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Medical Biochemistry > Hemostasis: Blood coagulation and fibirinolysis - Part 2 > Flashcards

Hemostasis: Blood coagulation and fibirinolysis - Part 2 Flashcards

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USMLE® Step 1 flashcards
1
Q

In general, the aim of the third step of Hemostasis, Blood Coagulation (secondary hemostasis), is what?

A

Convert soluble fibrinogen to insoluble fibrin

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2
Q

The conversion of fibrinogen to fibrin requires what?

A

Thrombin

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3
Q

The formation of Thrombin occurs via which 2 pathways?

A

1) Intrinsic

2) Extrinsic

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4
Q

Tissue injury initiates the release of what to being the extrinsic pathway.

A

Tissue factor (Factor III or Thromboplastin)

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5
Q

Thromboplastin is also known as what?

A

Factor III (Tissue factor) - initiator of Extrinsic pathway.

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6
Q

Factor VII, which is part of the extrinsic pathway, is activated by what?

A

Tissue factor (Thromboplastin / Factor III)

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7
Q

Factor VIIa and tissue factor, in the presence of ____ and ____ activate _______.

A

Calcium
Platelet phospholipids
Factor X.

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8
Q

Rough endothelial surface, due to pathological processes, lead to the exposure of collagen, which initiates what in the Instrinsic pathway?

A

Factor XII (Hageman factor)

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9
Q

What is factor XII, the first factor initiated in the Intrinsic pathway, also known as?

A

Hageman factor

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10
Q

Factor XIIa, a factor in the Intrinsic pathway, activated what?

A

XI –> XIa

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11
Q

Factor XIa of the intrinsic pathway activates what?

A

IX —> IXa

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12
Q

Thrombin (IIa) activates what in the intrinsic pathway?

A

VIII –»> VIIIa

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13
Q

What in the intrinsic pathway activates factor X

A

IXa,
VIIIa,
platelet phospholipids and Ca2+

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14
Q

What does Thrombin (IIa) activate in the common pathway?

A

V –> Va;
Firbinogen (I) —-> Fibrin (Ia);
XIII–> XIIIa

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15
Q

What does Xa combine with in the common pathway? To form what?

A

Va,
Tissue phospholipids,
Ca2+
- Forms prothrombinase complex

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16
Q

What does the prothrombinase complex do in the common pathway?

A

Splits prothromin (II) to thrombin (IIa)

17
Q

What factor forms Fibrin?

A

Thrombin (IIa)

18
Q

What is the role of Factor XIIIa?

A
  • Covalently cross links fibrin monomers to form cross-linked fibrin
  • Converts the fibrin polymer (soft clot) to a stable polymer (hard clot)
19
Q

Fibrinogen is a ____ that is synthesized by the ____.

A

Plasma protein

liver

20
Q

The fibrin monomers _______ and are linked to each other via _______, forming the ________.

A

Aggregate;
Hydrogen bonds;
Fibrin polymer (soft clot)

21
Q

Specifically, to form the covalent bond, XIIIa acts to do what?

A

Amino group of lysine on one fibrin molecule + amide nitrogen of glutamine on another fibrin molecule = covalent bond

22
Q

Factor XIIIa is a…

A

Highly specific transglutaminase

23
Q

Ultimate aim of hemostasis is the conversion of ____ to ____ and stabilization of _____ which requires ___.

A

Firbinogen
Fibrin (4c)
Fibrin (6c)
Thrombin (IIa)

24
Q

LAB TESTS: defect in clotting cascade results in ______

A

increased clotting time

25
Q

LAB TESTS: An extrinsic pathway defect results in:

A

Increased prothrombin time (INR)

26
Q

LAB TESTS: An intrinsic pathway defect results in:

A

Increased APTT

27
Q

Vitamin K is required for the hepatic synthesis of what?

A 
Prothrombin (Factor II)
VII
IX
X
Proteins C and S
28
Q

Which amino acid residues of Proteins C and S are acted upon by Vitamin K dependent gamma-carboxylation?

A

Glutamic acid

29
Q

What is the coenzyme for gamma-carboxylase?

A

Vitamin K

30
Q

gamma-carboxylation forms mature clotting factors that contains _____ and is capable of subsequent activation?

A

Gamma-carboxyglutamate (Gla)

31
Q

Gamma-carboxylation allows Ca2+ binding because of what?

A

2 adjacent negatively charged carboxylate groups

32
Q

Once gamma-carboxylation allows Ca2+ binding because of two adjacent negatively charged carboxylate groups, The clotting factor-Ca2+ complex can then bind to what?

A

phospholipids on the platelet membrane

33
Q

What is INR (Prothrombin time)?

A

A very sensitive indicator of vitamin K deficiency

Medical Biochemistry (35 decks)

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