Anaerobic Respiration

  • Anaerobic respiration is the process through which cells can break down sugars for energy when oxygen is not present or insufficient.
  • It takes place in the cytoplasm of cells, as opposed to aerobic respiration which takes place in mitochondria.
  • The process starts with glucose, a type of sugar that is a key player in both types of respiration.
  • The glucose is broken down in the process of glycolysis, which produces two molecules of pyruvate and releases a small amount of energy.
  • In the absence of oxygen, these pyruvate molecules are converted into lactic acid in muscles or ethanol and carbon dioxide in yeast and some bacteria. This process is known as fermentation.
  • Anaerobic respiration releases less energy compared to aerobic respiration, but it does so more quickly.
  • Lactic acid build-up in muscles during strenuous exercise can lead to muscle fatigue and pain.
  • The lactic acid must be broken down after the exercise, which requires oxygen. This results in an ‘oxygen debt’.
  • The rapid energy release from anaerobic respiration is necessary at times of high energy demand, such as during a sprint.
  • This process is less efficient than aerobic respiration because glucose is incompletely broken down.
  • Anaerobic respiration is important in biotechnology, for example in the production of yoghurt, bread and alcoholic drinks.
  • The by-products of anaerobic respiration in plants and yeast (ethanol and carbon dioxide) are commercially important in baking and brewing.
  • Anaerobic bacteria are widespread in the environment and play a significant role in the recycling of nutrients.
  • The word anaerobic means ‘without air’, referring to the absence of oxygen in this type of respiration.
  • Learning to recognise and understand the chemical equations associated with aerobic and anaerobic respiration can be especially helpful for understanding and remembering this process. For anaerobic respiration in muscles, glucose is converted into lactic acid. In anaerobic respiration in plants, glucose is converted into ethanol and carbon dioxide.