Glycolysis is the first step in cellular respiration. In this process a molecule of glucose is broken into two molecules of pyruvic acid.

In order to begin glycolysis a cell must have oxygen, a food molecule such as glucose and the cell has to provide 2 ATP molecules. After the process is finished 4 ATP molecules have been produced. As well as ATP molecules glycolysis produces 2 molecules of Pyruvic acid. This pyruvic acid is then transported across the cell to the mitochondria and contributes to the Krebs Cycle.