Dissimilation (biology)

Dissimilation ( Latin dissimilatio 'inequality' ) is the catabolic exchange of substances and energy in living beings , in which components of the organism ( e.g. fats , carbohydrates ) are broken down, usually with energy generation . A distinction can be made between carbon , nitrogen , sulfur , phosphate and mineral dissimilation. Assimilation refers to the reverse change of substances and energy, in which substances foreign to the organism are converted into substances inherent in the organism, usually with the addition of energy.

properties

Principle of dissimilation in carbohydrates

A distinction is made between breathing ( aerobic and anaerobic ) and fermentation . The released energy is used in the form of high-energy compounds, as adenosine triphosphate (ATP) or acetate, for energy-consuming life processes and / or for the formation of heat .

During breathing , substances (“substrates”) are oxidized . The electrons released during the oxidation are transferred to external electron acceptors via the respiratory chain .

• In aerobic respiration , oxygen (O ₂ ) serves as an electron acceptor. It occurs in all aerobic organisms and provides most of the energy ( free enthalpy ), based on the amount of degraded substance (substrate). Organic compounds as substrates are completely broken down into carbon dioxide (CO ₂ ) and water (H ₂ O).
• In the anaerobic respiration are used in place of oxygen other substances as external electron acceptors: nitrate (NO ₃ ^- ), fumarate , trivalent iron - ions (Fe ³⁺ ), sulfate (SO ₄ ^2- ). or organic sulfonates.

Fermentations take place without the consumption of external electron acceptors, without a respiratory chain. The degradation of the substrate is mostly incomplete, the degradation products are excreted. The ATP yield is relatively low and is around 2 to 4 moles of ATP per mole of substrate.

Word explanation

The term dissimilation is derived from the Latin dissimilis , i.e. H. dissimilar, educated and to be understood as the opposite of assimilation (biology) (Latin assimilatio , approximation '). Assimilation refers to the conversion of inorganic or foreign organic (= heterotrophic assimilation) substances absorbed from the environment into the body's own. During dissimilation, these substances are converted back into foreign substances that are excreted.

Web links

• Fermentation or breathing - the yeast is optimally adapted! , Yeast - Helpers in Biotechnological Processes, Katja Renz, approx. 2002, accessed in 2014
• The dissimilation of carbohydrates (free summary), textbook of plant physiology, Hans Mohr u. a., 1978, accessed 2014
• The metabolism of l-malate .. (Dissimilation of malic acid…, German, free abstract), K. Mayer u. a., 1963, accessed 2014

Individual evidence

1. ↑ AJ Wolfe: The acetate switch. In: Microbiology and molecular biology reviews: MMBR. Volume 69, Number 1, March 2005, pp. 12-50, ISSN  1092-2172 . doi : 10.1128 / MMBR.69.1.12-50.2005 . PMID 15755952 . PMC 1082793 (free full text).
2. ^ F. Grein, AR Ramos, SS Venceslau, IA Pereira: Unifying concepts in anaerobic respiration: insights from dissimilatory sulfur metabolism. In: Biochimica et Biophysica Acta . Volume 1827, Number 2, February 2013, pp. 145-160, ISSN  0006-3002 . doi : 10.1016 / j.bbabio.2012.09.001 . PMID 22982583 .
3. ↑ AM Cook, K. Denger: Dissimilation of the C2 sulfonates. In: Archives of microbiology. Volume 179, Number 1, December 2002, pp. 1-6, ISSN  0302-8933 . doi : 10.1007 / s00203-002-0497-0 . PMID 12471498 .
4. ↑ AM Cook, K. Denger, TH Smits: Dissimilation of C3-sulfonates. In: Archives of microbiology. Volume 185, Number 2, March 2006, pp. 83-90, ISSN  0302-8933 . doi : 10.1007 / s00203-005-0069-1 . PMID 16341843 .