Portal:Metabolism

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Metabolism

Simplified view of the cellular metabolism

Metabolism (/məˈtæbəlɪzəm/, from Greek: μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms. The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of nitrogenous wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. (The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transport of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism or intermediate metabolism).

Metabolic reactions may be categorized as catabolic - the breaking down of compounds (for example, the breaking down of glucose to pyruvate by cellular respiration); or anabolic - the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy.

The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. Enzymes act as catalysts - they allow a reaction to proceed more rapidly - and they also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell's environment or to signals from other cells.

The metabolic system of a particular organism determines which substances it will find nutritious and which poisonous. For example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The basal metabolic rate of an organism is the measure of the amount of energy consumed by all of these chemical reactions.

A striking feature of metabolism is the similarity of the basic metabolic pathways among vastly different species. For example, the set of carboxylic acids that are best known as the intermediates in the citric acid cycle are present in all known organisms, being found in species as diverse as the unicellular bacterium Escherichia coli and huge multicellular organisms like elephants. These similarities in metabolic pathways are likely due to their early appearance in evolutionary history, and their retention because of their efficacy.

Selected article

Nuvola apps ksig.png

No article is currently set as 'article of the month' for April

Did you know...

Nuvola apps package editors.png

Subcategories

Nuvola apps bookcase.svg
Gtk-dialog-info.svg Navigate by clicking on + to expand the tree section and - to hide the tree section. Click on a link to view the articles in that category.

Things you can do

Nuvola apps korganizer.svg

There is still a lot of work to do on Wikipedia's metabolism articles.

Visit the Metabolic Pathways task force page to see what needs doing to the wide range of metabolism-related articles, images and templates. In particular the roadmap for article development may be of interest.

On the more general front, the Molecular and Cellular Biology Wikiproject may also have projects of interest.

WikiProjects

Nuvola apps kcmsystem.png

This page is maintained by the Metabolic Pathways task force which is part of the Molecular and Cellular Biology Wikiproject.

The Metabolic Pathways task force is related to the Cell Signaling Wikiproject.

Related Portals

Associated Wikimedia

The following Wikimedia Foundation sister projects provide more on this subject:

Wikibooks
Books

Commons
Media

Wikinews 
News

Wikiquote 
Quotations

Wikisource 
Texts

Wikiversity
Learning resources

Wiktionary 
Definitions

Wikidata 
Database

Purge server cache