NBME Full Solution Pack – Bundled Exams with
Complete Explanations and Answer Keys
Biochemistry Section
Question 1:
A 45-year-old man presents with fatigue and hepatomegaly. Laboratory studies show elevated
AST and ALT. A deficiency of which enzyme is most likely responsible for his condition?
A) Glucose-6-phosphatase
B) Pyruvate dehydrogenase
C) Fructose-1,6-bisphosphatase
D) Carnitine acyltransferase I
Correct Answer: A
Explanation: A deficiency in glucose-6-phosphatase leads to glycogen storage disease type I
(von Gierke disease). This impairs the release of glucose from glycogen, causing hepatomegaly,
hypoglycemia, and elevated liver enzymes (AST, ALT). Pyruvate dehydrogenase deficiency (B)
causes lactic acidosis. Fructose-1,6-bisphosphatase deficiency (C) leads to fructose metabolism
issues. Carnitine acyltransferase I deficiency (D) affects fatty acid oxidation, not glycogen.
Question 2:
A 3-year-old boy has recurrent hypoglycemia and seizures. Laboratory findings show lactic
acidosis and hyperuricemia. Which pathway is most likely affected?
A) Gluconeogenesis
B) Glycolysis
C) Fatty acid oxidation
D) Citric acid cycle
Correct Answer: A
Explanation: The symptoms suggest glycogen storage disease type I (von Gierke), where
gluconeogenesis is impaired due to deficient glucose-6-phosphatase. This leads to
hypoglycemia, lactic acidosis (from accumulated glucose-6-phosphate shunted to glycolysis),
and hyperuricemia (from purine degradation). Glycolysis (B) is intact. Fatty acid oxidation (C) or
citric acid cycle (D) defects cause different metabolic profiles.
Question 3:
A 25-year-old woman has a mutation in the LDL receptor gene. Which condition is most likely?
A) Familial hypercholesterolemia
B) Gaucher disease
C) Tay-Sachs disease
,D) Niemann-Pick disease
Correct Answer: A
Explanation: A mutation in the LDL receptor gene causes familial hypercholesterolemia,
leading to elevated LDL cholesterol and early atherosclerosis. Gaucher (B), Tay-Sachs (C), and
Niemann-Pick (D) involve lysosomal storage defects, not LDL metabolism.
Physiology Section
Question 4:
A 60-year-old man with hypertension has a decreased glomerular filtration rate. Which
mechanism is most likely responsible?
A) Increased afferent arteriole resistance
B) Decreased efferent arteriole resistance
C) Increased glomerular capillary permeability
D) Decreased Bowman’s capsule pressure
Correct Answer: A
Explanation: Increased afferent arteriole resistance, common in hypertension, reduces renal
blood flow and glomerular filtration rate (GFR). Decreased efferent resistance (B) increases
GFR. Increased permeability (C) affects filtration fraction, not GFR directly. Decreased
Bowman’s pressure (D) is less relevant.
Question 5:
A 30-year-old man with asthma has bronchoconstriction. Which receptor is primarily involved?
A) Beta-2 adrenergic
B) Muscarinic M3
C) Histamine H1
D) Alpha-1 adrenergic
Correct Answer: C
Explanation: Histamine H1 receptors mediate bronchoconstriction in asthma via allergic
responses. Beta-2 (A) causes bronchodilation. Muscarinic M3 (B) is involved in parasympathetic
bronchoconstriction. Alpha-1 (D) affects vascular tone.
Pathology Section
Question 6:
A 55-year-old woman with breast cancer has bone pain. A bone scan shows lytic lesions. What
is the most likely mechanism?
A) Osteoclast activation
B) Osteoblast proliferation
, C) Decreased bone mineralization
D) Increased collagen synthesis
Correct Answer: A
Explanation: Breast cancer metastases to bone often cause lytic lesions via osteoclast
activation, driven by tumor-secreted factors like PTHrP. Osteoblast proliferation (B) causes
sclerotic lesions. Decreased mineralization (C) is seen in rickets. Increased collagen (D) is
unrelated.
Question 7:
A 40-year-old man with a history of smoking presents with hemoptysis. A lung biopsy shows
squamous cell carcinoma. Which is the most likely precursor lesion?
A) Bronchial squamous metaplasia
B) Adenomatous hyperplasia
C) Small cell carcinoma
D) Pulmonary fibrosis
Correct Answer: A
Explanation: Squamous cell carcinoma of the lung often arises from bronchial squamous
metaplasia, a precancerous change due to chronic irritation (e.g., smoking). Adenomatous
hyperplasia (B) precedes adenocarcinoma. Small cell carcinoma (C) is a distinct entity. Fibrosis
(D) is unrelated.
Microbiology Section
Question 8:
A 22-year-old college student has fever, neck stiffness, and a petechial rash. CSF analysis
shows gram-negative diplococci. Which organism is most likely?
A) Neisseria meningitidis
B) Streptococcus pneumoniae
C) Haemophilus influenzae
D) Listeria monocytogenes
Correct Answer: A
Explanation: Neisseria meningitidis causes meningococcal meningitis, characterized by fever,
neck stiffness, and petechial rash, with gram-negative diplococci in CSF. Streptococcus
pneumoniae (B) is gram-positive. Haemophilus influenzae (C) is less likely in vaccinated
populations. Listeria (D) affects neonates/elderly.
Question 9:
Complete Explanations and Answer Keys
Biochemistry Section
Question 1:
A 45-year-old man presents with fatigue and hepatomegaly. Laboratory studies show elevated
AST and ALT. A deficiency of which enzyme is most likely responsible for his condition?
A) Glucose-6-phosphatase
B) Pyruvate dehydrogenase
C) Fructose-1,6-bisphosphatase
D) Carnitine acyltransferase I
Correct Answer: A
Explanation: A deficiency in glucose-6-phosphatase leads to glycogen storage disease type I
(von Gierke disease). This impairs the release of glucose from glycogen, causing hepatomegaly,
hypoglycemia, and elevated liver enzymes (AST, ALT). Pyruvate dehydrogenase deficiency (B)
causes lactic acidosis. Fructose-1,6-bisphosphatase deficiency (C) leads to fructose metabolism
issues. Carnitine acyltransferase I deficiency (D) affects fatty acid oxidation, not glycogen.
Question 2:
A 3-year-old boy has recurrent hypoglycemia and seizures. Laboratory findings show lactic
acidosis and hyperuricemia. Which pathway is most likely affected?
A) Gluconeogenesis
B) Glycolysis
C) Fatty acid oxidation
D) Citric acid cycle
Correct Answer: A
Explanation: The symptoms suggest glycogen storage disease type I (von Gierke), where
gluconeogenesis is impaired due to deficient glucose-6-phosphatase. This leads to
hypoglycemia, lactic acidosis (from accumulated glucose-6-phosphate shunted to glycolysis),
and hyperuricemia (from purine degradation). Glycolysis (B) is intact. Fatty acid oxidation (C) or
citric acid cycle (D) defects cause different metabolic profiles.
Question 3:
A 25-year-old woman has a mutation in the LDL receptor gene. Which condition is most likely?
A) Familial hypercholesterolemia
B) Gaucher disease
C) Tay-Sachs disease
,D) Niemann-Pick disease
Correct Answer: A
Explanation: A mutation in the LDL receptor gene causes familial hypercholesterolemia,
leading to elevated LDL cholesterol and early atherosclerosis. Gaucher (B), Tay-Sachs (C), and
Niemann-Pick (D) involve lysosomal storage defects, not LDL metabolism.
Physiology Section
Question 4:
A 60-year-old man with hypertension has a decreased glomerular filtration rate. Which
mechanism is most likely responsible?
A) Increased afferent arteriole resistance
B) Decreased efferent arteriole resistance
C) Increased glomerular capillary permeability
D) Decreased Bowman’s capsule pressure
Correct Answer: A
Explanation: Increased afferent arteriole resistance, common in hypertension, reduces renal
blood flow and glomerular filtration rate (GFR). Decreased efferent resistance (B) increases
GFR. Increased permeability (C) affects filtration fraction, not GFR directly. Decreased
Bowman’s pressure (D) is less relevant.
Question 5:
A 30-year-old man with asthma has bronchoconstriction. Which receptor is primarily involved?
A) Beta-2 adrenergic
B) Muscarinic M3
C) Histamine H1
D) Alpha-1 adrenergic
Correct Answer: C
Explanation: Histamine H1 receptors mediate bronchoconstriction in asthma via allergic
responses. Beta-2 (A) causes bronchodilation. Muscarinic M3 (B) is involved in parasympathetic
bronchoconstriction. Alpha-1 (D) affects vascular tone.
Pathology Section
Question 6:
A 55-year-old woman with breast cancer has bone pain. A bone scan shows lytic lesions. What
is the most likely mechanism?
A) Osteoclast activation
B) Osteoblast proliferation
, C) Decreased bone mineralization
D) Increased collagen synthesis
Correct Answer: A
Explanation: Breast cancer metastases to bone often cause lytic lesions via osteoclast
activation, driven by tumor-secreted factors like PTHrP. Osteoblast proliferation (B) causes
sclerotic lesions. Decreased mineralization (C) is seen in rickets. Increased collagen (D) is
unrelated.
Question 7:
A 40-year-old man with a history of smoking presents with hemoptysis. A lung biopsy shows
squamous cell carcinoma. Which is the most likely precursor lesion?
A) Bronchial squamous metaplasia
B) Adenomatous hyperplasia
C) Small cell carcinoma
D) Pulmonary fibrosis
Correct Answer: A
Explanation: Squamous cell carcinoma of the lung often arises from bronchial squamous
metaplasia, a precancerous change due to chronic irritation (e.g., smoking). Adenomatous
hyperplasia (B) precedes adenocarcinoma. Small cell carcinoma (C) is a distinct entity. Fibrosis
(D) is unrelated.
Microbiology Section
Question 8:
A 22-year-old college student has fever, neck stiffness, and a petechial rash. CSF analysis
shows gram-negative diplococci. Which organism is most likely?
A) Neisseria meningitidis
B) Streptococcus pneumoniae
C) Haemophilus influenzae
D) Listeria monocytogenes
Correct Answer: A
Explanation: Neisseria meningitidis causes meningococcal meningitis, characterized by fever,
neck stiffness, and petechial rash, with gram-negative diplococci in CSF. Streptococcus
pneumoniae (B) is gram-positive. Haemophilus influenzae (C) is less likely in vaccinated
populations. Listeria (D) affects neonates/elderly.
Question 9:
