Glycolysis Lecture Notes

Introduction to Glycolysis

• Definition: Glycolysis is a metabolic pathway for the breakdown of glucose.
  • "Glyco" refers to glucose
  • "Lysis" means breakdown
• Location: Takes place in the cytosol of cells
• Function: Systematic breakdown of glucose to produce energy in the form of ATP and NADH

Overview of Glycolysis

• Initial Substrate: 1 molecule of glucose (6-carbon compound)
• End Product: 2 molecules of pyruvate (3-carbon compound)
• Energy Production:
  • ATP
  • NADH (further utilized in energy pathways)

Phases of Glycolysis

Phase 1: Energy Investment Phase

• Converts glucose to two molecules of glyceraldehyde 3-phosphate
• Reactions in Phase 1:
  1. Glucose to Glucose 6-phosphate
     • Catalyzed by hexokinase
     • Utilizes 1 ATP (converted to ADP)
  2. Glucose 6-phosphate to Fructose 6-phosphate
     • Catalyzed by isomerase (rearrangement reaction)
  3. Fructose 6-phosphate to Fructose 1,6-bisphosphate
     • Catalyzed by phosphofructokinase
     • Utilizes 1 ATP (converted to ADP)
  4. Fructose 1,6-bisphosphate to Glyceraldehyde 3-phosphate & Dihydroxyacetone phosphate
     • Catalyzed by aldolase
     • These are 3-carbon compounds and isomers interconvertible by isomerase

Phase 2: Energy Payoff Phase

• Glyceraldehyde 3-phosphate is converted to pyruvate
• Reactions in Phase 2:
  1. Glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate
     • Catalyzed by glyceraldehyde 3-phosphate dehydrogenase
     • NAD+ reduced to NADH
     • Utilizes inorganic phosphate
  2. 1,3-bisphosphoglycerate to 3-phosphoglycerate
     • Catalyzed by phosphoglycerate kinase
     • Produces 1 ATP
  3. 3-phosphoglycerate to 2-phosphoglycerate
     • Catalyzed by phosphoglycerate mutase
  4. 2-phosphoglycerate to phosphoenolpyruvate
     • Catalyzed by enolase
     • Requires magnesium ions
  5. Phosphoenolpyruvate to Pyruvate
     • Catalyzed by pyruvate kinase
     • Produces 1 ATP

Net Reaction of Glycolysis

• Reactants: 1 molecule of glucose, 2 ADP, 2 inorganic phosphate, 2 NAD+
• Products: 2 molecules of pyruvate, 2 ATP (net gain), 2 NADH

Conclusion

• Glycolysis is a crucial energy-yielding process
• Understanding glycolysis is essential for studying cellular metabolism
• Additional resources available on YouTube and Facebook for further study