecules of ATP, or adenosine triphosphate. ATP is a sort of "chemical currency" that cells can generate as they burn nutrient molecules, then use to provide for their energy needs as they generate products, produce movement or communicate.
Oxygen Needs
The process of respiration is oxygen-dependent. As your cells break down nutrient molecules, they generate molecules of a compound called acetyl-CoA. Through a series of reactions called the Kreb's Cycle, acetyl-CoA breaks down into carbon dioxide, which you exhale. A series of reactions collectively called oxidative phosphorylation then uses some of the products of the Kreb's Cycle to make ATP, a process that requires oxygen and results in the formation of water, which is the other waste product of respiration.
Other Aspects of Metabolism
While respiration is an important part of human metabolism -- and while the generation of energy by burning food is perhaps the most familiar of the metabolic reactions -- there are many other aspects to metabolism that don't relate to respiration. For example, cells engage in metabolic reactions to produce hormones and other molecules of communication, explains Dr. Lauralee Sherwood in her book "Human Physiology." Further, cells constantly produce and break down proteins and other structural and functional compounds. Metabolism encompasses a great variety of reactions, of which the reactions of respiration are only a small subset.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
Member Comments