Glycolysis Overview

Overview of Glycolysis

• Glycolysis is a metabolic pathway that converts glucose into pyruvate, producing energy in the form of ATP and NADH.
• It is the first step in cellular respiration and is common to all living organisms.

Steps of Glycolysis

1. Glucose phosphorylation: Glucose is converted into glucose-6-phosphate (G6P) using one ATP molecule.
2. Phosphoglucose isomerase: G6P is converted into fructose-6-phosphate (F6P).
3. Aldolase: F6P is converted into fructose-1,6-bisphosphate (F1,6BP).
4. Triosephosphate isomerase: F1,6BP is converted into glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP).
5. Glyceraldehyde-3-phosphate dehydrogenase: G3P is converted into 1,3-bisphosphoglycerate (1,3BPG), producing NADH.
6. Phosphoglycerate kinase: 1,3BPG is converted into 3-phosphoglycerate (3PG), producing ATP.
7. Phosphoglycerate mutase: 3PG is converted into 2-phosphoglycerate (2PG).
8. Enolase: 2PG is converted into enolpyruvate (ENO).
9. Pyruvate kinase: ENO is converted into pyruvate, producing ATP.

Regulation of Glycolysis

• Feedback inhibition: ATP and pyruvate inhibit phosphofructokinase-1, a key enzyme in glycolysis.
• Allosteric regulation: ATP and citrate inhibit phosphofructokinase-1, while ADP and AMP activate it.
• Hormonal regulation: Insulin stimulates glycolysis, while glucagon inhibits it.

Importance of Glycolysis

• Energy production: Glycolysis produces ATP and NADH, which are used in cellular respiration.
• Glucose metabolism: Glycolysis is the first step in glucose metabolism, and its regulation is critical for maintaining blood glucose levels.
• Cellular signaling: Glycolysis produces intermediates that can be used in signaling pathways.

Overview of Glycolysis

• Glycolysis is a metabolic pathway that converts glucose into pyruvate, producing energy in the form of ATP and NADH.
• It is the first step in cellular respiration and is common to all living organisms.

Steps of Glycolysis

• Glucose is converted into glucose-6-phosphate (G6P) using one ATP molecule through glucose phosphorylation.
• Phosphoglucose isomerase converts glucose-6-phosphate (G6P) into fructose-6-phosphate (F6P).
• Aldolase converts fructose-6-phosphate (F6P) into fructose-1,6-bisphosphate (F1,6BP).
• Triosephosphate isomerase converts fructose-1,6-bisphosphate (F1,6BP) into glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP).
• Glyceraldehyde-3-phosphate dehydrogenase converts glyceraldehyde-3-phosphate (G3P) into 1,3-bisphosphoglycerate (1,3BPG), producing NADH.
• Phosphoglycerate kinase converts 1,3-bisphosphoglycerate (1,3BPG) into 3-phosphoglycerate (3PG), producing ATP.
• Phosphoglycerate mutase converts 3-phosphoglycerate (3PG) into 2-phosphoglycerate (2PG).
• Enolase converts 2-phosphoglycerate (2PG) into enolpyruvate (ENO).
• Pyruvate kinase converts enolpyruvate (ENO) into pyruvate, producing ATP.

Regulation of Glycolysis

• ATP and pyruvate inhibit phosphofructokinase-1 through feedback inhibition.
• ATP and citrate inhibit phosphofructokinase-1, while ADP and AMP activate it through allosteric regulation.
• Insulin stimulates glycolysis, while glucagon inhibits it through hormonal regulation.

Importance of Glycolysis

• Glycolysis produces ATP and NADH, which are used in cellular respiration.
• Glycolysis is the first step in glucose metabolism, and its regulation is critical for maintaining blood glucose levels.
• Glycolysis produces intermediates that can be used in signaling pathways.

Glucose Phosphorylation

• Glucose is converted into glucose-6-phosphate (G6P) with the help of hexokinase
• This step is irreversible and commits the glucose molecule to the glycolytic pathway
• One ATP molecule is consumed in this step

Pyruvate Conversion

• Phosphoenolpyruvate (PEP) is converted into pyruvate by pyruvate kinase
• Pyruvate is the end product of glycolysis and can be further converted into ATP, NADH, or lactate
• The fate of pyruvate depends on the cell's energy needs

ATP Production

• ATP is produced in two stages of glycolysis through substrate-level phosphorylation
• 1,3-bisphosphoglycerate (1,3-BPG) is converted to 3-phosphoglycerate (3-PG), producing ATP
• Phosphoenolpyruvate (PEP) is converted to pyruvate, producing ATP
• A total of 2 ATP molecules are produced per glucose molecule during glycolysis

NADH Generation

• Glyceraldehyde-3-phosphate (G3P) is converted to 1,3-bisphosphoglycerate (1,3-BPG) by glyceraldehyde-3-phosphate dehydrogenase
• NADH is produced as a byproduct of glycolysis
• NADH can be used to generate ATP in the electron transport chain

Regulation of Glycolysis

• Glycolysis is regulated by allosteric control, where ATP and ADP molecules bind to enzymes
• ATP inhibits glycolysis by binding to phosphofructokinase-1 (PFK-1) and pyruvate kinase
• ADP activates glycolysis by binding to phosphofructokinase-1 (PFK-1) and pyruvate kinase
• High levels of ATP and NADH inhibit glycolysis through substrate inhibition
• Insulin promotes glycolysis, while glucagon inhibits it