In this article, we will examine in detail aerobic glycolysis, its processes, and analyze the stages and stages. We will 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 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 pyruvic acid molecules 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 - O 2 , but glycolysis processes can occur 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 from an energetic point of view, glycolysis without oxygen (anaerobic) is less beneficial. However, when oxygen enters the cell, the anaerobic oxidation process can turn into aerobic and proceed in full form.
Glycolysis Mechanisms
The glycolysis process 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 the ATP.
The glycolysis process of 2 stages and 10 stages is as follows:
- Stage 1, stage 1 - phosphorylation of glucose. At the sixth carbon atom in glucose, the saccharide itself is activated via phosphorylation.
- Stage 2 - isomerization of glucose-6-phosphate. At this stage, catalytic phosphoglucose isomerase converts glucose to fructose-6-phosphate.
- Stage 3 - Fructose-6-phosphate and its phosphorylation. This step consists in the formation of fructose-1,6-diphosphate (aldolase) by exposure to phosphofructokinase-1, which accompanies the phosphoryl group from adenosine triphosphoric acid to the fructose molecule.
- Stage 4 is the process of cleavage of the aldolase with the formation of two triosophosphate molecules, namely eldoses and ketoses.
- Stage 5 - triosophosphates and their isomerization. At this stage, glyceraldehyde-3-phosphate is sent to the subsequent stages of glucose breakdown, and dihydroxyacetone phosphate passes into the form of glyceraldehyde-3-phosphate under the influence of the enzyme.
- Stage 2, stage 6 (1) - Glyceraldehyde-3-phosphate and its oxidation - the stage in which this molecule is oxidized and phosphorylated to diphosphoglycerate-1,3.
- Stage 7 (2) - is aimed at transferring a group of phosphates to ADP from 1,3-diphosphoglycerate. The final products of this stage are the formation of 3-phosphoglycerate and ATP.
- Stage 8 (3) - the transition from 3-phosphoglycerate to 2-phosphoglycerate. This process occurs under the influence of the enzyme phosphoglyceratmutase. A prerequisite for a chemical reaction is the presence of magnesium (Mg).
- Stage 9 (4) - 2 phosphoglycerides are dehydrated.
- Stage 10 (5) - phosphates obtained as a result of passing through the previous stages are transferred to ADP and FEP. The energy from phosphoenylpyromatic is transferred to ADP. For the reaction to take place, the presence of potassium (K) and magnesium (Mg) ions is necessary.
Modified forms of glycolysis
The glycolysis process can be accompanied by additional production of 1,3 and 2,3-bisphosphoglycerates. 2,3-phosphoglycerate under the influence of biological catalysts is able to return to glycolysis and go into the form of 3-phosphoglycerate. The role of these enzymes is diverse, for example, 2,3-bisphosphoglycerate, being in hemoglobin, causes oxygen to pass into the tissues, promoting dissociation and lowering the affinity of O 2 and red blood cells.
Many bacteria change glycolysis forms at various stages, reducing their total number or modifying them under the influence of various enzymes. A small fraction of anaerobes have other carbohydrate decomposition methods. Many thermophiles have only 2 glycolysis enzymes, these are enolase and pyruvate kinase.
Glycogen and starch, disaccharides and other types of monosaccharides
Aerobic glycolysis is a process characteristic of other types of carbohydrates, namely 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 generating energy, but may differ in the specifics of their purpose, use, etc. For example, glycogen is amenable to glycogenesis, which in essence is a phospholytic mechanism aimed at generating energy by breaking down glycogen. Glycogen itself can be stored in the body as a backup source of energy. So, for example, glucose obtained during food intake, but not absorbed by the brain, accumulates in the liver and will be used if there is a lack of glucose in the body in order to protect the individual from serious failures of homeostasis.
The 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 occur only in this way, for example, in the brain and liver nephron cells. Other glucose oxidation methods are not used in these organs. However, not all glycolysis functions are the same. For example, adipose tissue and liver during digestion produce the necessary substrates from glucose for the synthesis of fats. Many plants use glycolysis as a way to extract most of the energy.