There are several examples of energy coupling mechanisms that use ATP hydrolysis. One type is ATP hydrolysis coupled with glucose to glucose-6-phosphate conversion. The enzyme hexokinase catalyzes the conversion of glucose to glucose-6-phosphate. This is an irreversible reaction and requires ATP. It is also a part of glycolysis. ATP hydrolysis is also coupled with the sodium and potassium pumps. This process moves sodium and potassium ions across the cell membrane through energy from ATP hydrolysis. It uses the enzyme Na+/K+-ATPase. ATP hydrolysis can also be coupled with starch/glycogen/cellulose formation. The enzyme starch synthase holds the glucose phosphate molecules together by utilizing the energy produced by ATP.