Cellular respiration occurs in both the cytoplasm and mitochondria of eukaryotic cells. In general, the complete process of cellular respiration is composed of two main parts: glycolysis in the cytoplasm, and the citric acid cycle in the mitochondria.
Cellular respiration is the process of using stored energy, usually in the form of glycogen, and creating adenosine tri-phosphate (ATP), a form of energy that all cells can use. The process begins with glycolysis, where glycogen is released and goes through a series of steps to liberate 2 ATP per glucose molecule. The by-products of glycolysis are used to begin the citric acid cycle, which produces a further 32 ATP molecules.