Insulin acts on glucose metabolism by:

B i.e. T permeability across cell membrane against glucose gradient Insulin increases glucose uptake by increasing the number of glucose transpoer in cell membrane. Direct insulin stimulated glucose uptake is mediated by Glut 4 and is seen only in: Muscle: Skeletal muscleQ and cardiac muscleQ Adipose tissueQ Glucose Transpoers In Mammals Facilitated Bidirection Diffusion Function Major Sites of Expression Km GLUT 1 Basal glucose uptake - Placenta, blood - brain barrier, Red cells, kidneys 1-2 GLUT 2 B cell glucose sensor; transpo out of intestinal & renal epithelial cells. - B cells of islets, Liver, Small intestine, Kidney 12-20 GLUT 3 Basal glucose uptake - Brain, placenta, kidney <1 GLUT 4 Insulin stimulated glucose uptakeQ - Skeletal & cardiac muscleQ - Adipose tissueQ 5 GLUT 5 Fructose transpo - Jejunum, Sperm 1-2 GLUT 6 None - Pseudogene ? GLUT 7 Glucose 6-PO4 transpoer in endoplasmic reticulum - Liver ? Secondary Active Transpo Na+ glucose cotranspo (unidirectional -transpoer) SGLT-1 Active uptake of glucose against Small intestine, renal tubule 0.1 - 1.0 SGLT-2 concentration gradient Renal tubule 1.6