Why is anaerobic respiration produce less energy than aerobic respiration?

Much less energy is released during anaerobic respiration than during aerobic respiration. This is because the breakdown of glucose is incomplete. Anaerobic respiration produces an oxygen debt. This is the amount of oxygen needed to oxidise lactic acid to carbon dioxide and water.

Because anaerobic respiration is simple and has a few steps were a little bit of ATP is used to break down glucose to produce pyruvate which is not very energetic on its own.

When there is oxygen then the pyruvate continues into a process called Kreb's cycle or the TCA cycle OR citric acid cycle (all the same). It is broken down into many more ATPs so there is more energy as ATP is the biological form of energy. There are MANY steps in the kreb's cycle meaning pyruvate is broken down a small bit each time, creating ATP on the way. THEN there is the electron transport chain which creates more ATP.

BASICALLY! Pyruvate can't be broken down completely without oxygen so the body can't get all the possible ATP out of it. That is why in anaerobic metabolism there is much less energy given out.

Thanks for helping