Mechanism of blood coagulation MCQs With Answer

Mechanism of blood coagulation MCQs With Answer is a focused resource for B. Pharm students to master the coagulation cascade, clotting factors, regulatory proteins, and clinical correlations. This concise introduction explores the intrinsic, extrinsic and common pathways, the role of vitamin K, thrombin generation, fibrin formation and stabilization, natural anticoagulants (antithrombin, Protein C/S), fibrinolysis, and laboratory tests like PT, aPTT and INR. Understanding these mechanisms is essential for interpreting coagulation disorders, anticoagulant pharmacology and therapeutic monitoring. The questions emphasize mechanism-based reasoning and clinical relevance to prepare you for exams and practice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What initiates the extrinsic pathway of coagulation?

• Exposure of collagen and activation of factor XII
• Platelet aggregation mediated by thromboxane A2
• Exposure of tissue factor (TF) and activation of factor VII
• Activation of factor IX by factor XIa

Correct Answer: Exposure of tissue factor (TF) and activation of factor VII

Q2. The intrinsic pathway of coagulation is primarily initiated by which event?

• Activation of factor VII by tissue factor
• Activation of factor XII on negatively charged surfaces
• Formation of the prothrombinase complex
• Cross-linking of fibrin by factor XIII

Correct Answer: Activation of factor XII on negatively charged surfaces

Q3. Which event marks the beginning of the common pathway?

• Activation of factor X to Xa
• Conversion of fibrinogen to fibrin
• Activation of factor VIII by thrombin
• Release of von Willebrand factor from endothelium

Correct Answer: Activation of factor X to Xa

Q4. What is the biochemical role of vitamin K in coagulation?

• Directly activating plasminogen to plasmin
• Gamma-carboxylation of glutamic acid residues on clotting factors and proteins C/S
• Binding calcium to platelet surfaces
• Cleaving fibrinogen into fibrin monomers

Correct Answer: Gamma-carboxylation of glutamic acid residues on clotting factors and proteins C/S

Q5. How does warfarin exert its anticoagulant effect?

• Enhancement of antithrombin III activity
• Direct inhibition of thrombin active site
• Inhibition of vitamin K epoxide reductase, reducing gamma-carboxylation of clotting factors
• Activation of protein C

Correct Answer: Inhibition of vitamin K epoxide reductase, reducing gamma-carboxylation of clotting factors

Q6. What is the primary mechanism of action of unfractionated heparin?

• Direct inhibition of factor Xa only
• Potentiation of antithrombin III, inhibiting thrombin and factor Xa
• Blockade of vitamin K recycling
• Activation of plasminogen to plasmin

Correct Answer: Potentiation of antithrombin III, inhibiting thrombin and factor Xa

Q7. Rivaroxaban and apixaban act by which mechanism?

• Direct inhibition of factor Xa
• Inhibition of thrombin (factor IIa)
• Activation of antithrombin III
• Inhibition of vitamin K epoxide reductase

Correct Answer: Direct inhibition of factor Xa

Q8. Which of the following is a primary action of thrombin in coagulation?

• Inhibition of fibrin polymerization
• Conversion of fibrinogen to fibrin and activation of factor XIII
• Degradation of fibrin into FDPs
• Activation of plasminogen to plasmin

Correct Answer: Conversion of fibrinogen to fibrin and activation of factor XIII

Q9. Factor XIII is responsible for which function?

• Initiating the intrinsic pathway
• Cleaving fibrinogen to fibrin
• Cross-linking and stabilization of fibrin meshwork
• Activating platelets via ADP release

Correct Answer: Cross-linking and stabilization of fibrin meshwork

Q10. Which laboratory test primarily assesses the extrinsic and common pathways?

• Activated partial thromboplastin time (aPTT)
• Bleeding time
• Prothrombin time (PT)
• Platelet aggregation study

Correct Answer: Prothrombin time (PT)

Q11. Which test is most sensitive to intrinsic pathway deficiencies?

• Prothrombin time (PT)
• Activated partial thromboplastin time (aPTT)
• Bleeding time
• D-dimer assay

Correct Answer: Activated partial thromboplastin time (aPTT)

Q12. What does the INR standardize?

• aPTT values across different labs
• PT values to monitor warfarin therapy
• Bleeding time for platelet function assessment
• Fibrinogen concentration measurements

Correct Answer: PT values to monitor warfarin therapy

Q13. How is Protein C activated and what is its anticoagulant action?

• Activated by plasmin to promote fibrinolysis
• Activated by thrombin-thrombomodulin complex and inactivates factors Va and VIIIa with protein S
• Activated by factor XIIa to initiate intrinsic pathway
• Activated by tissue plasminogen activator to cleave fibrin

Correct Answer: Activated by thrombin-thrombomodulin complex and inactivates factors Va and VIIIa with protein S

Q14. Deficiency of antithrombin III most commonly leads to:

• Excessive bleeding due to fibrinogen deficiency
• Increased susceptibility to thrombosis
• Prolonged bleeding time only
• Impaired platelet adhesion

Correct Answer: Increased susceptibility to thrombosis

Q15. Hemophilia A is due to deficiency of which factor?

• Factor VIII
• Factor IX
• Factor V
• Factor XI

Correct Answer: Factor VIII

Q16. Hemophilia B is caused by deficiency of which clotting factor?

• Factor IX
• Factor VIII
• Factor VII
• Factor XIII

Correct Answer: Factor IX

Q17. von Willebrand disease primarily affects which process?

• Conversion of fibrinogen to fibrin
• Platelet adhesion to subendothelium and vWF-mediated factor VIII stabilization
• Gamma-carboxylation of clotting factors
• Activation of factor XII on contact surfaces

Correct Answer: Platelet adhesion to subendothelium and vWF-mediated factor VIII stabilization

Q18. Which platelet receptor mediates fibrinogen-dependent platelet aggregation?

• Glycoprotein Ib-IX-V
• Glycoprotein IIb/IIIa (integrin αIIbβ3)
• P2Y12 ADP receptor
• Thromboxane A2 receptor

Correct Answer: Glycoprotein IIb/IIIa (integrin αIIbβ3)

Q19. Aspirin’s antiplatelet effect is due to irreversible inhibition of which enzyme?

• Phospholipase A2
• Cyclooxygenase (COX), reducing thromboxane A2 synthesis
• Thromboxane synthase
• ADP receptor P2Y12

Correct Answer: Cyclooxygenase (COX), reducing thromboxane A2 synthesis

Q20. Clopidogrel prevents platelet aggregation by blocking which target?

• Glycoprotein IIb/IIIa receptor
• P2Y12 ADP receptor on platelets
• Thromboxane A2 synthesis
• Platelet thrombin receptors

Correct Answer: P2Y12 ADP receptor on platelets

Q21. Which enzyme is responsible for fibrinolysis by degrading fibrin?

• Thrombin
• Plasmin
• Factor XIIIa
• Antithrombin III

Correct Answer: Plasmin

Q22. Elevated D-dimer is most useful clinically to rule out which condition?

• Hemophilia A
• Disseminated intravascular coagulation (DIC) and venous thromboembolism (VTE)
• von Willebrand disease
• Vitamin K deficiency

Correct Answer: Disseminated intravascular coagulation (DIC) and venous thromboembolism (VTE)

Q23. Tissue plasminogen activator (tPA) acts by:

• Directly degrading fibrin
• Converting plasminogen to plasmin
• Inhibiting antithrombin III
• Activating factor X

Correct Answer: Converting plasminogen to plasmin

Q24. Calcium (factor IV) is essential in coagulation primarily because it:

• Forms covalent bonds in fibrin mesh
• Acts as a cofactor enabling Gla-domain binding to phospholipid surfaces and complex assembly
• Directly cleaves prothrombin to thrombin
• Inactivates protein C

Correct Answer: Acts as a cofactor enabling Gla-domain binding to phospholipid surfaces and complex assembly

Q25. Why are platelet membrane phospholipids important in coagulation?

• They synthesize vitamin K
• They provide an anionic surface for assembly of enzyme-cofactor complexes like tenase and prothrombinase
• They inactivate thrombin
• They convert fibrinogen to fibrin

Correct Answer: They provide an anionic surface for assembly of enzyme-cofactor complexes like tenase and prothrombinase

Q26. Contact activation involves which non-enzymatic cofactors?

• Fibrinogen and fibrin
• High molecular weight kininogen (HMWK) and prekallikrein
• Protein C and protein S
• Calcium and phospholipids only

Correct Answer: High molecular weight kininogen (HMWK) and prekallikrein

Q27. Which class of enzymes predominates in the coagulation cascade?

• Serine proteases
• Metalloproteases
• Lipases
• Endonucleases

Correct Answer: Serine proteases

Q28. Thrombomodulin on endothelial cells modifies thrombin activity to:

• Enhance fibrin formation
• Convert thrombin into an activator of protein C, reducing coagulation
• Increase platelet aggregation
• Activate factor VII

Correct Answer: Convert thrombin into an activator of protein C, reducing coagulation

Q29. Which of the following is factor I in the coagulation cascade?

• Prothrombin
• Fibrinogen
• Calcium
• Factor XIII

Correct Answer: Fibrinogen

Q30. Disseminated intravascular coagulation (DIC) is best described as:

• Isolated platelet dysfunction without clotting factor involvement
• Systemic activation of coagulation leading to consumption of clotting factors and platelets, causing both thrombosis and bleeding
• Genetic deficiency of factor VIII only
• Exclusive overactivity of fibrinolysis without coagulation activation

Correct Answer: Systemic activation of coagulation leading to consumption of clotting factors and platelets, causing both thrombosis and bleeding

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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