COMSAE Phase 1–Form ASA 124
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 6-year-old boy presents with recurrent infections caused by
encapsulated bacteria. Laboratory testing reveals absent CD19+ B
cells and extremely low immunoglobulin levels. Which developmental
process is defective?
A. T-cell maturation in the thymus
B. B-cell maturation in bone marrow
C. Neutrophil oxidative burst
D. Complement activation
E. Macrophage antigen presentation
Answer: B. B-cell maturation in bone marrow
X-linked agammaglobulinemia results from a mutation in the Bruton
tyrosine kinase (BTK) gene, preventing maturation of B cells in the
bone marrow. Patients have decreased immunoglobulins and
recurrent infections with encapsulated organisms.
2. A researcher blocks formation of the peptide bond during protein
synthesis. Which cellular structure is directly affected?
,A. Lysosome
B. Ribosome
C. Golgi apparatus
D. Smooth endoplasmic reticulum
E. Peroxisome
Answer: B. Ribosome
Ribosomes catalyze peptide bond formation during translation. The
large ribosomal subunit contains peptidyl transferase activity
responsible for linking amino acids.
3. A patient develops metabolic acidosis due to lactic acid
accumulation after severe hypoxia. Which enzyme complex is
impaired?
A. Pyruvate dehydrogenase
B. Succinate dehydrogenase
C. Citrate synthase
D. Malate dehydrogenase
E. ATP synthase
Answer: A. Pyruvate dehydrogenase
Without oxygen, pyruvate cannot efficiently enter the citric acid cycle.
Pyruvate is converted to lactate through anaerobic metabolism,
causing lactic acidosis.
4. A mutation prevents production of type IV collagen. Which
structure is primarily affected?
A. Basement membrane
B. Elastic fibers
,C. Smooth muscle cells
D. Cartilage matrix
E. Microtubules
Answer: A. Basement membrane
Type IV collagen is a major component of basement membranes.
Defects can affect kidneys, eyes, and hearing as seen in Alport
syndrome.
5. A patient taking a medication develops prolonged bleeding time
but normal PT and PTT. Which drug is most likely responsible?
A. Warfarin
B. Heparin
C. Aspirin
D. Dabigatran
E. Factor VIII concentrate
Answer: C. Aspirin
Aspirin irreversibly inhibits COX-1 in platelets, reducing thromboxane
A2 and impairing platelet aggregation. Platelet disorders increase
bleeding time while PT/PTT remain normal.
6. A newborn has cyanosis that improves when oxygen is
administered. Which embryologic structure normally closes after birth
to separate pulmonary and systemic circulation?
A. Ductus venosus
B. Foramen ovale
C. Umbilical artery
, D. Vitelline duct
E. Neural tube
Answer: B. Foramen ovale
The foramen ovale allows fetal right-to-left atrial blood flow.
Increased left atrial pressure after birth closes the flap, separating
atrial chambers.
7. A patient with Graves disease has increased thyroid hormone
production. Which receptor mediates thyroid-stimulating hormone
effects?
A. Nuclear receptor
B. G protein–coupled receptor
C. Intracellular steroid receptor
D. Ion channel receptor
E. Tyrosine kinase receptor
Answer: B. G protein–coupled receptor
The TSH receptor is a G protein–coupled receptor activating cAMP
signaling pathways in thyroid follicular cells.
8. A patient with chronic kidney disease develops anemia. Deficiency
of which hormone contributes?
A. Renin
B. Erythropoietin
C. Aldosterone
D. ADH
E. Angiotensin II
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 6-year-old boy presents with recurrent infections caused by
encapsulated bacteria. Laboratory testing reveals absent CD19+ B
cells and extremely low immunoglobulin levels. Which developmental
process is defective?
A. T-cell maturation in the thymus
B. B-cell maturation in bone marrow
C. Neutrophil oxidative burst
D. Complement activation
E. Macrophage antigen presentation
Answer: B. B-cell maturation in bone marrow
X-linked agammaglobulinemia results from a mutation in the Bruton
tyrosine kinase (BTK) gene, preventing maturation of B cells in the
bone marrow. Patients have decreased immunoglobulins and
recurrent infections with encapsulated organisms.
2. A researcher blocks formation of the peptide bond during protein
synthesis. Which cellular structure is directly affected?
,A. Lysosome
B. Ribosome
C. Golgi apparatus
D. Smooth endoplasmic reticulum
E. Peroxisome
Answer: B. Ribosome
Ribosomes catalyze peptide bond formation during translation. The
large ribosomal subunit contains peptidyl transferase activity
responsible for linking amino acids.
3. A patient develops metabolic acidosis due to lactic acid
accumulation after severe hypoxia. Which enzyme complex is
impaired?
A. Pyruvate dehydrogenase
B. Succinate dehydrogenase
C. Citrate synthase
D. Malate dehydrogenase
E. ATP synthase
Answer: A. Pyruvate dehydrogenase
Without oxygen, pyruvate cannot efficiently enter the citric acid cycle.
Pyruvate is converted to lactate through anaerobic metabolism,
causing lactic acidosis.
4. A mutation prevents production of type IV collagen. Which
structure is primarily affected?
A. Basement membrane
B. Elastic fibers
,C. Smooth muscle cells
D. Cartilage matrix
E. Microtubules
Answer: A. Basement membrane
Type IV collagen is a major component of basement membranes.
Defects can affect kidneys, eyes, and hearing as seen in Alport
syndrome.
5. A patient taking a medication develops prolonged bleeding time
but normal PT and PTT. Which drug is most likely responsible?
A. Warfarin
B. Heparin
C. Aspirin
D. Dabigatran
E. Factor VIII concentrate
Answer: C. Aspirin
Aspirin irreversibly inhibits COX-1 in platelets, reducing thromboxane
A2 and impairing platelet aggregation. Platelet disorders increase
bleeding time while PT/PTT remain normal.
6. A newborn has cyanosis that improves when oxygen is
administered. Which embryologic structure normally closes after birth
to separate pulmonary and systemic circulation?
A. Ductus venosus
B. Foramen ovale
C. Umbilical artery
, D. Vitelline duct
E. Neural tube
Answer: B. Foramen ovale
The foramen ovale allows fetal right-to-left atrial blood flow.
Increased left atrial pressure after birth closes the flap, separating
atrial chambers.
7. A patient with Graves disease has increased thyroid hormone
production. Which receptor mediates thyroid-stimulating hormone
effects?
A. Nuclear receptor
B. G protein–coupled receptor
C. Intracellular steroid receptor
D. Ion channel receptor
E. Tyrosine kinase receptor
Answer: B. G protein–coupled receptor
The TSH receptor is a G protein–coupled receptor activating cAMP
signaling pathways in thyroid follicular cells.
8. A patient with chronic kidney disease develops anemia. Deficiency
of which hormone contributes?
A. Renin
B. Erythropoietin
C. Aldosterone
D. ADH
E. Angiotensin II
