Acell releases energy from food without using oxygen by

The process of releasing energy from breaking down of food (eg sugar) without the presence of oxygen is celled anaerobic respiration.

Comparing to aerobic respiration, the one that uses oxygen, anaerobic respiration releases less energy. It also does not oxidize sugar completely.

Theres 2 main kinds of anaerobic respiration, which includes muscles respiration and yeast fermentation.

Muscles usually undergo anaerobic respiration to convert glucose to lactic acid and energy, which builds up oxygen debt, that explains why we breathe harder and faster after exercising.

Yeast fermentation is usually used in the industries of wine brewing or bread making, which releases ethanol and carbon dioxide in additional.