, Question 1
A cell is deprived of oxygen, leading to ATP depletion. Which of the following
best explains why the sodium-potassium ATPase pump fails first, and what
immediate consequence follows?
A. Failure of the pump causes intracellular sodium accumulation, which
draws water in and leads to cellular swelling.
B. Failure of the pump causes intracellular potassium accumulation,
which draws water out and leads to cellular shrinkage.
C. Failure of the pump causes calcium influx, which activates proteases
and directly lyses the cell membrane.
D. Failure of the pump causes anaerobic glycolysis to cease, leading to
immediate cell death.
Correct Answer: A - Failure of the pump causes intracellular
sodium accumulation, which draws water in and leads to cellular
swelling.
RATIONALE
The Na+/K+ ATPase is highly ATP-dependent; when ATP falls, it
fails, causing Na+ to accumulate intracellularly, followed by osmotic
water influx and swelling (hydropic change). This is a classic early
reversible injury. Options B, C, and D misrepresent ion gradients or
timing; calcium influx occurs later, and anaerobic glycolysis may
continue briefly.
Question 2
During an acute inflammatory response, which sequence of
leukocyte-endothelial interactions correctly describes the transition from
rolling to firm adhesion?
A. Selectins mediate rolling, then integrins mediate firm adhesion via
ICAM-1 on endothelium.
B. Integrins mediate rolling, then selectins mediate firm adhesion via
Page 2
, VCAM-1 on endothelium.
C. PECAM-1 mediates rolling, then selectins mediate firm adhesion via
ICAM-1 on endothelium.
D. Selectins mediate firm adhesion, then integrins mediate transmigration
via PECAM-1.
Correct Answer: A - Selectins mediate rolling, then integrins
mediate firm adhesion via ICAM-1 on endothelium.
RATIONALE
Selectins (L-, P-, E-) mediate initial rolling by binding sialylated
ligands; then chemokines activate integrins (LFA-1, MAC-1) on
leukocytes, which bind ICAM-1 on endothelium for firm adhesion.
Transmigration follows via PECAM-1. Options B, C, and D reverse or
misassign these roles.
Question 3
Which statement best distinguishes apoptosis from necrosis in terms of cellular
content release and inflammatory response?
A. Apoptosis releases cellular contents that trigger inflammation, whereas
necrosis is silent.
B. Necrosis is an energy-dependent process that avoids inflammation,
whereas apoptosis causes inflammation.
C. Apoptosis is energy-dependent and avoids inflammation, whereas
necrosis releases contents that trigger inflammation.
D. Both apoptosis and necrosis are energy-independent and cause
identical inflammatory responses.
Correct Answer: C - Apoptosis is energy-dependent and avoids
inflammation, whereas necrosis releases contents that trigger
inflammation.
Page 3
, RATIONALE
Apoptosis is a regulated, ATP-dependent process where the cell
shrinks and forms apoptotic bodies that are phagocytosed without
inflammation. Necrosis is typically energy-independent, causing cell
swelling, membrane rupture, and release of DAMPs that incite
inflammation. Options A, B, and D incorrectly describe these
mechanisms.
Question 4
A patient has a deficiency in C3. Which of the following immune functions
would be most directly impaired?
A. Opsonization of bacteria and clearance of immune complexes
B. Direct lysis of gram-negative bacteria via membrane attack complex
C. Neutralization of viruses by antibodies
D. Activation of T lymphocytes by antigen-presenting cells
Correct Answer: A - Opsonization of bacteria and clearance of
immune complexes
RATIONALE
C3 is central to all complement pathways; its cleavage product C3b is
a major opsonin and is required for clearance of immune complexes.
The membrane attack complex (B) requires C5-C9, though C3
deficiency can reduce its formation, but opsonization is the most direct
defect. Neutralization (C) is antibody-mediated, and T-cell activation
(D) is not directly complement-dependent.
Question 5
A patient with a wound infection has a wound culture positive for
Staphylococcus aureus. The wound is red, warm, swollen, and painful. Which
of the following best describes the primary vascular change that produces these
signs?
A. Vasoconstriction followed by vasodilation and increased capillary
Page 4
A cell is deprived of oxygen, leading to ATP depletion. Which of the following
best explains why the sodium-potassium ATPase pump fails first, and what
immediate consequence follows?
A. Failure of the pump causes intracellular sodium accumulation, which
draws water in and leads to cellular swelling.
B. Failure of the pump causes intracellular potassium accumulation,
which draws water out and leads to cellular shrinkage.
C. Failure of the pump causes calcium influx, which activates proteases
and directly lyses the cell membrane.
D. Failure of the pump causes anaerobic glycolysis to cease, leading to
immediate cell death.
Correct Answer: A - Failure of the pump causes intracellular
sodium accumulation, which draws water in and leads to cellular
swelling.
RATIONALE
The Na+/K+ ATPase is highly ATP-dependent; when ATP falls, it
fails, causing Na+ to accumulate intracellularly, followed by osmotic
water influx and swelling (hydropic change). This is a classic early
reversible injury. Options B, C, and D misrepresent ion gradients or
timing; calcium influx occurs later, and anaerobic glycolysis may
continue briefly.
Question 2
During an acute inflammatory response, which sequence of
leukocyte-endothelial interactions correctly describes the transition from
rolling to firm adhesion?
A. Selectins mediate rolling, then integrins mediate firm adhesion via
ICAM-1 on endothelium.
B. Integrins mediate rolling, then selectins mediate firm adhesion via
Page 2
, VCAM-1 on endothelium.
C. PECAM-1 mediates rolling, then selectins mediate firm adhesion via
ICAM-1 on endothelium.
D. Selectins mediate firm adhesion, then integrins mediate transmigration
via PECAM-1.
Correct Answer: A - Selectins mediate rolling, then integrins
mediate firm adhesion via ICAM-1 on endothelium.
RATIONALE
Selectins (L-, P-, E-) mediate initial rolling by binding sialylated
ligands; then chemokines activate integrins (LFA-1, MAC-1) on
leukocytes, which bind ICAM-1 on endothelium for firm adhesion.
Transmigration follows via PECAM-1. Options B, C, and D reverse or
misassign these roles.
Question 3
Which statement best distinguishes apoptosis from necrosis in terms of cellular
content release and inflammatory response?
A. Apoptosis releases cellular contents that trigger inflammation, whereas
necrosis is silent.
B. Necrosis is an energy-dependent process that avoids inflammation,
whereas apoptosis causes inflammation.
C. Apoptosis is energy-dependent and avoids inflammation, whereas
necrosis releases contents that trigger inflammation.
D. Both apoptosis and necrosis are energy-independent and cause
identical inflammatory responses.
Correct Answer: C - Apoptosis is energy-dependent and avoids
inflammation, whereas necrosis releases contents that trigger
inflammation.
Page 3
, RATIONALE
Apoptosis is a regulated, ATP-dependent process where the cell
shrinks and forms apoptotic bodies that are phagocytosed without
inflammation. Necrosis is typically energy-independent, causing cell
swelling, membrane rupture, and release of DAMPs that incite
inflammation. Options A, B, and D incorrectly describe these
mechanisms.
Question 4
A patient has a deficiency in C3. Which of the following immune functions
would be most directly impaired?
A. Opsonization of bacteria and clearance of immune complexes
B. Direct lysis of gram-negative bacteria via membrane attack complex
C. Neutralization of viruses by antibodies
D. Activation of T lymphocytes by antigen-presenting cells
Correct Answer: A - Opsonization of bacteria and clearance of
immune complexes
RATIONALE
C3 is central to all complement pathways; its cleavage product C3b is
a major opsonin and is required for clearance of immune complexes.
The membrane attack complex (B) requires C5-C9, though C3
deficiency can reduce its formation, but opsonization is the most direct
defect. Neutralization (C) is antibody-mediated, and T-cell activation
(D) is not directly complement-dependent.
Question 5
A patient with a wound infection has a wound culture positive for
Staphylococcus aureus. The wound is red, warm, swollen, and painful. Which
of the following best describes the primary vascular change that produces these
signs?
A. Vasoconstriction followed by vasodilation and increased capillary
Page 4
