Understanding Glycolysis Metabolic Pathway

Sep 25, 2024

Glycolysis Lecture Notes

Introduction to Glycolysis

  • Definition: Glycolysis is a metabolic pathway breaking down glucose to produce energy.
  • Location: Occurs in the cytosol of cells.
  • Components of the Term:
    • "Glyco" means glucose.
    • "Lysis" means breakdown.

Overview of Glycolysis

  • Input: One molecule of glucose (6-carbon compound).
  • Output: Two molecules of pyruvate (3-carbon compound).
  • Energy Production: Produces ATP and NADH.
  • Further Utilization: Pyruvate is used in other pathways for more energy production.

Phases of Glycolysis

Phase 1: Energy Investment Phase

  • Conversion of glucose to two molecules of glyceraldehyde 3-phosphate.
  • Net Energy: Uses energy (ATP).

Phase 2: Energy Pay-Off Phase

  • Conversion of glyceraldehyde 3-phosphate to pyruvate.
  • Net Energy: Produces energy (ATP and NADH).

Reactions in Glycolysis

Initial Steps

  1. Glucose to Glucose 6-Phosphate

    • Enzyme: Hexokinase
    • Process: Phosphate from ATP added to glucose.
    • Energy Use: Consumes 1 ATP.

  2. Glucose 6-Phosphate to Fructose 6-Phosphate

    • Enzyme: Isomerase
    • Process: Simple rearrangement.

  3. Fructose 6-Phosphate to Fructose 1,6-Bisphosphate

    • Enzyme: Phosphofructokinase
    • Process: Adds phosphate, uses ATP.
    • Energy Use: Consumes 1 ATP.

Splitting and Isomerization

  1. Fructose 1,6-Bisphosphate Split

    • Enzyme: Aldolase
    • Products: Glyceraldehyde 3-phosphate and dihydroxyacetone phosphate.

  2. Isomerization of Dihydroxyacetone Phosphate

    • Enzyme: Isomerase
    • Equilibrium towards: Glyceraldehyde 3-phosphate.

Energy Generation Steps

  1. Glyceraldehyde 3-Phosphate to 1,3-Bisphosphoglycerate

    • Enzyme: Glyceraldehyde 3-phosphate dehydrogenase
    • Coenzyme: NAD+ reduced to NADH.
    • Inorganic Phosphate: Utilized.

  2. 1,3-Bisphosphoglycerate to 3-Phosphoglycerate

    • Enzyme: Phosphoglycerate kinase
    • Product: ATP generated.

  3. 3-Phosphoglycerate to 2-Phosphoglycerate

    • Enzyme: Phosphoglycerate mutase
    • Process: Rearrangement.

  4. 2-Phosphoglycerate to Phosphoenolpyruvate

    • Enzyme: Enolase
    • Co-factor: Magnesium ions.

  5. Phosphoenolpyruvate to Pyruvate

    • Enzyme: Pyruvate kinase
    • Product: ATP generated.

Net Reaction Summary

  • Glucose (6C) splits into 2 Pyruvate (3C).
  • Net ADP Use: 2 ADP (4 ATP produced in phase 2 minus 2 ATP used in phase 1).
  • Inorganic Phosphate: 2 molecules utilized.
  • NADH Production: 2 NAD+ reduced to NADH during glyceraldehyde 3-phosphate conversion.

Conclusion

  • Glycolysis is an essential energy-producing process in cells.
  • The lecture provides a detailed breakdown of the steps involved in glycolysis.
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