GLUT 4 glucose transport molecules

Liver Insulin increases the storage of glucose as glycogen in the liver. This involves the insertion of additional GLUT 2 glucose transport molecules in cell walls, increased synthesis of the enzymes pyruvate kinase, phosphofructokinase. and glucokina.se, and the suppression of several other enzymes. Insulin also decreases protein catabolism. 

Muscle Insulin stimulates glycogen synthesis and protein synthesis. Glucose transport into muscle cells is facilitated by insertion of additional GLUT 4 transport molecules into cell walls. 

GLUT-4 transporters reenter the cytoplasm by invagination of the plasma membrane and the formation of vesicles via endocytosis. Thus the number of GLUT-4 molecules on the cell surface is reduced, leaving only GLUT-1 to mediate a basal rate of glucose transport. 

The cartoon of Figure 7.1 is modeled by the molecular mechanism illustrated in the left panel of Figure 7.2. One glucose molecule is transported from the outside to the inside of the cell every time one GLUT undergoes a forward catalytic cycle through the states 1—s 2— 3—>-4— . The overall reaction is... 

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