Medical Definition of Respiration

"Respiration" denotes inhaling and exhaling, but this fairly common word has a less familiar meaning, too. Well-known in medicine, it refers to the conversion of energy into forms that cells can use.

Breathing

• As does common understanding, medicine defines "respiration" to include breathing, according to Taber's Cyclopedic Medical Dictionary.

Cellular Respiration

• In addition, however, medicine views respiration more broadly to include the acquisition of useable energy by cells---a process that may or may not involve breathing, as note Neil A. Campbell, Ph.D. and his co-writers in the book "Biology."

Scope

• In this more purely medical sense of the word, respiration occurs not only in animals or in the cells composing animals, but also in plant cells and unicellular organisms such as bacteria, fungi, algae and protozoa.

Aerobic

• Relying on free oxygen (O2) to accept electrons at the ends of energy-yielding chemical reactions, aerobic respiration produces lots of energy a cell can use, according to Jacquelyn G. Black, Ph.D. in her book "Microbiology: Principles and Explorations."

Anaerobic

• In the absence of O2, cells can acquire energy using inorganic oxygen-containing molecules such as nitrate, nitrite and sulfate, although this yields 19 times less energy per glucose molecule than does aerobic respiration, notes Dr. Black.