COMSAE Phase 1 – Form ASA 113 (Secure
Browser Testing Standard; Videos) (2026
Edition): Comprehensive Multiple-Choice
Questions, Answers, and Detailed Rationales
Question 1
A 6-year-old boy has recurrent respiratory infections and
steatorrhea. Genetic testing reveals a mutation affecting
chloride transport across epithelial membranes.
Which protein is defective?
A. Dystrophin
B. Fibrillin-1
C. CFTR
D. Spectrin
E. Ankyrin
Answer: C. CFTR
CFTR is a chloride channel found in epithelial cells. Mutations
cause cystic fibrosis, leading to thick secretions, recurrent
pulmonary infections, pancreatic insufficiency, and
malabsorption. The disease is inherited in an autosomal
recessive pattern.
Question 2
,A researcher administers a drug that selectively blocks
voltage-gated sodium channels.
Which phase of the neuronal action potential is most directly
affected?
A. Hyperpolarization
B. Resting membrane potential
C. Repolarization
D. Depolarization
E. Synaptic vesicle release
Answer: D. Depolarization
Voltage-gated sodium channels open during depolarization,
allowing rapid sodium influx. Blocking these channels
prevents initiation and propagation of action potentials.
Question 3
A patient develops weakness after prolonged corticosteroid
therapy. Muscle biopsy shows atrophy of fast-twitch fibers.
Which mechanism best explains this finding?
A. Increased protein synthesis
B. Increased glycogen storage
C. Enhanced protein catabolism
D. Increased calcium uptake
E. Enhanced mitochondrial proliferation
Answer: C. Enhanced protein catabolism
,Glucocorticoids stimulate protein breakdown, particularly in
skeletal muscle, leading to proximal muscle weakness and
muscle wasting.
Question 4
A 48-year-old woman presents with fatigue and pallor.
Laboratory studies reveal microcytic hypochromic anemia.
Which laboratory finding is most likely?
A. Increased ferritin
B. Increased transferrin saturation
C. Elevated vitamin B12
D. Low serum ferritin
E. Macrocytosis
Answer: D. Low serum ferritin
Iron deficiency anemia is characterized by decreased ferritin,
reflecting depleted iron stores. Microcytic hypochromic red
blood cells are typically present.
Question 5
A patient with chronic alcoholism develops confusion,
ophthalmoplegia, and ataxia.
Which vitamin deficiency is responsible?
A. Vitamin B6
B. Vitamin B12
C. Folate
, D. Vitamin C
E. Thiamine (Vitamin B1)
Answer: E. Thiamine (Vitamin B1)
The triad of confusion, ophthalmoplegia, and ataxia describes
Wernicke encephalopathy, caused by thiamine deficiency,
commonly associated with alcoholism.
Question 6
A newborn develops severe jaundice shortly after birth.
Laboratory studies show elevated unconjugated bilirubin.
Which enzyme deficiency is most likely?
A. Ornithine transcarbamylase
B. Phenylalanine hydroxylase
C. UDP-glucuronosyltransferase
D. Hexokinase
E. Galactokinase
Answer: C. UDP-glucuronosyltransferase
Deficiency of UDP-glucuronosyltransferase impairs bilirubin
conjugation, resulting in unconjugated hyperbilirubinemia as
seen in Crigler-Najjar syndrome.
Question 7
A patient has hypercalcemia due to primary
hyperparathyroidism.
Which effect is expected?
Browser Testing Standard; Videos) (2026
Edition): Comprehensive Multiple-Choice
Questions, Answers, and Detailed Rationales
Question 1
A 6-year-old boy has recurrent respiratory infections and
steatorrhea. Genetic testing reveals a mutation affecting
chloride transport across epithelial membranes.
Which protein is defective?
A. Dystrophin
B. Fibrillin-1
C. CFTR
D. Spectrin
E. Ankyrin
Answer: C. CFTR
CFTR is a chloride channel found in epithelial cells. Mutations
cause cystic fibrosis, leading to thick secretions, recurrent
pulmonary infections, pancreatic insufficiency, and
malabsorption. The disease is inherited in an autosomal
recessive pattern.
Question 2
,A researcher administers a drug that selectively blocks
voltage-gated sodium channels.
Which phase of the neuronal action potential is most directly
affected?
A. Hyperpolarization
B. Resting membrane potential
C. Repolarization
D. Depolarization
E. Synaptic vesicle release
Answer: D. Depolarization
Voltage-gated sodium channels open during depolarization,
allowing rapid sodium influx. Blocking these channels
prevents initiation and propagation of action potentials.
Question 3
A patient develops weakness after prolonged corticosteroid
therapy. Muscle biopsy shows atrophy of fast-twitch fibers.
Which mechanism best explains this finding?
A. Increased protein synthesis
B. Increased glycogen storage
C. Enhanced protein catabolism
D. Increased calcium uptake
E. Enhanced mitochondrial proliferation
Answer: C. Enhanced protein catabolism
,Glucocorticoids stimulate protein breakdown, particularly in
skeletal muscle, leading to proximal muscle weakness and
muscle wasting.
Question 4
A 48-year-old woman presents with fatigue and pallor.
Laboratory studies reveal microcytic hypochromic anemia.
Which laboratory finding is most likely?
A. Increased ferritin
B. Increased transferrin saturation
C. Elevated vitamin B12
D. Low serum ferritin
E. Macrocytosis
Answer: D. Low serum ferritin
Iron deficiency anemia is characterized by decreased ferritin,
reflecting depleted iron stores. Microcytic hypochromic red
blood cells are typically present.
Question 5
A patient with chronic alcoholism develops confusion,
ophthalmoplegia, and ataxia.
Which vitamin deficiency is responsible?
A. Vitamin B6
B. Vitamin B12
C. Folate
, D. Vitamin C
E. Thiamine (Vitamin B1)
Answer: E. Thiamine (Vitamin B1)
The triad of confusion, ophthalmoplegia, and ataxia describes
Wernicke encephalopathy, caused by thiamine deficiency,
commonly associated with alcoholism.
Question 6
A newborn develops severe jaundice shortly after birth.
Laboratory studies show elevated unconjugated bilirubin.
Which enzyme deficiency is most likely?
A. Ornithine transcarbamylase
B. Phenylalanine hydroxylase
C. UDP-glucuronosyltransferase
D. Hexokinase
E. Galactokinase
Answer: C. UDP-glucuronosyltransferase
Deficiency of UDP-glucuronosyltransferase impairs bilirubin
conjugation, resulting in unconjugated hyperbilirubinemia as
seen in Crigler-Najjar syndrome.
Question 7
A patient has hypercalcemia due to primary
hyperparathyroidism.
Which effect is expected?
