Chemotroph

Chemotrophie ( from AltGr. Χυμειοτροφεῖα chymeiotropheía, "chemical food " ) is the predominant in certain living organisms obtaining energy from chemical ( exergonic ) nutrient cycling. Such creatures are called chemotroph.

Types of Chemotrophie

If during the chemical reactions organics implemented ( exclusively or in combination with inorganic substances ), refers to the Chemotrophie as Chemoorganotrophie and the corresponding organisms. Chemoorganotroph than ( or as organotroph )

If during the chemical reactions, however, only inorganic substances implemented, is referred to as the Chemotrophie chemolithotrophy and the corresponding creatures as chemolithotroph (or lithotroph, from the Greek λίθος, líthos - the stone) or chemoautotroph (of autotrophy, the ability of organisms to focus exclusively build up of inorganic substances).

Examples of chemoorganotrophic creatures and chemoorganotrophic nutrient cycling:

• Lactic acid bacteria:

• Animals, humans, many bacteria:

Examples of chemolithotrophic organisms and chemolithotrophic nutrient cycling:

• Hydrogenotrophic bacteria such as the genus Ralstonia:

• Bacteria of the genus Thiobacillus thiooxidans:

• Sulfate-reducing bacteria such as the genus Desulfovibrio:

Energy storage and transfer

When Chemotrophie the exergonic chemical substance reaction is coupled in various ways with the endergonic attachment of phosphate to adenosine diphosphate ( ADP phosphorylation ), so that higher energy adenosine triphosphate ( ATP) is formed, which function as an intermediary and short-term memory of the vacated at the exergonic matter transformation energy serves. A distinction substrate phosphorylation and Elektronentransportphosphorylierung.

(1 ) The substrate phosphorylation, a phosphate residue is added ( inorganic phosphate ) to a layer formed by the chemical reaction of an organic substance intermediate. This phosphate group is characterized by a low group transfer potential. The phosphorylated organic intermediate is now changed so that the phosphate group is replaced by a high group transfer potential. Now he can be transferred to adenosine diphosphate ( ADP ), whereby the energy-rich adenosine triphosphate ( ATP) is produced.

( 2) The Elektronentransportphosphorylierung occurs in chemical reactions that are associated with oxidations and reductions ( " oxidative energy metabolism "). This one recorded from the outside fabric of the electrons is easily releases ( reductant with a low redox potential ), oxidized by electrons going to be denied. These electrons are transported through various cascade membrane bound intermediate carriers with higher and higher redox potential, on the one hand on a pure electron transfer agent (such as cytochrome c), and on the other hand by means of hydrogen transfer agents (such as ubiquinone ). Finally they are transferred to a material taken from the outside (for example, oxygen), which has a high redox potential, so easily accepts electrons ( oxidant ). The components involved in this process are located in or on a biomembrane that separates two compartments. In prokaryotes, these are the inside of the cell and the external space, in eukaryotes, two intracellular compartments, in the mitochondria.

This flow of electrons, protons are the same from the cell interior to the exterior ( in prokaryotes ) or ( in eukaryotes ) of a mitochondrial compartment transported to the other ( see picture).

Electrons are transferred from one electron carrier with a low redox potential to a higher redox potential. However, this does not happen directly, but via a hydrogen carrier. This takes two electrons together with two protons ( hydrogen ions) from one compartment ( in prokaryotes from the cell interior ). In each case, an electron and a proton give a hydrogen atom. The two hydrogen atoms are bonded to the hydrogen carrier. Thereafter, the hydrogen transfer agent is hydrogen separated into two electrons and two protons again, the electrons in a second electron transfer agent with a higher redox potential, protons ( hydrogen ion ) in the other compartment ( in prokaryotes to the exterior ). Protons are, then, driven by the flow of electrons, is transported from one compartment to the other. This device is called an electron -driven proton pump that generates a proton concentration difference (potential energy).

This proton concentration difference is then due to reflux of protons across a biological membrane bound in the ATP synthase (an enzyme ) compensated. The released energy is used by the ATP synthase to attach a phosphate group to adenosine diphosphate ( ADP ), whereby the energy-rich adenosine triphosphate ( ATP) is produced.