COMSAE Phase 1 Form ASA 111
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 24-year-old medical student has been awake for 36 hours
preparing for examinations. He notices difficulty concentrating
and impaired short-term memory. Which neurotransmitter
system is most directly involved in promoting wakefulness and
attention within the cerebral cortex?
A. Gamma-aminobutyric acid (GABA)
B. Glycine
C. Norepinephrine
D. Substance P
E. Enkephalin
Answer: C. Norepinephrine
Rationale: The locus coeruleus releases norepinephrine throughout
the cerebral cortex and is critically involved in arousal, vigilance,
attention, and wakefulness. GABA and glycine are inhibitory
neurotransmitters, while substance P and enkephalins are primarily
involved in pain pathways.
2. A researcher administers a drug that selectively inhibits
dihydrofolate reductase in bacterial cells. Which cellular process
will be most directly impaired?
,A. Translation
B. DNA synthesis
C. Glycolysis
D. Protein folding
E. Lipid oxidation
Answer: B. DNA synthesis
Rationale: Dihydrofolate reductase regenerates tetrahydrofolate,
which is required for thymidine and purine synthesis. Inhibition
decreases DNA replication by limiting nucleotide production.
3. A patient with chronic renal failure develops normocytic anemia.
Reduced production of which substance is the primary cause?
A. Hepcidin
B. Renin
C. Aldosterone
D. Erythropoietin
E. Thrombopoietin
Answer: D. Erythropoietin
Rationale: Erythropoietin is synthesized primarily by peritubular
interstitial cells of the kidney. Chronic kidney disease decreases
erythropoietin production, resulting in normocytic normochromic
anemia.
4. During vigorous exercise, skeletal muscle increases glucose uptake
independently of insulin. Which transporter is primarily involved?
A. GLUT1
,B. GLUT2
C. GLUT3
D. GLUT4
E. GLUT5
Answer: D. GLUT4
Rationale: Skeletal muscle contraction stimulates translocation of
GLUT4 transporters to the plasma membrane independent of insulin
signaling, enhancing glucose uptake.
5. A deficiency of homogentisate oxidase leads to accumulation of
homogentisic acid. Which disorder results?
A. Maple syrup urine disease
B. Alkaptonuria
C. Phenylketonuria
D. Hartnup disease
E. Cystinuria
Answer: B. Alkaptonuria
Rationale: Alkaptonuria results from homogentisate oxidase
deficiency in tyrosine metabolism. Patients may develop dark urine,
ochronosis, and degenerative arthritis.
6. Which phase of the cardiac action potential in ventricular
myocytes is primarily maintained by calcium influx through L-type
calcium channels?
A. Phase 0
B. Phase 1
, C. Phase 2
D. Phase 3
E. Phase 4
Answer: C. Phase 2
Rationale: The plateau phase (Phase 2) results from a balance
between calcium influx through L-type channels and potassium efflux.
This prolongs ventricular contraction.
7. A patient develops a lesion involving the optic chiasm. Which
visual deficit is expected?
A. Right homonymous hemianopia
B. Left homonymous hemianopia
C. Bitemporal hemianopia
D. Monocular blindness
E. Quadrantanopia
Answer: C. Bitemporal hemianopia
Rationale: Fibers from the nasal retina cross in the optic chiasm.
Compression disrupts temporal visual fields bilaterally, causing
bitemporal hemianopia.
8. A child develops recurrent infections with catalase-positive
organisms. Neutrophils demonstrate inability to generate reactive
oxygen species. Which enzyme is deficient?
A. Myeloperoxidase
B. Superoxide dismutase
C. NADPH oxidase
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 24-year-old medical student has been awake for 36 hours
preparing for examinations. He notices difficulty concentrating
and impaired short-term memory. Which neurotransmitter
system is most directly involved in promoting wakefulness and
attention within the cerebral cortex?
A. Gamma-aminobutyric acid (GABA)
B. Glycine
C. Norepinephrine
D. Substance P
E. Enkephalin
Answer: C. Norepinephrine
Rationale: The locus coeruleus releases norepinephrine throughout
the cerebral cortex and is critically involved in arousal, vigilance,
attention, and wakefulness. GABA and glycine are inhibitory
neurotransmitters, while substance P and enkephalins are primarily
involved in pain pathways.
2. A researcher administers a drug that selectively inhibits
dihydrofolate reductase in bacterial cells. Which cellular process
will be most directly impaired?
,A. Translation
B. DNA synthesis
C. Glycolysis
D. Protein folding
E. Lipid oxidation
Answer: B. DNA synthesis
Rationale: Dihydrofolate reductase regenerates tetrahydrofolate,
which is required for thymidine and purine synthesis. Inhibition
decreases DNA replication by limiting nucleotide production.
3. A patient with chronic renal failure develops normocytic anemia.
Reduced production of which substance is the primary cause?
A. Hepcidin
B. Renin
C. Aldosterone
D. Erythropoietin
E. Thrombopoietin
Answer: D. Erythropoietin
Rationale: Erythropoietin is synthesized primarily by peritubular
interstitial cells of the kidney. Chronic kidney disease decreases
erythropoietin production, resulting in normocytic normochromic
anemia.
4. During vigorous exercise, skeletal muscle increases glucose uptake
independently of insulin. Which transporter is primarily involved?
A. GLUT1
,B. GLUT2
C. GLUT3
D. GLUT4
E. GLUT5
Answer: D. GLUT4
Rationale: Skeletal muscle contraction stimulates translocation of
GLUT4 transporters to the plasma membrane independent of insulin
signaling, enhancing glucose uptake.
5. A deficiency of homogentisate oxidase leads to accumulation of
homogentisic acid. Which disorder results?
A. Maple syrup urine disease
B. Alkaptonuria
C. Phenylketonuria
D. Hartnup disease
E. Cystinuria
Answer: B. Alkaptonuria
Rationale: Alkaptonuria results from homogentisate oxidase
deficiency in tyrosine metabolism. Patients may develop dark urine,
ochronosis, and degenerative arthritis.
6. Which phase of the cardiac action potential in ventricular
myocytes is primarily maintained by calcium influx through L-type
calcium channels?
A. Phase 0
B. Phase 1
, C. Phase 2
D. Phase 3
E. Phase 4
Answer: C. Phase 2
Rationale: The plateau phase (Phase 2) results from a balance
between calcium influx through L-type channels and potassium efflux.
This prolongs ventricular contraction.
7. A patient develops a lesion involving the optic chiasm. Which
visual deficit is expected?
A. Right homonymous hemianopia
B. Left homonymous hemianopia
C. Bitemporal hemianopia
D. Monocular blindness
E. Quadrantanopia
Answer: C. Bitemporal hemianopia
Rationale: Fibers from the nasal retina cross in the optic chiasm.
Compression disrupts temporal visual fields bilaterally, causing
bitemporal hemianopia.
8. A child develops recurrent infections with catalase-positive
organisms. Neutrophils demonstrate inability to generate reactive
oxygen species. Which enzyme is deficient?
A. Myeloperoxidase
B. Superoxide dismutase
C. NADPH oxidase
