Biochem of Coag

Question 1

What proteases does antithrombin III block?

Answer 1

IXa, Xa, XIa, and XIIa

Question 2

Warfarin initially promotes clotting because of inhibition of these proteins.

Answer 2

S and C

Question 3

Describe the mechanism of warfarin

Answer 3

Warfarin competes with Vitamin K by blocking vit. K reductase enzymes and preventing the carboxylation of factors II, VII, IX, X (and proteins C and S)

Question 4

Why is ASA an irreversible platlet inhibitor?

Answer 4

Because it convalently binds COX and platelets can’t make more

Question 5

Name and describe the 3 forms of Heparin

Answer 5

HMW(unfractionated) - binds Xa and ATIII
LMW(fractionated) - Xa and some ATIII
Fondapurinax(fractionated) - Xa

Question 6

vWf facilitates binding of subendothelium to what portion of the platelet?

Answer 6

GP1B-V-IX

Question 7

What enzyme does warfarin inhibit? What is the role of the enzyme in coagulation?

Answer 7

Vitamin K reductase enzymes

Reduce vitamin K to make prothrombin from prothrombin precursors

Question 8

What is the activity of thromboxane (TXA)?

Answer 8

platelet aggregation and vasoconstriction