3.3 Anaerobic Respiration and Fermentation

Anaerobic Respiration and Fermentation

Anaerobic Cellular Respiration

• Definition: A metabolic pathway in which an inorganic molecule other than oxygen serves as the final electron acceptor during the chemiosmotic synthesis of ATP.

Anaerobic Fermentation

• Description: A cellular respiration pathway that transfers electrons from NADH to an organic acceptor molecule.

Types of Fermentation

Lactate (Lactic Acid) Fermentation

• Occurrence:

  • Takes place in muscle cells and certain types of bacteria.

• Product:

  • Produces lactate (lactic acid).

• Process:

  • After glycolysis:

    • Sufficient oxygen:

      • Pyruvate goes through oxidation, Krebs cycle, electron transport chain (ETC), and chemiosmosis.

    • Insufficient oxygen:

      • Undergoes fermentation instead.

Glycolysis and Lactate Production

• Equation:

  • Glucose → 2 Pyruvate → 2 Lactate

  • Involves regeneration of NAD+ from NADH to keep glycolysis going, producing 2 ATP and 2 NADH in the process.

Ethanol Fermentation

• Occurrence:

  • Occurs in yeast cells and certain bacteria.

• Products:

  • Produces ethanol (alcohol) and carbon dioxide.

• Glycolysis and Ethanol Production:

  • Process:

    • Glucose → 2 Acetaldehyde → 2 Ethanol

    • Involves regeneration of NAD+ from NADH, leading to the production of 2 ATP and CO2.

Key Chemical Reactions

Lactate Fermentation

• Chemical Reaction:

  • Glucose ➔ 2 Pyruvate ➔ 2 Lactate + 2 NAD+ + 2 ATP + 2 NADH

Ethanol Fermentation

• Chemical Reaction:

  • Glucose ➔ 2 Pyruvate ➔ 2 Acetaldehyde ➔ 2 Ethanol + 2 NAD+ + 2 ATP + CO2

Application Questions

• Muscle Burn Sensation:

  • Explain the causes behind the burning sensation in muscles during intense exercise using lactate fermentation principles.

• Ethanol Fermentation in Industry:

  • Describe how ethanol fermentation is utilized in industries for the production of baked goods and alcoholic beverages.