COMSAE PHASE 1 FORM 114 EXAM PRACTICE | ADVANCED STUDY GUIDE |
COMPREHENSIVE TESTBANK | PRACTICE QUESTIONS & ANSWERS | LATEST UPDATE
2026/2027
i. Gross Anatomy, Embryology, and Histology
ii. Biochemistry, Genetics, and Molecular Biology
iii. Physiology and Pathophysiology
iv. Microbiology, Immunology, and Infectious Disease
v. Pharmacology and Therapeutics
vi. Behavioral Science, Ethics, and Biostatistics
vii. Integrated Clinical and Foundational Science Applications
INTRODUCTION
This comprehensive COMSAE Phase 1 Form 114 practice set is designed to reinforce
foundational biomedical science concepts through integrated, clinically oriented
questions. The material emphasizes mechanisms, interpretation of findings,
pathophysiologic reasoning, pharmacologic principles, microbiology, anatomy,
physiology, genetics, immunology, and evidence-based decision-making. Questions are
intentionally written at an advanced level, requiring students to connect multiple
disciplines rather than rely on isolated factual recall. The set is intended as study
material and is not a reproduction of COMSAE or NBOME examination content.
Students should expect challenging clinical vignettes, mechanism-based reasoning,
laboratory interpretation, and carefully constructed distractors resembling the level of
reasoning expected in advanced medical education.
Question 1
A 24-year-old woman develops severe diarrhea after completing a course of broad-
spectrum antibiotics. Colonoscopy demonstrates raised yellow-white plaques overlying
an inflamed colonic mucosa. The responsible organism produces toxins that disrupt
cytoskeletal regulation by modifying intracellular signaling proteins. Which cellular
process is most directly impaired by this toxin?
A. Ribosomal translocation during protein synthesis
B. Actin cytoskeletal organization and tight-junction integrity
C. DNA replication through inhibition of DNA gyrase
D. Peptidoglycan cross-linking in the bacterial cell wall
,🔴 Correct Answer: B. Actin cytoskeletal organization and tight-junction integrity.
🔵 Explanation: The toxins produced by Clostridioides difficile inactivate Rho-family
GTPases, disrupting actin organization and epithelial barrier function. This produces
mucosal injury and the characteristic pseudomembranous colitis.
Question 2
A newborn develops profound hypoglycemia, lactic acidosis, hyperuricemia, and
hepatomegaly. Laboratory studies demonstrate markedly impaired conversion of
glucose-6-phosphate into free glucose. Which additional finding is most likely?
A. Increased fasting ketogenesis
B. Decreased glycogen storage
C. Increased glycogen and triglyceride accumulation in hepatocytes
D. Increased renal glucose excretion despite normal serum glucose
🔴 Correct Answer: C. Increased glycogen and triglyceride accumulation in
hepatocytes.
🔵 Explanation: Glucose-6-phosphatase deficiency causes glycogen storage disease type
I. Glucose-6-phosphate accumulates and is diverted toward glycogen synthesis, glycolysis,
and lipogenesis, producing hepatomegaly, hypoglycemia, lactic acidosis, and
hyperlipidemia.
Question 3
A patient with a lesion affecting the left medial frontal lobe has difficulty initiating
voluntary movement of the right lower extremity. The upper extremity is relatively
preserved. Which cortical region is most likely involved?
A. Lateral precentral gyrus
B. Medial precentral gyrus
C. Superior temporal gyrus
D. Lateral postcentral gyrus
🔴 Correct Answer: B. Medial precentral gyrus.
🔵 Explanation: The medial portion of the primary motor cortex contains the cortical
representation of the contralateral lower extremity. A lesion in this region therefore
preferentially affects voluntary movement of the opposite leg.
Question 4
,A 58-year-old man develops polyuria and intense thirst after undergoing neurosurgery
near the hypothalamus. His serum sodium concentration is elevated, and urine
osmolality remains very low despite increasing plasma osmolality. Administration of
desmopressin markedly increases urine concentration. Which renal change normally
mediates the action of the missing hormone?
A. Increased sodium reabsorption through ENaC
B. Increased aquaporin-2 insertion into collecting duct principal cells
C. Increased bicarbonate reabsorption in proximal tubules
D. Increased calcium reabsorption in the thick ascending limb
🔴 Correct Answer: B. Increased aquaporin-2 insertion into collecting duct principal
cells.
🔵 Explanation: Central diabetes insipidus results from deficient antidiuretic hormone
secretion. ADH normally activates V2 receptors, increasing cAMP and promoting
aquaporin-2 insertion into collecting duct membranes, thereby increasing water
reabsorption.
Question 5
A 6-year-old boy has recurrent bacterial respiratory infections and markedly decreased
serum concentrations of multiple immunoglobulin classes. Flow cytometry
demonstrates an absence of mature B cells. Which genetic defect best explains this
presentation?
A. Defective CD40 ligand expression
B. Defective Bruton's tyrosine kinase signaling
C. Defective adenosine deaminase activity
D. Defective NADPH oxidase activity
🔴 Correct Answer: B. Defective Bruton's tyrosine kinase signaling.
🔵 Explanation: X-linked agammaglobulinemia results from defective Bruton's tyrosine
kinase, which prevents maturation of B-cell precursors. Patients consequently have very
low immunoglobulin levels and recurrent infections with encapsulated organisms.
Question 6
A patient receives a competitive antagonist of a receptor normally activated by a
neurotransmitter. Increasing the concentration of the neurotransmitter eventually
, produces the same maximal response as before treatment. Which pharmacologic
change has occurred?
A. Decreased efficacy with unchanged potency
B. Decreased potency with unchanged efficacy
C. Increased efficacy with decreased potency
D. Irreversible receptor blockade
🔴 Correct Answer: B. Decreased potency with unchanged efficacy.
🔵 Explanation: A competitive antagonist shifts the agonist dose-response curve to the
right without changing the maximal response. More agonist is required to produce the
same effect, indicating decreased potency but preserved efficacy.
Question 7
A pregnant woman presents with vaginal bleeding and abdominal cramping at 9
weeks' gestation. Serum β-hCG concentrations are substantially lower than expected
for gestational age, and ultrasound shows no viable intrauterine pregnancy. Which
hormone is normally responsible for maintaining the corpus luteum during the early
first trimester?
A. Follicle-stimulating hormone
B. Luteinizing hormone
C. Human chorionic gonadotropin
D. Human placental lactogen
🔴 Correct Answer: C. Human chorionic gonadotropin.
🔵 Explanation: Early in pregnancy, hCG produced by syncytiotrophoblasts maintains the
corpus luteum, allowing continued progesterone production until placental
steroidogenesis becomes sufficient.
Question 8
A patient develops hemolytic anemia after receiving an oxidant medication. Peripheral
smear demonstrates bite cells and Heinz bodies. Which metabolic pathway is primarily
responsible for protecting the patient's erythrocytes from this oxidative injury?
A. Conversion of pyruvate to lactate
B. Production of NADPH through the pentose phosphate pathway
C. Generation of FADH₂ through the citric acid cycle
D. Oxidative phosphorylation through mitochondrial complexes
COMPREHENSIVE TESTBANK | PRACTICE QUESTIONS & ANSWERS | LATEST UPDATE
2026/2027
i. Gross Anatomy, Embryology, and Histology
ii. Biochemistry, Genetics, and Molecular Biology
iii. Physiology and Pathophysiology
iv. Microbiology, Immunology, and Infectious Disease
v. Pharmacology and Therapeutics
vi. Behavioral Science, Ethics, and Biostatistics
vii. Integrated Clinical and Foundational Science Applications
INTRODUCTION
This comprehensive COMSAE Phase 1 Form 114 practice set is designed to reinforce
foundational biomedical science concepts through integrated, clinically oriented
questions. The material emphasizes mechanisms, interpretation of findings,
pathophysiologic reasoning, pharmacologic principles, microbiology, anatomy,
physiology, genetics, immunology, and evidence-based decision-making. Questions are
intentionally written at an advanced level, requiring students to connect multiple
disciplines rather than rely on isolated factual recall. The set is intended as study
material and is not a reproduction of COMSAE or NBOME examination content.
Students should expect challenging clinical vignettes, mechanism-based reasoning,
laboratory interpretation, and carefully constructed distractors resembling the level of
reasoning expected in advanced medical education.
Question 1
A 24-year-old woman develops severe diarrhea after completing a course of broad-
spectrum antibiotics. Colonoscopy demonstrates raised yellow-white plaques overlying
an inflamed colonic mucosa. The responsible organism produces toxins that disrupt
cytoskeletal regulation by modifying intracellular signaling proteins. Which cellular
process is most directly impaired by this toxin?
A. Ribosomal translocation during protein synthesis
B. Actin cytoskeletal organization and tight-junction integrity
C. DNA replication through inhibition of DNA gyrase
D. Peptidoglycan cross-linking in the bacterial cell wall
,🔴 Correct Answer: B. Actin cytoskeletal organization and tight-junction integrity.
🔵 Explanation: The toxins produced by Clostridioides difficile inactivate Rho-family
GTPases, disrupting actin organization and epithelial barrier function. This produces
mucosal injury and the characteristic pseudomembranous colitis.
Question 2
A newborn develops profound hypoglycemia, lactic acidosis, hyperuricemia, and
hepatomegaly. Laboratory studies demonstrate markedly impaired conversion of
glucose-6-phosphate into free glucose. Which additional finding is most likely?
A. Increased fasting ketogenesis
B. Decreased glycogen storage
C. Increased glycogen and triglyceride accumulation in hepatocytes
D. Increased renal glucose excretion despite normal serum glucose
🔴 Correct Answer: C. Increased glycogen and triglyceride accumulation in
hepatocytes.
🔵 Explanation: Glucose-6-phosphatase deficiency causes glycogen storage disease type
I. Glucose-6-phosphate accumulates and is diverted toward glycogen synthesis, glycolysis,
and lipogenesis, producing hepatomegaly, hypoglycemia, lactic acidosis, and
hyperlipidemia.
Question 3
A patient with a lesion affecting the left medial frontal lobe has difficulty initiating
voluntary movement of the right lower extremity. The upper extremity is relatively
preserved. Which cortical region is most likely involved?
A. Lateral precentral gyrus
B. Medial precentral gyrus
C. Superior temporal gyrus
D. Lateral postcentral gyrus
🔴 Correct Answer: B. Medial precentral gyrus.
🔵 Explanation: The medial portion of the primary motor cortex contains the cortical
representation of the contralateral lower extremity. A lesion in this region therefore
preferentially affects voluntary movement of the opposite leg.
Question 4
,A 58-year-old man develops polyuria and intense thirst after undergoing neurosurgery
near the hypothalamus. His serum sodium concentration is elevated, and urine
osmolality remains very low despite increasing plasma osmolality. Administration of
desmopressin markedly increases urine concentration. Which renal change normally
mediates the action of the missing hormone?
A. Increased sodium reabsorption through ENaC
B. Increased aquaporin-2 insertion into collecting duct principal cells
C. Increased bicarbonate reabsorption in proximal tubules
D. Increased calcium reabsorption in the thick ascending limb
🔴 Correct Answer: B. Increased aquaporin-2 insertion into collecting duct principal
cells.
🔵 Explanation: Central diabetes insipidus results from deficient antidiuretic hormone
secretion. ADH normally activates V2 receptors, increasing cAMP and promoting
aquaporin-2 insertion into collecting duct membranes, thereby increasing water
reabsorption.
Question 5
A 6-year-old boy has recurrent bacterial respiratory infections and markedly decreased
serum concentrations of multiple immunoglobulin classes. Flow cytometry
demonstrates an absence of mature B cells. Which genetic defect best explains this
presentation?
A. Defective CD40 ligand expression
B. Defective Bruton's tyrosine kinase signaling
C. Defective adenosine deaminase activity
D. Defective NADPH oxidase activity
🔴 Correct Answer: B. Defective Bruton's tyrosine kinase signaling.
🔵 Explanation: X-linked agammaglobulinemia results from defective Bruton's tyrosine
kinase, which prevents maturation of B-cell precursors. Patients consequently have very
low immunoglobulin levels and recurrent infections with encapsulated organisms.
Question 6
A patient receives a competitive antagonist of a receptor normally activated by a
neurotransmitter. Increasing the concentration of the neurotransmitter eventually
, produces the same maximal response as before treatment. Which pharmacologic
change has occurred?
A. Decreased efficacy with unchanged potency
B. Decreased potency with unchanged efficacy
C. Increased efficacy with decreased potency
D. Irreversible receptor blockade
🔴 Correct Answer: B. Decreased potency with unchanged efficacy.
🔵 Explanation: A competitive antagonist shifts the agonist dose-response curve to the
right without changing the maximal response. More agonist is required to produce the
same effect, indicating decreased potency but preserved efficacy.
Question 7
A pregnant woman presents with vaginal bleeding and abdominal cramping at 9
weeks' gestation. Serum β-hCG concentrations are substantially lower than expected
for gestational age, and ultrasound shows no viable intrauterine pregnancy. Which
hormone is normally responsible for maintaining the corpus luteum during the early
first trimester?
A. Follicle-stimulating hormone
B. Luteinizing hormone
C. Human chorionic gonadotropin
D. Human placental lactogen
🔴 Correct Answer: C. Human chorionic gonadotropin.
🔵 Explanation: Early in pregnancy, hCG produced by syncytiotrophoblasts maintains the
corpus luteum, allowing continued progesterone production until placental
steroidogenesis becomes sufficient.
Question 8
A patient develops hemolytic anemia after receiving an oxidant medication. Peripheral
smear demonstrates bite cells and Heinz bodies. Which metabolic pathway is primarily
responsible for protecting the patient's erythrocytes from this oxidative injury?
A. Conversion of pyruvate to lactate
B. Production of NADPH through the pentose phosphate pathway
C. Generation of FADH₂ through the citric acid cycle
D. Oxidative phosphorylation through mitochondrial complexes
