COMSAE Phase 1 Form ASA 117
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 24-year-old man has a mutation causing defective collagen type I
synthesis. Which structure is most likely affected?
A. Basement membrane
B. Cartilage matrix
C. Bone and tendon
D. Elastic arteries
Answer: C. Bone and tendon
Rationale: Type I collagen is the major collagen in bone, tendons,
ligaments, and skin. Defects cause disorders such as osteogenesis
imperfecta with fragile bones and connective tissue abnormalities.
2. A patient has a deficiency of pyruvate dehydrogenase. Which
metabolic process is directly impaired?
A. Conversion of glucose to pyruvate
B. Conversion of pyruvate to acetyl-CoA
C. Conversion of acetyl-CoA to citrate
D. Conversion of lactate to pyruvate
Answer: B. Conversion of pyruvate to acetyl-CoA
,Rationale: Pyruvate dehydrogenase converts pyruvate into acetyl-
CoA, linking glycolysis to the citric acid cycle. Deficiency causes lactic
acidosis and neurologic symptoms.
3. A patient develops hemolytic anemia after taking an oxidant
medication. Deficiency of which enzyme is responsible?
A. Hexokinase
B. Pyruvate kinase
C. Glucose-6-phosphate dehydrogenase
D. Lactate dehydrogenase
Answer: C. Glucose-6-phosphate dehydrogenase
Rationale: G6PD generates NADPH required to maintain reduced
glutathione. Without it, RBCs are vulnerable to oxidative stress,
causing hemolysis.
4. Which immunoglobulin is primarily responsible for immediate
hypersensitivity reactions?
A. IgA
B. IgG
C. IgE
D. IgM
Answer: C. IgE
Rationale: IgE binds mast cells and basophils. Allergen exposure
triggers degranulation and release of histamine in type I
hypersensitivity reactions.
,5. A drug blocks bacterial protein synthesis by binding the 30S
ribosomal subunit. Which drug is most likely responsible?
A. Macrolide
B. Tetracycline
C. Penicillin
D. Vancomycin
Answer: B. Tetracycline
Rationale: Tetracyclines inhibit attachment of aminoacyl-tRNA to the
30S ribosomal subunit, preventing bacterial protein synthesis.
6. The resting membrane potential of neurons is primarily maintained
by which mechanism?
A. Calcium influx
B. Sodium-potassium ATPase
C. Chloride secretion
D. Potassium influx
Answer: B. Sodium-potassium ATPase
Rationale: The Na⁺/K⁺ ATPase pumps 3 sodium ions out and 2
potassium ions into the cell, maintaining electrochemical gradients.
7. A lesion damages the left corticospinal tract above the spinal cord
level. What deficit occurs?
A. Left-sided paralysis
B. Right-sided paralysis
C. Bilateral paralysis
D. Loss of vibration only
, Answer: A. Left-sided paralysis
Rationale: The corticospinal tract crosses at the medullary pyramidal
decussation. Lesions above the crossing cause contralateral deficits;
below cause ipsilateral deficits.
8. Which enzyme is responsible for DNA synthesis during replication?
A. RNA polymerase
B. DNA polymerase
C. Topoisomerase
D. Helicase
Answer: B. DNA polymerase
Rationale: DNA polymerase adds nucleotides to the growing DNA
strand during replication. Helicase unwinds DNA, while topoisomerase
relieves tension.
9. A patient with hypothyroidism has decreased metabolic rate.
Which hormone normally increases basal metabolic rate?
A. Cortisol
B. Thyroxine
C. Insulin
D. Aldosterone
Answer: B. Thyroxine
Rationale: Thyroid hormone increases oxygen consumption,
mitochondrial activity, and basal metabolic rate.
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 24-year-old man has a mutation causing defective collagen type I
synthesis. Which structure is most likely affected?
A. Basement membrane
B. Cartilage matrix
C. Bone and tendon
D. Elastic arteries
Answer: C. Bone and tendon
Rationale: Type I collagen is the major collagen in bone, tendons,
ligaments, and skin. Defects cause disorders such as osteogenesis
imperfecta with fragile bones and connective tissue abnormalities.
2. A patient has a deficiency of pyruvate dehydrogenase. Which
metabolic process is directly impaired?
A. Conversion of glucose to pyruvate
B. Conversion of pyruvate to acetyl-CoA
C. Conversion of acetyl-CoA to citrate
D. Conversion of lactate to pyruvate
Answer: B. Conversion of pyruvate to acetyl-CoA
,Rationale: Pyruvate dehydrogenase converts pyruvate into acetyl-
CoA, linking glycolysis to the citric acid cycle. Deficiency causes lactic
acidosis and neurologic symptoms.
3. A patient develops hemolytic anemia after taking an oxidant
medication. Deficiency of which enzyme is responsible?
A. Hexokinase
B. Pyruvate kinase
C. Glucose-6-phosphate dehydrogenase
D. Lactate dehydrogenase
Answer: C. Glucose-6-phosphate dehydrogenase
Rationale: G6PD generates NADPH required to maintain reduced
glutathione. Without it, RBCs are vulnerable to oxidative stress,
causing hemolysis.
4. Which immunoglobulin is primarily responsible for immediate
hypersensitivity reactions?
A. IgA
B. IgG
C. IgE
D. IgM
Answer: C. IgE
Rationale: IgE binds mast cells and basophils. Allergen exposure
triggers degranulation and release of histamine in type I
hypersensitivity reactions.
,5. A drug blocks bacterial protein synthesis by binding the 30S
ribosomal subunit. Which drug is most likely responsible?
A. Macrolide
B. Tetracycline
C. Penicillin
D. Vancomycin
Answer: B. Tetracycline
Rationale: Tetracyclines inhibit attachment of aminoacyl-tRNA to the
30S ribosomal subunit, preventing bacterial protein synthesis.
6. The resting membrane potential of neurons is primarily maintained
by which mechanism?
A. Calcium influx
B. Sodium-potassium ATPase
C. Chloride secretion
D. Potassium influx
Answer: B. Sodium-potassium ATPase
Rationale: The Na⁺/K⁺ ATPase pumps 3 sodium ions out and 2
potassium ions into the cell, maintaining electrochemical gradients.
7. A lesion damages the left corticospinal tract above the spinal cord
level. What deficit occurs?
A. Left-sided paralysis
B. Right-sided paralysis
C. Bilateral paralysis
D. Loss of vibration only
, Answer: A. Left-sided paralysis
Rationale: The corticospinal tract crosses at the medullary pyramidal
decussation. Lesions above the crossing cause contralateral deficits;
below cause ipsilateral deficits.
8. Which enzyme is responsible for DNA synthesis during replication?
A. RNA polymerase
B. DNA polymerase
C. Topoisomerase
D. Helicase
Answer: B. DNA polymerase
Rationale: DNA polymerase adds nucleotides to the growing DNA
strand during replication. Helicase unwinds DNA, while topoisomerase
relieves tension.
9. A patient with hypothyroidism has decreased metabolic rate.
Which hormone normally increases basal metabolic rate?
A. Cortisol
B. Thyroxine
C. Insulin
D. Aldosterone
Answer: B. Thyroxine
Rationale: Thyroid hormone increases oxygen consumption,
mitochondrial activity, and basal metabolic rate.
