COMSAE Phase 1 Form ASA 102
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 respiratory infections,
chronic diarrhea, and failure to thrive. Flow cytometry
demonstrates absent CD19-positive B lymphocytes. Genetic
testing reveals a mutation in the BTK gene. Which process is
primarily impaired?
A. Class switching in mature B cells
B. T-cell receptor rearrangement
C. Maturation of pre-B cells into mature B cells
D. Activation of macrophages by IFN-γ
Answer: C. Maturation of pre-B cells into mature B cells
Rationale: Bruton's tyrosine kinase (BTK) is required for B-cell
maturation. X-linked agammaglobulinemia results in absent mature B
cells and severely decreased immunoglobulin levels. T-cell function
remains largely intact.
2. A researcher administers a drug that irreversibly inhibits
cyclooxygenase-1 in platelets. Which mediator will show the
greatest reduction?
,A. Leukotriene B4
B. Prostacyclin
C. Thromboxane A2
D. Nitric oxide
Answer: C. Thromboxane A2
Rationale: Platelets rely on COX-1 for thromboxane A2 synthesis.
Aspirin irreversibly inhibits COX-1, reducing platelet aggregation for
the life of the platelet.
3. During prolonged fasting, which enzyme becomes most important
for hepatic ketone body synthesis?
A. Acetyl-CoA carboxylase
B. HMG-CoA synthase
C. Hormone-sensitive lipase
D. Pyruvate kinase
Answer: B. HMG-CoA synthase
Rationale: HMG-CoA synthase is the rate-limiting enzyme of
ketogenesis. Increased fatty acid oxidation during fasting generates
acetyl-CoA, which is converted into ketone bodies.
4. A patient develops nephrotic syndrome due to minimal change
disease. Which change is expected?
A. Increased plasma oncotic pressure
B. Hyperalbuminemia
C. Hyperlipidemia
D. Decreased hepatic lipoprotein production
,Answer: C. Hyperlipidemia
Rationale: Loss of albumin lowers plasma oncotic pressure. The liver
compensates by increasing synthesis of proteins and lipoproteins,
causing hyperlipidemia.
5. A 23-year-old woman has episodic palpitations and anxiety.
Laboratory studies reveal elevated catecholamines.
Catecholamines are synthesized from which amino acid?
A. Phenylalanine
B. Tryptophan
C. Tyrosine
D. Histidine
Answer: C. Tyrosine
Rationale: Tyrosine is converted to DOPA, dopamine, norepinephrine,
and epinephrine within chromaffin cells and sympathetic neurons.
6. Which cranial nerve carries parasympathetic fibers to the parotid
gland?
A. Facial nerve
B. Glossopharyngeal nerve
C. Vagus nerve
D. Trigeminal nerve
Answer: B. Glossopharyngeal nerve
Rationale: CN IX provides parasympathetic innervation to the parotid
gland through the otic ganglion.
, 7. A mutation causes constitutive activation of Ras proteins. What is
the most likely consequence?
A. Increased apoptosis
B. Impaired cell proliferation
C. Uncontrolled cell signaling and growth
D. Enhanced DNA repair
Answer: C. Uncontrolled cell signaling and growth
Rationale: Ras is a GTP-binding protein involved in growth signaling
pathways. Activating mutations are common oncogenic drivers.
8. A patient with pernicious anemia lacks intrinsic factor. Which
nutrient absorption is most directly impaired?
A. Iron
B. Folate
C. Vitamin B12
D. Calcium
Answer: C. Vitamin B12
Rationale: Intrinsic factor secreted by gastric parietal cells is essential
for vitamin B12 absorption in the terminal ileum.
9. Which immunoglobulin is the first produced during a primary
immune response?
A. IgA
B. IgE
C. IgG
D. IgM
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 respiratory infections,
chronic diarrhea, and failure to thrive. Flow cytometry
demonstrates absent CD19-positive B lymphocytes. Genetic
testing reveals a mutation in the BTK gene. Which process is
primarily impaired?
A. Class switching in mature B cells
B. T-cell receptor rearrangement
C. Maturation of pre-B cells into mature B cells
D. Activation of macrophages by IFN-γ
Answer: C. Maturation of pre-B cells into mature B cells
Rationale: Bruton's tyrosine kinase (BTK) is required for B-cell
maturation. X-linked agammaglobulinemia results in absent mature B
cells and severely decreased immunoglobulin levels. T-cell function
remains largely intact.
2. A researcher administers a drug that irreversibly inhibits
cyclooxygenase-1 in platelets. Which mediator will show the
greatest reduction?
,A. Leukotriene B4
B. Prostacyclin
C. Thromboxane A2
D. Nitric oxide
Answer: C. Thromboxane A2
Rationale: Platelets rely on COX-1 for thromboxane A2 synthesis.
Aspirin irreversibly inhibits COX-1, reducing platelet aggregation for
the life of the platelet.
3. During prolonged fasting, which enzyme becomes most important
for hepatic ketone body synthesis?
A. Acetyl-CoA carboxylase
B. HMG-CoA synthase
C. Hormone-sensitive lipase
D. Pyruvate kinase
Answer: B. HMG-CoA synthase
Rationale: HMG-CoA synthase is the rate-limiting enzyme of
ketogenesis. Increased fatty acid oxidation during fasting generates
acetyl-CoA, which is converted into ketone bodies.
4. A patient develops nephrotic syndrome due to minimal change
disease. Which change is expected?
A. Increased plasma oncotic pressure
B. Hyperalbuminemia
C. Hyperlipidemia
D. Decreased hepatic lipoprotein production
,Answer: C. Hyperlipidemia
Rationale: Loss of albumin lowers plasma oncotic pressure. The liver
compensates by increasing synthesis of proteins and lipoproteins,
causing hyperlipidemia.
5. A 23-year-old woman has episodic palpitations and anxiety.
Laboratory studies reveal elevated catecholamines.
Catecholamines are synthesized from which amino acid?
A. Phenylalanine
B. Tryptophan
C. Tyrosine
D. Histidine
Answer: C. Tyrosine
Rationale: Tyrosine is converted to DOPA, dopamine, norepinephrine,
and epinephrine within chromaffin cells and sympathetic neurons.
6. Which cranial nerve carries parasympathetic fibers to the parotid
gland?
A. Facial nerve
B. Glossopharyngeal nerve
C. Vagus nerve
D. Trigeminal nerve
Answer: B. Glossopharyngeal nerve
Rationale: CN IX provides parasympathetic innervation to the parotid
gland through the otic ganglion.
, 7. A mutation causes constitutive activation of Ras proteins. What is
the most likely consequence?
A. Increased apoptosis
B. Impaired cell proliferation
C. Uncontrolled cell signaling and growth
D. Enhanced DNA repair
Answer: C. Uncontrolled cell signaling and growth
Rationale: Ras is a GTP-binding protein involved in growth signaling
pathways. Activating mutations are common oncogenic drivers.
8. A patient with pernicious anemia lacks intrinsic factor. Which
nutrient absorption is most directly impaired?
A. Iron
B. Folate
C. Vitamin B12
D. Calcium
Answer: C. Vitamin B12
Rationale: Intrinsic factor secreted by gastric parietal cells is essential
for vitamin B12 absorption in the terminal ileum.
9. Which immunoglobulin is the first produced during a primary
immune response?
A. IgA
B. IgE
C. IgG
D. IgM
