17. Glycolysis – biological importance in catabolism and anabolism, chemical reactions, energy production under anaerobic and aerobic conditions, regulation, tissue specificity. Metabolic fate of pyruvate and NADH in aerobic conditions: shuttle systems, pyruvate dehydrogenase reaction – regulation.

Glycolysis: Importance, Chemical Reactions, and Energy Balance

Importance of Glycolysis

• Fundamental Pathway: Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism.
• Universal Pathway: Present in nearly all organisms, reflecting its evolutionary importance.
• Anaerobic Energy Production: Allows cells to produce ATP without oxygen, crucial in anaerobic conditions.

GLYCOLYSIS

• glucose

1. 1 HEXOKINASE ATP → ADP

• glucose 6-phosphate

1. 2 PHOSPHOGLUCOISOMRASE

• fructose 6-phosphate

1. 3 PHOSPHOFRUCTOKINASE ATP → ADP

• fructose 1,6-bisphosphate

1. 4 ALDOLASE

• glyceraldehyde 3-phosphate (G3P) ↔ dehydroxyacetone phosphate (DHAP)

5. ISOMERASE
6. TRIOSE PHOSPHATE DEHYDROGENASE 2 NAD⁺ → 2 NADH + 2 H⁺

• 1,3-bisphosphoglycerate

1. 7 PHOSPHOGLYCEROKINASE 2 ADP → 2 ATP

• 3-phosphoglycerate

1. 8 PHOSPHOGLYCEROMUTASE

• 2-phosphoglycerate

1. 9 ENOLASE → 2 H₂O

• phosphoenolpyruvate (PEP)

1. 10 PYRUVATE KINASE 2 ADP → 2 ATP

• pyruvate

Chemical Reactions of Glycolysis

• Ten Enzyme-Catalyzed Steps: Converts glucose to pyruvate, generating ATP and NADH.

Key Steps:

• Phosphorylation of glucose to glucose-6-phosphate (Hexokinase).
• Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate (Phosphofructokinase).
• Cleavage of fructose-1,6-bisphosphate into two three-carbon molecules, and subsequent conversion to pyruvate.