Metabolism Definition in Science

What Does Metabolism Mean in Science?

Metabolism refers to the set of biochemical reactions that occur in a cell or organism.
Metabolism refers to the set of biochemical reactions that occur in a cell or organism. Yagi Studio / Getty Images

Metabolism is the set of biochemical reactions involved in storing fuel molecules and converting fuel molecules into energy. Metabolism may also refer to the sequence of biochemical reactions compounds undergo inside a living cell. The word "metabolism" comes from the Greek word metabolē, which means "change."

Anabolism and Catabolism

Metabolism or metabolic reactions include anabolic reactions and catabolic reactions. Anabolic reactions synthesize or build compounds, such as proteins, nucleic acids, carbohydrates, and lipids. Catabolic reactions break down complex molecules into simpler ones, often releasing energy in the process. A good example of a catabolic reaction is the breakdown of glucose into pyruvate by cellular respiration.

Functions of Metabolism

Metabolism serves three key functions:

  1. It converts food into the energy required to run the cell and the body.
  2. It converts food into building blocks used to make molecules the cell and body need.
  3. It eliminates nitrogenous wastes.


The study of metabolism dates back at least to the time of the ancient Greeks. Aristotle's The Parts of Animals described the process of transforming food into usable materials, the release of heat as food was used, and the excretion of urine and feces. In 1260 AD, Ibn al-Nafis described the constant building and dissolution within the body in his work Al-Risalah al-Kaniliyyah fil Siera al-Nabawiyyah (The Treatise of Kamil on the Prophet's Biography). Santorio Santorio conducted controlled experiments on metabolism in 1614, which he outlined in his book Ars de statica medicina. The chemical mechanisms of metabolism weren't really understood until the 19th century, while the structures of the molecules weren't known until the 20th century.


  • Berg, J.; Tymoczko, J.; Stryer, L. (2002). Biochemistry. W. H. Freeman and Company. ISBN 0-7167-4955-6.
  • Rose, S.; Mileusnic, R. (1999). The Chemistry of Life. Penguin Press Science. ISBN 0-14-027273-9.
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Helmenstine, Anne Marie, Ph.D. "Metabolism Definition in Science." ThoughtCo, Aug. 26, 2020, Helmenstine, Anne Marie, Ph.D. (2020, August 26). Metabolism Definition in Science. Retrieved from Helmenstine, Anne Marie, Ph.D. "Metabolism Definition in Science." ThoughtCo. (accessed April 11, 2021).