COMSAE Phase 1 – ASA 107i Style
Practice Questions and answers with
detailedrationles
Master COMSAE Phase 1 with 150 original board-style practice questions, verified answers, and
detailed rationales covering high-yield topics, OMM, and foundational sciences for comprehensive
COMLEX-USA Level 1 preparation.
1.
A 23-year-old woman develops fatigue, heat intolerance, weight loss, and palpitations. Laboratory
studies reveal elevated free T4 and suppressed TSH. Which mechanism best explains her disease?
A. Destruction of thyroid follicles by cytotoxic T cells
B. Autoantibodies stimulating the TSH receptor
C. Pituitary adenoma secreting TSH
D. Defective thyroid peroxidase
E. Excess calcitonin secretion
Answer: B
Rationale: Graves disease is caused by thyroid-stimulating immunoglobulins that activate the TSH
receptor, producing hyperthyroidism.
2.
A patient with bacterial meningitis is treated with ceftriaxone. Ceftriaxone primarily acts by
inhibiting:
A. DNA gyrase
B. Protein synthesis
C. Peptidoglycan cross-linking
D. RNA polymerase
E. Folate synthesis
Answer: C
Rationale: Third-generation cephalosporins inhibit bacterial cell-wall synthesis by binding penicillin-
binding proteins.
3.
,A mutation causes red blood cells to become sickle shaped during hypoxia. Which amino acid
substitution is responsible?
A. Glycine → Valine
B. Glutamic acid → Valine
C. Lysine → Arginine
D. Histidine → Glycine
E. Aspartic acid → Alanine
Answer: B
Rationale: Sickle cell disease results from substitution of valine for glutamic acid at the sixth position
of the β-globin chain.
4.
A patient develops weakness after prolonged corticosteroid therapy. Which pituitary hormone is
expected to be suppressed?
A. Growth hormone
B. Prolactin
C. ACTH
D. FSH
E. LH
Answer: C
Rationale: Exogenous glucocorticoids suppress hypothalamic CRH and pituitary ACTH secretion
through negative feedback.
5.
Which cranial nerve carries parasympathetic fibres responsible for pupillary constriction?
A. CN II
B. CN III
C. CN IV
D. CN V
E. CN VI
Answer: B
Rationale: The oculomotor nerve carries parasympathetic fibres from the Edinger–Westphal nucleus
to the sphincter pupillae muscle.
,6.
A patient has an elevated anion gap metabolic acidosis due to diabetic ketoacidosis. Which
compensatory change is expected?
A. Increased bicarbonate retention
B. Increased PaCO₂
C. Decreased PaCO₂ due to hyperventilation
D. Respiratory acidosis
E. Increased aldosterone secretion
Answer: C
Rationale: Respiratory compensation occurs through hyperventilation (Kussmaul respirations),
lowering PaCO₂.
7.
A child has recurrent Neisseria infections due to deficiency of which complement component?
A. C1 inhibitor
B. C3
C. C5–C9
D. Factor B
E. Properdin
Answer: C
Rationale: Deficiency of the membrane attack complex (C5–C9) predisposes patients to recurrent
Neisseria infections.
8.
Restriction of the right thoracic diaphragm is most likely associated with dysfunction involving which
spinal levels?
A. C1–C3
B. C4–C5
C. C3–C5
D. T6–T8
E. L1–L3
, Answer: C
Rationale: The diaphragm receives motor innervation from the phrenic nerve (C3–C5), making these
segments important in osteopathic evaluation.
9.
Which cardiac action potential phase is primarily mediated by rapid sodium influx?
A. Phase 1
B. Phase 0
C. Phase 2
D. Phase 3
E. Phase 4
Answer: B
Rationale: Phase 0 depolarisation in ventricular myocytes results from rapid opening of fast voltage-
gated sodium channels.
10.
A researcher administers a drug that competitively inhibits an enzyme. Which kinetic change is
expected?
A. Decreased Vmax
B. Increased Km with unchanged Vmax
C. Increased Vmax
D. Decreased Km
E. No change in Km or Vmax
Answer: B
Rationale: Competitive inhibitors increase the apparent Km because more substrate is needed to
achieve half-maximal velocity, while Vmax remains unchanged.
11.
A 45-year-old man with long-standing hypertension develops concentric left ventricular hypertrophy.
Which cellular adaptation is primarily responsible?
A. Hyperplasia
B. Hypertrophy
C. Metaplasia
D. Dysplasia
E. Atrophy
Practice Questions and answers with
detailedrationles
Master COMSAE Phase 1 with 150 original board-style practice questions, verified answers, and
detailed rationales covering high-yield topics, OMM, and foundational sciences for comprehensive
COMLEX-USA Level 1 preparation.
1.
A 23-year-old woman develops fatigue, heat intolerance, weight loss, and palpitations. Laboratory
studies reveal elevated free T4 and suppressed TSH. Which mechanism best explains her disease?
A. Destruction of thyroid follicles by cytotoxic T cells
B. Autoantibodies stimulating the TSH receptor
C. Pituitary adenoma secreting TSH
D. Defective thyroid peroxidase
E. Excess calcitonin secretion
Answer: B
Rationale: Graves disease is caused by thyroid-stimulating immunoglobulins that activate the TSH
receptor, producing hyperthyroidism.
2.
A patient with bacterial meningitis is treated with ceftriaxone. Ceftriaxone primarily acts by
inhibiting:
A. DNA gyrase
B. Protein synthesis
C. Peptidoglycan cross-linking
D. RNA polymerase
E. Folate synthesis
Answer: C
Rationale: Third-generation cephalosporins inhibit bacterial cell-wall synthesis by binding penicillin-
binding proteins.
3.
,A mutation causes red blood cells to become sickle shaped during hypoxia. Which amino acid
substitution is responsible?
A. Glycine → Valine
B. Glutamic acid → Valine
C. Lysine → Arginine
D. Histidine → Glycine
E. Aspartic acid → Alanine
Answer: B
Rationale: Sickle cell disease results from substitution of valine for glutamic acid at the sixth position
of the β-globin chain.
4.
A patient develops weakness after prolonged corticosteroid therapy. Which pituitary hormone is
expected to be suppressed?
A. Growth hormone
B. Prolactin
C. ACTH
D. FSH
E. LH
Answer: C
Rationale: Exogenous glucocorticoids suppress hypothalamic CRH and pituitary ACTH secretion
through negative feedback.
5.
Which cranial nerve carries parasympathetic fibres responsible for pupillary constriction?
A. CN II
B. CN III
C. CN IV
D. CN V
E. CN VI
Answer: B
Rationale: The oculomotor nerve carries parasympathetic fibres from the Edinger–Westphal nucleus
to the sphincter pupillae muscle.
,6.
A patient has an elevated anion gap metabolic acidosis due to diabetic ketoacidosis. Which
compensatory change is expected?
A. Increased bicarbonate retention
B. Increased PaCO₂
C. Decreased PaCO₂ due to hyperventilation
D. Respiratory acidosis
E. Increased aldosterone secretion
Answer: C
Rationale: Respiratory compensation occurs through hyperventilation (Kussmaul respirations),
lowering PaCO₂.
7.
A child has recurrent Neisseria infections due to deficiency of which complement component?
A. C1 inhibitor
B. C3
C. C5–C9
D. Factor B
E. Properdin
Answer: C
Rationale: Deficiency of the membrane attack complex (C5–C9) predisposes patients to recurrent
Neisseria infections.
8.
Restriction of the right thoracic diaphragm is most likely associated with dysfunction involving which
spinal levels?
A. C1–C3
B. C4–C5
C. C3–C5
D. T6–T8
E. L1–L3
, Answer: C
Rationale: The diaphragm receives motor innervation from the phrenic nerve (C3–C5), making these
segments important in osteopathic evaluation.
9.
Which cardiac action potential phase is primarily mediated by rapid sodium influx?
A. Phase 1
B. Phase 0
C. Phase 2
D. Phase 3
E. Phase 4
Answer: B
Rationale: Phase 0 depolarisation in ventricular myocytes results from rapid opening of fast voltage-
gated sodium channels.
10.
A researcher administers a drug that competitively inhibits an enzyme. Which kinetic change is
expected?
A. Decreased Vmax
B. Increased Km with unchanged Vmax
C. Increased Vmax
D. Decreased Km
E. No change in Km or Vmax
Answer: B
Rationale: Competitive inhibitors increase the apparent Km because more substrate is needed to
achieve half-maximal velocity, while Vmax remains unchanged.
11.
A 45-year-old man with long-standing hypertension develops concentric left ventricular hypertrophy.
Which cellular adaptation is primarily responsible?
A. Hyperplasia
B. Hypertrophy
C. Metaplasia
D. Dysplasia
E. Atrophy
