, Question 1
A cell exposed to a prolonged hypoxic insult activates a transcriptional
program that increases glucose uptake and shifts metabolism toward anaerobic
glycolysis. Which molecular sensor most directly mediates this adaptation?
A. Mammalian target of rapamycin (mTOR)
B. Hypoxia-inducible factor 1 (HIF-1)
C. Nuclear factor kappa B (NF-B)
D. Tumor protein p53
Correct Answer: B - Hypoxia-inducible factor 1 (HIF-1)
RATIONALE
HIF-1 is the master regulator of oxygen homeostasis, inducing genes
for glucose transporters and glycolytic enzymes under hypoxia.
mTOR regulates cell growth, NF-B drives inflammation, and p53
controls apoptosis and DNA repair.
Question 2
Which immunoglobulin is most efficient at activating the classical complement
pathway and is the first to appear in a primary immune response?
A. IgA
B. IgE
C. IgM
D. IgG
Correct Answer: C - IgM
RATIONALE
IgM is a pentamer with high avidity for complement C1q, making it
the most efficient activator of the classical pathway; it is also the first
antibody produced in a primary response. IgA is mucosal, IgE
mediates allergy, and IgG is the most abundant but appears later.
Page 2
, Question 3
A patient with severe vomiting has an arterial blood gas: pH 7.48, PaCO2 48
mm Hg, HCO3- 34 mEq/L. Which acid-base disturbance is present?
A. Respiratory alkalosis with metabolic compensation
B. Metabolic alkalosis with respiratory compensation
C. Metabolic acidosis with respiratory compensation
D. Respiratory acidosis with metabolic compensation
Correct Answer: B - Metabolic alkalosis with respiratory
compensation
RATIONALE
Elevated pH and HCO3- indicate metabolic alkalosis; the elevated
PaCO2 reflects compensatory hypoventilation. In respiratory alkalosis,
pH would be high but HCO3- low; metabolic acidosis would show
low pH and low HCO3-.
Question 4
Which pathophysiologic mechanism best explains the development of
megaloblastic anemia in a patient with a strict vegan diet?
A. Impaired globin chain synthesis due to iron deficiency
B. Defective DNA synthesis from vitamin B12 deficiency
C. Increased erythrocyte destruction due to membrane defects
D. Bone marrow infiltration by malignant cells
Correct Answer: B - Defective DNA synthesis from vitamin B12
deficiency
RATIONALE
Vitamin B12 deficiency impairs DNA synthesis, causing
asynchronous nuclear-cytoplasmic maturation and megaloblastic
changes. Iron deficiency causes microcytic anemia, membrane defects
cause hemolysis, and marrow infiltration causes myelophthisic
anemia.
Page 3
, Question 5
In heart failure, which compensatory mechanism initially maintains cardiac
output but ultimately worsens myocardial workload and remodeling?
A. Activation of the renin-angiotensin-aldosterone system
B. Release of natriuretic peptides
C. Parasympathetic vagal stimulation
D. Decreased sympathetic nervous system activity
Correct Answer: A - Activation of the
renin-angiotensin-aldosterone system
RATIONALE
RAAS activation increases preload and afterload via sodium and water
retention and vasoconstriction, which initially supports output but
promotes adverse remodeling. Natriuretic peptides counteract RAAS,
and parasympathetic activity reduces workload.
Question 6
Which alteration in respiratory mechanics is most characteristic of emphysema
and directly leads to air trapping?
A. Increased mucus production and bronchial plugging
B. Loss of elastic recoil and alveolar wall destruction
C. Thickening of the bronchial smooth muscle
D. Fibrotic changes in the lung interstitium
Correct Answer: B - Loss of elastic recoil and alveolar wall
destruction
RATIONALE
Emphysema involves destruction of alveolar walls and loss of elastic
recoil, causing airway collapse on expiration and air trapping. Mucus
plugging is typical of chronic bronchitis, smooth muscle thickening of
asthma, and fibrosis of restrictive lung diseases.
Page 4
A cell exposed to a prolonged hypoxic insult activates a transcriptional
program that increases glucose uptake and shifts metabolism toward anaerobic
glycolysis. Which molecular sensor most directly mediates this adaptation?
A. Mammalian target of rapamycin (mTOR)
B. Hypoxia-inducible factor 1 (HIF-1)
C. Nuclear factor kappa B (NF-B)
D. Tumor protein p53
Correct Answer: B - Hypoxia-inducible factor 1 (HIF-1)
RATIONALE
HIF-1 is the master regulator of oxygen homeostasis, inducing genes
for glucose transporters and glycolytic enzymes under hypoxia.
mTOR regulates cell growth, NF-B drives inflammation, and p53
controls apoptosis and DNA repair.
Question 2
Which immunoglobulin is most efficient at activating the classical complement
pathway and is the first to appear in a primary immune response?
A. IgA
B. IgE
C. IgM
D. IgG
Correct Answer: C - IgM
RATIONALE
IgM is a pentamer with high avidity for complement C1q, making it
the most efficient activator of the classical pathway; it is also the first
antibody produced in a primary response. IgA is mucosal, IgE
mediates allergy, and IgG is the most abundant but appears later.
Page 2
, Question 3
A patient with severe vomiting has an arterial blood gas: pH 7.48, PaCO2 48
mm Hg, HCO3- 34 mEq/L. Which acid-base disturbance is present?
A. Respiratory alkalosis with metabolic compensation
B. Metabolic alkalosis with respiratory compensation
C. Metabolic acidosis with respiratory compensation
D. Respiratory acidosis with metabolic compensation
Correct Answer: B - Metabolic alkalosis with respiratory
compensation
RATIONALE
Elevated pH and HCO3- indicate metabolic alkalosis; the elevated
PaCO2 reflects compensatory hypoventilation. In respiratory alkalosis,
pH would be high but HCO3- low; metabolic acidosis would show
low pH and low HCO3-.
Question 4
Which pathophysiologic mechanism best explains the development of
megaloblastic anemia in a patient with a strict vegan diet?
A. Impaired globin chain synthesis due to iron deficiency
B. Defective DNA synthesis from vitamin B12 deficiency
C. Increased erythrocyte destruction due to membrane defects
D. Bone marrow infiltration by malignant cells
Correct Answer: B - Defective DNA synthesis from vitamin B12
deficiency
RATIONALE
Vitamin B12 deficiency impairs DNA synthesis, causing
asynchronous nuclear-cytoplasmic maturation and megaloblastic
changes. Iron deficiency causes microcytic anemia, membrane defects
cause hemolysis, and marrow infiltration causes myelophthisic
anemia.
Page 3
, Question 5
In heart failure, which compensatory mechanism initially maintains cardiac
output but ultimately worsens myocardial workload and remodeling?
A. Activation of the renin-angiotensin-aldosterone system
B. Release of natriuretic peptides
C. Parasympathetic vagal stimulation
D. Decreased sympathetic nervous system activity
Correct Answer: A - Activation of the
renin-angiotensin-aldosterone system
RATIONALE
RAAS activation increases preload and afterload via sodium and water
retention and vasoconstriction, which initially supports output but
promotes adverse remodeling. Natriuretic peptides counteract RAAS,
and parasympathetic activity reduces workload.
Question 6
Which alteration in respiratory mechanics is most characteristic of emphysema
and directly leads to air trapping?
A. Increased mucus production and bronchial plugging
B. Loss of elastic recoil and alveolar wall destruction
C. Thickening of the bronchial smooth muscle
D. Fibrotic changes in the lung interstitium
Correct Answer: B - Loss of elastic recoil and alveolar wall
destruction
RATIONALE
Emphysema involves destruction of alveolar walls and loss of elastic
recoil, causing airway collapse on expiration and air trapping. Mucus
plugging is typical of chronic bronchitis, smooth muscle thickening of
asthma, and fibrosis of restrictive lung diseases.
Page 4
