Haemostasis: Role of Clotting Factors

Question 1

What expresses the tissue factor in the clotting cascade?

Answer 1

Adventitial fibroblasts

Question 2

Define blood coagulation,

Answer 2

The transformation of blood into a solid gel called a clot or thrombus

Question 3

What does the clot contain?

Answer 3

Fibrin and trapped blood cells

Question 4

What initiates clotting?

Answer 4

When injury to a vessel disrupts endothelium and permits blood to contact underlying tissue

Question 5

What do many clotting factors contain in their catalytic protein domain?

Answer 5

Serine proteases

Question 6

How are serine proteases activated?

Answer 6

By proteolytic cleavage

Question 7

What is the liver’s role in haemostasis?

Answer 7

Producing and modifying blood-borne proteins

Question 8

What is required for the carboxylation of clotting factors?

Answer 8

Vitamin K

Question 9

How is vitmain K absorbed from the GIT?

Answer 9

By bile salts

Question 10

What drug is an antagonist of Vitamin K?

Answer 10

Warfarin

Question 11

What is fibrinogen composed of?

Answer 11

3 pairs of polypeptide chains

Question 12

What peptides does Thrombin cleave off?

Answer 12

A and B

Question 13

What does peptide cleaving result in?

Answer 13

Uncovering polymerization sites -> formation of fibrin gel

Question 14

What is the fibrin network stabilized by?

Answer 14

Formation of covalent cross-linkages by Factor XIII

Question 15

What is Factor XIII?

Answer 15

Transglutaminase activated by thrombin

Question 16

What do many clotting factors need to achieve full catalytic activity?

Answer 16

Extracellular surface of cell membranes

Question 17

What is involved in membrane attachment of clotting factors?

Answer 17

Gla domains - contain modified glutamate residue

Question 18

What do Gla residues allow?

Answer 18

Clotting factors to bind positively charged calcium ions -> attachement to -ve membrane surface