Comprehensive Osteopathic Medical
Licensing Examination of the United
States (COMLEX-USA) Level 1
Comprehensive Practice Examination
1. A 24-year-old man presents with fever, sore throat, and posterior cervical
lymphadenopathy. A heterophile antibody test is positive. Which organism
is responsible?
A. Cytomegalovirus
B. Epstein-Barr virus
C. Adenovirus
D. Herpes simplex virus
Answer: Epstein-Barr virus
Rationale: Epstein-Barr virus causes infectious mononucleosis, characterized by
fever, pharyngitis, posterior cervical lymphadenopathy, and a positive
heterophile antibody (Monospot) test.
2. Which cranial nerve is primarily responsible for sensation over the anterior
two-thirds of the tongue?
A. Glossopharyngeal nerve
B. Facial nerve via chorda tympani
,C. Trigeminal nerve (V3)
D. Hypoglossal nerve
Answer: Trigeminal nerve (V3)
Rationale: General sensation from the anterior two-thirds of the tongue is
supplied by the lingual nerve, a branch of CN V3. Taste is supplied by the chorda
tympani of CN VII.
3. A patient develops hypercalcemia due to excessive secretion of parathyroid
hormone. Which cells normally secrete this hormone?
A. Chief cells
B. Oxyphil cells
C. Follicular cells
D. Parafollicular cells
Answer: Chief cells
Rationale: Chief cells of the parathyroid glands produce parathyroid hormone
(PTH), which increases serum calcium concentration.
4. Which enzyme converts angiotensin I to angiotensin II?
A. Renin
B. Angiotensin-converting enzyme
C. Aldosterone synthase
D. Cathepsin D
Answer: Angiotensin-converting enzyme
Rationale: ACE converts angiotensin I into angiotensin II, a potent
vasoconstrictor that stimulates aldosterone secretion.
, 5. A deficiency of vitamin C most directly impairs which process?
A. DNA synthesis
B. Hydroxylation of collagen
C. Fat absorption
D. Coagulation factor activation
Answer: Hydroxylation of collagen
Rationale: Vitamin C is required for hydroxylation of proline and lysine residues
during collagen synthesis.
6. Which type of hypersensitivity reaction is mediated by IgE?
A. Type I
B. Type II
C. Type III
D. Type IV
Answer: Type I
Rationale: Type I hypersensitivity reactions are immediate allergic reactions
mediated by IgE antibodies and mast cell degranulation.
7. The sinoatrial node is primarily supplied by which coronary artery in most
individuals?
A. Left anterior descending artery
B. Right coronary artery
C. Circumflex artery
D. Posterior descending artery
Answer: Right coronary artery
, Rationale: The SA node receives blood supply from the right coronary artery in
approximately 60% of people.
8. Which electrolyte abnormality is most likely to produce peaked T waves on
ECG?
A. Hypokalemia
B. Hyperkalemia
C. Hypercalcemia
D. Hypocalcemia
Answer: Hyperkalemia
Rationale: Hyperkalemia classically causes tall peaked T waves and can progress
to widened QRS complexes and arrhythmias.
9. Which nephron segment is impermeable to water?
A. Proximal convoluted tubule
B. Thin descending limb
C. Thick ascending limb
D. Collecting duct under ADH
Answer: Thick ascending limb
Rationale: The thick ascending limb actively reabsorbs sodium, potassium, and
chloride but is impermeable to water.
10.A patient with chronic alcohol use develops confusion, ophthalmoplegia,
and ataxia. Which vitamin deficiency is responsible?
A. Vitamin B6
B. Vitamin B12
Licensing Examination of the United
States (COMLEX-USA) Level 1
Comprehensive Practice Examination
1. A 24-year-old man presents with fever, sore throat, and posterior cervical
lymphadenopathy. A heterophile antibody test is positive. Which organism
is responsible?
A. Cytomegalovirus
B. Epstein-Barr virus
C. Adenovirus
D. Herpes simplex virus
Answer: Epstein-Barr virus
Rationale: Epstein-Barr virus causes infectious mononucleosis, characterized by
fever, pharyngitis, posterior cervical lymphadenopathy, and a positive
heterophile antibody (Monospot) test.
2. Which cranial nerve is primarily responsible for sensation over the anterior
two-thirds of the tongue?
A. Glossopharyngeal nerve
B. Facial nerve via chorda tympani
,C. Trigeminal nerve (V3)
D. Hypoglossal nerve
Answer: Trigeminal nerve (V3)
Rationale: General sensation from the anterior two-thirds of the tongue is
supplied by the lingual nerve, a branch of CN V3. Taste is supplied by the chorda
tympani of CN VII.
3. A patient develops hypercalcemia due to excessive secretion of parathyroid
hormone. Which cells normally secrete this hormone?
A. Chief cells
B. Oxyphil cells
C. Follicular cells
D. Parafollicular cells
Answer: Chief cells
Rationale: Chief cells of the parathyroid glands produce parathyroid hormone
(PTH), which increases serum calcium concentration.
4. Which enzyme converts angiotensin I to angiotensin II?
A. Renin
B. Angiotensin-converting enzyme
C. Aldosterone synthase
D. Cathepsin D
Answer: Angiotensin-converting enzyme
Rationale: ACE converts angiotensin I into angiotensin II, a potent
vasoconstrictor that stimulates aldosterone secretion.
, 5. A deficiency of vitamin C most directly impairs which process?
A. DNA synthesis
B. Hydroxylation of collagen
C. Fat absorption
D. Coagulation factor activation
Answer: Hydroxylation of collagen
Rationale: Vitamin C is required for hydroxylation of proline and lysine residues
during collagen synthesis.
6. Which type of hypersensitivity reaction is mediated by IgE?
A. Type I
B. Type II
C. Type III
D. Type IV
Answer: Type I
Rationale: Type I hypersensitivity reactions are immediate allergic reactions
mediated by IgE antibodies and mast cell degranulation.
7. The sinoatrial node is primarily supplied by which coronary artery in most
individuals?
A. Left anterior descending artery
B. Right coronary artery
C. Circumflex artery
D. Posterior descending artery
Answer: Right coronary artery
, Rationale: The SA node receives blood supply from the right coronary artery in
approximately 60% of people.
8. Which electrolyte abnormality is most likely to produce peaked T waves on
ECG?
A. Hypokalemia
B. Hyperkalemia
C. Hypercalcemia
D. Hypocalcemia
Answer: Hyperkalemia
Rationale: Hyperkalemia classically causes tall peaked T waves and can progress
to widened QRS complexes and arrhythmias.
9. Which nephron segment is impermeable to water?
A. Proximal convoluted tubule
B. Thin descending limb
C. Thick ascending limb
D. Collecting duct under ADH
Answer: Thick ascending limb
Rationale: The thick ascending limb actively reabsorbs sodium, potassium, and
chloride but is impermeable to water.
10.A patient with chronic alcohol use develops confusion, ophthalmoplegia,
and ataxia. Which vitamin deficiency is responsible?
A. Vitamin B6
B. Vitamin B12
