What is anaerobic respiration?

What Does Anaerobic respiration Mean

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

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 . In other words, in this process glucose is oxidized to obtain energy , without the presence of oxygen. That is, 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, anaerobic uses other types of chemical elements or even more complex organic molecules , through an electron transport chain.

Nor should it be confused with fermentation , since it does not involve the electron transport chain . 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 with little or no oxygen presence. However, in many cases it can also constitute a secondary process, let's say an emergency, given the unexpected shortage of this element in the environment .

It can help you: Prokaryotic cell

Types of anaerobic respiration

Anaerobic respiration 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 are:

  • Anaerobic respiration through nitrates. In this case, the microorganisms consume nitrates (NO 3 - ) to reduce them to nitrites (NO 2 - ) by incorporating electrons into them. However, since nitrites are usually toxic to most forms of life , it is much more common for the end product of this process to go further, to biatomic nitrogen (N 2 ) which is an inert gas. This process is known as denitrification.
  • Anaerobic respiration through sulfates. Similar to the previous case, but with sulfur derivatives (SO 4 2- ), it is a much rarer case, belonging to totally anaerobic bacteria, while the previous case can occur as an alternative to the momentary shortage of oxygen. In this sulfate reduction process, sulfur radicals (S 2- ) are by-produced.
  • Anaerobic respiration by carbon dioxide. Some groups of methane gas-producing archaea (CH 4 ) consume carbon dioxide (CO 2 ) to use as an electron receptor. Of this nature are the microorganisms that inhabit the digestive tract of ruminants, 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 (Fe 3+ ), reducing them to ferrous ions (Fe 2+ ), since this type of iron molecules are very common in the earth's crust . This is what happens at the bottom of swamps, where important iron sediments occur due to bacterial action.

Examples of anaerobic respiration

Organisms that live in hot springs perform anaerobic respiration.

Examples of this type of process 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 intestines of higher animals.
  • The seabed and abyssal crevices.
  • The geothermal locks through which the magma gushes 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 in oxygen.


Glycolysis or glycolysis is the metabolic pathway that allows you to obtain energy from glucose . In other words, it is a successive series of biochemical reactions, applied by most living beings , to break down the glucose molecule (C 6 H 12 O 6 ) and obtain the necessary chemical energy (in the form of ATP ) from it. to keep cellular metabolism going .

Glycolysis consists of 10 enzymatic reactions that occur consecutively, either in the presence (aerobic) or in the absence (anaerobic) of oxygen . As a result, it produces the formation of two molecules of pyruvate or pyruvic acid (C 3 H 4 O 3 ), which feed other metabolic routes to continue obtaining energy for the body (the so-called Krebs Cycle).

Follow on: Glycolysis

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