The mechanism of glycolysis, also known as the Embden-Meyerhof pathway, involves a series of enzymatic reactions that break down glucose into two molecules of pyruvate. This process occurs in the cytoplasm of the cell and is the first step in both aerobic and anaerobic respiration.
The overall reaction of glycolysis can be simplified as:
Glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 Pyruvate + 2 NADH + 2 ATP + 2 H2O
The mechanism of glycolysis can be divided into three main phases: energy investment, cleavage, and energy generation.
1. Energy Investment:
- Activation of glucose: Glucose is phosphorylated by the enzyme hexokinase using ATP as a phosphate donor. This creates glucose-6-phosphate.
- Conversion to fructose-6-phosphate: Glucose-6-phosphate is converted to fructose-6-phosphate by the enzyme phosphoglucose isomerase.
- Phosphorylation of fructose-6-phosphate: Fructose-6-phosphate is phosphorylated by ATP and the enzyme phosphofructokinase, creating fructose-1,6-bisphosphate. This step is considered the commitment step of glycolysis, where glucose is committed to the pathway and irreversible.
2. Cleavage:
- Cleavage of fructose-1,6-bisphosphate: The enzyme aldolase cleaves fructose-1,6-bisphosphate into two three-carbon molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P). DHAP is quickly converted to G3P by the enzyme triose phosphate isomerase.
3. Energy Generation:
- Oxidation and ATP production: Glyceraldehyde-3-phosphate is oxidized by the enzyme glyceraldehyde-3-phosphate dehydrogenase, producing NADH from NAD+. Simultaneously, inorganic phosphate (Pi) is added to glyceraldehyde-3-phosphate, forming 1,3-bisphosphoglycerate.
- ATP production: 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate by the enzyme phosphoglycerate kinase. During this conversion, one molecule of ATP is produced.
- Conversion to pyruvate: 3-phosphoglycerate is converted to 2-phosphoglycerate by the enzyme phosphoglycerate mutase. Then, enolase acts on 2-phosphoglycerate to form phosphoenolpyruvate (PEP).
- ATP production: Phosphoenolpyruvate is converted to pyruvate by the enzyme pyruvate kinase. This last step generates the final molecule of ATP, along with pyruvate.
Overall, the mechanism of glycolysis converts one molecule of glucose into two molecules of pyruvate, producing a net gain of two molecules of ATP (four produced minus two used) and two molecules of NADH. These products can further enter various metabolic pathways for energy production or other biochemical processes depending on the cellular conditions and organism's needs.
Explain the megnism of glycol us is
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