Glucose Some glucose is converted to lactic acid by astrocytes, which is then utilized as an energy source by brain cells; some glucose is used by intestinal cells and red blood cells, while the rest reaches the liver, adipose tissue and muscle cells, where it is absorbed and stored as glycogen (under the influence of insulin). Liver cell glycogen can be converted to glucose and returned to the blood when insulin is low or absent; muscle cell glycogen is not returned to the blood because of a lack of enzymes. In fat cells, glucose is used to power reactions that synthesize
Glucose The free energy of formation of α-D-glucose is 917.2 kilojoules per mole. In humans, gluconeogenesis occurs in the liver and kidney, but also in other cell types. In the liver about 150 g of glycogen are stored, in skeletal muscle about 250 g.<ref name="Löffler/Petrides 389">Peter C. Heinrich: "Löffler/Petrides Biochemie und Pathobiochemie." Springer-Verlag, 2014, , p. 389. (german)</ref> However, the glucose released in muscle cells upon cleavage of the glycogen can not be delivered to the circulation because glucose is phosphorylated by the hexokinae, and a glucose-6-phosphatase is not expressed to remove the phosphate group. Unlike for glucose, there is no