Metabolism
Metabolism (from μεταβολισμος ("metabolismos")) is the
biochemical modification of
chemical compounds in
living organisms and
cells. This includes the
biosynthesis of complex
organic molecules (
anabolism) and their breakdown (
catabolism). Metabolism usually consists of sequences of
enzymatic steps, also called
metabolic pathways. The
total metabolism are all biochemical processes of an organism. The
cell metabolism includes all chemical processes in a cell.The
Dynamic Energy Budget theory aims to quantify the metabolic organisation of individual organisms; many species are unicellular.
The term is derived from the
Greek word for "change", or "overthrow" (
Etymonline)).
Important metabolic pathways are:
General pathways
*
Carbohydrate metabolism*
Fatty acid metabolism*
Protein metabolism*
Nucleic Acid metabolismAnabolism
Anabolic pathways that create building blocks and compounds from simple precursors:
*
Glycogenesis*
Gluconeogenesis*
Porphyrin synthesis pathway
*
HMG-CoA reductase pathway, leading to
cholesterol and
isoprenoids.
*
Secondary metabolism, metabolic pathways that are not essential for growth, development or reproduction, but that usually have
ecological function.
*
Photosynthesis**
Light-dependent reaction (light reaction)
**
Light-independent reaction (dark reaction)
*
Calvin cycle*
Carbon fixation*
Glyoxylate cycleCatabolism
*
Glucose catabolismDrug metabolism
Drug metabolism pathways, the modification or degradation of
drugs and other
xenobiotic compounds through specialized enzyme systems:
*
Cytochrome P450 oxidase system
*
Flavin-containing monooxygenase system*
Alcohol metabolismNitrogen metabolism
Nitrogen metabolism includes the pathways for turnover and
excretion of nitrogen in organisms as well as the biological processes of the
biogeochemical nitrogen cycle:
*
Urea cycle, important for excretion of nitrogen as urea.
* Biological
nitrogen fixation*
Nitrogen assimilation*
Nitrification*
DenitrificationOther
*
Human iron metabolismThe first controlled experiments in human metabolism were published by
Santorio Santorio in
1614 in his book
Ars de statica medecina that made him famous throughout
Europe. He describes his long series of experiments in which he weighed himself in a chair suspended from a steelyard balance (see image), before and after eating, sleeping, working, sex, fasting, depriving from drinking, and excreting. He found that by far the greatest part of the food he took in was lost from the body through
perspiratio insensibilis (insensible perspiration).
*
Cell metabolism*
Metabolomics*
Metabolome*
Metabolite*
Basal metabolic rate*
Thermic effect of food*
Iron-sulfur world theory, a "metabolism first" theory of the
origin of life.
*
Biodegradation*
Calorimetry*
Respirometry*
Microbial metabolism*
Metabolic network modelling*
Interactive Flow Chart of the Major Metabolic Pathways*
Metabolism, Cellular Respiration and Photosynthesis - The Virtual Library of Biochemistry and Cell Biology*
The Biochemistry of Metabolism at Rensselaer Polytechnic Institute*
Flow Chart of Metabolic Pathways at ExPASy*
Santorio Santorio's experiments*
KEGG: Kyoto Encyclopedia of Genes and Genomes
