Lecture 21 - Gluconeognesis

Question 1

What are potential precursors of gluconeogenesis and at what steps can they enter the pathway?

L21 S5

Answer 1

Glycerol:
-enters as DHAP and is converted to glyceraldehyde 3-phosphate

Amino acids:
-can enter as oxaloacetate or pyruvate

Lactate:
-can enter as pyruvate (Cori cycle)

Question 3

What are the irreversible steps of glycolysis that must be overcome by gluconeogenesis and what are the enzymes for these steps in gluconeogenesis?

L21 S6

Answer 3

• glucose-6-phosphate to glucose (glucose-6-phosphatase)
• fructose 1,6-bisphosphatase
• oxaloacetate to phosphoenolpyruvate (phosphoenolpyruvate carboxylase)
• pyruvate to oxaloacetate (pyruvate carboxylase)

Question 4

Where are the different enzymes of gluconeogenesis located?

L21 S9;11

Answer 4

Mitochondria:
-pyruvate carboxylase

Cytoplasm:

• PEP carboxylase
• fructose 1,6-bisphosphatase

ER lumen:
-glucose 6-phosphatase

Question 5

What are the ER protiens associated with glucose 6-phosphatase and their functions?

L21 S11

Answer 5

T1:
-transports glucose 6-phosphatase into ER lumen

T2:
-transports inorganic phosphate out of ER lumen

T3:
-transports glucose out of ER lumen

Question 6

What is the Cori cycle?

L21 S17

Answer 6

Lactate produced in the muscles can be converted into pyruvate in the liver which can then be used for gluconeogenesis to regenerate glucose.