Anaerobic Respiration (WJEC GCSE Biology)

Anaerobic Respiration

• Anaerobic respiration is a process that occurs in the absence of oxygen

• Glucose is incompletely broken down to release energy and lactic acid

• This occurs when the body can’t supply enough oxygen for aerobic respiration, such as during vigorous exercise

  • When we exercise vigorously, our muscles have a higher demand for energy than when we are resting or exercising normally. Our bodies can only deliver so much oxygen to our muscle cells for aerobic respiration

  • In this instance, as much glucose as possible is broken down with oxygen, but some glucose is broken down without oxygen, producing lactic acid instead

The oxygen debt

• An oxygen debt occurs as a result of anaerobic respiration

• Lactic acid builds up in muscle cells and lowers the pH of the cells (making them more acidic)

• This is harmful to the body as it could denature the enzymes in cells so lactic acid needs to be removed by oxygen 

• This is the reason we continue to breathe heavily and our heart rate remains high even after finishing exercise - we need to take in oxygen to oxidise the lactic acid that has built up during anaerobic respiration

• This is known as ‘repaying the oxygen debt’

• Anaerobic respiration is represented by the equation:

Word equation for anaerobic respiration in animals – some bacterial cells respire in this way too

Comparing Aerobic & Anaerobic Respiration

Higher Tier Only

Comparison of aerobic and anaerobic respiration table