PATHOLOGY MCQs: CELL INJURY, DEATH, AND ADAPTATIONS

Question 1

Which of the following best describes the relationship between etiology and pathogenesis?

Accepted Answer

Etiology identifies the initiating cause, while pathogenesis explains the sequence of events leading to disease — Etiology refers to the cause of disease (genetic or environmental factors), while pathogenesis describes the molecular, biochemical, and cellular events that follow the etiologic agent and lead to the development of disease manifestations. ---

Question 2

A 45-year-old patient presents with chest pain. After 30 minutes of ischemia, the cardiomyocytes show cellular swelling and fat accumulation but maintain intact cell membranes. What stage of cell injury is this?

Accepted Answer

Reversible injury — The key features indicating reversible injury are cellular swelling, fatty change, and intact cell membranes. These changes can be corrected if the damaging stimulus (ischemia) is removed. Irreversible injury would show mitochondrial damage with dense deposits and plasma membrane rupture. ---

Question 3

In reversible cell injury, why does the cytoplasm appear more eosinophilic (pink) on H&E staining?

Accepted Answer

Loss of cytoplasmic RNA — RNA normally binds the blue hematoxylin dye. When cells are injured, ribosomes detach from the endoplasmic reticulum and RNA is lost, reducing the basophilia (blue color) and making the cytoplasm appear more eosinophilic (pink/red). ---

Question 4

Which of the following represents the earliest morphologic manifestation of almost all forms of cell injury?

Accepted Answer

Cellular swelling — Cellular swelling is the earliest visible sign of cell injury, resulting from failure of the ATP-dependent Na+-K+ pump, leading to sodium and water accumulation inside the cell. This occurs before any nuclear changes or membrane disruption. ---

Question 5

A researcher observes cells under electron microscopy 2 hours after ischemic injury. Which finding would indicate the point of no return (irreversibility)?

Accepted Answer

Severe mitochondrial swelling with large amorphous densities — Two phenomena consistently characterize irreversibility: inability to reverse mitochondrial dysfunction and profound membrane disturbances. Severe mitochondrial damage with amorphous densities (calcium and protein precipitates) indicates irreversible injury, while the other options can occur in reversible injury. ## SECTION 2: CAUSES AND MECHANISMS OF CELL INJURY ---

Question 6

Which cause of hypoxia differs from ischemia in that it allows anaerobic glycolysis to continue?

Accepted Answer

Carbon monoxide poisoning — Carbon monoxide poisoning causes hypoxia by reducing oxygen-carrying capacity of blood, but blood flow continues, allowing delivery of glucose for anaerobic glycolysis. In ischemia (b, c, d), blood flow is reduced, compromising delivery of substrates for glycolysis, making ischemia more injurious than hypoxia alone. ---

Question 7

A patient with tuberculosis shows areas of lung tissue with a friable, white, "cheese-like" appearance. What type of necrosis is this?

Accepted Answer

Caseous necrosis — Caseous necrosis is characteristic of tuberculous infection, appearing grossly as friable, white, cheese-like material. Microscopically, it shows structureless collection of fragmented cells and granular debris enclosed within a granulomatous inflammatory border. ---

Question 8

Why does ischemic injury to the brain result in liquefactive necrosis rather than coagulative necrosis seen in other organs?

Accepted Answer

Hypoxic death of CNS cells manifests as liquefactive necrosis for unknown reasons — For unknown reasons, hypoxic death of cells within the central nervous system often manifests as liquefactive necrosis, which is an exception to the general rule that ischemia causes coagulative necrosis in most organs. ---

Question 9

A patient with acute pancreatitis develops chalky-white areas in the peritoneal cavity. What is the mechanism of this pathologic finding?

Accepted Answer

Release of pancreatic lipases causing fat necrosis with saponification — In acute pancreatitis, pancreatic enzymes leak and liquefy fat cell membranes, releasing triglycerides. Pancreatic lipases split these into fatty acids, which combine with calcium to produce grossly visible chalky-white areas (fat saponification), characteristic of fat necrosis. ---

Question 10

Which nuclear change in necrosis is characterized by nuclear shrinkage and increased basophilia?

Accepted Answer

Pyknosis — Pyknosis is characterized by nuclear shrinkage and increased basophilia due to chromatin condensation into a dense, shrunken basophilic mass. Karyolysis is fading of chromatin, and karyorrhexis is fragmentation of the pyknotic nucleus. ## SECTION 3: NECROSIS VS APOPTOSIS ---

Question 11

Which feature distinguishes necrosis from apoptosis?

Accepted Answer

Necrosis involves cell swelling while apoptosis involves cell shrinkage — Necrosis is characterized by cell swelling due to membrane damage and loss of osmotic regulation, while apoptosis involves cell shrinkage with intact membranes. DNA fragmentation occurs in both, but caspase activation is specific to apoptosis, not necrosis. ---

Question 12

Why doesn't apoptosis elicit an inflammatory response?

Accepted Answer

Dead cells are rapidly phagocytosed before membrane rupture and content leakage — In apoptosis, the plasma membrane remains intact and apoptotic bodies are rapidly phagocytosed by macrophages before contents leak out. This prevents release of cellular contents that would trigger inflammation, unlike necrosis where membrane rupture releases DAMPs. ---

Question 13

A pathologist observes cells with intensely eosinophilic cytoplasm, dense chromatin masses at the nuclear periphery, and membrane-bound fragments without adjacent inflammation. What process is occurring?

Accepted Answer

Apoptosis — The key features of apoptosis are present: cell shrinkage (dense eosinophilic cytoplasm), chromatin condensation at the nuclear membrane periphery, formation of apoptotic bodies (membrane-bound fragments), and absence of inflammation. ---

Question 14

What is the primary reason that cardiac troponins can be detected in blood 2 hours after myocardial infarction?

Accepted Answer

Release through damaged plasma membranes during necrosis — Necrosis involves loss of membrane integrity, leading to leakage of intracellular proteins into the circulation. Cardiac-specific troponins leak out through damaged plasma membranes and serve as biomarkers for myocardial necrosis, detectable well before histologic changes appear. ---

Question 15

Which BCL2 family protein is pro-apoptotic and forms channels in the mitochondrial membrane?

Accepted Answer

BAX and BAK — BAX and BAK are pro-apoptotic proteins with BH1-3 domains that oligomerize and form channels in the outer mitochondrial membrane, allowing cytochrome c leakage. BCL2 and BCL-XL are anti-apoptotic, while BID is a BH3-only sensor protein. ---

Question 16

What is the function of BH3-only proteins in apoptosis?

Accepted Answer

They act as sensors of cellular stress and activate BAX/BAK — BH3-only proteins (BAD, BIM, BID, Puma, Noxa) are regulated apoptosis initiators that sense cellular stress and damage. When upregulated, they directly activate BAX/BAK to permeabilize mitochondrial membranes and can also neutralize anti-apoptotic BCL2 proteins. ---

Question 17

During apoptosis, what signal promotes phagocytosis of apoptotic cells?

Accepted Answer

Externalization of phosphatidylserine on the outer membrane leaflet — In healthy cells, phosphatidylserine is on the inner leaflet of the plasma membrane. During apoptosis, it flips to the outer surface, where it serves as an "eat me" signal recognized by macrophage receptors, promoting efferocytosis without inflammation. ---

Question 18

Which cellular process is impaired in patients with chronic granulomatous disease?

Accepted Answer

Generation of superoxide by leukocytes — Chronic granulomatous disease results from defects in NADPH oxidase, which is required for the respiratory burst that generates superoxide (O2•−) in leukocytes. This impairs their ability to kill phagocytosed microbes, leading to recurrent infections. ## SECTION 5: OTHER MECHANISMS OF CELL DEATH ---

Question 19

What distinguishes necroptosis from classical necrosis?

Accepted Answer

Necroptosis is a regulated process involving specific signaling pathways — Necroptosis is "programmed necrosis" - it resembles necrosis morphologically but is triggered by defined signaling pathways (RIPK1/RIPK3/MLKL). It is caspase-independent, unlike apoptosis. Classical necrosis is passive cell death from severe injury. ---

Question 20

A patient with viral infection shows cell death accompanied by IL-1 release and fever. Which mechanism is most likely?

Accepted Answer

Pyroptosis — Pyroptosis is characterized by caspase-1 activation (by the inflammasome in response to microbial products), which cleaves pro-IL-1 to active IL-1 (causing fever - "pyro"). The caspases also cause cell death with inflammatory response, unlike classical apoptosis. ---

Question 21

Which protein must be phosphorylated by RIPK3 to execute necroptosis?

Accepted Answer

MLKL — In necroptosis, RIPK3 phosphorylates MLKL (mixed lineage kinase domain-like protein), which then oligomerizes and translocates to the plasma membrane, causing membrane disruption characteristic of necrotic cell death. ---

Question 22

Ferroptosis is characterized by which primary mechanism?

Accepted Answer

Unchecked lipid peroxidation of cellular membranes — Ferroptosis occurs when iron or ROS overwhelm glutathione-dependent antioxidant defenses, causing unchecked lipid peroxidation of membranes. This disrupts membrane function and leads to cell death. It's iron-dependent (hence "ferro") and can be prevented by reducing iron levels. ## SECTION 6: AUTOPHAGY ---

Question 23

What is the primary function of autophagy in starved cells?

Accepted Answer

Recycle cellular components to generate metabolites and energy — Autophagy is a survival mechanism where cells digest their own contents (organelles, proteins) and recycle the products for energy and metabolite production. In starvation, cells "cannibalize" themselves to survive until nutrients become available again. ---

Question 24

Which cellular structure is believed to be the primary source of the autophagosome isolation membrane?

Accepted Answer

Endoplasmic reticulum — The isolation membrane (phagophore) that forms the autophagosome is believed to be primarily derived from the ER, though other membrane sources like plasma membrane and mitochondria may contribute. ---

Question 25

PE-lipidated LC3 is a marker for which cellular process?

Accepted Answer

Autophagy — LC3 (microtubule-associated protein light chain 3) becomes covalently linked to phosphatidylethanolamine (PE) during autophagy. PE-lipidated LC3 increases during autophagy and is a useful marker for identifying cells undergoing this process. ---

Question 26

Which change best indicates that a cell has progressed from reversible to irreversible injury?

Accepted Answer

Opening of the mitochondrial permeability transition pore — Two phenomena consistently characterize irreversibility: inability to reverse mitochondrial dysfunction and profound membrane disturbances. Opening of the mitochondrial permeability transition pore leads to loss of membrane potential, irreversible failure of ATP generation, and progression to necrosis. ---

Question 27

In ATP-depleted cells, which metabolic pathway attempts to maintain energy production?

Accepted Answer

Glycolysis (anaerobic) — When ATP is depleted (e.g., from ischemia), cells stimulate glycogenolysis and glycolysis to generate ATP anaerobically from glucose. This produces much less ATP than oxidative phosphorylation and leads to lactic acid accumulation, but is the only energy source when oxygen is unavailable. ---

Question 28

What is the consequence of ATP depletion on the Na+-K+ ATPase pump?

Accepted Answer

Decreased pump activity leading to sodium influx and cell swelling — The Na+-K+ ATPase pump requires ATP to maintain low intracellular sodium. When ATP is depleted, pump activity fails, sodium accumulates inside cells, water follows osmotically, and cells swell. This is one of the earliest manifestations of reversible injury. ---

Question 29

Which organelle releases cytochrome c into the cytoplasm during the intrinsic apoptosis pathway?

Accepted Answer

Mitochondria — In the intrinsic (mitochondrial) pathway of apoptosis, BAX/BAK form channels in the mitochondrial outer membrane, allowing cytochrome c and other pro-apoptotic proteins to leak from the mitochondrial intermembrane space into the cytoplasm, where cytochrome c initiates caspase activation. ---

Question 30

Why does lactic acid accumulate in ischemic tissue?

Accepted Answer

Anaerobic glycolysis produces lactate as an end product — During ischemia, cells rely on anaerobic glycolysis for ATP production. This pathway converts glucose to pyruvate, which is then reduced to lactate (lactic acid) instead of entering the citric acid cycle. Accumulation of lactic acid reduces intracellular pH. ## SECTION 8: MEMBRANE DAMAGE AND CALCIUM ---

Question 31

Myelin figures observed in injured cells are composed of which substance?

Accepted Answer

Phospholipids from damaged membranes — Myelin figures are whorled phospholipid precipitates derived from damaged cellular membranes. They appear in both reversible and irreversible injury and may be phagocytosed or further degraded into fatty acids, which can calcify. ---

Question 32

What is the primary consequence of lysosomal membrane damage in injured cells?

Accepted Answer

Release of hydrolytic enzymes that digest cellular components — Lysosomal membrane damage releases acid hydrolases (RNases, DNases, proteases, etc.) into the acidic cytoplasm of injured cells, where they become activated and degrade cellular proteins, nucleic acids, and other components, pushing cells toward necrosis. ## SECTION 9: OXIDATIVE STRESS AND FREE RADICALS ---

Question 33

Which enzyme converts superoxide to hydrogen peroxide?

Accepted Answer

Superoxide dismutase — Superoxide dismutase (SOD) converts superoxide (O2•−) to hydrogen peroxide (H2O2): 2O2•− + 2H+ → H2O2 + O2. Catalase and glutathione peroxidase then break down H2O2 to water. SOD exists as manganese-SOD (mitochondria) and copper-zinc-SOD (cytoplasm). ---

Question 34

In the Fenton reaction, which transition metal catalyzes the formation of hydroxyl radicals?

Accepted Answer

Iron — The Fenton reaction is: H2O2 + Fe2+ → Fe3+ + •OH + OH−. Iron (and copper) donate or accept electrons and catalyze free radical formation. Most intracellular iron is in the Fe3+ state and must be reduced to Fe2+ (by superoxide) to participate in this reaction. ---

Question 35

How do transferrin, ferritin, and ceruloplasmin help prevent free radical damage?

Accepted Answer

They bind iron and copper, preventing their participation in ROS generation — Free iron and copper catalyze ROS formation (Fenton reaction). Storage and transport proteins (transferrin, ferritin, lactoferrin, ceruloplasmin) bind these metals and minimize their reactivity, preventing them from participating in reactions that generate harmful free radicals. ---

Question 36

What is the significance of the GSSG/GSH ratio in cells?

Accepted Answer

It reflects the oxidative state and ability to detoxify ROS — The ratio of oxidized glutathione (GSSG) to reduced glutathione (GSH) reflects the oxidative state of the cell. Glutathione peroxidase uses GSH to break down H2O2 and free radicals, producing GSSG. A high GSSG/GSH ratio indicates oxidative stress and reduced capacity to detoxify ROS. ---

Question 37

What is the unfolded protein response designed to do?

Accepted Answer

Restore protein homeostasis by increasing chaperones and reducing protein load — The unfolded protein response is activated when misfolded proteins accumulate in the ER. It attempts to restore homeostasis by: 1) increasing chaperone production, 2) enhancing proteasomal degradation, and 3) slowing protein translation. If unsuccessful, it triggers apoptosis. ---

Question 38

In α1-antitrypsin deficiency, where do the mutant proteins accumulate?

Accepted Answer

In the endoplasmic reticulum of hepatocytes — Mutant α1-antitrypsin misfolds slowly, and partially folded intermediates aggregate in the ER of hepatocytes rather than being secreted. This causes ER stress and liver damage. The absence of the enzyme in circulation leads to emphysema because the enzyme normally protects lungs from protease damage. ---

Question 39

Russell bodies in plasma cells represent accumulation of which substance?

Accepted Answer

Immunoglobulins in distended endoplasmic reticulum — Russell bodies are large homogeneous eosinophilic inclusions in plasma cells actively synthesizing excessive amounts of immunoglobulins. The ER becomes hugely distended with accumulated secretory proteins, creating these characteristic structures. ## SECTION 11: ISCHEMIA AND REPERFUSION INJURY ---

PATHOLOGY MCQs: CELL INJURY, DEATH, AND ADAPTATIONS

Questions, Answers & Explanations