Exam 1 - GLUTS

Question 1

How many GLUT isoforms have been identified?

Answer 1

14 isoforms

Question 2

What function do GLUTs have?

Answer 2

They facilitate the transport of hexose and pentose sugars

Question 3

What are the substrates and major sites of expressions for GLUT1?

Answer 3

• substrates: glucose, galactose, mannose, glucosamine
• expression: RBC, CNS, blood-brain barrier, placenta, fetal tissue
• High affinity for glucose

Question 4

What are the substrates and major sites of expressions for GLUT2?

Answer 4

• glucose, galactose, fructose, mannose, glucosamine
• liver, B-cells of pancreas, kidney, small intestine

Question 5

What are the substrates and major sites of expressions for GLUT3?

Answer 5

• glucose, galactose, mannose, xylose, dehydroascorbic acid
• brain (neurons)
• high affinity for glucose

Question 6

What are the substrates and major sites of expressions for GLUT4?

Answer 6

• glucose, glucosamine, dehydroascorbic acid
• muscle, adipocytes
• high affinity for glucose
• INSULIN DEPENDENT!

Question 7

What are the substrates and major sites of expressions for GLUT5?

Answer 7

• fructose only
• intestine, kidney, brain, skeletal muscle, adipose tissue

Question 8

What are the 4 places that regulate cellular glucose uptake?

Answer 8

1. Brain & RBC
2. Liver
3. Muscle & adipose
4. pancreas

Question 9

How does the Brain & RBC regulate cellular glucose uptake?

Answer 9

• GLUT1
• high affinity for glucose, and is always saturated

Question 10

How does the Liver regulate cellular glucose uptake?

Answer 10

• GLUT2
• low affinity for glucose and high capacity

Question 11

How does the muscle & adipose regulate cellular glucose uptake?

Answer 11

• GLUT4
• sensitive to insulin

Question 12

How does the Pancreas regulate cellular glucose uptake?

Answer 12

• GLUT2 acts as glucose sensor
• increased glucose through GLUT2 leads to insulin being released