Glycolysis: what is it and what are its 10 phases?

One of the main ways by which our body obtains energy from food.

Glycolysis is a chemical process that allows cellular respiration and metabolism, specifically through the breakdown of glucose.

In this article we will see in more detail what glycolysis is and what it is used for, as well as its 10 phases of action.

What is glycolysis?

The term "glycolysis" is composed of the Greek "glycos" meaning "sugar", and "lysis" meaning "breakdown". In this sense, glycolysis is the process by which the composition of glucose is modified to extract sufficient energy for the benefit of the cells. In fact, it not only acts as a source of energy, but also has an impact on the cellular activity of the cells. has an impact on cellular activity in several wayswithout necessarily generating additional energy.

For example, it produces a high yield of molecules that enable both aerobic and anaerobic metabolism and cellular respiration. Broadly speaking, aerobic is a type of metabolism that consists of extracting energy from organic molecules from the oxidation of carbon by oxygen. In anaerobic metabolism, the element used to achieve oxidation is not oxygen but sulfate or nitrate.

In turn, glucose is an organic molecule composed of a 6-ring membrane, which is found in the blood. which is found in the blood, and which is generally the result of the transformation of carbohydrates into sugars. In order to enter the cells, glucose travels through the proteins responsible for transporting it from the outside of the cell to the cytosol (intracellular fluid, i.e. the liquid found in the center of the cells).

Through glycolysis, glucose is converted into an acid called "pivuric" or "pyruvate" which plays a very important role in biochemical activity. This process occurs in the cytoplasm (the part of the cell between the nucleus and the membrane). But for glucose to be converted into pyruvate, a very complex chemical mechanism composed of different phases must occur.

Its 10 phases

Glycolysis is a process that has been studied since the second decade of the 19th century, when chemists Louis Pasteur, Eduard Buchner, Arthur Harden and William Young began to detail the mechanism of fermentation. These studies provided insight into the development and different forms of reaction in the composition of molecules.

It is one of the most ancient cellular mechanisms, and it is also one of the most important in the world. the fastest way to obtain energy and metabolize carbohydrates.. This requires the occurrence of 10 different chemical reactions, divided into two main phases. The first of these consists of expending energy by transforming the glucose molecule into two different molecules; while the second phase is the obtaining of energy by transforming the two molecules generated in the previous stage.

Having said this, we will now see the 10 phases of glycolysis.

1. Hexokinase

The first step in glycolysis consists of converting the D-glucose molecule into a glucose-6-phosphate molecule (glucose-phosphorylated molecule at carbon 6). This reaction requires the participation of an enzyme known as Hexokinase, and its function is to activate glucose so that it can be used in subsequent processes..

2. Phosphoglucose isomerase (Glucose-6 P isomerase)

The second reaction of glycolysis is the transformation of glucose-6-phosphate into fructose-6-phosphate. For this, an enzyme called phosphoglucose isomerase an enzyme called phosphoglucose isomerase must act.. This is the phase of definition of the molecular composition that will allow the consolidation of glycolysis in the two stages that follow.

3. Phosphofructokinase

In this phase, fructose-6-phosphate is converted into fructose 1.6-bisphosphate, by means of the action of phosphofructokinase and magnesium. This is an irreversible phase, which generates that glycolysis begins to stabilize.

4. Aldolase

Now fructose 1.6-bisphosphate is split into two isomer-type sugars, that is, two molecules with the same formula, but whose atoms are arranged differently, so they also have different properties. The two sugars are dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP), and cleavage occurs by aldolase enzyme activity. occurs by the activity of the enzyme aldolase..

5. Triphosphate isomerase

Step 5 consists of reserving the glyceraldehyde phosphate for the next stage of glycolysis. This requires the action of an enzyme called triphosphate isomerase within the two sugars obtained in the previous stage (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate). This is where the first of the major stages described at the beginning of this numbering ends, whose function is to generate the energy expenditure.

6. Glyceraldehyde-3-phosphate Dehydrogenase

In this phase, the obtaining of energy begins (during the 5 previous ones it had only been expended). We continue with the two sugars generated previously and its activity is as follows: to produce 1.3-bisophosphoglycerateby adding an inorganic phostate to the glyceraldehyde 3-phosphate.

In order to add this phosphate, the other molecule (glyceraldehyde-3-phosphate dehydrogenase) must be dehydrogenated. This means that the energy of the compound begins to increase.

7. Phosphoglycerate kinase

In this phase there is another transfer of a phosphate, in order to form adenosine triphosphate and 3-phosphoglycerate. It is the 1,3-bisphosphoglycerate molecule that receives a phosphate group from phosphoglycerate kinase.

8. Phosphoglycerate mutase

From the previous reaction 3-phosphoglycerate was obtained. It is now necessary to generate 2-phosphoglycerate, by the action of an enzyme called phosphoglycerate mutase.. The latter relocates the position of the phosphate from the third carbon (C3) to the second carbon (C2), and the expected molecule is obtained.

9. Enolase

An enzyme called enolase is responsible for removing the water molecule from 2-phosphoglycerate. In this way the precursor of pyruvic acid is obtained. and we are approaching the end of the glycolysis process. This precursor is phosphoenolpyruvate.

10. Pyruvate kinase

Finally, a transfer of phosphorus from phosphoenolpyruvate to adenosine diphosphate occurs. This reaction occurs by the action of the enzyme pyruvate kinase, and allows glucose to complete its transformation into pyruvic acid.

Bibliographic references:

• Glycolysis-10 steps explained steps by steps with diagram (2018). MicrobiologyInfo.com. Retrieved September 26, 2018. Available at https://microbiologyinfo.com/glycolysis-10-steps-explained-steps-by-steps-with-diagram/.