Carbohydrate metabolism

Question 1

GLUT 1/GLUT 3

Answer 1

• high affinity, low capacity- Km= 1mM
• expressed in all cells except hepatocytes and pancreatic beta cells
• part of blood-brain barrier and blood-placenta barrier

Question 2

GLUT 2

Answer 2

• low affinity, high capacity- Km=12mM
• expressed in hepatocytes and pancreatic beta cells
• make glucose uptake proportional with blood glucose conc.

Question 3

GLUT 4

Answer 3

• intermediate affinity- Km=5mM
• insulin-regulated
• expressed in skeletal muscle and adipocytes
• adjust consumption to availability

Question 4

GLUT 5

Answer 4

• expressed in intestinal epithelial cells and renal tubular epithelial cells
• fructose absorption and reabsorption
• works together with Na+/K+ ATPase and glucose-Na+ symport