, Question 1
A cell is exposed to a toxin that opens the mitochondrial permeability
transition pore (mPTP). Which sequence of events BEST explains the resulting
necrotic (rather than apoptotic) cell death?
A. Cytochrome c release -> caspase-9 activation -> orderly DNA
fragmentation
B. Loss of mitochondrial membrane potential -> ATP depletion -> failure
of Na+/K+-ATPase -> osmotic swelling and lysis
C. Bcl-2 upregulation -> Bax inhibition -> preservation of outer
membrane integrity
D. Phosphatidylserine externalization -> macrophage recognition ->
lysosomal digestion without inflammation
Correct Answer: B - Loss of mitochondrial membrane potential
-> ATP depletion -> failure of Na+/K+-ATPase -> osmotic
swelling and lysis
RATIONALE
mPTP opening dissipates the proton gradient, collapsing ATP
synthesis; without ATP, ion pumps fail, water enters, and the cell
swells and lyses-the hallmark of necrosis. Option A describes intrinsic
apoptosis, C is cytoprotective, and D describes apoptotic clearance,
none of which follow mPTP opening.
Question 2
A patient with a heterozygous gain-of-function mutation in PIK3CA (PI3K)
shows tissue overgrowth. Which molecular consequence most directly explains
this phenotype?
A. Constitutive AKT activation driving mTOR-dependent proliferation
and survival
B. Loss of PTEN-mediated dephosphorylation of PIP3
C. Impaired RAS GTPase activity with sustained MAPK signaling
Page 2
, D. Enhanced p53 tetramerization and cell-cycle arrest
Correct Answer: A - Constitutive AKT activation driving
mTOR-dependent proliferation and survival
RATIONALE
Gain-of-function PIK3CA increases PIP3, recruiting PDK1/AKT and
activating mTOR, which promotes growth and survival. PTEN loss
(B) mimics but is not the mutation described; RAS (C) and p53 (D)
are unrelated pathways.
Question 3
In a patient with chronic obstructive pulmonary disease (COPD) and chronic
CO retention, which arterial blood gas pattern best reflects fully compensated
respiratory acidosis?
A. pH 7.32, PaCO 60 mmHg, HCO 30 mEq/L
B. pH 7.36, PaCO 60 mmHg, HCO 34 mEq/L
C. pH 7.48, PaCO 30 mmHg, HCO 22 mEq/L
D. pH 7.40, PaCO 40 mmHg, HCO 24 mEq/L
Correct Answer: B - pH 7.36, PaCO 60 mmHg, HCO 34 mEq/L
RATIONALE
Full compensation returns pH toward normal; with chronic CO
retention, renal HCO reabsorption raises bicarbonate, yielding a
near-normal pH. Option A is uncompensated, C is respiratory
alkalosis, and D is normal.
Question 4
A patient with heart failure has an echocardiogram showing an E/A ratio <0.8
and an E/e' ratio of 15. These findings are most consistent with which
pathophysiologic mechanism?
A. Impaired myocardial relaxation with elevated filling pressures
(diastolic dysfunction)
Page 3
, B. Reduced contractility with decreased ejection fraction (systolic
dysfunction)
C. Pericardial constriction limiting ventricular filling
D. Mitral regurgitation causing volume overload
Correct Answer: A - Impaired myocardial relaxation with
elevated filling pressures (diastolic dysfunction)
RATIONALE
A low E/A ratio indicates impaired relaxation (grade I diastolic
dysfunction), and elevated E/e' reflects increased left atrial pressure.
Systolic dysfunction would primarily reduce ejection fraction, while
constriction and regurgitation have different Doppler patterns.
Question 5
Which renal mechanism most directly explains the hyperkalemia observed in a
patient with metabolic acidosis from chronic kidney disease?
A. Increased aldosterone secretion enhancing K excretion
B. Shift of K into cells due to H buffering by intracellular proteins
C. Impaired distal Na delivery and reduced K secretion in the collecting
duct
D. Respiratory compensation causing hypoventilation and K retention
Correct Answer: C - Impaired distal Na delivery and reduced K
secretion in the collecting duct
RATIONALE
In CKD, reduced nephron mass and distal Na delivery limit
aldosterone-driven K secretion, causing hyperkalemia. Acidosis shifts
K out of cells (not in), and aldosterone is often insufficient, so A and
B are incorrect; D is not a direct renal mechanism.
Page 4
A cell is exposed to a toxin that opens the mitochondrial permeability
transition pore (mPTP). Which sequence of events BEST explains the resulting
necrotic (rather than apoptotic) cell death?
A. Cytochrome c release -> caspase-9 activation -> orderly DNA
fragmentation
B. Loss of mitochondrial membrane potential -> ATP depletion -> failure
of Na+/K+-ATPase -> osmotic swelling and lysis
C. Bcl-2 upregulation -> Bax inhibition -> preservation of outer
membrane integrity
D. Phosphatidylserine externalization -> macrophage recognition ->
lysosomal digestion without inflammation
Correct Answer: B - Loss of mitochondrial membrane potential
-> ATP depletion -> failure of Na+/K+-ATPase -> osmotic
swelling and lysis
RATIONALE
mPTP opening dissipates the proton gradient, collapsing ATP
synthesis; without ATP, ion pumps fail, water enters, and the cell
swells and lyses-the hallmark of necrosis. Option A describes intrinsic
apoptosis, C is cytoprotective, and D describes apoptotic clearance,
none of which follow mPTP opening.
Question 2
A patient with a heterozygous gain-of-function mutation in PIK3CA (PI3K)
shows tissue overgrowth. Which molecular consequence most directly explains
this phenotype?
A. Constitutive AKT activation driving mTOR-dependent proliferation
and survival
B. Loss of PTEN-mediated dephosphorylation of PIP3
C. Impaired RAS GTPase activity with sustained MAPK signaling
Page 2
, D. Enhanced p53 tetramerization and cell-cycle arrest
Correct Answer: A - Constitutive AKT activation driving
mTOR-dependent proliferation and survival
RATIONALE
Gain-of-function PIK3CA increases PIP3, recruiting PDK1/AKT and
activating mTOR, which promotes growth and survival. PTEN loss
(B) mimics but is not the mutation described; RAS (C) and p53 (D)
are unrelated pathways.
Question 3
In a patient with chronic obstructive pulmonary disease (COPD) and chronic
CO retention, which arterial blood gas pattern best reflects fully compensated
respiratory acidosis?
A. pH 7.32, PaCO 60 mmHg, HCO 30 mEq/L
B. pH 7.36, PaCO 60 mmHg, HCO 34 mEq/L
C. pH 7.48, PaCO 30 mmHg, HCO 22 mEq/L
D. pH 7.40, PaCO 40 mmHg, HCO 24 mEq/L
Correct Answer: B - pH 7.36, PaCO 60 mmHg, HCO 34 mEq/L
RATIONALE
Full compensation returns pH toward normal; with chronic CO
retention, renal HCO reabsorption raises bicarbonate, yielding a
near-normal pH. Option A is uncompensated, C is respiratory
alkalosis, and D is normal.
Question 4
A patient with heart failure has an echocardiogram showing an E/A ratio <0.8
and an E/e' ratio of 15. These findings are most consistent with which
pathophysiologic mechanism?
A. Impaired myocardial relaxation with elevated filling pressures
(diastolic dysfunction)
Page 3
, B. Reduced contractility with decreased ejection fraction (systolic
dysfunction)
C. Pericardial constriction limiting ventricular filling
D. Mitral regurgitation causing volume overload
Correct Answer: A - Impaired myocardial relaxation with
elevated filling pressures (diastolic dysfunction)
RATIONALE
A low E/A ratio indicates impaired relaxation (grade I diastolic
dysfunction), and elevated E/e' reflects increased left atrial pressure.
Systolic dysfunction would primarily reduce ejection fraction, while
constriction and regurgitation have different Doppler patterns.
Question 5
Which renal mechanism most directly explains the hyperkalemia observed in a
patient with metabolic acidosis from chronic kidney disease?
A. Increased aldosterone secretion enhancing K excretion
B. Shift of K into cells due to H buffering by intracellular proteins
C. Impaired distal Na delivery and reduced K secretion in the collecting
duct
D. Respiratory compensation causing hypoventilation and K retention
Correct Answer: C - Impaired distal Na delivery and reduced K
secretion in the collecting duct
RATIONALE
In CKD, reduced nephron mass and distal Na delivery limit
aldosterone-driven K secretion, causing hyperkalemia. Acidosis shifts
K out of cells (not in), and aldosterone is often insufficient, so A and
B are incorrect; D is not a direct renal mechanism.
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