Anaerobic Respiration

This lesson covers anaerobic respiration — respiration without oxygen — as required by the Edexcel GCSE Combined Science specification (1SC0). You need to know the word equations for anaerobic respiration in animals and in yeast/plants, understand the concept of oxygen debt and compare aerobic with anaerobic respiration.

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What Is Anaerobic Respiration?

Anaerobic means "without oxygen." Anaerobic respiration is the release of energy from glucose without using oxygen. It occurs when cells cannot get enough oxygen to meet their energy demands — for example, during vigorous exercise.

Anaerobic respiration releases much less energy per molecule of glucose than aerobic respiration because glucose is only partially broken down.

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Anaerobic Respiration in Animals

In animal cells (including humans), the word equation is:

$\text{glucose} \rightarrow \text{lactic acid} + \text{energy}$glucose→lactic acid+energy

Key points:

• The glucose molecule is not fully broken down — lactic acid still contains a lot of chemical energy.
• No carbon dioxide or water is produced (unlike aerobic respiration).
• The process takes place in the cytoplasm, not the mitochondria.
• It releases much less energy than aerobic respiration.