lecture 3 Glycolysis:

Question 1

What are key regulatory enzymes?

Answer 1

All catalyze irreversible steps; equilibrium is far to the right!

Question 2

What is the function and characteristic of Hexokinase?

Answer 2

• Commits glucose for intracellular use (Takes out of circulation)
• GLc6P stops or reduce its function (feed-back inhibition, allosteric)

Question 3

What is the function and characteristic of glucokinase (in liver)?

Answer 3

• Substrate level regulation (High Km) prinicpal mechanism for blood (GLc) homeostasis (mas action.
• Insensitive to Glc6P inhibition
• Transcriptional control.

Question 4

What is the function and characteristic of phosphofructokinase (PFK-1)

Answer 4

• Commits Glc to glycolisis
• Increase in activity with AMP, ADP (at allosteric sites and Fru2,6P.
• Decrease in activity with ATP and citrate (allosteric).

Question 5

What is the function and characteristic of pyruvate Kinase?

Answer 5

• Determines Flux through entire pathway; distinct regulation in liver vs the rest of the tissues.
• Enhanced when Fru1,6 BP and AMP.
• Deactivated by ATP, AcCoA, FA, Ala.

In the liver phosphorylation and Gulcagon also inhibits it.

Question 6

What is the energy yield of glycolysis?

Answer 6

Net= +2 ATP, 2 NADH

1. Hexokinase -1 ATP
2. PFK-1 also -1 ATP
3. GAPDH +1 NADH x2= 2NADH
4. PGK +1 ATPx 2= 2ATP
5. PK +1 ATP x2 = 2ATP

Question 7

what is substrate level phosphorylation?

Answer 7

-is a type of metabolic reaction that results in the formation of ATP by direct transfer and donation of a PO3 group to ADP from a phosphorylated reactive intermediate.

Question 8

What is glucokinase?

Answer 8

o Glucokinase: substrate-level regulation. Principal mechanism for blood glucose homeostasis
 Insensitive to glucose6phosphate inhibition and has transcriptional control