I85PREP
⌘ K
FCPS Part-1 study materials
FCPS Part-1 study resources

FCPS Part-1 practice questions

One question at a time. Build your FCPS Part-1 understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which molecule is the primary immediate energy source for the Na+/K+ ATPase pump in the cell membrane?

  1. ATP Correct answer.
  2. NADH
  3. Glucose
  4. Creatine phosphate

Explanation

The Na+/K+ ATPase is an active transport pump that directly hydrolyses one molecule of ATP to move three sodium ions out and two potassium ions into the cell. ATP is therefore the immediate energy currency used by this pump, not a storage or electron-carrier molecule.

Question 2Basic Sciences (as defined by the relevant specialty faculty curriculum)

A ribosome is translating an mRNA strand. Which sequence on the mRNA signals the start of translation?

  1. UAA codon
  2. AUG codon Correct answer.
  3. Poly-A tail
  4. TATA box

Explanation

Translation begins when the ribosome recognises the start codon AUG, which also codes for methionine. This sets the reading frame for all subsequent codons, so the correct answer is AUG.

Question 3Basic Sciences (as defined by the relevant specialty faculty curriculum)

During which phase of the cell cycle does DNA replication occur?

  1. M phase
  2. G1 phase
  3. G2 phase
  4. S phase Correct answer.

Explanation

DNA replication takes place during the S (synthesis) phase of interphase, when each chromosome is duplicated into two sister chromatids. G1 and G2 are gap phases, and M phase is when the duplicated chromosomes are segregated and the cell divides.

Question 4Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which enzyme catalyses the rate-limiting step of glycolysis?

  1. Hexokinase
  2. Aldolase
  3. Pyruvate kinase
  4. Phosphofructokinase-1 Correct answer.

Explanation

Phosphofructokinase-1 catalyses the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, the slowest and most regulated step of glycolysis. It is the key control point responsive to ATP and AMP levels.

Question 5Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which immunoglobulin class is the first antibody produced in a primary immune response?

  1. IgE
  2. IgM Correct answer.
  3. IgA
  4. IgG

Explanation

IgM is the first antibody class produced during a primary immune response, forming a pentamer that efficiently activates complement. IgG appears later and dominates secondary responses, while IgA and IgE serve mucosal and allergic roles.

Question 6Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which vitamin deficiency is classically associated with night blindness?

  1. Vitamin A Correct answer.
  2. Vitamin C
  3. Vitamin B12
  4. Vitamin D

Explanation

Vitamin A is required to synthesise rhodopsin, the photopigment in rod cells that mediates vision in dim light. Deficiency therefore impairs dark adaptation and causes night blindness, and may later progress to xerophthalmia.

Question 7Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which part of the nephron is primarily responsible for the reabsorption of approximately 65% of filtered sodium and water?

  1. Collecting duct
  2. Distal convoluted tubule
  3. Descending limb of the loop of Henle
  4. Proximal convoluted tubule Correct answer.

Explanation

The proximal convoluted tubule reabsorbs about two-thirds of filtered sodium and water, largely through sodium-glucose and sodium-amino acid cotransport and aquaporins. This bulk reabsorption is essential for maintaining fluid balance.

Question 8Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which neurotransmitter is released at the neuromuscular junction to stimulate skeletal muscle contraction?

  1. Noradrenaline
  2. Acetylcholine Correct answer.
  3. GABA
  4. Dopamine

Explanation

Motor neurons release acetylcholine at the neuromuscular junction, which binds nicotinic receptors on the motor end plate and triggers muscle depolarisation. This cholinergic transmission is essential for voluntary movement.

Question 9Basic Sciences (as defined by the relevant specialty faculty curriculum)

A patient with severe diarrhoea has a blood pH of 7.28 and low plasma bicarbonate. Which acid-base disturbance is most likely?

  1. Metabolic alkalosis
  2. Metabolic acidosis Correct answer.
  3. Respiratory alkalosis
  4. Respiratory acidosis

Explanation

Severe diarrhoea causes loss of bicarbonate-rich intestinal fluid, lowering plasma bicarbonate and producing a metabolic acidosis with a low pH. The primary defect is metabolic, not respiratory, because bicarbonate is lost rather than carbon dioxide being retained.

Question 10Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 45-year-old man has a fasting plasma glucose of 7.8 mmol/L on two occasions. Which diagnosis is most likely?

  1. Impaired fasting glucose only
  2. Normal glucose tolerance
  3. Diabetes mellitus Correct answer.
  4. Hypoglycaemia

Explanation

A fasting plasma glucose of 7.0 mmol/L or higher on two occasions meets the diagnostic criteria for diabetes mellitus. A value of 7.8 mmol/L clearly exceeds this threshold, so the diagnosis is diabetes rather than impaired fasting glucose or normal tolerance.

Question 11Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 25-year-old woman develops haemolytic anaemia after taking primaquine. Which enzyme deficiency is most likely responsible?

  1. Hexokinase
  2. Glucokinase
  3. Pyruvate kinase
  4. Glucose-6-phosphate dehydrogenase Correct answer.

Explanation

Glucose-6-phosphate dehydrogenase deficiency reduces NADPH production, leaving red cells vulnerable to oxidative stress from drugs such as primaquine. This causes haemolysis with Heinz body formation.

Question 12Basic Sciences (as defined by the relevant specialty faculty curriculum)

A patient with chronic liver disease has prolonged prothrombin time. Which vitamin deficiency is most likely responsible?

  1. Vitamin B6
  2. Vitamin C
  3. Vitamin B1
  4. Vitamin K Correct answer.

Explanation

Vitamin K is required for gamma-carboxylation of clotting factors II, VII, IX and X, so deficiency prolongs the prothrombin time. Chronic liver disease impairs vitamin K-dependent factor synthesis and bile-dependent absorption, explaining the coagulopathy.

Question 13Basic Sciences (as defined by the relevant specialty faculty curriculum)

A newborn presents with ambiguous genitalia and severe salt-wasting crises. Which enzyme deficiency is most likely?

  1. 17-alpha-hydroxylase
  2. 11-beta-hydroxylase
  3. 21-hydroxylase Correct answer.
  4. Aromatase

Explanation

21-hydroxylase deficiency is the most common form of congenital adrenal hyperplasia and causes cortisol and aldosterone deficiency with excess androgen production. The salt-wasting form presents with hyponatraemia, hyperkalaemia and ambiguous genitalia in female infants.

Question 14Basic Sciences (as defined by the relevant specialty faculty curriculum)

A patient with a pulmonary embolism develops sudden breathlessness. Which change in arterial blood gas is most consistent with this condition?

  1. Increased PaO2 with increased PaCO2
  2. Increased PaCO2 with normal PaO2
  3. Normal PaO2 with increased bicarbonate
  4. Decreased PaO2 with decreased PaCO2 Correct answer.

Explanation

Pulmonary embolism causes ventilation-perfusion mismatch and right-to-left shunting, lowering arterial oxygen. Hyperventilation driven by hypoxia lowers carbon dioxide, producing hypoxaemia with hypocapnia.

Question 15Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 60-year-old man has a serum calcium of 2.9 mmol/L and an inappropriately normal PTH. Which mechanism best explains his hypercalcaemia?

  1. Decreased intestinal calcium absorption
  2. Increased renal calcium excretion
  3. Increased bone resorption mediated by PTH Correct answer.
  4. Reduced vitamin D activation

Explanation

Primary hyperparathyroidism causes excess PTH, which increases bone resorption, renal calcium reabsorption and vitamin D activation, raising serum calcium. An inappropriately normal PTH in the face of hypercalcaemia supports this diagnosis.

Question 16Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which feature best distinguishes apoptosis from necrosis?

  1. Random DNA fragmentation with membrane rupture
  2. Controlled energy-dependent cell death without inflammation Correct answer.
  3. Ischaemic injury with neutrophil infiltration
  4. Cell swelling with inflammation

Explanation

Apoptosis is an active, ATP-dependent process of programmed cell death that preserves membrane integrity and avoids inflammation. Necrosis is passive, involves cell swelling and membrane rupture, and provokes an inflammatory response.

Question 17Basic Sciences (as defined by the relevant specialty faculty curriculum)

A tumour is described as having cells that closely resemble the tissue of origin with well-formed glands. Which term best describes this?

  1. Well differentiated Correct answer.
  2. Metastatic
  3. Anaplastic
  4. Poorly differentiated

Explanation

Well-differentiated tumours retain morphological features resembling their tissue of origin, including organised gland formation. Poorly differentiated and anaplastic tumours show increasing loss of such features and greater pleomorphism.

Question 18Basic Sciences (as defined by the relevant specialty faculty curriculum)

A patient with chronic obstructive pulmonary disease has chronic hypoxaemia. Which compensatory mechanism increases oxygen delivery to tissues?

  1. Increased plasma bicarbonate
  2. Decreased cardiac output
  3. Increased erythropoietin secretion Correct answer.
  4. Reduced 2,3-BPG levels

Explanation

Chronic hypoxaemia stimulates renal erythropoietin release, raising red cell mass and oxygen-carrying capacity. This secondary polycythaemia is a key adaptation to sustained low oxygen levels.

Question 19Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 30-year-old woman has recurrent infections and low CD4+ T-cell counts. Which function is most directly impaired?

  1. Complement activation
  2. Cell-mediated immunity and macrophage activation Correct answer.
  3. Neutrophil chemotaxis
  4. Antibody production by plasma cells

Explanation

CD4+ T helper cells coordinate cell-mediated immunity by activating macrophages and supporting cytotoxic T-cell and B-cell responses. Their loss impairs defence against intracellular pathogens and increases opportunistic infections.

Question 20Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which ion is primarily responsible for the depolarisation phase of a neuronal action potential?

  1. Potassium influx
  2. Calcium influx
  3. Chloride influx
  4. Sodium influx Correct answer.

Explanation

Depolarisation of a neuron results from opening of voltage-gated sodium channels, allowing sodium to rush into the cell and reverse the membrane potential. Repolarisation follows as potassium channels open and potassium leaves the cell.

Question 21Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 55-year-old man has a blood pressure of 160/100 mmHg. Which mechanism is most likely contributing to sustained hypertension?

  1. Decreased peripheral vascular resistance
  2. Increased renal sodium excretion
  3. Reduced sympathetic outflow
  4. Increased renin-angiotensin-aldosterone activity Correct answer.

Explanation

Activation of the renin-angiotensin-aldosterone system raises blood pressure through vasoconstriction and sodium and water retention. Increased sympathetic tone and reduced renal sodium excretion also contribute to sustained hypertension.

Question 22Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which genetic mechanism best explains the phenotypic variability of a disease caused by a single gene mutation in different family members?

  1. Codominance
  2. Pleiotropy
  3. Variable expressivity Correct answer.
  4. Complete penetrance

Explanation

Variable expressivity describes how individuals carrying the same genotype can show different severity or features of a disorder. It explains why family members with the same mutation may be affected differently.

Question 23Basic Sciences (as defined by the relevant specialty faculty curriculum)

A patient with chronic kidney disease has a low serum calcium and high phosphate. Which mechanism best explains the low calcium?

  1. Increased PTH-mediated bone resorption
  2. Phosphate binding to calcium and reduced calcitriol synthesis Correct answer.
  3. Increased intestinal calcium absorption
  4. Increased renal phosphate excretion

Explanation

In chronic kidney disease, reduced phosphate excretion raises serum phosphate, which binds calcium and lowers ionised calcium. Impaired renal 1-alpha-hydroxylation also reduces calcitriol, decreasing intestinal calcium absorption.

Question 24Basic Sciences (as defined by the relevant specialty faculty curriculum)

A tumour suppressor gene is best described by which property?

  1. It encodes proteins that promote cell cycle progression
  2. Loss of function of both alleles contributes to tumour formation Correct answer.
  3. A single mutated copy is sufficient to cause cancer
  4. It is always inherited in an autosomal dominant manner

Explanation

Tumour suppressor genes normally restrain cell growth, so both alleles must typically be inactivated for loss of function to contribute to tumourigenesis. This two-hit concept contrasts with oncogenes, where a single activating mutation can be sufficient.

Question 25Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 70-year-old man has a serum osmolality of 300 mOsm/kg, a serum sodium of 150 mmol/L and a urine osmolality of 900 mOsm/kg. Which condition is most likely?

  1. Dehydration with intact ADH action Correct answer.
  2. Primary polydipsia
  3. Osmotic diuresis
  4. Diabetes insipidus

Explanation

Hypernatraemia with concentrated urine indicates that ADH is acting appropriately to conserve water, as occurs in dehydration. The kidney is responding by reabsorbing water, so the defect is water loss rather than an ADH problem.

Question 26Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which component of the cell membrane is primarily responsible for forming the lipid bilayer?

  1. Glycolipids
  2. Integral proteins
  3. Cholesterol
  4. Phospholipids Correct answer.

Explanation

Phospholipids are amphipathic molecules with a hydrophilic head and hydrophobic tails. In an aqueous environment, they spontaneously arrange into a bilayer with tails facing inward, forming the fundamental structure of the membrane. Other components are embedded within or attached to this bilayer.

Question 27Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which type of collagen is most abundant in the human body and provides tensile strength to connective tissues?

  1. Type III collagen
  2. Type IV collagen
  3. Type I collagen Correct answer.
  4. Type II collagen

Explanation

Type I collagen is the most abundant collagen in the body, forming large fibrils that provide tensile strength to skin, bone, tendons, and ligaments. Type II is found mainly in cartilage, type III in reticular fibers, and type IV in basement membranes.

Question 28Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which enzyme catalyzes the rate-limiting step in glycolysis?

  1. Hexokinase
  2. Aldolase
  3. Phosphofructokinase-1 Correct answer.
  4. Pyruvate kinase

Explanation

Phosphofructokinase-1 (PFK-1) catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, which is the committed and rate-limiting step in glycolysis. It is allosterically regulated by ATP, citrate, and AMP. Hexokinase and pyruvate kinase also catalyze irreversible steps but are not rate-limiting.

Question 29Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which phase of the cardiac cycle is associated with the first heart sound (S1)?

  1. Atrial systole
  2. Isovolumetric relaxation
  3. Isovolumetric contraction Correct answer.
  4. Ventricular ejection

Explanation

The first heart sound (S1) is caused by the closure of the mitral and tricuspid valves at the beginning of ventricular systole, during the isovolumetric contraction phase. This occurs when ventricular pressure exceeds atrial pressure, causing the AV valves to close. It marks the onset of systole.

Question 30Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which lung volume or capacity is defined as the volume of air remaining in the lungs after a maximal expiration?

  1. Functional residual capacity
  2. Expiratory reserve volume
  3. Residual volume Correct answer.
  4. Vital capacity

Explanation

Residual volume (RV) is the volume of air that remains in the lungs after a maximal forced expiration. It cannot be exhaled and prevents alveolar collapse. Functional residual capacity is the volume after normal expiration, expiratory reserve volume is the additional air exhaled after normal expiration, and vital capacity is the maximum air exhaled after maximal inspiration.

Question 31Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which hormone is primarily responsible for the milk ejection reflex during breastfeeding?

  1. Estrogen
  2. Prolactin
  3. Oxytocin Correct answer.
  4. Progesterone

Explanation

Oxytocin, released from the posterior pituitary, causes contraction of myoepithelial cells surrounding alveoli in the mammary glands, leading to milk ejection. Prolactin stimulates milk production, while estrogen and progesterone support breast development during pregnancy.

Question 32Basic Sciences (as defined by the relevant specialty faculty curriculum)

Which immunoglobulin class is the first to be produced in a primary immune response?

  1. IgE
  2. IgA
  3. IgG
  4. IgM Correct answer.

Explanation

IgM is the first antibody class produced during a primary immune response. It is a pentamer that is effective at activating complement and agglutinating pathogens. IgG appears later and dominates the secondary response.

Question 33Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 50-year-old man with a history of alcohol abuse presents with confusion, ataxia, and ophthalmoplegia. Which vitamin deficiency is most likely responsible?

  1. Niacin (B3)
  2. Thiamine (B1) Correct answer.
  3. Riboflavin (B2)
  4. Pyridoxine (B6)

Explanation

The triad of confusion, ataxia, and ophthalmoplegia is characteristic of Wernicke encephalopathy, which is caused by thiamine deficiency, commonly seen in alcoholics. Thiamine is a cofactor for enzymes in glucose metabolism and neurotransmitter synthesis. Prompt thiamine replacement is essential to prevent progression to Korsakoff syndrome.

Question 34Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 28-year-old woman has a history of recurrent kidney stones. Genetic testing reveals a defect in the renal tubular reabsorption of cystine and other dibasic amino acids. Which transport system is most likely defective?

  1. Sodium-glucose cotransporter
  2. Cystine transporter in the proximal tubule Correct answer.
  3. Sodium-potassium ATPase
  4. Aquaporin-2 water channels

Explanation

Cystinuria is caused by a defect in the renal tubular transporter for cystine and dibasic amino acids (ornithine, lysine, arginine) in the proximal tubule. This leads to increased urinary excretion of cystine, which is poorly soluble and forms stones. The other transporters are not involved in cystine reabsorption.

Question 35Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 60-year-old man with chronic bronchitis has a persistent cough and excessive mucus production. Which cell type is primarily responsible for the increased mucus in his airways?

  1. Goblet cells Correct answer.
  2. Club cells
  3. Alveolar macrophages
  4. Type I pneumocytes

Explanation

Goblet cells are specialized epithelial cells that secrete mucus in the respiratory tract. In chronic bronchitis, goblet cell hyperplasia and hypertrophy lead to excessive mucus production, contributing to airway obstruction. Type I pneumocytes form the alveolar lining, macrophages phagocytose particles, and club cells secrete surfactant components.

Question 36Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 45-year-old woman with a history of gallstones presents with severe epigastric pain radiating to the back. Serum amylase and lipase are markedly elevated. Which mechanism best explains the pancreatic injury?

  1. Autoimmune destruction of pancreatic beta cells
  2. Ischemic necrosis due to arterial thrombosis
  3. Premature activation of pancreatic enzymes within the pancreas Correct answer.
  4. Impaired secretion of pancreatic enzymes into the duodenum

Explanation

Acute pancreatitis is often caused by premature activation of digestive enzymes (e.g., trypsinogen to trypsin) within the pancreas, leading to autodigestion and inflammation. Gallstones can obstruct the pancreatic duct, triggering this activation. The other options do not describe the primary mechanism of acute pancreatitis.

Question 37Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 32-year-old woman has a deep vein thrombosis. Genetic testing shows a mutation in the gene encoding prothrombin. Which effect does this mutation most likely have?

  1. Decreased prothrombin activity
  2. Defective platelet aggregation
  3. Impaired vitamin K-dependent carboxylation
  4. Increased prothrombin levels Correct answer.

Explanation

The prothrombin G20210A mutation leads to increased levels of prothrombin (factor II), which promotes a hypercoagulable state and increases the risk of venous thrombosis. It does not affect the function of prothrombin or vitamin K-dependent carboxylation. Platelet aggregation is not directly affected.

Question 38Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 55-year-old man with long-standing hypertension develops heart failure. Which compensatory mechanism initially maintains cardiac output but eventually contributes to disease progression?

  1. Activation of the renin-angiotensin-aldosterone system Correct answer.
  2. Increased parasympathetic tone
  3. Decreased circulating catecholamines
  4. Upregulation of beta-adrenergic receptors

Explanation

In heart failure, reduced cardiac output triggers activation of the renin-angiotensin-aldosterone system (RAAS), leading to vasoconstriction and sodium/water retention, which initially maintains blood pressure and perfusion. However, chronic RAAS activation causes adverse remodeling, fibrosis, and worsening heart failure. The other options would not compensate for reduced output.

Question 39Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 60-year-old man with chronic kidney disease has a serum potassium of 6.2 mmol/L. Which ECG finding is most characteristic of hyperkalemia?

  1. Prolonged QT interval
  2. Prominent U waves
  3. Peaked T waves Correct answer.
  4. ST-segment elevation

Explanation

Hyperkalemia classically causes tall, peaked T waves on ECG, which can progress to widened QRS complexes and sine waves. Prolonged QT interval is associated with hypocalcemia or hypokalemia, prominent U waves with hypokalemia, and ST elevation with myocardial infarction or pericarditis.

Question 40Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 25-year-old man sustains a traumatic injury and loses a large volume of blood. Which immediate compensatory change maintains blood pressure?

  1. Increased urine output
  2. Arteriolar vasoconstriction Correct answer.
  3. Increased baroreceptor firing
  4. Decreased heart rate

Explanation

Hemorrhage leads to decreased arterial pressure, which reduces baroreceptor firing and triggers sympathetic activation. This causes arteriolar vasoconstriction, increasing peripheral resistance and helping maintain blood pressure. Heart rate typically increases, and urine output decreases due to renal vasoconstriction and aldosterone release.

Question 41Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 40-year-old woman has a benign tumor of the adrenal medulla. Which substance is most likely elevated in her blood?

  1. Catecholamines Correct answer.
  2. Cortisol
  3. Aldosterone
  4. Renin

Explanation

A tumor of the adrenal medulla is a pheochromocytoma, which secretes excess catecholamines (epinephrine and norepinephrine). This causes episodic hypertension, palpitations, and sweating. Cortisol and aldosterone are produced by the adrenal cortex, and renin is produced by the kidney.

Question 42Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 30-year-old woman has a mutation in a gene that encodes a protein involved in the G1 to S phase transition of the cell cycle. Which protein is most likely affected?

  1. Cyclin B
  2. Cyclin A
  3. Cyclin E
  4. Cyclin D Correct answer.

Explanation

Cyclin D, in complex with CDK4/6, is a key regulator of the G1 to S phase transition by phosphorylating retinoblastoma protein. Cyclin B is involved in the G2 to M transition, cyclin A in S phase and G2, and cyclin E in the G1 to S transition but later than cyclin D. The question asks for the most likely affected in G1 to S; cyclin D is the primary regulator.

Question 43Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 50-year-old man with a history of peptic ulcer disease develops severe abdominal pain and rigidity. Imaging shows free air under the diaphragm. Which type of necrosis is most likely occurring in his bowel wall?

  1. Caseous necrosis
  2. Fat necrosis
  3. Liquefactive necrosis Correct answer.
  4. Coagulative necrosis

Explanation

Free air under the diaphragm suggests a perforated peptic ulcer, leading to peritonitis. The bowel wall undergoes liquefactive necrosis due to enzymatic digestion by pancreatic enzymes and bacterial action. Coagulative necrosis occurs in ischemic organs, caseous necrosis in tuberculosis, and fat necrosis in pancreatitis.

Question 44Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 60-year-old woman with a history of smoking presents with a persistent cough and weight loss. Biopsy of a lung mass shows small round cells with hyperchromatic nuclei and scant cytoplasm. Which immunohistochemical marker is most likely positive?

  1. CD45
  2. Vimentin
  3. Synaptophysin Correct answer.
  4. Cytokeratin

Explanation

The description suggests small cell lung carcinoma, a neuroendocrine tumor that expresses neuroendocrine markers such as synaptophysin, chromogranin, and CD56. Cytokeratin is positive in epithelial tumors but not specific for neuroendocrine differentiation. Vimentin is a mesenchymal marker, and CD45 is a leukocyte marker.

Question 45Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 35-year-old woman has a history of recurrent infections and is found to have a deficiency in the oxidative burst of neutrophils. Which enzyme is most likely defective?

  1. Superoxide dismutase
  2. NADPH oxidase Correct answer.
  3. Catalase
  4. Myeloperoxidase

Explanation

Chronic granulomatous disease is caused by a defect in NADPH oxidase, which is responsible for the respiratory burst that generates superoxide radicals to kill phagocytosed bacteria. Myeloperoxidase deficiency is usually asymptomatic, superoxide dismutase converts superoxide to hydrogen peroxide, and catalase breaks down hydrogen peroxide.

Question 46Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 28-year-old woman has a history of recurrent pregnancy loss. Testing reveals a balanced translocation. Which genetic mechanism best explains her recurrent miscarriages?

  1. Defective DNA repair
  2. Formation of unbalanced gametes Correct answer.
  3. Abnormal methylation patterns
  4. Increased rate of point mutations

Explanation

A balanced translocation carrier can produce gametes with unbalanced chromosome complements due to abnormal segregation during meiosis. These unbalanced gametes can lead to nonviable embryos and recurrent pregnancy loss. Point mutations, DNA repair defects, and methylation abnormalities do not explain the recurrent loss associated with translocations.

Question 47Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 45-year-old man has a mutation in a tumor suppressor gene. Which characteristic is typical of tumor suppressor genes?

  1. They are always located on sex chromosomes.
  2. They are recessive and typically require loss of both alleles. Correct answer.
  3. They are dominant and require one mutated allele for cancer.
  4. They encode proteins that stimulate cell division.

Explanation

Tumor suppressor genes are typically recessive at the cellular level, meaning both alleles must be inactivated for loss of function, as described by the two-hit hypothesis. Oncogenes are dominant and require only one mutated allele. Tumor suppressor genes normally inhibit cell division, and they are located on autosomes as well as sex chromosomes.

Question 48Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 60-year-old man with cirrhosis develops ascites. Which mechanism best explains the accumulation of fluid in the peritoneal cavity?

  1. Decreased aldosterone secretion
  2. Increased lymphatic drainage
  3. Increased portal venous pressure
  4. Decreased plasma oncotic pressure due to hypoalbuminemia Correct answer.

Explanation

In cirrhosis, reduced hepatic albumin synthesis leads to hypoalbuminemia, which decreases plasma oncotic pressure and promotes fluid movement into the peritoneal cavity, causing ascites. While portal hypertension also contributes, the question asks for the mechanism best explaining the accumulation, and hypoalbuminemia is a key factor. Increased lymphatic drainage would reduce ascites, and aldosterone is typically increased, not decreased.

Question 49Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 70-year-old man with long-standing hypertension and diabetes develops progressive renal failure. Biopsy shows nodular glomerulosclerosis. Which pathogenic mechanism best explains these lesions?

  1. Crescent formation in Bowman's space
  2. Nonenzymatic glycation of proteins Correct answer.
  3. Immune complex deposition in glomeruli
  4. Amyloid deposition

Explanation

Nodular glomerulosclerosis (Kimmelstiel-Wilson nodules) is characteristic of diabetic nephropathy. Chronic hyperglycemia leads to nonenzymatic glycation of proteins, forming advanced glycation end products that cause mesangial expansion and nodule formation. Immune complex deposition occurs in glomerulonephritis, amyloid in amyloidosis, and crescents in rapidly progressive glomerulonephritis.

Question 50Basic Sciences (as defined by the relevant specialty faculty curriculum)

A 55-year-old woman with a history of breast cancer presents with bone pain and hypercalcemia. Which mechanism best explains the hypercalcemia?

  1. Vitamin D intoxication
  2. Osteolytic metastases Correct answer.
  3. Increased renal tubular reabsorption of calcium
  4. Ectopic production of parathyroid hormone

Explanation

Hypercalcemia in a patient with breast cancer and bone pain is most commonly due to osteolytic metastases, where tumor cells stimulate osteoclasts to resorb bone, releasing calcium. Ectopic PTH production is extremely rare; PTHrP is more common. Increased renal reabsorption and vitamin D intoxication are less likely in this context.