Metabolism
Say it: muh-TAB-uh-liz-um
Metabolism is the full set of chemical reactions in a cell or organism, both those that break molecules down for energy and those that build them up.
Definition
What is metabolism?
Metabolism is the total of all chemical reactions that keep a cell or organism alive. These reactions are organized into metabolic pathways, chains of steps in which the product of one reaction becomes the starting material for the next, and nearly every step is speeded up by its own enzyme. Pathways fall into two opposite groups. Catabolism breaks large molecules such as glucose, fats and proteins into smaller ones and releases energy. Anabolism uses energy to build large molecules, such as proteins from amino acids or DNA from nucleotides.
ATP links the two sides: catabolic pathways such as glycolysis and the citric acid cycle make it, and anabolic pathways spend it. Carriers such as NADH move electrons between pathways, and much of the energy released is lost as heat. Hormones keep the balance; insulin favors building and storing fuel after a meal, while glucagon and cortisol favor breaking stores down when fuel is needed.
In medicine, the word also covers how the body processes drugs, and inherited faults in single enzymes cause a group of conditions known as inborn errors of metabolism.
Word parts
Where does the word “metabolism” come from?
- meta-
- change, beyondGreek meta
- -bol-
- to throwGreek ballein
Practice it
Where you'll meet it
Quizzes that use it
Related
Terms that go with it
- EnzymeAn enzyme is a biological catalyst, usually a protein, that speeds up a specific chemical reaction without being used up in the process.
- ATPATP (adenosine triphosphate) is the molecule cells use as their main short-term energy carrier, releasing energy when a phosphate group is removed.
- GlycolysisGlycolysis is the ten-step metabolic pathway that splits one glucose molecule into two pyruvate molecules, giving a net gain of two ATP.
- Citric acid cycleThe citric acid cycle is a loop of reactions in mitochondria that breaks down acetyl groups to carbon dioxide, capturing energy as NADH and FADH2.
- HomeostasisHomeostasis is the body's ability to keep internal conditions, such as temperature, blood glucose and pH, steady while conditions around it change.
- InsulinInsulin is a peptide hormone made by beta cells in the pancreas that lowers blood glucose by helping body cells take up and store sugar.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 6.1 Energy and Metabolism
- OpenStax Anatomy and Physiology 2e, 24.1 Overview of Metabolic Reactions
- MedlinePlus Medical Encyclopedia: Metabolism
Last updated
Spotted a mistake? Tell us and we'll correct it.
Practice Biochemistry
Free biochemistry quizzes, with an explanation for every answer.
See the Quizzes