Glucose enters cells by facilitated diffusion or by secondary active transport with Sodium(in intestine and kidneys)
Glucose transporters(Glut 1-7) are responsible for facilitated diffusion of glucose across cell membranes.
They differ from sodium dependant glucose transporters(SGLT1 and 2)
Glucose Transporters and their functions
GLUT-1
Basal glucose uptake
Present in brain,kidney,colon,placenta and erythrocytes.
GLUT 2
Beta cell glucose sensor
Transport glucose out of intestinal and renal epithelial cells
Beta cells of pancreas,liver,Small Intestine,Kidneys.
GLUT 3
Basal glucose uptake
Brain,placenta,Kidney
GLUT4
Insulin stimulated glucose uptake
Present in skeletal and cardiac muscle,adipose tissue.
GLUT 5
Fructose transport
Jejunum and sperm
Glut 6
Pseudogene
GLUT 7
Glucose 6 phosphate transporter in endoplasmic reticulum.
Liver
Na+ Glucose co-transporters
SGLT 1
Absorption of glucose from Small Intestine and renal tubules
SGLT 2
Absorption of glucose from renal tubules.
Important points
- Basal glucose uptake by- GLUT1 and GLUT3
- GLUT 2 is present in beta cells of pancreas, so it controls postprandial hyperglycemia
- GLUT4 is insulin dependent so no of GLUT4 decreases after overnight fasting.
Good