How the body uses carbohydrates

The organs, systems and cells of a human body run on glucose, a sugar molecule the body burns to produce the energy it needs. The body gets the necessary glucose from carbohydrates, which are composed of molecules of sugar.

If you need the glucose for instant energy, your body burns it right away. If you have enough glucose for your immediate needs, the extra supply on hand is converted to glycogen and tucked away as stored energy in your liver and muscle cells.

Anaerobic glycolysis
Anaerobic glycolysis is the transformation of glucose to pyruvate when limited amounts of oxygen are available. During this process 2 ATP molecules per glucose molecule are produced. ATP (adenosine triphosphate) is a molecule that transports chemical energy within the cells. Thus the anaerobic glycolysis is a process in which glucose is transformed into energy. 

Aerobic glycolysis
The Krebs cycle is a series of chemical reactions occurring in all cells that use oxygen as part of their respiration. This process takes place during aerobic glycolysis and produces carbon dioxide, water and ATP. Compared to anaerobic glycolysis, aerobic glycolysis produces a lot more energy: during this process in fact 38 ATP molecules per glucose molecule are produced.