Key Points on Aerobic and Anaerobic Respiration

  • Cellular Respiration Basics

    • When O2 is absent or insufficient:
    • Lactate (Lactic Acid) Fermentation
    • Alcohol (Ethanol) Fermentation

  • Fate of Pyruvate

    • Presence of O2:
    • Goes to Krebs Cycle & ETC (Aerobic Cellular Respiration)
    • Absence of O2:
    • Converts to lactate or ethanol (Fermentation)

  • Anaerobic Respiration

    • Occurs without oxygen
    • Cells lacking mitochondria rely solely on glycolysis to make ATP
    • Glycolysis must couple with fermentation to regenerate NAD+

  • Types of Anaerobic Fermentation

    • Alcohol Fermentation:
    • Pyruvate → Ethanol + CO2
    • Lactate Fermentation:
    • Pyruvate → Lactate

  • Lactate Fermentation

    • Occurs in humans, some fungi, and bacteria
    • Lactate dehydrogenase converts pyruvate to lactate
    • NADH → NAD+ regeneration allows glycolysis to continue
    • Causes muscle fatigue and soreness due to lactic acid buildup

  • Alcohol Fermentation

    • Occurs in yeast
    • Pyruvate → Acetaldehyde + CO2 → Ethanol
    • Used in brewing and baking (CO2 makes bread rise)

  • Purpose of Fermentation

    • Continues ATP production when oxygen is not available
    • Essential for recycling NAD+

  • Fermentation Summary

    • Lactate Fermentation:
    • 2 Pyruvate → 2 Lactate
    • NADH → NAD+
    • Alcohol Fermentation:
    • 2 Pyruvate → 2 Acetaldehyde → 2 Ethanol + 2 CO2
    • NADH → NAD+

  • Molecule Count

    • Anaerobic Process:
    • Glycolysis ATP: 2, NADH: 2
    • Fermentation ATP: 0, NADH: -2
    • Total ATP: 2
    • Total NADH: 0
    • FADH2: 0