View source for Catabolism

{{Short description|Set of metabolic pathways that breaks down molecules into smaller units}}
{{For|the accelerated changes that occur when certain chemical agents are introduced|Catalysis}}
{{Missing citations|date=April 2023}}
[[File:Catabolism schematic.svg|thumb|250px|right|Schematic breakdown of large [[biomolecule]]s to release energy for fueling the [[Cell (biology)|cell]] [[metabolism]] by producing [[Adenosine triphosphate|ATP]], the energy currency of the cell]]
[[File:Carbon Catabolism.png|thumb|500px|Carbon Catabolism pathway map for free energy including carbohydrate and lipid sources of energy]]

'''Catabolism''' ({{IPAc-en|k|ə|ˈ|t|æ|b|ə|l|ɪ|z|ə|m}}) is the set of [[Metabolism|metabolic]] pathways that breaks down [[molecule]]s into smaller units that are either oxidized to release [[energy]] or used in other [[anabolic]] reactions.<ref>{{cite web |url=http://www.chem.qmul.ac.uk/iupac/bioinorg/CD.html#8 |title=Glossary of Terms Used in Bioinorganic Chemistry: Catabolism |access-date=2007-10-30 |last=de Bolster |first=M.W.G. |year=1997 |publisher=International Union of Pure and Applied Chemistry |archive-url=https://web.archive.org/web/20170121172848/http://www.chem.qmul.ac.uk/iupac/bioinorg/CD.html#8#8 |archive-date=2017-01-21 |url-status=dead }}</ref> Catabolism breaks down large molecules (such as [[polysaccharide]]s, [[lipid]]s, [[nucleic acid]]s, and [[protein]]s) into smaller units (such as [[monosaccharide]]s, [[fatty acid]]s, [[nucleotide]]s, and [[amino acid]]s, respectively). Catabolism is the breaking-down aspect of [[metabolism]], whereas anabolism is the building-up aspect.

Cells use the monomers released from breaking down polymers to either construct new polymer molecules or degrade the monomers further to simple waste products, releasing energy. Cellular wastes include [[lactic acid]], [[acetic acid]], [[carbon dioxide]], [[ammonia]], and [[urea]]. The formation of these wastes is usually an [[oxidation]] process involving a release of chemical free energy, some of which is lost as [[heat]], but the rest of which is used to drive the synthesis of [[adenosine triphosphate]] (ATP). This molecule acts as a way for the cell to transfer the energy released by catabolism to the energy-requiring reactions that make up [[anabolism]].

Catabolism is a destructive [[metabolism]] and anabolism is a constructive metabolism. Catabolism, therefore, provides the chemical energy necessary for the maintenance and growth of cells. Examples of catabolic processes include [[glycolysis]], the [[citric acid cycle]], the breakdown of muscle protein in order to use amino acids as [[substrate (biochemistry)|substrate]]s for [[gluconeogenesis]], the breakdown of [[fat]] in [[adipose tissue]] to [[fatty acid]]s, and [[oxidative deamination]] of neurotransmitters by [[monoamine oxidase]].

== Catabolic hormones ==
There are many signals that control catabolism. Most of the known signals are [[hormone]]s and the molecules involved in metabolism itself. [[Endocrinologist]]s have traditionally classified many of the hormones as [[anabolic]] or catabolic, depending on which part of metabolism they stimulate. The so-called classic catabolic hormones known since the early 20th century are [[cortisol]], [[glucagon]], and [[adrenaline]] (and other [[catecholamine]]s). In recent decades, many more hormones with at least some catabolic effects have been discovered, including [[cytokine]]s, [[orexin]] (known as [[hypocretin]]), and [[melatonin]].{{Citation needed|date=April 2010}}

{| class="wikitable" 
|-
! style="vertical-align:bottom; font-weight:bold; background-color:#FFF;" | Hormone
! style="vertical-align:bottom; font-weight:bold; background-color:#FFF;" | Function<ref name="Openstax Anatomy & Physiology attribution">{{CC-notice|cc=by4|url=https://openstax.org/books/anatomy-and-physiology/pages/24-1-overview-of-metabolic-reactions}} {{cite book|last1=Betts|first1=J Gordon|last2=Desaix|first2=Peter|last3=Johnson|first3=Eddie|last4=Johnson|first4=Jody E|last5=Korol|first5=Oksana|last6=Kruse|first6=Dean|last7=Poe|first7=Brandon|last8=Wise|first8=James|last9=Womble|first9=Mark D|last10=Young|first10=Kelly A|title=Anatomy & Physiology|location=Houston|publisher=OpenStax CNX|isbn=978-1-947172-04-3|date=June 8, 2023|at=24.1 Overview of metabolic reactions}}</ref>
|-
| style="vertical-align:middle; background-color:#FFF;" | [[Cortisol]]
| style="vertical-align:middle; background-color:#FFF;" | Released from the [[adrenal gland]] in response to stress; its main role is to increase blood [[glucose]] levels by [[gluconeogenesis]].
|-
| style="vertical-align:middle; background-color:#FFF;" | [[Glucagon]]
| style="vertical-align:middle; background-color:#FFF;" | Released from alpha cells in the [[pancreas]] either when starving or when the body needs to generate additional energy; it stimulates the breakdown of [[glycogen]] in the [[liver]] to increase blood glucose levels; its effect is the opposite of [[insulin]]; glucagon and insulin are a part of a [[Negative feedback|negative-feedback]] system that stabilizes blood glucose levels.
|-
| style="vertical-align:middle; background-color:#FFF;" | [[Adrenaline]]
| style="vertical-align:middle; background-color:#FFF;" | Released in response to the activation of the [[sympathetic nervous system]]; increases heart rate and heart contractility, [[Vasoconstriction|constricts]] blood vessels, is a [[bronchodilator]] that opens (dilates) the [[Bronchus|bronchi]] of the [[lung]]s to increase air volume and oxygen supply in the lungs, and stimulates [[gluconeogenesis]].
|}

== Etymology ==
The word ''catabolism'' is from [[Neo-Latin]], which got the roots from [[Ancient Greek|Greek]]: κάτω ''kato'', "downward" and βάλλειν ''ballein'', "to throw".

== See also ==
* [[Autophagy]]
* [[Dehydration synthesis]]
* [[Hydrolysis]]
* [[Nocturnal post absorptive catabolism]]
* [[Psilacetin#Pharmacology|Psilacetin § Pharmacology]]
* [[Sarcopenia]]

== References ==
{{Reflist}}

== External links ==
* {{Commons category-inline}}

{{Metabolism}}
{{Authority control}}

[[Category:Metabolism]]

[[File:Catabolism of Glucose.svg|thumb|]]