BIO 156 Exam 3 Exam with answers in bold
and rationale updated 2026
Section 1: The Cardiovascular System – Blood (Questions 1–30)
1. Which of the following is NOT a formed element of blood?
A) Erythrocyte
B) Leukocyte
C) Platelet
D) Plasma protein
Rationale: Plasma proteins are dissolved in plasma, not formed elements. Formed elements include
erythrocytes, leukocytes, and platelets.
2. The hematocrit is a measure of the percentage of blood volume occupied by:
A) Erythrocytes
B) Leukocytes
C) Platelets
D) Plasma
Rationale: Hematocrit specifically measures the packed volume of red blood cells after
centrifugation.
3. Which plasma protein is most abundant?
A) Globulin
B) Fibrinogen
C) Albumin
D) Prothrombin
Rationale: Albumin constitutes about 60% of plasma proteins and maintains osmotic pressure.
4. The primary function of erythrocytes is:
A) Immune defense
B) Blood clotting
C) Oxygen transport
D) Nutrient storage
Rationale: Erythrocytes contain hemoglobin, which binds and transports oxygen.
5. Hemoglobin contains which metal ion essential for oxygen binding?
A) Copper
B) Zinc
C) Iron
D) Magnesium
Rationale: Iron in the heme group binds oxygen reversibly.
6. The process of red blood cell formation is called:
A) Hemolysis
B) Erythropoiesis
C) Leukopoiesis
,D) Thrombopoiesis
Rationale: Erythropoiesis is the production of erythrocytes, primarily in red bone marrow.
7. Erythropoietin is produced primarily by the:
A) Liver
B) Kidneys
C) Spleen
D) Bone marrow
Rationale: The kidneys detect hypoxia and release erythropoietin to stimulate RBC production.
8. Which vitamin is essential for DNA synthesis and RBC maturation?
A) Vitamin A
B) Vitamin C
C) Vitamin B12
D) Vitamin K
Rationale: Vitamin B12 (and folate) are required for normal DNA synthesis and nuclear maturation
of RBCs.
9. A deficiency of iron would most directly affect:
A) White blood cell count
B) Hemoglobin synthesis
C) Platelet aggregation
D) Plasma volume
Rationale: Iron is a key component of heme; deficiency leads to microcytic, hypochromic anemia.
10. Which leukocyte is the most abundant in a normal differential count?
A) Lymphocyte
B) Monocyte
C) Neutrophil
D) Eosinophil
Rationale: Neutrophils constitute 50–70% of circulating leukocytes.
11. Which leukocyte is primarily responsible for phagocytosis of bacteria?
A) Basophil
B) Neutrophil
C) Eosinophil
D) Lymphocyte
Rationale: Neutrophils are the first responders and primary phagocytes against bacteria.
12. Which cell type produces antibodies?
A) T lymphocytes
B) B lymphocytes (plasma cells)
C) Neutrophils
D) Monocytes
Rationale: B lymphocytes differentiate into plasma cells that secrete antibodies.
13. Platelets are derived from which precursor cell?
A) Reticulocyte
B) Myeloblast
C) Megakaryocyte
, D) Monoblast
Rationale: Megakaryocytes fragment into platelets under thrombopoietin stimulation.
14. The primary function of platelets is:
A) Oxygen transport
B) Hemostasis
C) Immune defense
D) Protein synthesis
Rationale: Platelets are essential for blood clotting (hemostasis).
15. Which of the following is NOT a step in hemostasis?
A) Vascular spasm
B) Platelet plug formation
C) Fibrinolysis
D) Coagulation
Rationale: Fibrinolysis is the breakdown of clots, not a step in clot formation.
16. The conversion of fibrinogen to fibrin is catalyzed by:
A) Prothrombin
B) Thrombin
C) Plasmin
D) Tissue factor
Rationale: Thrombin converts soluble fibrinogen into insoluble fibrin strands.
17. Which vitamin is required for the synthesis of several clotting factors?
A) Vitamin A
B) Vitamin C
C) Vitamin K
D) Vitamin D
Rationale: Vitamin K is essential for synthesis of prothrombin and factors VII, IX, and X.
18. A person with type AB blood has:
A) Anti-A antibodies
B) Anti-B antibodies
C) Neither anti-A nor anti-B antibodies
D) Both anti-A and anti-B antibodies
Rationale: Type AB blood has both A and B antigens, so no antibodies are produced.
19. Which blood type is considered the universal donor?
A) Type A
B) Type B
C) Type AB
D) Type O
Rationale: Type O has no A or B antigens, so it can be donated to any ABO type.
20. Hemolytic disease of the newborn (HDN) is most commonly associated with:
A) ABO incompatibility
B) Rh incompatibility
C) Iron deficiency
D) Vitamin K deficiency
and rationale updated 2026
Section 1: The Cardiovascular System – Blood (Questions 1–30)
1. Which of the following is NOT a formed element of blood?
A) Erythrocyte
B) Leukocyte
C) Platelet
D) Plasma protein
Rationale: Plasma proteins are dissolved in plasma, not formed elements. Formed elements include
erythrocytes, leukocytes, and platelets.
2. The hematocrit is a measure of the percentage of blood volume occupied by:
A) Erythrocytes
B) Leukocytes
C) Platelets
D) Plasma
Rationale: Hematocrit specifically measures the packed volume of red blood cells after
centrifugation.
3. Which plasma protein is most abundant?
A) Globulin
B) Fibrinogen
C) Albumin
D) Prothrombin
Rationale: Albumin constitutes about 60% of plasma proteins and maintains osmotic pressure.
4. The primary function of erythrocytes is:
A) Immune defense
B) Blood clotting
C) Oxygen transport
D) Nutrient storage
Rationale: Erythrocytes contain hemoglobin, which binds and transports oxygen.
5. Hemoglobin contains which metal ion essential for oxygen binding?
A) Copper
B) Zinc
C) Iron
D) Magnesium
Rationale: Iron in the heme group binds oxygen reversibly.
6. The process of red blood cell formation is called:
A) Hemolysis
B) Erythropoiesis
C) Leukopoiesis
,D) Thrombopoiesis
Rationale: Erythropoiesis is the production of erythrocytes, primarily in red bone marrow.
7. Erythropoietin is produced primarily by the:
A) Liver
B) Kidneys
C) Spleen
D) Bone marrow
Rationale: The kidneys detect hypoxia and release erythropoietin to stimulate RBC production.
8. Which vitamin is essential for DNA synthesis and RBC maturation?
A) Vitamin A
B) Vitamin C
C) Vitamin B12
D) Vitamin K
Rationale: Vitamin B12 (and folate) are required for normal DNA synthesis and nuclear maturation
of RBCs.
9. A deficiency of iron would most directly affect:
A) White blood cell count
B) Hemoglobin synthesis
C) Platelet aggregation
D) Plasma volume
Rationale: Iron is a key component of heme; deficiency leads to microcytic, hypochromic anemia.
10. Which leukocyte is the most abundant in a normal differential count?
A) Lymphocyte
B) Monocyte
C) Neutrophil
D) Eosinophil
Rationale: Neutrophils constitute 50–70% of circulating leukocytes.
11. Which leukocyte is primarily responsible for phagocytosis of bacteria?
A) Basophil
B) Neutrophil
C) Eosinophil
D) Lymphocyte
Rationale: Neutrophils are the first responders and primary phagocytes against bacteria.
12. Which cell type produces antibodies?
A) T lymphocytes
B) B lymphocytes (plasma cells)
C) Neutrophils
D) Monocytes
Rationale: B lymphocytes differentiate into plasma cells that secrete antibodies.
13. Platelets are derived from which precursor cell?
A) Reticulocyte
B) Myeloblast
C) Megakaryocyte
, D) Monoblast
Rationale: Megakaryocytes fragment into platelets under thrombopoietin stimulation.
14. The primary function of platelets is:
A) Oxygen transport
B) Hemostasis
C) Immune defense
D) Protein synthesis
Rationale: Platelets are essential for blood clotting (hemostasis).
15. Which of the following is NOT a step in hemostasis?
A) Vascular spasm
B) Platelet plug formation
C) Fibrinolysis
D) Coagulation
Rationale: Fibrinolysis is the breakdown of clots, not a step in clot formation.
16. The conversion of fibrinogen to fibrin is catalyzed by:
A) Prothrombin
B) Thrombin
C) Plasmin
D) Tissue factor
Rationale: Thrombin converts soluble fibrinogen into insoluble fibrin strands.
17. Which vitamin is required for the synthesis of several clotting factors?
A) Vitamin A
B) Vitamin C
C) Vitamin K
D) Vitamin D
Rationale: Vitamin K is essential for synthesis of prothrombin and factors VII, IX, and X.
18. A person with type AB blood has:
A) Anti-A antibodies
B) Anti-B antibodies
C) Neither anti-A nor anti-B antibodies
D) Both anti-A and anti-B antibodies
Rationale: Type AB blood has both A and B antigens, so no antibodies are produced.
19. Which blood type is considered the universal donor?
A) Type A
B) Type B
C) Type AB
D) Type O
Rationale: Type O has no A or B antigens, so it can be donated to any ABO type.
20. Hemolytic disease of the newborn (HDN) is most commonly associated with:
A) ABO incompatibility
B) Rh incompatibility
C) Iron deficiency
D) Vitamin K deficiency
