Biochemistry

Question 1

What are the different types of glucose transporter and where are they located?

Answer 1

GLUT3 - expressed mainly by the brain, low Km, high affinity
GLUT4 - expressed in muscle and adipose issue - insulin sensitive
GLUT2 - expressed in liver, kidney, intestine, higher Km

Question 2

What does insulin receptor stimulation do in regards to GLUT?

Answer 2

Controls GLUT4 translocation to plasma membrane, activating the protein kinase Akt and actin cycling

Question 3

What is the rate limiting step in glycogen breakdown?

Answer 3

Phosphorylase

Question 4

What is the rate limiting step in glycogen synthesis?

Answer 4

Glycogen synthase

Question 5

What is glucagon?

Answer 5

Peptide hormone synthesised in alpha cells of the pancreas

• secreted into the blood when glucose concentration falls below 4.5mM
• activates glycogen phosphorylase –> glycogenolysis

Question 6

What are the 3 main precursors of gluconeogenesis? How are they used?

Answer 6

Lactate - Cori cycle
Alanine - alanine cycle
Glycerol

Question 7

What are the effects of glucagon?

Answer 7

• increased glycogenolysis
• increased gluconeogenesis
• reduced glycogen synthesis
• reduced glycolysis

Question 8

What are the effects of insulin?

Answer 8

• GLUT4 to membrane (muscle and adipose tissue)
• increased glycogen synthesis
• increased fatty acid synthesis
• increased glycolysis
• decreased glycogen breakdown
• decreased gluconeogenesis
• decreased TAG breakdown