Pyruvate Kinase: Step 9 of Glycolysis

Question 1

What reaction does pyruvate kinase catalyze?

Answer 1

The conversion of phosphoenolpyruvate to pyruvate (and, with this, the synthesis of ATP from ADP).

Question 2

Is the reaction of PEP to pyruvate reversible?

Answer 2

No

Question 3

Why are 4 molecules of ATP generated in the second half of glycolysis?

Answer 3

Fructose 1,6-bisphosphate is effectively converted to 2 molecules of GAP (because the DHAP is converted to GAP as GAP is used downstream). So the second half of glycolysis effectively happens for two molecules, producing 2 ATP at the 1,3-BPG to 3PG step and 2 ATP at the PEP to pyruvate step.

Question 4

True or false: The energy derived from the conversion of PEP to pyruvate is highly exergonic and provides enough energy for substrate level ATP synthesis.

Answer 4

True

Question 5

What are the two reaction steps in the conversion of PEP to pyruvate?

Answer 5

1) Hydrolysis (release of the high energy phosphate)

2) Tautomerization: enol to ketone

Question 6

Which step in the reaction of PEP to pyruvate releases the most free energy?

Answer 6

Tautomerization of enol pyruvate to keto pyruvate

Question 7

What metal cofactors are required for pyruvate kinase (PK) to catalyze PEP to pyruvate?

Answer 7

K+ and Mg2+