Metabolism

As metabolism or metabolism (Greek μεταβολισμός, metabolismós " metabolism ", provided with a Latin ending) refers to the totality of the chemical processes in living organisms, ie the transformation of materials. It consists of the uptake, transport and chemical transformation of materials into an organism and the release of metabolic waste products into the environment. All the substances involved are called metabolites.

These biochemical processes (eg internal and external respiration, transport processes, food ) are used for building and maintaining the body substance ( anabolism ) and energy ( energy metabolism ) for energy-consuming activities, thereby maintaining body functions. It is essential for the metabolism are enzymes that speed up chemical reactions and steer ( catalyze ).

The entire metabolism can be divided into catabolic reactions which simpler substances provide by the degradation of chemically complex food materials energy and anabolic reactions which make up the body's own substances from simple building blocks with consumption of energy. However, the entire metabolism is a complex network of different reactions, which together form pathways. This can (eg B.Citratzyklus ) be linear (eg glycolysis ) or cyclically. Most metabolic pathways are amphibol: They run in different steps from catabolic as anabolic. Although metabolic pathways are reversible in many individual steps, they are always irreversible as a whole, since at least one reaction step proceeds only in anabolic or catabolic direction.

Be implemented externally recorded, foreign substances, so one speaks also of xenobiotic metabolism.

The study of the metabolism takes place mainly with methods of physiology and biochemistry.

The metabolism can also be understood as an exchange of free energy or order. Creatures increase in the order ( decrease in entropy ) at the expense of increase of disorder, ie of entropy in the environment. It has therefore been referred to as living beings Negentropen.

Erwin Schrödinger pointed out that the term metabolism can be easily misunderstood. One could say that it was an exchange of substances ( "Every atom of nitrogen, oxygen, sulfur, etc. is worth the same as any other of its kind as well, and what could be gained by their exchange "). In fact, a chemical change of substances is meant.

• 2.1 Classification according to the function of the metabolic reaction in the organism
• 2.2 Classification by changing the molecules

Reaction types

Enzyme- catalyzed reactions

In the IUPAC / IUBMB enzyme classification system, there are six main types of enzyme reactions. This will also help the metabolism, are catalyzed by enzymes in the reactions, are also divided into six groups of reactions, namely in redox reactions, group transfer reactions, hydrolysis reactions lyase reactions (addition, hydration ), isomerization reactions and ligation reactions.

Transport

The transport of substances through transport proteins can be done away within cellular compartments, outside cells, or compartment boundaries ( biomembrane ). It may be pure diffusion processes, facilitated diffusion or active, ATP -consuming membrane transport.

The Transporter Classification Database ( TCDB ​​) is sanctioned by the IUBMB classification of transport proteins are available, in addition to the function is based on the descent of the proteins. With this definition of transportation, however, are all proteins, only temporarily bind the materials and transported in this period itself ( for example, the circulation ), not recorded. The main groups in the TCDB ​​are porins and ion channels, potential -driven transporters, primary active transporters, phosphotransferases, transmembrane electron carriers, auxiliary trucks and other.

Metabolic processes

Classification according to the function of the metabolic reaction in the organism

• Energy metabolism - exergonic chemical reactions for the purpose of energy
• Basal metabolic rate - metabolism of an organism at complete rest
• Hunger metabolism - adaptation of the organism to low food supply
• Change in building materials - building materials that make up the organism
• Assimilation - conversion organisms pollutants in organisms own materials
• Dissimilation - breakdown organisms own materials, mostly for the purpose of energy
• Glucose metabolism
• Amino acid metabolism
• Iron metabolism
• Biotransformation - mining and removal of harmful organisms of own and foreign substances

Classification by changing the molecules

• Material production ( biosynthesis ) ( anabolism)
• Material alteration / degradation ( catabolism)

Examples of metabolic processes

In photosynthesis convert specific metabolic processes (usually that of the Calvin cycle ) using the energy of light carbon dioxide (originating in land plants from the air), water and other basic materials into the substances to which either immediately to the further development and growth of the organism used or stored, for example, carbohydrates. These reserve materials can be processed in constructive metabolism or energy metabolism later.

Animals metabolize ( metabolize ) in their digestive other organisms or their storage substances (such as carbohydrates, proteins and fats).