According to the biology department at Georgia Tech, glycolysis occurs in the cytoplasm in eukaryotic cells. This process converts glucose into pyruvic acid though a chemical reaction.
Glycolysis starts with glucose molecules that have been transferred to the eukaryotic cell from the bloodstream to the cell's cytoplasm. The glucose gains two phosphate molecules as it reacts with two ATP units. The resulting molecule splits into two halves. Several chemical reactions convert each half molecule into a pyruvate molecule. As electrons transfer during the reactions, four ATP units form, for a net gain of two ATP units. If oxygen is present, the pyruvate then oxidizes for a larger ATP gain.