In this article we will take a closer look at aerobic glycolysis, its processes, and analyze the stages and stages. Let's get acquainted with the anaerobic oxidation of glucose, learn about the evolutionary modifications of this process and determine its biological significance.
What is glycolysis
Glycolysis is one of the three forms of glucose oxidation, in which the oxidation process itself is accompanied by the release of energy, which is stored in NADH and ATP. In the process of glycolysis, two molecules of pyruvic acid are obtained from a glucose molecule.
Glycolysis is a process that occurs under the influence of various biological catalysts - enzymes. The main oxidizing agent is oxygen - O2, however, glycolysis processes can proceed in its absence. This type of glycolysis is called anaerobic glycolysis.
The process of glycolysis in the absence of oxygen
Anaerobic glycolysis is a stepwise process of glucose oxidation in which glucose is not completely oxidized. One molecule of pyruvic acid is formed. And with energypoint of view, glycolysis without the participation of oxygen (anaerobic) is less beneficial. However, when oxygen enters the cell, the anaerobic oxidation process can turn into an aerobic one and proceed in a full form.
Mechanisms of glycolysis
The process of glycolysis is the decomposition of six-carbon glucose into three-carbon pyruvate in the form of two molecules. The process itself is divided into 5 stages of preparation and 5 stages in which energy is stored in ATP.
Glycolysis process of 2 steps and 10 steps is as follows:
- 1 stage, stage 1 - phosphorylation of glucose. At the sixth carbon in glucose, the saccharide itself is activated via phosphorylation.
- Step 2 - isomerization of glucose-6-phosphate. At this stage, phosphoglucoseimerase catalytically converts glucose into fructose-6-phosphate.
- Stage 3 - Fructose-6-phosphate and its phosphorylation. This step consists in the formation of fructose-1,6-diphosphate (aldolase) by the action of phosphofructokinase-1, which accompanies the phosphoryl group from adenosine triphosphoric acid to the fructose molecule.
- Step 4 is the process of cleavage of aldolase to form two molecules of triose phosphate, namely eldose and ketose.
- Stage 5 - triose phosphates and their isomerization. At this stage, glyceraldehyde-3-phosphate is sent to the subsequent stages of glucose breakdown, and dihydroxyacetone phosphate is converted to the form of glyceraldehyde-3-phosphate under the influence of the enzyme.
- 2 stage, stage 6 (1) - Glyceraldehyde-3-phosphate and its oxidation - the stage in which this molecule is oxidized and phosphorylated todiphosphoglycerate-1, 3.
- Stage 7 (2) - aimed at transferring the phosphate group to ADP from 1,3-diphosphoglycerate. The end products of this step are the formation of 3-phosphoglycerate and ATP.
- Step 8 (3) - transition from 3-phosphoglycerate to 2-phosphoglycerate. This process occurs under the influence of the enzyme phosphoglycerate mutase. A prerequisite for the flow of a chemical reaction is the presence of magnesium (Mg).
- Step 9 (4) - 2 phosphoglycerta dehydrated.
- Stage 10 (5) - phosphates obtained as a result of the previous stages are transferred to ADP and PEP. Energy from phosphoenulpyrovate is transferred to ADP. The reaction requires the presence of potassium (K) and magnesium (Mg) ions.
Modified forms of glycolysis
The process of glycolysis can be accompanied by additional production of 1, 3 and 2, 3-biphosphoglycerates. 2,3-phosphoglycerate, under the influence of biological catalysts, is able to return to glycolysis and transform into the form of 3-phosphoglycerate. The role of these enzymes is diverse, for example, 2, 3-biphosphoglycerate, being in hemoglobin, causes oxygen to pass into tissues, promoting dissociation and lowering the affinity of O2 and erythrocytes.
Many bacteria change the forms of glycolysis at various stages, reducing their total number or modifying them under the influence of different enzymes. A small part of anaerobes have other methods of carbohydrate decomposition. Many thermophiles have only 2 glycolysis enzymes at all, these are enolase and pyruvate kinase.
Glycogen and starch, disaccharides andother types of monosaccharides
Aerobic glycolysis is a process inherent in other types of carbohydrates, and specifically it is inherent in starch, glycogen, most disaccharides (manose, galactose, fructose, sucrose and others). The functions of all types of carbohydrates are generally aimed at obtaining energy, but may differ in the specifics of their purpose, use, etc. For example, glycogen lends itself to glycogenesis, which in fact is a phospholytic mechanism aimed at obtaining energy from the breakdown of glycogen. Glycogen itself can be stored in the body as a reserve source of energy. So, for example, glucose obtained during a meal, but not absorbed by the brain, accumulates in the liver and will be used when there is a lack of glucose in the body in order to protect the individual from serious disruptions in homeostasis.
Meaning of glycolysis
Glycolysis is a unique, but not the only type of glucose oxidation in the body, the cell of both prokaryotes and eukaryotes. Glycolysis enzymes are water soluble. The glycolysis reaction in some tissues and cells can only occur in this way, for example, in the brain and liver nephron cells. Other ways of oxidizing glucose in these organs are not used. However, the functions of glycolysis are not the same everywhere. For example, adipose tissue and the liver in the process of digestion extract the necessary substrates from glucose for the synthesis of fats. Many plants use glycolysis as a way to extract the bulk of their energy.
