Metabolism: Difference between revisions
Created page with "{{Short description|Set of chemical reactions in organisms}} {{redirect|Cellular metabolism|the journal|Cell Metabolism}} {{for multi|the journal 'Metabolism'|Metabolism: Clinical and Experimental|the architectural movement|Metabolism (architecture)}} thumb|Simplified view of the cellular metabolism thumb|right|Structure of [[adenosine triphosphate (ATP), a central intermediate in energy metabolism]] {{Biochemistry sidebar}..." |
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{{further|Biomolecule|Cell (biology)|Biochemistry}} | {{further|Biomolecule|Cell (biology)|Biochemistry}} | ||
[[File:Trimyristin-3D-vdW.png|right|thumb|upright=1.15|Structure of a [[triacylglycerol]] lipid]] | [[File:Trimyristin-3D-vdW.png|right|thumb|upright=1.15|Structure of a [[triacylglycerol]] lipid]] | ||
[[File:Human Metabolism - Pathways.jpg|thumb|This is a diagram depicting a large set of human metabolic pathways. | [[File:Human Metabolism - Pathways.jpg|thumb|This is a diagram depicting a large set of human metabolic pathways.]] | ||
Most of the structures that make up animals, plants and microbes are made from four basic classes of [[molecule]]s: [[amino acid]]s, [[carbohydrate]]s, [[nucleic acid]] and [[lipid]]s (often called [[fat]]s). As these molecules are vital for life, metabolic reactions either focus on making these molecules during the construction of cells and tissues, or on breaking them down and using them to obtain energy, by their digestion. These biochemicals can be joined to make [[polymer]]s such as [[DNA]] and [[protein]]s, essential [[macromolecules]] of life. | Most of the structures that make up animals, plants and microbes are made from four basic classes of [[molecule]]s: [[amino acid]]s, [[carbohydrate]]s, [[nucleic acid]] and [[lipid]]s (often called [[fat]]s). As these molecules are vital for life, metabolic reactions either focus on making these molecules during the construction of cells and tissues, or on breaking them down and using them to obtain energy, by their digestion. These biochemicals can be joined to make [[polymer]]s such as [[DNA]] and [[protein]]s, essential [[macromolecules]] of life. | ||
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===Lipids=== | ===Lipids=== | ||
{{Main|Biolipid}} | {{Main|Biolipid}} | ||
Lipids are the most diverse group of biochemicals. Their main structural uses are as part of [[biological membrane]]s both internal and external, such as the [[cell membrane]]. Their [[chemical energy]] can also be used. Lipids are the polymers of fatty acids | Lipids are the most diverse group of biochemicals. Their main structural uses are as part of [[biological membrane]]s both internal and external, such as the [[cell membrane]]. Their [[chemical energy]] can also be used. Lipids are the polymers of fatty acids that contain a long, non-polar hydrocarbon chain with a small polar region containing oxygen. Lipids are usually defined as [[hydrophobe|hydrophobic]] or [[amphiphiles|amphipathic]] biological molecules but will dissolve in [[organic solvent]]s such as [[ethanol]], [[benzene]] or [[chloroform]]. The [[fat]]s are a large group of compounds that contain [[fatty acid]]s and [[glycerol]]; a glycerol molecule attached to three fatty acids by [[ester]] linkages is called a [[triglyceride|triacylglyceride]]. Several variations on this basic structure exist, including backbones such as [[sphingosine]] in [[sphingomyelin]], and [[hydrophile|hydrophilic]] groups such as [[phosphate]] as in [[phospholipid]]s. [[Steroid]]s such as [[sterol]] are another major class of lipids. | ||
===Carbohydrates=== | ===Carbohydrates=== | ||
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Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their [[Gastrointestinal tract|guts]], including the [[stomach]] and [[pancreas]], and in [[salivary gland]]s. The amino acids or sugars released by these extracellular enzymes are then pumped into cells by [[active transport]] proteins. | Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their [[Gastrointestinal tract|guts]], including the [[stomach]] and [[pancreas]], and in [[salivary gland]]s. The amino acids or sugars released by these extracellular enzymes are then pumped into cells by [[active transport]] proteins. | ||
[[File:Catabolism schematic.svg|thumb|left|upright=1.35|A simplified outline of the catabolism of [[protein]]s, [[carbohydrate]]s and [[fat]]s | [[File:Catabolism schematic.svg|thumb|left|upright=1.35|A simplified outline of the catabolism of [[protein]]s, [[carbohydrate]]s and [[fat]]s]] | ||
===Energy from organic compounds=== | ===Energy from organic compounds=== | ||
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{{further|Metabolic pathway|Metabolic control analysis|Hormone|Regulatory enzymes|Cell signaling}} | {{further|Metabolic pathway|Metabolic control analysis|Hormone|Regulatory enzymes|Cell signaling}} | ||
As the environments of most organisms are constantly changing, the reactions of metabolism must be finely [[Control theory|regulated]] to maintain a constant set of conditions within cells, a condition called [[homeostasis]]. Metabolic regulation also allows organisms to respond to signals and interact actively with their environments. Two closely linked concepts are important for understanding how metabolic pathways are controlled. Firstly, the ''regulation'' of an enzyme in a pathway is how its activity is increased and decreased in response to signals. Secondly, the ''control'' exerted by this enzyme is the effect that these changes in its activity have on the overall rate of the pathway (the [[flux]] through the pathway). For example, an enzyme may show large changes in activity (''i.e.'' it is highly regulated) but if these changes have little effect on the flux of a metabolic pathway, then this enzyme is not involved in the control of the pathway. | As the environments of most organisms are constantly changing, the reactions of metabolism must be finely [[Control theory|regulated]] to maintain a constant set of conditions within cells, a condition called [[homeostasis]]. Metabolic regulation also allows organisms to respond to signals and interact actively with their environments. Two closely linked concepts are important for understanding how metabolic pathways are controlled. Firstly, the ''regulation'' of an enzyme in a pathway is how its activity is increased and decreased in response to signals. Secondly, the ''control'' exerted by this enzyme is the effect that these changes in its activity have on the overall rate of the pathway (the [[flux]] through the pathway). For example, an enzyme may show large changes in activity (''i.e.'' it is highly regulated) but if these changes have little effect on the flux of a metabolic pathway, then this enzyme is not involved in the control of the pathway. | ||
[[File:Insulin glucose metabolism ZP.svg|thumb|right|upright=1.35|'''Effect of insulin on glucose uptake and metabolism.''' Insulin binds to its receptor (1), which in turn starts many protein activation cascades (2). These include: translocation of Glut-4 transporter to the [[plasma membrane]] and influx of glucose (3), [[glycogen]] synthesis (4), [[glycolysis]] (5) and [[fatty acid]] synthesis (6). | [[File:Insulin glucose metabolism ZP.svg|thumb|right|upright=1.35|'''Effect of insulin on glucose uptake and metabolism.''' Insulin binds to its receptor (1), which in turn starts many protein activation cascades (2). These include: translocation of Glut-4 transporter to the [[plasma membrane]] and influx of glucose (3), [[glycogen]] synthesis (4), [[glycolysis]] (5) and [[fatty acid]] synthesis (6).]] | ||
There are multiple levels of metabolic regulation. In intrinsic regulation, the metabolic pathway self-regulates to respond to changes in the levels of substrates or products; for example, a decrease in the amount of product can increase the [[flux]] through the pathway to compensate. This type of regulation often involves [[allosteric regulation]] of the activities of multiple enzymes in the pathway. Extrinsic control involves a cell in a multicellular organism changing its metabolism in response to signals from other cells. These signals are usually in the form of water-soluble messengers such as [[hormone]]s and [[growth factor]]s and are detected by specific [[receptor (biochemistry)|receptors]] on the cell surface. These signals are then transmitted inside the cell by [[second messenger system]]s that often involved the [[phosphorylation]] of proteins. | There are multiple levels of metabolic regulation. In intrinsic regulation, the metabolic pathway self-regulates to respond to changes in the levels of substrates or products; for example, a decrease in the amount of product can increase the [[flux]] through the pathway to compensate. This type of regulation often involves [[allosteric regulation]] of the activities of multiple enzymes in the pathway. Extrinsic control involves a cell in a multicellular organism changing its metabolism in response to signals from other cells. These signals are usually in the form of water-soluble messengers such as [[hormone]]s and [[growth factor]]s and are detected by specific [[receptor (biochemistry)|receptors]] on the cell surface. These signals are then transmitted inside the cell by [[second messenger system]]s that often involved the [[phosphorylation]] of proteins. |