A metabolic disorder is a medical disorder which affects the production of energy within individual human (or animal) cells. Most metabolic disorders are genetic, though a few are "acquired" as a result of diet, toxins, infections, etc. Genetic metabolic disorders are also known as inborn errors of metabolism. Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, sometimes called the building blocks of life. ... A genetic disorder, or genetic disease is a disease caused, at least in part, by the genes of the person with the disease. ... A toxin, in a scientific context, is a biologically produced substance that causes injury to the health of a living thing on contact or absorption, typically by interacting with biological macromolecules such as enzymes and receptors. ... An infection is the detrimental colonization of a host organism by a foreign species. ... Inborn errors of metabolism are a large group of rare but often serious metabolic disorders that generally arise from deficiency or malfunction of enzymes that regulate conversion of various substances into others. ...

In general, the genetic metabolic disorders are caused by genetic defects that result in missing or improperly constructed enzymes necessary for some step in the metabolic process of the cell. A ribbon diagram showing the tertiary structure of neuraminidase Factor D enzyme crystal prevents the immune system from inappropriately running out of control An enzyme (in Greek en = in and zyme = leaven) is a protein, that catalyzes a chemical reaction. ...

The three largest classes of metabolic disorders are:

• Glycogen storage diseases -- disorders affecting carbohydrate metabolism
• Fatty oxidation disorders -- disorders affecting the metabolism of fat components
• Mitochondrial disorders -- disorders affecting the mitochondria which are the central "powerhouses" of the cells.

A fourth class, the channelopathies (some of which cause periodic paralysis and/or malignant hyperthermia) could be considered to be metabolic disorders as well, though they are not always classified as such. These disorders affect the ion channels in the cell and organelle membranes, resulting in improper or inefficient transfer of ions through the membranes. Glycogen storage disease is any one of several inborn errors of metabolism that result from enzyme defects that affect the processing of glycogen synthesis or breakdown within muscles, liver, and other cell types. ... Carbohydrates (literally hydrates of carbon) are chemical compounds that act as the primary biological means of storing or consuming energy, other forms being fat and protein. ... A fatty oxidation disorder (sometimes referred to as a lipid storage disorder) is any one of several inborn errors of metabolism that result from enzyme defects affecting the ability of the body to oxidize fatty acids in order to produce energy within muscles, liver, and other cell types. ... Mitochondrial diseases are a group of disorders relating to the mitochondria, the organelles that are the powerhouses of the eukaryotic cells that comprise higher-order lifeforms (including humans). ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Malignant hyperthermia (MH or MHS for malignant hyperthermia syndrome) is a life-threatening condition resulting from a genetic sensitivity of skeletal muscles to volatile anaesthetics and depolarizing neuromuscular blocking drugs that occurs during or after anaesthesia. ... Another, unrelated ion channeling process is part of ion implantation. ... In cell biology, an organelle is one of several structures with specialized functions, suspended in the cytoplasm of a eukaryotic cell. ... It has been suggested that Net flux be merged into this article or section. ... An ion is an elementary particle or system of elementary particles with a net electric charge. ...

There are also a number of other metabolic disorders (such as myoadenylate deaminase deficiency) which do not cleanly fit into any of the above classifications. Myoadenylate deaminase deficiency (MADD) is a recessive genetic metabolic disorder that affects approximately 1-2% of populations of European descent (making it a not particularly rare rare disease). ...