In eukaryotic cells, glycolysis takes place in the cytosol. After glycolysis, the products can be further broken down in the mitochondria.
Glycolysis describes a series of chemical reactions that a cell undergoes in order to produce energy quickly. A series of reactions in a cell is called a metabolic pathway. Glycolysis begins with stored glucose molecules in the form of glycogen being released and transformed into a compound called glucose 6-phosphate. Two molecules of adenosine triphosphate, which is the energy source of a cell, are needed for this first step. In total, glycolysis produces a total of 4 ATP per molecule of glucose, which means that there is a net gain of 2 ATP per glucose molecule from this pathway.