COMSAE Phase 1 Form 109 Questions With
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1.
A 24-year-old woman presents with fatigue, pallor, and glossitis. Lab
studies show hemoglobin 9.2 g/dL, MCV 112 fL. Which of the following
is the most likely cause?
A. Iron deficiency anemia
B. Vitamin B12 deficiency
C. Acute blood loss
D. Thalassemia trait
Correct Answer: B. Vitamin B12 deficiency
Rationale: Macrocytic anemia (MCV > 100 fL) with neurologic or
mucosal findings such as glossitis is most consistent with vitamin B12
deficiency.
2.
,Which of the following is the primary site of aldosterone action?
A. Proximal tubule
B. Thick ascending limb
C. Distal convoluted tubule
D. Collecting duct
Correct Answer: D. Collecting duct
Rationale: Aldosterone acts primarily on principal cells in the
collecting duct to increase sodium reabsorption and potassium
excretion.
3.
A patient has a pH of 7.25, PaCO₂ of 50 mmHg, and normal HCO₃⁻. What
is the primary disorder?
A. Metabolic acidosis
B. Metabolic alkalosis
C. Respiratory acidosis
D. Respiratory alkalosis
Correct Answer: C. Respiratory acidosis
,Rationale: Elevated PaCO₂ with low pH indicates primary respiratory
acidosis.
4.
Which enzyme is deficient in phenylketonuria (PKU)?
A. Homogentisate oxidase
B. Phenylalanine hydroxylase
C. Tyrosinase
D. DOPA decarboxylase
Correct Answer: B. Phenylalanine hydroxylase
Rationale: PKU results from deficiency of phenylalanine hydroxylase,
leading to accumulation of phenylalanine.
5.
A 65-year-old man has exertional chest pain relieved by rest. What is
the most likely mechanism?
A. Coronary artery spasm
B. Atherosclerotic plaque causing fixed obstruction
, C. Myocarditis
D. Aortic dissection
Correct Answer: B. Atherosclerotic plaque causing fixed obstruction
Rationale: Stable angina is caused by fixed atherosclerotic narrowing
of coronary arteries.
6.
Which vitamin is required for gamma-carboxylation of clotting factors II,
VII, IX, and X?
A. Vitamin A
B. Vitamin C
C. Vitamin D
D. Vitamin K
Correct Answer: D. Vitamin K
Rationale: Vitamin K is essential for activation of clotting factors via
gamma-carboxylation.
7.
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1.
A 24-year-old woman presents with fatigue, pallor, and glossitis. Lab
studies show hemoglobin 9.2 g/dL, MCV 112 fL. Which of the following
is the most likely cause?
A. Iron deficiency anemia
B. Vitamin B12 deficiency
C. Acute blood loss
D. Thalassemia trait
Correct Answer: B. Vitamin B12 deficiency
Rationale: Macrocytic anemia (MCV > 100 fL) with neurologic or
mucosal findings such as glossitis is most consistent with vitamin B12
deficiency.
2.
,Which of the following is the primary site of aldosterone action?
A. Proximal tubule
B. Thick ascending limb
C. Distal convoluted tubule
D. Collecting duct
Correct Answer: D. Collecting duct
Rationale: Aldosterone acts primarily on principal cells in the
collecting duct to increase sodium reabsorption and potassium
excretion.
3.
A patient has a pH of 7.25, PaCO₂ of 50 mmHg, and normal HCO₃⁻. What
is the primary disorder?
A. Metabolic acidosis
B. Metabolic alkalosis
C. Respiratory acidosis
D. Respiratory alkalosis
Correct Answer: C. Respiratory acidosis
,Rationale: Elevated PaCO₂ with low pH indicates primary respiratory
acidosis.
4.
Which enzyme is deficient in phenylketonuria (PKU)?
A. Homogentisate oxidase
B. Phenylalanine hydroxylase
C. Tyrosinase
D. DOPA decarboxylase
Correct Answer: B. Phenylalanine hydroxylase
Rationale: PKU results from deficiency of phenylalanine hydroxylase,
leading to accumulation of phenylalanine.
5.
A 65-year-old man has exertional chest pain relieved by rest. What is
the most likely mechanism?
A. Coronary artery spasm
B. Atherosclerotic plaque causing fixed obstruction
, C. Myocarditis
D. Aortic dissection
Correct Answer: B. Atherosclerotic plaque causing fixed obstruction
Rationale: Stable angina is caused by fixed atherosclerotic narrowing
of coronary arteries.
6.
Which vitamin is required for gamma-carboxylation of clotting factors II,
VII, IX, and X?
A. Vitamin A
B. Vitamin C
C. Vitamin D
D. Vitamin K
Correct Answer: D. Vitamin K
Rationale: Vitamin K is essential for activation of clotting factors via
gamma-carboxylation.
7.
