Anaerobic Respiration | Biology for GCSE/IGCSE - Year 11 PDF Download

Anaerobic Respiration - Respiration Without Oxygen

• Anaerobic respiration is a process that does not require oxygen. It involves the chemical reactions in cells that break down nutrient molecules to release energy without the use of oxygen.
• Unlike aerobic respiration, which fully breaks down glucose, anaerobic respiration is an incomplete breakdown of glucose, resulting in the release of a relatively small amount of energy for cell processes.
• The products produced during anaerobic respiration vary depending on the organism in which the process is occurring.
• It is essential to understand the specific equations for anaerobic respiration in humans (animals) and the microorganism yeast.

Anaerobic Respiration in Muscle Cells

• Anaerobic respiration primarily occurs in muscle cells during intense exercise.
• During vigorous physical activity, muscles require more energy compared to when at rest or during moderate exercise.
• Muscle cells face limitations in receiving sufficient oxygen for aerobic respiration during intense exercise.
• In situations where oxygen availability is limited, glucose is partially broken down without oxygen, leading to the production of lactic acid.
• Although less energy is released during anaerobic breakdown of glucose, there is still stored energy within lactic acid molecules that cells can utilize.

Anaerobic Respiration in Yeast

• We utilize the byproducts of anaerobic respiration in yeast for various purposes:
  • Bread Making: In this process, the carbon dioxide produced is responsible for causing the dough to rise.
  • Brewing: Here, the ethanol produced imparts the alcoholic nature to beer, while the carbon dioxide adds fizz.

• Examples:

  • Bread Making: The carbon dioxide generated during anaerobic respiration in yeast is crucial for the rising of dough, creating fluffy bread.
  • Brewing: The ethanol produced gives beer its characteristic alcoholic content, while the carbon dioxide contributes to its effervescence.

Balanced Chemical Equation for Anaerobic Respiration

• The balanced chemical equation for anaerobic respiration in yeast is:

Anaerobic Respiration & Oxygen Debt: Extended

• Lactic acid accumulation in muscle cells reduces their pH, making them more acidic.
• This acidity can potentially disrupt cellular enzymes, necessitating its removal.
• Muscle cells expel lactic acid into the bloodstream, where it is subsequently absorbed by liver cells during circulation.
• Within liver cells, lactic acid undergoes oxidation, yielding carbon dioxide and water.
• Consequently, post-exercise, heightened breathing and heart rates persist to facilitate the transport of lactic acid to the liver and ensure ample oxygen supply for its oxidation.
• This process is termed "repaying the oxygen debt."

Comparing Aerobic & Anaerobic Respiration

Comparing types of respiration: