Lecture 18: Clotting Cascade Flashcards
Hemostasis occurs in how many steps?
3 steps
What is primary hemostasis?
Formation of a primary plug - clumping of blood platelets at site of injury
What is secondary hemostasis?
Formation of blood clot
Secondary hemostatic plug is formed by depositing of?
Insoluble strands of fibrin on the primary plug
What occurs during the 3rd sage of hemostasis?
Fibrinolysis - removal of clot
3 characteristics of hemostasis?
1) Must be fast
2) Localized
3) Carefully controlled
Goal of fibrin clot is altering which soluble protein into which insoluble one?
Fibrinogen (soluble)—–> Fibrin (insoluble)
What is the largest plasma protein and accounts for 4% of the total plasma proteins?
Fibrinogen
What is a zymogen and how is it activated?
Inactive form of an enzyme that can be activated by proteolysis.
What are the two sites on a zymogen and their function?
1) Pre- For secretion
2) Pro- Keeps it inactive
Zymogens are made where?
Liver
Zymogen are released into blood plasma and what makes them active?
Cleavage of the Pro- site by a protease in coagulating blood
Each zymogen serves first as a ________, then as a ______?
First as a substrate, then as an enzyme
The final substrate is?
Fibrinogen
Fibrinogen (factor I) is acted on by which enzyme and becomes?
Acted on by Thrombin (IIa), becomes fibrin
What is factor II and factor IIa?
Factor II = Prothrombin
Factor IIa = Thrombin
What does fibrin form at site of injury?
Polymerizes into clot - forms insoluble crosslink dam
What is factor III?
Tissue factor (TF)
What is factor IX?
Christmas Factor
What is factor XII?
Contact Factor
What is factor XIII?
Plasma transglutimase
Factor IX deficiency causes?
Hemophilia B: Christmas disease
Prothrombin is activated to thrombin by what kind of cleavage?
Proteolytic cleavage with a serine protease (prothrombinase)
Thrombin is itself a ________ and cuts at sites with which amino acids?
Serine protease and cuts at sites with ARG-GLY