2.34 describe the differences between aerobic and anaerobic respiration

Aerobic respiration occurs when oxygen is present, it is the most efficient way to release energy from glucose and is the respiration humans use most of the time. 

Anaerobic respiration in animals occurs when there is no oxygen present, for example, when you do lots of exercise. When you do lots of exercise your body can't supply enough oxygen to your muscles for aerobic respiration, therefore, your muscles must anaerobically respire.

Anaerobic respiration releases less energy than aerobic respiration and therefore it is not the best way to convert glucose into energy. In anaerobic respiration, glucose is only partially broken down (this produces lactic acid)

This lactic acid builds up in muscles and gets very painful (sometimes leads to cramp)

Anaerobic respiration in plants is the same as animals only ethanol and CO₂ is produced in place of lactic acid