Part 2: Blood Groups and Coagulation (25 MCQs)

Q1. The ABO blood group system is based on the presence of:

A. Antigens on WBCs
B. Antibodies in plasma
C. Antigens on RBCs
D. Antibodies on RBCs

Answer: C

Explanation:

A. Incorrect: WBCs don’t define ABO groups.
B. Incorrect: Antibodies in plasma are important, but groups are based on RBC antigens.
C. Correct: ABO groups depend on A/B antigens on RBC surface.
D. Incorrect: Antibodies are in plasma, not on RBCs.

Q2. A person with blood group AB has:

A. Antigen A only
B. Antigen B only
C. Both Antigen A and B
D. No antigens

Answer: C

Explanation:

A. Incorrect: Only antigen A = Group A.
B. Incorrect: Only antigen B = Group B.
C. Correct: Group AB has both antigens.
D. Incorrect: No antigen = Group O.

Q3. A person with blood group O has:

A. Both A and B antigens
B. No antigens
C. Antigen A only
D. Antigen B only

Answer: B

Explanation:

A. Incorrect: That’s AB group.
B. Correct: O group has no antigens.
C. Incorrect: A group has antigen A.
D. Incorrect: B group has antigen B.

Q4. Blood group O is called a universal donor because:

A. Its plasma lacks antibodies
B. Its RBCs lack antigens
C. Its plasma contains both antigens
D. It has only antigen A

Answer: B

Explanation:

A. Incorrect: Plasma has antibodies (anti-A, anti-B).
B. Correct: RBCs have no antigens, so won’t be attacked.
C. Incorrect: Plasma does not contain antigens.
D. Incorrect: Wrong statement.

Q5. Blood group AB is called a universal recipient because:

A. It lacks antibodies in plasma
B. Its RBCs lack antigens
C. It contains both antibodies
D. It contains no plasma

Answer: A

Explanation:

A. Correct: AB plasma lacks anti-A and anti-B → can receive any blood.
B. Incorrect: RBCs have both antigens.
C. Incorrect: No antibodies present.
D. Incorrect: Plasma is present.

Q6. Rh factor is based on the presence of:

A. Antigen A
B. Antigen B
C. Antigen D
D. Antibodies

Answer: C

Explanation:

A. Incorrect: Antigen A → Group A.
B. Incorrect: Antigen B → Group B.
C. Correct: Rh system depends on antigen D on RBCs.
D. Incorrect: Antibodies are secondary.

Q7. A person with Rh-negative blood can safely receive Rh-positive blood:

A. Always
B. Only once
C. Never
D. Only in emergencies

Answer: B

Explanation:

A. Incorrect: Not always safe.
B. Correct: First transfusion → body makes anti-Rh antibodies. Later transfusions dangerous.
C. Incorrect: It is possible once.
D. Incorrect: Emergency does not change antibody response.

Q8. Erythroblastosis fetalis occurs when:

A. Rh– mother carries Rh+ fetus
B. Rh+ mother carries Rh– fetus
C. Both mother and fetus are Rh–
D. Father is Rh– and mother Rh+

Answer: A

Explanation:

A. Correct: Mother forms anti-Rh antibodies → attack Rh+ fetal RBCs in next pregnancy.
B. Incorrect: Rh+ mother with Rh– fetus is safe.
C. Incorrect: Both Rh– → no antibodies.
D. Incorrect: Father’s Rh status alone doesn’t cause disease.

Q9. Which injection is given to prevent erythroblastosis fetalis?

A. Rh immunoglobulin (RhoGAM)
B. Insulin
C. Heparin
D. Albumin

Answer: A

Explanation:

A. Correct: RhoGAM prevents anti-Rh antibody formation.
B. Incorrect: Insulin regulates glucose.
C. Incorrect: Heparin is anticoagulant.
D. Incorrect: Albumin maintains osmotic pressure.

Q10. Which step occurs first during blood clotting?

A. Conversion of prothrombin to thrombin
B. Conversion of fibrinogen to fibrin
C. Platelet plug formation
D. Retraction of clot

Answer: C

Explanation:

A. Incorrect: Prothrombin activation is later.
B. Incorrect: Fibrin formation is later.
C. Correct: Platelets stick and form a temporary plug first.
D. Incorrect: Retraction occurs after clot forms.

Q11. Which ion is essential for blood clotting?

A. Na⁺
B. K⁺
C. Ca²⁺
D. Mg²⁺

Answer: C

Explanation:

A. Incorrect: Na⁺ maintains osmotic balance.
B. Incorrect: K⁺ maintains potential, not clotting.
C. Correct: Ca²⁺ is required for prothrombin activation.
D. Incorrect: Mg²⁺ not directly used.

Q12. Prothrombin is converted into thrombin by:

A. Calcium ions and thromboplastin
B. Platelets and WBCs
C. Fibrinogen and globulin
D. Antithrombin

Answer: A

Explanation:

A. Correct: Thromboplastin + Ca²⁺ converts prothrombin → thrombin.
B. Incorrect: WBCs not involved.
C. Incorrect: Fibrinogen → fibrin, not this step.
D. Incorrect: Antithrombin inhibits clotting.

Q13. Thrombin converts:

A. Fibrinogen into fibrin
B. Albumin into globulin
C. Prothrombin into fibrinogen
D. RBCs into platelets

Answer: A

Explanation:

A. Correct: Thrombin converts fibrinogen → fibrin mesh.
B. Incorrect: Albumin not involved.
C. Incorrect: Prothrombin already converted earlier.
D. Incorrect: RBCs never become platelets.

Q14. Deficiency of Vitamin K affects:

A. Clotting of blood
B. Oxygen transport
C. Immunity
D. Osmotic pressure

Answer: A

Explanation:

A. Correct: Vitamin K needed for synthesis of clotting factors.
B. Incorrect: O₂ transport → RBC/Hb.
C. Incorrect: Immunity → WBCs.
D. Incorrect: Osmotic balance → albumin.

Q15. Which disorder is characterized by prolonged bleeding due to clotting factor deficiency?

A. Leukemia
B. Hemophilia
C. Anemia
D. Polycythemia

Answer: B

Explanation:

A. Incorrect: Leukemia = WBC cancer.
B. Correct: Hemophilia = clotting disorder due to factor VIII/IX deficiency.
C. Incorrect: Anemia = low RBC/Hb.
D. Incorrect: Polycythemia = excess RBCs.

Q16. Which condition occurs if blood clots inside a blood vessel?

A. Hemophilia
B. Thrombosis
C. Embolism
D. Leukopenia

Answer: B

Explanation:

A. Incorrect: Hemophilia = lack of clotting.
B. Correct: Thrombosis = clot formation inside vessel.
C. Incorrect: Embolism = clot dislodges and moves.
D. Incorrect: Leukopenia = low WBC.

Q17. Which blood group is most common in India?

A. A
B. B
C. AB
D. O

Answer: B

Explanation:

A. Incorrect: Group A less common.
B. Correct: Blood group B is most common in India.
C. Incorrect: AB is rare.
D. Incorrect: O is more common worldwide, but not in India.

Q18. Which blood group is rarest globally?

A. O+
B. AB–
C. B+
D. A+

Answer: B

Explanation:

A. Incorrect: O+ is very common.
B. Correct: AB– is rarest worldwide.
C. Incorrect: B+ is common in Asia.
D. Incorrect: A+ is common in Europe.

Q19. In blood transfusion, incompatibility arises mainly due to:

A. Plasma proteins
B. Antigens and antibodies reaction
C. pH difference
D. Osmotic pressure difference

Answer: B

Explanation:

A. Incorrect: Plasma proteins not main cause.
B. Correct: Antibodies in recipient react with donor RBC antigens.
C. Incorrect: pH difference not critical.
D. Incorrect: Osmotic pressure not cause.

Q20. Which of the following is NOT a step in blood clotting?

A. Prothrombin → Thrombin
B. Fibrinogen → Fibrin
C. Antibody formation
D. Platelet plug formation

Answer: C

Explanation:

A. Correct step.
B. Correct step.
C. Correct answer: Antibodies are immune, not clotting.
D. Correct step.

Q21. A person with A blood group can safely receive blood from:

A. O and A
B. A and B
C. AB and A
D. O and AB

Answer: A

Explanation:

A. Correct: Group A can receive A (same antigen) and O (no antigen).
B. Incorrect: B has antigen B → incompatible.
C. Incorrect: AB has both antigens → antibodies react.
D. Incorrect: AB unsafe.

Q22. Hemophilia is more common in males because:

A. Y chromosome carries gene
B. X chromosome carries gene
C. It is autosomal
D. It is dominant in females

Answer: B

Explanation:

A. Incorrect: Y does not carry gene.
B. Correct: Hemophilia is X-linked recessive → more males affected.
C. Incorrect: Not autosomal.
D. Incorrect: Not dominant.

Q23. Which anticoagulant is present naturally in blood to prevent clotting inside vessels?

A. Fibrin
B. Heparin
C. Prothrombin
D. Vitamin K

Answer: B

Explanation:

A. Incorrect: Fibrin forms clots.
B. Correct: Heparin prevents clotting inside vessels.
C. Incorrect: Prothrombin is clotting protein.
D. Incorrect: Vitamin K promotes clotting.

Q24. Which disorder involves low platelet count?

A. Leukemia
B. Thrombocytopenia
C. Polycythemia
D. Anemia

Answer: B

Explanation:

A. Incorrect: Leukemia = WBC cancer.
B. Correct: Thrombocytopenia = low platelets.
C. Incorrect: Polycythemia = excess RBCs.
D. Incorrect: Anemia = low Hb/RBC.

Q25. The clot formed in blood vessels that blocks blood flow is called:

A. Thrombus
B. Embolus
C. Plaque
D. Fibrin

Answer: A

Explanation:

A. Correct: Thrombus = stationary clot.
B. Incorrect: Embolus = moving clot.
C. Incorrect: Plaque = cholesterol deposit.
D. Incorrect: Fibrin = mesh, not full clot.

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Part 2: Blood Groups and Coagulation (25 MCQs)