Glucose uptake of hepatocytes and pancreatic beta cells (in mice, but GLUT1 in human beta cells; see Reference 1). The high Km of GLUT2 allows for glucose sensing; rate of glucose entry is proportional to blood glucose levels. GLUT4 transporters are insulin sensitive, and are found in muscle and adipose tissue. As muscle is a principal storage site for glucose and adipose tissue for triglyceride (into which glucose can be converted for storage), GLUT4 is important in post-prandial uptake of excess glucose from the bloodstream. Moreover, several recent papers show that GLUT 4 is present in the brain also. The drug metformin
Glycogen energy reserves of triglycerides (lipids). As such it is also found as storage reserve in many parasitic protozoa. Glycogen is a branched biopolymer consisting of linear chains of glucose residues with an average chain length of approximately 8–12 glucose units. Glucose units are linked together linearly by α(1→4) glycosidic bonds from one glucose to the next. Branches are linked to the chains from which they are branching off by α(1→6) glycosidic bonds between the first glucose of the new branch and a glucose on the stem chain. Due to the way glycogen is synthesised, every glycogen granule has at its