Metabolic regulation is the process by which cells control chemical processes necessary for life. Enzymes and other factors regulate metabolic pathways, which coordinate functions from cellular respiration to growth and reproduction. Metabolic disorders can be caused by the absence of key enzymes, and external factors like hormones can control metabolic rates. In animals, metabolic rate controls functions from respiration to body fat. There are many metabolic disorders, including congenital deficiencies and thyroid disease, which can be treated medically.
Metabolic regulation is the process by which all cells, from bacteria to humans, control the chemical processes necessary for life. Metabolism is organized into complex step-dependent reactions called metabolic pathways. Ubiquitous special proteins called enzymes are the main way to regulate these pathways, although the concentration of nutrients, waste products and hormones can control metabolic rates. Metabolic disorders are inherited disorders caused by the absence of key enzymes that disrupt the normal regulation of a given pathway.
Metabolism describes the chemical reactions through which organisms function, from cellular respiration to the events underlying digestion, growth and reproduction. Systems called metabolic pathways coordinate these functions and are usually started or stopped by proteins called enzymes. Metabolic regulation underlies the biological control of metabolism, allowing living cells to direct these pathways. In non-living systems, equilibrium with the external environment occurs at the conclusion of chemical reactions, which would kill a living cell. Thus metabolic regulation helps keep the living system in a chemically balanced state, called homeostasis.
The most basic form of metabolic regulation occurs when genes instruct cells to make enzymes and regulate their amounts. Furthermore, in a metabolic pathway, molecules undergo significant changes and are either used by the cell or processed to generate another step in the pathway. Some of these molecules, called substrates, are effective means of metabolic regulation through their concentration. The rate of a metabolic pathway will change, depending on the availability and concentration of a substrate, which must bind to an enzyme to function. In addition to substrates, enzymes are often dependent on other enzymes and vitamins.
In addition to the more passive “feedback” type of metabolic regulation by substrate concentration, there are direct controls in most multicellular organisms. Plants also use hormones to control their metabolism. In higher animals, the external regulation of metabolism can come from chemical signals that control enzyme activity, either by acting directly on the enzymes or by influencing the genes that regulate their production. Some forms of metabolic regulation only change the rate at which a biochemical process occurs; others activate a process or prevent it from starting. In animals, metabolic rate controls functions from respiration to body fat.
There are many metabolic disorders, including thousands of congenital deficiencies of genes coding for essential enzymes. Thyroid disease can radically change the metabolic rate, causing obesity or near starvation. Sometimes, human metabolism is excessively slow or fast due to disease states and can be treated medically. Some drugs or nutrients can be said to increase metabolic rates by changing the rate of pathways involved in the digestion of carbohydrates or fats. In patients with diabetes mellitus, for example, the effects of the hormone insulin on sugar metabolism are impaired and synthetic insulin must be administered to restore normal metabolic regulation.
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