Anaerobic Respiration (Meaning and Explanation)

We explain what anaerobic or anaerobic respiration is in biology, what types exist and examples of regions where it occurs.

anaerobic respiration anaerobic bacteria — Anaerobic respiration is unique to prokaryotic organisms, such as bacteria.

What is anaerobic respiration?

In biology, the metabolic process of oxidoreduction of sugars is called anaerobic respiration or anaerobic respiration. That is, in this process glucose is oxidized to obtain energy, without the presence of oxygen. That is to say, a process of cellular respiration in which oxygen molecules do not intervene.

Anaerobic respiration differs from aerobic or aerobic respiration since the latter requires oxygen to process sugar molecules. On the contrary, anaerobes use other types of chemical elements or even more complex organic molecules, through an electron transport chain.

It should also not be confused with fermentation, since the electron transport chain does not intervene in it. However, both processes have in common that they occur in the absence of oxygen.

This type of cellular respiration is exclusive to certain prokaryotic organisms (bacteria or archaea), especially those that live in conditions of little or no oxygen presence. However, in many cases it can also constitute a secondary process, let's say an emergency, due to the unexpected shortage of this element in the environment.

Types of anaerobic respiration

Anaerobic respiration It can be classified according to the type of chemical element used to replace oxygen that is, as an electron receptor during the metabolic process. Thus, there can be many types of processes of this nature, but the main and most common ones are:

Anaerobic respiration through nitrates In this case the microorganisms consume nitrates (NOT₃^–) to reduce them to nitrites (NO₂^–) by adding electrons to them. However, since nitrites are typically toxic to most life forms, it is much more common for the end product of this process to go further to diatomic nitrogen (N₂) which is an inert gas. This process is known as denitrification.
Anaerobic respiration through sulfates Similar to the previous case, but with sulfur derivatives (SO₄^2-), is a much rarer case, belonging to totally anaerobic bacteria, while the previous case can occur as an alternative to momentary oxygen shortage. In this sulfate reduction process, sulfur radicals (S^2-).
Anaerobic respiration using carbon dioxide Some groups of methane gas-producing archaea (CH₄) consume carbon dioxide (CO₂) to use it as an electron acceptor. The microorganisms that live in the digestive tract of ruminants are of this nature, for example, where other microorganisms supply them with the hydrogen they require for the process.
Anaerobic respiration through iron ions This last case is common among certain bacteria, capable of consuming ferric ions (Fe³⁺), reducing them to ferrous ions (Fe²⁺), since this type of iron molecules are very common in the Earth's crust. This is what happens at the bottom of the swamps, where important iron sediments occur due to bacterial action.

Examples of anaerobic respiration

anaerobic anaerobic respiration example thermal water — Organisms that live in hot springs perform anaerobic respiration.

Examples of these types of processes are common in the prokaryotic world, especially in the most inhospitable regions of the planet but not for that reason devoid of life. Such regions are:

The bowels of higher animals.
He seabed and the abyssal cracks.
The geothermal locks where magma gushes out to the bottom of the sea.
Geysers, hot springs and other forms of geothermal outbreak.
The swamps and clay waters full of organic matter and low oxygen.

Glycolysis

Glycolysis or glycolysis It is the metabolic pathway that allows us to obtain energy from glucose. That is to say, it is a successive series of biochemical reactions, applied by most living beings, to break down the glucose molecule (C₆h₁₂EITHER₆) and obtain from it the necessary chemical energy (in the form of ATP) to keep cellular metabolism going.

Glycolysis consists of 10 enzymatic reactions that occur consecutively, either in the presence (aerobic) or absence (anaerobic) of oxygen. It results in the formation of two molecules of pyruvate or pyruvic acid (C₃h₄EITHER₃), which feed other metabolic pathways to continue obtaining energy for the body (the so-called Krebs Cycle).

Continue in: Glycolysis