COMSAE PHASE 1 FORM 104 EXAM with
Questions and Answers/Plus a Rationale Updated
2026 A+/Instant Download PDF
EXAM COVERAGE
1. Osteopathic Principles and Practice (OPP) and Osteopathic Manipulative Treatment (OMT)
2. Foundational Biomedical Sciences: Anatomy and Embryology
3. Physiology and Pathophysiology
4. Pharmacology and Toxicology
5. Pathology and Pathobiology
6. Microbiology and Immunology
7. Biochemistry, Molecular Biology, and Genetics
8. Behavioral Science, Public Health, and Biostatistics
1. A 45-year-old male presents with chronic lower back pain. Physical examination reveals an
apparent short left leg, a left posterior superior iliac spine (PSIS) that is superior compared to the
right, and a sacral diagnosis reflecting a left-on-left sacral torsion. Which of the following
describes the axis about which the L5 vertebrae must rotate in this condition to compensate
according to Type II mechanics?
A. A rotation of L5 occurs in the opposite direction of sacral sidebending
B. A rotation of L5 occurs in the same direction as sacral rotation
C. A rotation of L5 occurs in the same direction as sacral sidebending
D. A rotation of L5 occurs about a vertical axis independent of sacral axes
, CORRECT ANSWER : A
Rationale: In a forward sacral torsion (such as left-on-left), the L5 vertebra rotates in the
direction opposite to the sacral rotation to maintain visual level horizons and posture, following
type II-like mechanics at the lumbosacral junction where sidebending and rotation are coupled
in the same direction for individual segments. Options B, C, and D misstate the specific coupling
mechanics and axes of the lumbosacral junction during sacral torsions.
2. A 62-year-old male with long-standing poorly controlled hypertension presents for a routine
checkup. Echocardiography demonstrates concentric left ventricular hypertrophy. Which cellular
adaptation mechanism is primarily responsible for the increase in myocardial wall thickness?
A. Hyperplasia of cardiac myocytes
B. Hypertrophy of existing cardiac myocytes
C. Metaplasia of cardiac connective tissue
D. Apoptosis of subendocardial muscle fibers
CORRECT ANSWER : B
Rationale: Adult cardiac myocytes are terminally differentiated cells with a very limited capacity
to divide; therefore, an increased functional load results in cellular enlargement (hypertrophy)
via increased protein synthesis rather than cell division (hyperplasia). Metaplasia involves the
reversible replacement of one adult cell type by another, and apoptosis refers to programmed
cell death, neither of which explains the adaptive response to increased afterload.
3. A researcher is studying enzyme kinetics and designs an experiment using a competitive
inhibitor. Which of the following parameters of the Michaelis-Menten enzyme kinetics will be
altered in the presence of a competitive inhibitor?
A. Maximal velocity ($V_{max}$) is decreased
B. Michaelis constant ($K_m$) is increased
C. Both $V_{max}$ and $K_m$ are decreased
D. Neither $V_{max}$ nor $K_m$ is affected
CORRECT ANSWER : B
Rationale: A competitive inhibitor binds reversibly to the active site of the enzyme, competing
with the substrate. This increases the apparent $K_m$ (requiring a higher substrate
concentration to reach half-maximal velocity) while leaving $V_{max}$ unchanged because high
concentrations of substrate can outcompete the inhibitor.
,4. A 28-year-old female at 32 weeks gestation presents with painful uterine contractions. She is
administered a tocolytic medication that acts as a beta-2 adrenergic receptor agonist. Which of
the following intracellular signaling pathways is directly activated by this drug to achieve uterine
relaxation?
A. Activation of phospholipase C and increased intracellular calcium
B. Stimulation of adenylate cyclase and increased cyclic AMP (cAMP)
C. Inhibition of protein kinase A and closure of potassium channels
D. Activation of guanylyl cyclase and elevation of cyclic GMP
CORRECT ANSWER : B
Rationale: Beta-2 adrenergic agonists (e.g., terbutaline) couple to Gs proteins, which stimulate
adenylate cyclase, leading to an intracellular increase in cyclic AMP (cAMP). Elevated cAMP
activates protein kinase A, which subsequently phosphorylates and inactivates myosin light-
chain kinase, leading to smooth muscle relaxation. Phospholipase C activation increases
calcium and causes contraction, making options A, C, and D incorrect.
5. A 54-year-old male is evaluated for acute chest pain radiating to his jaw. An electrocardiogram
reveals ST-segment elevations in leads II, III, and aVF. Coronary angiography demonstrates an
occlusion of the right coronary artery. Which anatomic structure is most commonly supplied by
this vessel?
A. Posterior descending artery and the AV node
B. Anterior two-thirds of the interventricular septum
C. Lateral wall of the left ventricle
D. Left bundle branch of the conduction system
CORRECT ANSWER : A
Rationale: In a right-dominant circulation (present in about 85 percent of individuals), the right
coronary artery gives rise to the posterior descending artery (PDA) and supplies the
atrioventricular (AV) node. The anterior two-thirds of the interventricular septum and left
bundle branch are supplied by the left anterior descending artery, while the lateral wall is
supplied by the left circumflex artery.
6. A 3-year-old boy presents with developmental delay, coarse facial features, and restricted joint
mobility. Laboratory evaluation shows elevated lysosomal enzymes in the plasma coupled with
their deficiency within cellular lysosomes. A defect in which of the following post-translational
modifications is responsible for this condition?
, A. Hydroxylation of proline residues
B. Phosphorylation of mannose residues on glycoproteins
C. Gamma-carboxylation of glutamic acid residues
D. Addition of a glycosylphosphatidylinositol anchor
CORRECT ANSWER : B
Rationale: I-cell disease (mucolipidosis II) is caused by a deficiency in N-acetylglucosaminyl-1-
phosphotransferase, which prevents the phosphorylation of mannose residues to form mannose-
6-phosphate on lysosomal enzymes. Without this marker, enzymes are secreted extracellularly
instead of being targeted to lysosomes. The other modifications listed subserve different protein
trafficking and functional roles.
7. A microbiology laboratory isolates a Gram-positive bacillus from a deep puncture wound of a
farm worker. The organism is spore-forming and obligate anaerobic. Production of an exotoxin
with zinc metalloprotease activity results in cleavage of synaptobrevin. Which clinical finding is
characteristic of this condition?
A. Flaccid paralysis due to blockade of acetylcholine release at the neuromuscular junction
B. Spastic paralysis resulting from disinhibition of lower motor neurons
C. Massive exudative enterocolitis with pseudomembrane formation
D. Centripetal ascending paralysis starting from the lower extremities
CORRECT ANSWER : B
Rationale: The organism described is Clostridium tetani, which produces tetanospasmin. This
toxin travels retrogradely to the central nervous system where it blocks the release of inhibitory
neurotransmitters (glycine and gamma-aminobutyric acid) from Renshaw cells, causing
unopposed muscle contraction and spastic paralysis. Clostridium botulinum toxin cleaves
SNARE proteins to cause flaccid paralysis.
8. A 35-year-old male presents with recurrent nephrolithiasis and bone pain. Serum chemistry
reveals hypercalcemia, hypophosphatemia, and elevated parathyroid hormone (PTH) levels.
Which of the following histological findings is most likely to be found in a bone biopsy from this
patient?
A. Thickened bone trabeculae with mosaic patterns of lamellar bone
B. Subperiosteal resorption and osteoclastic bone tunneling (osteitis fibrosa cystica)
Questions and Answers/Plus a Rationale Updated
2026 A+/Instant Download PDF
EXAM COVERAGE
1. Osteopathic Principles and Practice (OPP) and Osteopathic Manipulative Treatment (OMT)
2. Foundational Biomedical Sciences: Anatomy and Embryology
3. Physiology and Pathophysiology
4. Pharmacology and Toxicology
5. Pathology and Pathobiology
6. Microbiology and Immunology
7. Biochemistry, Molecular Biology, and Genetics
8. Behavioral Science, Public Health, and Biostatistics
1. A 45-year-old male presents with chronic lower back pain. Physical examination reveals an
apparent short left leg, a left posterior superior iliac spine (PSIS) that is superior compared to the
right, and a sacral diagnosis reflecting a left-on-left sacral torsion. Which of the following
describes the axis about which the L5 vertebrae must rotate in this condition to compensate
according to Type II mechanics?
A. A rotation of L5 occurs in the opposite direction of sacral sidebending
B. A rotation of L5 occurs in the same direction as sacral rotation
C. A rotation of L5 occurs in the same direction as sacral sidebending
D. A rotation of L5 occurs about a vertical axis independent of sacral axes
, CORRECT ANSWER : A
Rationale: In a forward sacral torsion (such as left-on-left), the L5 vertebra rotates in the
direction opposite to the sacral rotation to maintain visual level horizons and posture, following
type II-like mechanics at the lumbosacral junction where sidebending and rotation are coupled
in the same direction for individual segments. Options B, C, and D misstate the specific coupling
mechanics and axes of the lumbosacral junction during sacral torsions.
2. A 62-year-old male with long-standing poorly controlled hypertension presents for a routine
checkup. Echocardiography demonstrates concentric left ventricular hypertrophy. Which cellular
adaptation mechanism is primarily responsible for the increase in myocardial wall thickness?
A. Hyperplasia of cardiac myocytes
B. Hypertrophy of existing cardiac myocytes
C. Metaplasia of cardiac connective tissue
D. Apoptosis of subendocardial muscle fibers
CORRECT ANSWER : B
Rationale: Adult cardiac myocytes are terminally differentiated cells with a very limited capacity
to divide; therefore, an increased functional load results in cellular enlargement (hypertrophy)
via increased protein synthesis rather than cell division (hyperplasia). Metaplasia involves the
reversible replacement of one adult cell type by another, and apoptosis refers to programmed
cell death, neither of which explains the adaptive response to increased afterload.
3. A researcher is studying enzyme kinetics and designs an experiment using a competitive
inhibitor. Which of the following parameters of the Michaelis-Menten enzyme kinetics will be
altered in the presence of a competitive inhibitor?
A. Maximal velocity ($V_{max}$) is decreased
B. Michaelis constant ($K_m$) is increased
C. Both $V_{max}$ and $K_m$ are decreased
D. Neither $V_{max}$ nor $K_m$ is affected
CORRECT ANSWER : B
Rationale: A competitive inhibitor binds reversibly to the active site of the enzyme, competing
with the substrate. This increases the apparent $K_m$ (requiring a higher substrate
concentration to reach half-maximal velocity) while leaving $V_{max}$ unchanged because high
concentrations of substrate can outcompete the inhibitor.
,4. A 28-year-old female at 32 weeks gestation presents with painful uterine contractions. She is
administered a tocolytic medication that acts as a beta-2 adrenergic receptor agonist. Which of
the following intracellular signaling pathways is directly activated by this drug to achieve uterine
relaxation?
A. Activation of phospholipase C and increased intracellular calcium
B. Stimulation of adenylate cyclase and increased cyclic AMP (cAMP)
C. Inhibition of protein kinase A and closure of potassium channels
D. Activation of guanylyl cyclase and elevation of cyclic GMP
CORRECT ANSWER : B
Rationale: Beta-2 adrenergic agonists (e.g., terbutaline) couple to Gs proteins, which stimulate
adenylate cyclase, leading to an intracellular increase in cyclic AMP (cAMP). Elevated cAMP
activates protein kinase A, which subsequently phosphorylates and inactivates myosin light-
chain kinase, leading to smooth muscle relaxation. Phospholipase C activation increases
calcium and causes contraction, making options A, C, and D incorrect.
5. A 54-year-old male is evaluated for acute chest pain radiating to his jaw. An electrocardiogram
reveals ST-segment elevations in leads II, III, and aVF. Coronary angiography demonstrates an
occlusion of the right coronary artery. Which anatomic structure is most commonly supplied by
this vessel?
A. Posterior descending artery and the AV node
B. Anterior two-thirds of the interventricular septum
C. Lateral wall of the left ventricle
D. Left bundle branch of the conduction system
CORRECT ANSWER : A
Rationale: In a right-dominant circulation (present in about 85 percent of individuals), the right
coronary artery gives rise to the posterior descending artery (PDA) and supplies the
atrioventricular (AV) node. The anterior two-thirds of the interventricular septum and left
bundle branch are supplied by the left anterior descending artery, while the lateral wall is
supplied by the left circumflex artery.
6. A 3-year-old boy presents with developmental delay, coarse facial features, and restricted joint
mobility. Laboratory evaluation shows elevated lysosomal enzymes in the plasma coupled with
their deficiency within cellular lysosomes. A defect in which of the following post-translational
modifications is responsible for this condition?
, A. Hydroxylation of proline residues
B. Phosphorylation of mannose residues on glycoproteins
C. Gamma-carboxylation of glutamic acid residues
D. Addition of a glycosylphosphatidylinositol anchor
CORRECT ANSWER : B
Rationale: I-cell disease (mucolipidosis II) is caused by a deficiency in N-acetylglucosaminyl-1-
phosphotransferase, which prevents the phosphorylation of mannose residues to form mannose-
6-phosphate on lysosomal enzymes. Without this marker, enzymes are secreted extracellularly
instead of being targeted to lysosomes. The other modifications listed subserve different protein
trafficking and functional roles.
7. A microbiology laboratory isolates a Gram-positive bacillus from a deep puncture wound of a
farm worker. The organism is spore-forming and obligate anaerobic. Production of an exotoxin
with zinc metalloprotease activity results in cleavage of synaptobrevin. Which clinical finding is
characteristic of this condition?
A. Flaccid paralysis due to blockade of acetylcholine release at the neuromuscular junction
B. Spastic paralysis resulting from disinhibition of lower motor neurons
C. Massive exudative enterocolitis with pseudomembrane formation
D. Centripetal ascending paralysis starting from the lower extremities
CORRECT ANSWER : B
Rationale: The organism described is Clostridium tetani, which produces tetanospasmin. This
toxin travels retrogradely to the central nervous system where it blocks the release of inhibitory
neurotransmitters (glycine and gamma-aminobutyric acid) from Renshaw cells, causing
unopposed muscle contraction and spastic paralysis. Clostridium botulinum toxin cleaves
SNARE proteins to cause flaccid paralysis.
8. A 35-year-old male presents with recurrent nephrolithiasis and bone pain. Serum chemistry
reveals hypercalcemia, hypophosphatemia, and elevated parathyroid hormone (PTH) levels.
Which of the following histological findings is most likely to be found in a bone biopsy from this
patient?
A. Thickened bone trabeculae with mosaic patterns of lamellar bone
B. Subperiosteal resorption and osteoclastic bone tunneling (osteitis fibrosa cystica)
