Derived terms for living beings
As aerobic or as an aerobic refers to living organisms , the elementary to life oxygen (O 2 need). The oxygen is mainly required for oxidative metabolism in the energy metabolism , such as the breathing of higher living beings.
Living things that need oxygen but prefer low oxygen concentrations are called microaerophilic .
From a chemical point of view, aerobic processes are oxidations . If the oxygen supply is interrupted or if a system based on oxidation is overwhelmed, anaerobic biochemical reactions , especially fermentation processes, can predominate or completely gain the upper hand.
An example of this is the metabolism of muscles, also in humans. At low intensity, energy is obtained mainly aerobically through the oxidation of fatty acids and aerobic metabolism of the pyruvate or lactate that is formed from glucose by way of glycolysis.
If the muscle is used more, the proportion of energy generated by glycolysis increases (see aerobic threshold ). However, the lactate that accumulates in increasing amounts can still be metabolized further - in small amounts in glycolytic muscle fibers , especially in ST fibers and in the heart muscle if the condition is good , so that the blood lactate level does not rise excessively. Only when this oxygen-dependent system is overwhelmed (which is not due to a lack of oxygen) does a sudden increase in lactate occur (reaching the individual anaerobic threshold ).
Examples of aerobic processes:
Because of its importance for many life processes, oxygen is an important abiotic factor in ecology.
Occurrence in nature
Oxygen-containing habitats are described as oxic , habitats without oxygen as anoxic . In biotopes in which the oxygen content is different, one speaks of oxic and anoxic zones.
For example, in the mud flats of the Wadden Sea, the upper zone is bright and relatively well supplied with oxygen. It represents an oxic zone. The redox potential here is above +100 mV (millivolts). Oxygen can be detected chemically. This part of the mud flats is extremely densely populated. The appearance changes at a depth of a few millimeters to centimeters: the mud flats look black; the color is caused by sulphides of heavy metals, in particular iron monosulphide (FeS). There is a typical odor of hydrogen sulfide . The redox potential here is below −200 mV. Molecular oxygen is only detectable in traces. In this anoxic zone, only those living beings can exist that either manage without oxygen (anaerobes) or draw oxygen from the surface through special respiratory organs ( siphon in mussels ) or their behavior ( lugworm ).
- Georg Fuchs, Thomas Eitinger, Hans Günter Schlegel: General microbiology. Georg Thieme, 2007. ISBN 9783134446081 . P. 13.