We explain what glycolysis is, its phases, functions and importance in metabolism. Also, what is gluconeogenesis.
What is glycolysis?
Glycolysis or glycolysis is a metabolic pathway that serves as an initial step for carbohydrate catabolism in living beings . It consists essentially of the breakdown of glucose molecules by oxidation of the glucose molecule, thus obtaining amounts of chemical energy usable by the cells.
Glycolysis is not a simple process, but consists of a series of ten consecutive enzymatic chemical reactions , which transform a molecule of glucose (C 6 H 12 O 6 ) into two of pyruvate (C 3 H 4 O 3 ), useful for other metabolic processes that continue to provide energy to the body.
This series of processes can occur in the presence or absence of oxygen, and occurs in the cytosol of cells , as an initial part of cellular respiration. In the case of plants, it is part of the Calvin cycle .
The reaction rate of glycolysis is so high that it was always difficult to study. It was formally discovered in 1940 by Otto Meyerhoff and a few years later by Luis Leloir, although all this thanks to previous work of the late nineteenth century.
This metabolic route is usually named through the surnames of the greatest contributors to its discovery: the Embden-Meyerhoff-Parnas route. On the other hand, the word “glycolysis” comes from the Greek glycos , “sugar,” and lysis , “break.”
Phases of glycolysis
Glycolysis is studied in two distinct phases, which are:
First phase: energy expenditure
In this first stage , the glucose molecule is transformed into two of glyceraldehyde , a low-energy molecule. Two biochemical energy units ( ATP , Adenosine Triphosphate) are consumed for this . However, in the next phase the energy obtained will be doubled thanks to this initial investment.
Thus, phosphoric acids are obtained from ATP, which provide phosphate groups with glucose, composing a new and unstable sugar. This sugar soon divides and results in two similar molecules, phosphated and with three carbons .
Despite having the same structure, one of them is different, so it is additionally treated with enzymes to make it identical to the other, thus obtaining two identical compounds. All of this occurs in a chain of five-step reactions.
Second phase: obtaining energy
The glyceraldehyde of the first phase becomes the second in a compound of high biochemical energy . To do this, it is coupled with new phosphate groups, after losing two protons and electrons .
Thus, these intermediate sugars are subjected to a process of change that gradually releases their phosphates, to obtain four ATP molecules (double the amount invested in the previous step) and two pyruvate molecules, which will continue their cycle on your own, glycolysis is over. This second phase of reactions consists of five more steps.
The main functions of glycolysis are simple: obtaining the necessary biochemical energy for the different cellular processes . Thanks to the ATP obtained from the breakdown of glucose, numerous life forms get the energy to survive or to fire much more complex chemical processes.
Therefore, glycolysis usually acts as a trigger or biochemical detonator for other major mechanisms , such as the Calvin cycle or the Krebs cycle. Both eukaryotes and prokaryotes are glycolysis practitioners.
Importance of glycolysis
Glycolysis is a very important process in the field of biochemistry . On the one hand it has great evolutionary importance, since it is the base reaction for the increasingly complex life and for the support of cell life . On the other hand, his study reveals details about the various existing metabolic pathways and about other aspects of the life of our cells.
For example, recent studies at universities in Spain and the University Hospital of Salamanca detected links between neuronal survival in the brain and the increase in glycolysis to which neurons can be subjected. This could be key in understanding diseases such as Parkinson’s disease or Alzheimer’s disease.
Glycolysis and gluconeogenesis
If glycolysis is the metabolic pathway that breaks the glucose molecule for energy, gluconeogenesis is a metabolic pathway that goes the opposite way: the construction of a glucose molecule from non-glycidic precursors , that is, not linked at all With the sugars.
This process is almost exclusive to the liver (90%) and the kidneys (10%) , and takes advantage of resources such as amino acids, lactate, pyruvate, glycerol and any carboxylic acid as a carbon source. In the absence of glucose, such as fasting, they allow the body to remain stable and functioning during a prudential period, while glycogen stores in the liver last.