Anaerobic and Aerobic Respiration

Key Points

• Respiration is a chemical reaction that releases energy from glucose in all living cells.
• Anaerobic respiration occurs without oxygen, releasing less energy but more quickly than aerobic respiration.
• In microorganisms, anaerobic respiration is referred to as fermentation.

Types of Respiration

• Respiration is a chemical reaction occurring in the mitochondria of all cells, not to be confused with breathing.
• Aerobic respiration:
  • Requires oxygen.
  • Occurs in mitochondria.
  • Takes place in most cells most of the time.
• Anaerobic respiration:
  • Occurs without oxygen.
  • Happens less frequently than aerobic respiration.
  • Used by humans when oxygen is scarce, e.g., during intense exercise.
• Fermentation:
  • A form of anaerobic respiration in yeast and bacteria.
  • Converts glucose into alcohol (ethanol) and carbon dioxide.

Anaerobic Respiration in Humans

• Occurs during vigorous exercise when oxygen supply is insufficient.
• Reaction: Glucose → Lactic Acid
• Releases energy quickly but in smaller amounts.
• Lactic acid buildup leads to muscle pain and cramps.
• Post-exercise, deep breathing (EPOC) helps convert lactic acid into carbon dioxide and water, releasing more energy.

Anaerobic Respiration in Bacteria and Fungi

• Yeast and some bacteria use fermentation for energy.
• Formula: Glucose → Ethanol + Carbon Dioxide
• In bread making, alcohol evaporates during baking, and CO2 helps dough rise.
• In beverages, CO2 creates bubbles.

Quiz Questions

1. Conditions for Anaerobic Respiration: Lack of oxygen.
2. Product in Human Muscle Cells: Lactic acid.
3. Foods Using Fermentation: Bread, yoghurt, beer, wine.
4. Products of Fermentation: Ethanol and carbon dioxide.

Additional Information

• Teaching Resources: Videos and resources for understanding respiration further available on BBC Bitesize.
• Quiz Explanation: Beer contains alcohol due to fermentation, while in bread, alcohol evaporates during baking.