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Flashcards in 12.7 C Deck (41):
1

What is hemostasis?

the cellular and noncellular process that prevents blood loss following injury

2

What are the three main steps of hemostasis?

- platelet plug formation
- coagulation
- firbinolysis

3

What gives a hard clot its tensile strength?

fibrin polymers

4

Platelet plug formation has what two steps?

- platelet adhesion
- platelet aggregation

5

What is Von Willebrand Factor?

a plasma protein that binds collagen and links it to Glycoprotein Ib-V-IX

6

What is glycoprotein Ib-V-IX?

a transmembrane protein found on platelets that binds VWF at the site of injury

7

Where is Von Willebrand Factor produced?

endothelial cells and platelets

8

What are Weibel-Palade bodies?

stores of Von Willebrand Factor found in endothelial cells

9

What are alpha granules?

granules within platelets that store Von Willebrand Factor

10

Describe the quaternary structure of Von Willebrand Factor.

it forms massive multiers

11

What is ADAMTS-13?

a protease that cleaves ultra large Von Willeband Factor into its active unit

12

When Von Willeband Factor is produced, it is in what form?

the ultra large form

13

Most Von Willeband Factor is produced by what cells?

endothelial cells

14

Von Willeband Factor production in endothelial cells is controlled by what?

- induced hormonally
- but also produced constitutively

15

Von Willeband Factor has what two functions?

- platelet adhesion
- factor VIII carrier protein which extends the half life

16

Platelets are cross-linked by what protein?

fibrinogen

17

Describe the structure of fibrinogen?

is bipolar such that it can bind and cross-link two platelets

18

What are the five most signficant platelet activating factors?

ADP, collagen, thrombin, thromboxane A2, epinephrine

19

Where is tissue factor found?

on the surface of endothelial cells, fibroblasts, and platelets

20

How does tissue factor get activated?

by injury to its host cell (fibroblast, endothelial, or platelet)

21

The coagulation cascade can generally be described as a series of what?

zymogen activation steps

22

What is the first and last enzyme activated in the coagulation cascade?

tissue factor to thrombin

23

What enzyme cleaves fibrinogen into a fibrin monomer?

thrombin

24

Which coagulation cascade proteins are Vitamin K dependent?

F2, F7, F9, F10

25

Vitamin K is improtant to the coagulation cascade because it is necessary for what process?

the post-translational gamma-carboxylation of glutamic acid residues, forming gamma-carboxyglutamic acid

26

Why is post-translational gamma-carboxylation of glutamic acid residues important to the coagulation cascade?

- adds a second negative charge so that the residue can bind calcium
- binding calcium alters the conformation of prothrombin allowing it to insert into a phospholipid membrane on a platelet

27

How does Warfarin prevent clotting?

by preventing regeneration of the active form of vitamin K

28

Why is prothrombin insertion into the platelet plasma membrane important?

because only then can it interact with phosphatidylserine, its alloactive cofactor

29

What happens to phosphatidylserine when a platelet gets activated?

it is flipped to the outer leaflet of the plasma membrane

30

Phosphatiylserine is flipped to the outer leaflet of a platelet plasma membrane so that what can occur?

assembly of various complexes important to the coagulation cascade

31

What is a tenase complex?

a complex that forms on platelet membranes in conjunction with PS to generate Factor Xa, which goes on to cleave prothrombin into thrombin

32

What is a prothrombinase complex?

a complex of Factor Xa and prothrombin (FII) that generates thrombin

33

What is the name for FII?

prothrombin

34

What does thrombin do in the coagulation cascade?

it cleaves portions off of fibrinogen to form fibrin monomers which can then spontaneously assemble into multimers

35

What is the importance of Factor VIIIa in the coagulation cascade?

it catalyzes the transglutaminase reaction, covalently cross-linking D domains of fibrin monomers

36

What protein is responsible for fibrinolysis?

plasmin

37

What is plasminogen?

a zymogen produced by the liver which gets cleaved into plasmin for fibrinolysis

38

What is t-PA?

the enzyme that cleaves plasminogen into plasmin for fibrinolysis

39

What are PAI-1 and PAI-2?

enzymes secreted by endothelial cells to inhibit t-PA and thereby inhibit fibrinolysis

40

What is a2-AP?

a protein secreted by the liver that inhibits plasmin and therefore inhibits fibrinolysis

41

What are the end products of fibrinolysis?

E monomers, D monomers, and D dimers