What is aerobic respiration?

We explain what aerobic respiration is, how it is carried out and examples. In addition, its different stages and anaerobic respiration.

  1. What is aerobic respiration?

It is known as aerobic respiration or aerobic respiration to a series of metabolic reactions  that take place within the  cells of living beings, through which chemical energy is obtained  from the breakdown of organic molecules (cellular respiration).

It is a complex process of obtaining energy , which consumes glucose (C6H12O6) as fuel and oxygen as the final electron receptor (oxidant) in reaction with pyruvic acid (C3H4O3). In this way,  carbon dioxide (CO2) , water (H2O) and numerous quantities of Adenosyntrifosphate (ATP) are obtained, the quintessential biochemical energy molecule.

This process is typical of eukaryotes and certain forms of bacteria , and occurs according to the following formula:  12  + 6O  → 6CO  + 6H O + ATP .

  1. Examples of aerobic respiration

Aerobic Breathing
Birds use their lungs to get oxygen from the air.

Some examples of aerobic respiration are:

  • The metabolism  of humans, reptiles, birds and mammals in their entirety, which use their lungs to obtain oxygen from the air.
  • The metabolism of fish and other aquatic beings, which have gills to obtain oxygen from water .
  • The metabolism of insects, which incorporate oxygen from the air through a series of tracheas throughout your body. Another case is worms and worms, which do the same for the skin (skin breathing).
  1. Stages of aerobic respiration

Aerobic respiration is a complex process that involves a series of stages in a prolonged chemical reaction. These stages are:

  • Glycolysis . The initial step of aerobic respiration occurs in the cytoplasm of the cell and is the oxidation of glucose (and glycerol from triglycerides, if any). This process breaks the bonds of each molecule of this sugar and obtains two molecules of pyruvic acid in return, together with two molecules of ATP .
  •  Oxidative decarboxylation of pyruvic acid . Pyruvic acid molecules enter from the cytoplasm to the matrix of the mitochondria (energy organelles of the cell), where they are processed by a complex of  enzymes (pyruvate dehydrogenase) that tear off a carbon atom (decarboxylation), released as CO2, and then two hydrogen atoms (dehydrogenation). As a result, acetyl radicals (-CO-CH3) are obtained with which the next phase is started.
  • Krebs cycle . The last phase of respiration occurs in a metabolic cycle in the mitochondrial matrix, known as the Krebs Cycle. This begins with the acetyl from the previous phase, subjected to oxidation to produce two molecules of CO2 and energy in the form of guanosyntriphosphate (GTP) and other usable reducing molecules.

Then there is a chain of chemical reactions that re-oxidize the reduced enzyme components in the previous phase, making them available for new use, and obtaining new ATP in the process .

The latter occurs already in the inner membrane of the mitochondria . The electrons and protons released in the process are received by the oxygen that is then reduced to water.

  1. Anaerobic respiration

Aerobic respiration
Anaerobic respiration is distinguished from aerobic by the presence of oxygen.

Anaerobic or anaerobic respiration differs from aerobicity in one thing: the presence of oxygen. This type of cellular respiration consists in the oxidoreduction of monosaccharide sugars, using an element other than oxygen for oxidation : nitrogen derivatives (nitrates), sulfur (sulfates and sulphides), carbon dioxide, iron or manganese ions, Selenium (seleniates), arsenic (arsenate), among others. These molecules are less effective and less energy is generated than using oxygen.

Anaerobic respiration is different from fermentation , and yields various substances as byproducts, depending on the element used as an electron acceptor . This metabolic mechanism is typical of certain prokaryotic bacteria and microorganisms that inhabit oxygen-poor environments.

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