Biochemistry LE 1: Hemostasis, Thrombosis, and Coagulation
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Questions and Answers

What is Factor III more commonly known as?

  • Tissue Factor (correct)
  • Calcium
  • Serine Protease
  • Prothrombin

    • What is the main function of cofactors in the clotting mechanism?

  • To regulate the activity of regulatory proteins
  • To catalyze the activation of proenzymes
  • To inhibit the activity of serine proteases
  • To serve as binding sites for other factors (correct)

    • Which factor is regulated by proteolytic cleavage?

  • Tissue Factor
  • Protein S
  • Prothrombin
  • Protein C (correct)

    • What is the outcome of the activation of Factor VIIa?

    <p>Activation of both Factor X and Factor IX</p> Signup and view all the answers

    What is the time it takes to form a clot in the extrinsic pathway?

    <p>12 seconds</p> Signup and view all the answers

    What is the trigger for the extrinsic pathway?

    <p>Trauma</p> Signup and view all the answers

    What is the role of Tissue Factor in the extrinsic pathway?

    <p>To bind with Factor VII</p> Signup and view all the answers

    What is the sequential activation of serine proteases in the clotting cascade result in?

    <p>Amplification and acceleration of the response</p> Signup and view all the answers

    What is the result of Thrombin formation in the Coagulation Cascade?

    <p>It feeds itself by promoting activation of the factors needed for its own formation</p> Signup and view all the answers

    What is the role of the intrinsic pathway in the Coagulation Cascade?

    <p>It sustains the coagulation response</p> Signup and view all the answers

    What is the major substrate of Thrombin?

    <p>Fibrinogen</p> Signup and view all the answers

    What is the result of the conversion of fibrin monomers to fibrin clot?

    <p>A soft clot is formed</p> Signup and view all the answers

    What is the role of Vitamin K in the Coagulation Cascade?

    <p>It is required for the carboxylation of Glutamate residues</p> Signup and view all the answers

    What is the function of Factor XIII in the Coagulation Cascade?

    <p>It cross-links fibrin molecules to form a hard and stable clot</p> Signup and view all the answers

    What is the purpose of the extrinsic pathway in the Coagulation Cascade?

    <p>It initiates the coagulation response</p> Signup and view all the answers

    What is the function of the Vit-K dependent carboxylase?

    <p>It carboxylates Glutamate residues</p> Signup and view all the answers

    What is the normal value of Prothrombin Time (PT)?

    <p>11-12.5 seconds</p> Signup and view all the answers

    Which pathway is measured by the Partial Thromboplastin Time (PTT)?

    <p>Intrinsic Pathway</p> Signup and view all the answers

    What is the normal value of Platelet Count?

    <p>150,000-400,000/mm3</p> Signup and view all the answers

    What is the result of a low Platelet Count?

    <p>Thrombocytopenia</p> Signup and view all the answers

    What is the purpose of the Coagulation Factor Assay?

    <p>To diagnose deficiencies in coagulation factors</p> Signup and view all the answers

    Which disease is associated with a prolonged Partial Thromboplastin Time (PTT)?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of the Platelet Function Assay?

    <p>To diagnose Platelet dysfunction</p> Signup and view all the answers

    What does the mnemonic ❗️HELPFUL stand for?

    <p>Playing Table Tennis (PTT) INdoors: Test for the Intrinsic Pathway</p> Signup and view all the answers

    A mutation in which proenzyme would lead to uncontrolled blood clotting?

    <p>Factor XIII</p> Signup and view all the answers

    Which factor is directly activated by factor Xa?

    <p>Factor II</p> Signup and view all the answers

    What is the primary cause of classical hemophilia A?

    <p>Absence of factor VIII</p> Signup and view all the answers

    Which factor is necessary for the activation of factor X by factor IXa?

    <p>Factor VIII</p> Signup and view all the answers

    Warfarin inhibits the reduction of which vitamin?

    <p>Vitamin K</p> Signup and view all the answers

    What is the result of an inability to form clotting factor complexes on cell membranes?

    <p>Bleeding disorder</p> Signup and view all the answers

    Which factor is directly activated by factor XIa?

    <p>Factor IX</p> Signup and view all the answers

    What is the primary cause of the bleeding disorder in the infant?

    <p>Decreased levels of circulating vWF</p> Signup and view all the answers

    Why is the patient at risk for further clots?

    <p>Due to the increased vitamin K in the patient's diet and circulation</p> Signup and view all the answers

    What is the function of Streptokinase?

    <p>Activating plasminogen to plasmin</p> Signup and view all the answers

    What is the role of Protein C in the body?

    <p>Inhibiting the clotting cascade</p> Signup and view all the answers

    Why is the liver important in hemostasis?

    <p>It is the site of synthesis of many clotting factors</p> Signup and view all the answers

    What is the function of Urokinase?

    <p>Activating plasminogen to plasmin</p> Signup and view all the answers

    What is the effect of Warfarin on the body?

    <p>It acts as a vitamin K antagonist</p> Signup and view all the answers

    What is the role of PAI-1 in the body?

    <p>It inhibits plasminogen activator</p> Signup and view all the answers

    What is the function of t-PA in the body?

    <p>It activates plasminogen to plasmin</p> Signup and view all the answers

    Why is the liver important for vitamin K absorption?

    <p>It is the site of vitamin K absorption from the diet</p> Signup and view all the answers

    What is the effect of green leafy vegetables on Warfarin?

    <p>It reduces the action of Warfarin</p> Signup and view all the answers

    Study Notes

    Blood Coagulation Cascade

    • Intrinsic Pathway: triggered by internal stimuli, involves serine proteases that cleave the next proenzyme in the cascade, resulting in a rapid response
    • Extrinsic Pathway: triggered by trauma, involves Tissue Factor (Factor III) and Factor VII, leading to the activation of Factor X and the coagulation cascade

    Factors and Cofactors

    • Factor II (Prothrombin): a key factor in the coagulation cascade
    • Factor III (Tissue Factor): an integral membrane protein that does not require cleavage for activation
    • Factor VII: binds to Tissue Factor to auto-catalyze its activation to VIIa
    • Factor X: activated by Factor VIIa, leads to the formation of Thrombin (Factor IIa)
    • Calcium (Ca2+): a cofactor that facilitates the clotting mechanism
    • Protein C: a regulatory protein that is activated by proteolytic cleavage and inhibits the clotting cascade

    Coagulation Cascade

    • Tissue Factor and VIIa: key process involved in the initiation of blood coagulation in vivo
    • Steps of Extrinsic Pathway:
      • Trauma causes damaged tissues to present Tissue Factor (Factor III) to blood at injured site
      • Factor VII binds to Tissue Factor to auto-catalyze its activation to VIIa
      • Factor VIIa activates Factor X (to Xa) and Factor IX (to IXa)
    • Activation of Factor IIa (Thrombin): leads to the formation of a "soft" clot, which is then cross-linked to form a "hard and stable" fibrin clot

    Vitamin K Dependence

    • Factors VII, IX, X, and II: require Vitamin K for their activation
    • Vitamin K-dependent carboxylase: necessary for the activation of these factors
    • HELPFUL MNEMONIC: 1972 → Factor X, II

    Coagulation Assays

    • Coagulation Factor Assay: measures the extrinsic pathway (III, VII) and common pathway (X, V, II, I)
    • Prothrombin Time (PT): measures the extrinsic pathway
    • Partial Thromboplastin Time (PTT): measures the intrinsic pathway
    • Platelet Function Assay: measures platelet function and counts

    Pathology and Disease

    • Prolonged PT and aPTT: indicative of acquired or congenital deficiency of coagulation factors, Vitamin K deficiency, or liver disease
    • Hemophilia A: results from a deficiency in Factor VIII
    • Hemophilia B: results from a deficiency in Factor IX
    • Von Willebrand Disease: a bleeding disorder characterized by a deficiency in von Willebrand Factor (vWF)

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