The breathing (from Latin respiration) it’s a physiological process which consists of the gas exchange with the environment. Breathing involves absorbing air, taking part of its substances and expelling it after having modified it. The cell, on the other hand, is the fundamental unit of living organisms which has independent playback capability.

These definitions allow us to approach the cellular respiration, a set of biochemical reactions that takes place in most cells. The process involves the splitting of pyruvic acid (produced by glycolysis) into carbon dioxide and water, together with the production of molecules of adenosine triphosphate (ATP).

Metabolic process

Cellular respiration encompasses different biochemical reactions.

In other words, cellular respiration involves a metabolic process by which cells reduce the oxygen and produce Energy and water. These reactions are indispensable for the Cell nutrition.

The release of energy takes place in a controlled manner. A part of this energy is incorporated into ATP molecules that, thanks to this process, can be used in processes endothermic such as anabolism (the maintenance and development of the body).

Types of cellular respiration

It is possible to divide cellular respiration into two types: aerobic respiration and the anaerobic respiration. In aerobic respiration, oxygen intervenes as an acceptor of the electrons released by organic substances. Anaerobic respiration, on the other hand, does not have the participation of oxygen, but rather electrons they fall on other acceptors that are often by-products of the metabolism of other organisms.

It is important to distinguish between anaerobic respiration and fermentation, which is a process of internal reduction of the processed molecule.

Cell process

Cellular respiration can be divided into anaerobic and aerobic.


Also known as lysis or glucose cleavage, glycolysis takes place through nine reactions well defined, which catalyze nine different enzymes. At the end of the process, two of ATP (adenosine triphosphate) and two of NADH (the reduced form of NAD +, nicotinamide adenine dinucleotide) are obtained from each glucose molecule.

The nine phases of glycolysis are detailed below:

1) It all starts with the activation of glucose (glucose + ATP -> glucose 6-phosphate + ADP). A percentage of the energy that is released during the production of glucose 6-phosphate and ADP remains in the bond that relates the glucose molecule to the phosphate;

2) An isomerase catalyzes a reaction that rearranges glucose 6-phosphate, resulting in the training fructose 6-phosphate;

3) ATP gives fructose 6-phosphate a new phosphate, to produce fructose 1,6-diphosphate (fructose with phosphates in the first and sixth positions). This reaction is regulated by the enzyme phosphofructokinase. Up to this point, two ATP molecules have been reversed and there has been no energy recovery;

4) The division of fructose 1,6-diphosphate in two 3-carbon sugars: dihydroxyacetone phosphate and glyceraldehyde 3-phosphate;

5) The oxidation of the glyceraldehyde 3-phosphate molecules takes place, that is, the elimination of atoms of hydrogen and the nicotinamide adenine dinucleotide (NAD +) is reduced to NADH. It is the first reaction that leads to a certain energy recovery. The compound produced in this phase is phosphoglycerate, which when reacting with an inorganic phosphate gives rise to 1,3 diphosphoglycerate;

6) The reaction of phosphate with ADP forms ATP, two for each glucose molecule, through a process of energy transfer known as phosphorylation;

7) There is an enzymatic transfer of the remaining phosphate group from position three to position two;

8) A molecule of Water it is removed from compound 3 carbon, which concentrates energy near the phosphate group and produces phosphoenolpyruvic acid (PEP);

9 Phosphoenolpyruvic acid transfers its phosphate group to an ADP molecule and thus forms pyruvic acid and ATP.