• Process that breaks down glucose and releases energy to form:
    • 2 Pyruvate (stores potential energy)
      • Pyruvate is acidic
    • 2 (net) ATP (from ADP)
    • NADH (from NAD+)
    • Inorganic phosphate
  • 2 Stages
    • Energy Investment: invests 2 ATP to get glycolysis started
    • Energy Payoff: creates 4 ATP
  • Occurs in the cytosol of the cell with or without oxygen


  • NAD+ combines with 1 proton and 2 electrons to make NADH (reduction)
    • Reverse: NADH broken down to form NAD+
  • NADH: reducing agent, carries the electrons to the ETC in mitochondria

Pyruvate Oxidation

  • Pyruvate is actively transported from the cytosol to the mitochondrial matrix where further oxidation occurs
    • Transportation depends on proton-motive force (H+ gradient)
  • Pyruvate loses carbon from acetyl group→ remaining carbon transferred to coenzyme A (CoA)
    • Result: 2 acetyl CoA, 2 NADH & 2 CO2 made
  • Acetyl CoA: coenzyme, high potential energy, will be oxidized in Krebs Cycle