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BSMMU Residency Phase-A study materials
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BSMMU Residency Phase-A practice questions

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Question 1Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which nerve passes through the foramen ovale of the sphenoid bone?

  1. Maxillary division of the trigeminal nerve
  2. Facial nerve
  3. Mandibular division of the trigeminal nerve Correct answer.
  4. Ophthalmic division of the trigeminal nerve

Explanation

The foramen ovale transmits the mandibular division (V3) of the trigeminal nerve along with the accessory meningeal artery and the lesser petrosal nerve. The maxillary division leaves through the foramen rotundum, and the ophthalmic division exits via the superior orbital fissure. The facial nerve exits the skull through the stylomastoid foramen.

Question 2Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

The axillary nerve is most closely related to which surgical neck structure and is at risk in fractures there?

  1. Lateral epicondyle of the humerus
  2. Radial groove of the humerus
  3. Surgical neck of the humerus Correct answer.
  4. Medial epicondyle of the humerus

Explanation

The axillary nerve winds around the surgical neck of the humerus together with the posterior circumflex humeral vessels. Fractures at this site may injure the nerve, producing deltoid weakness and sensory loss over the lateral shoulder. The radial groove is related to the radial nerve, and the epicondyles are not the site of axillary nerve injury.

Question 3Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which muscle is the chief flexor of the hip joint?

  1. Piriformis
  2. Biceps femoris
  3. Gluteus maximus
  4. Iliopsoas Correct answer.

Explanation

The iliopsoas, formed by iliacus and psoas major, is the most powerful flexor of the hip. It acts strongly in activities such as climbing stairs and rising from a seated position. Gluteus maximus is primarily an extensor, and the hamstrings are hip extensors.

Question 4Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which vessel supplies the sinoatrial node in the majority of people?

  1. Left anterior descending artery
  2. Left circumflex artery
  3. Right coronary artery Correct answer.
  4. Posterior descending artery

Explanation

In most individuals the sinoatrial node is supplied by a branch of the right coronary artery, usually the sinoatrial nodal artery arising near its proximal portion. The left circumflex may supply it in a minority. The left anterior descending and posterior descending arteries are not the usual nodal supply.

Question 5Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which lung surface feature is created by the arch of the aorta?

  1. Cardiac impression
  2. Aortic impression on the left lung Correct answer.
  3. Groove for the superior vena cava
  4. Groove for the azygos vein

Explanation

The arch of the aorta leaves a distinct groove, the aortic impression, on the mediastinal surface of the left lung above the hilum. The cardiac impression is produced by the heart, and the superior vena cava and azygos vein leave grooves on the right lung.

Question 6Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which hormone is released from the posterior pituitary?

  1. Antidiuretic hormone Correct answer.
  2. Adrenocorticotropic hormone
  3. Prolactin
  4. Growth hormone

Explanation

The posterior pituitary stores and releases antidiuretic hormone and oxytocin, which are synthesized in the hypothalamic nuclei. Adrenocorticotropic hormone, prolactin, and growth hormone are anterior pituitary hormones.

Question 7Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which phase of the cardiac cycle corresponds to the first heart sound?

  1. Atrial systole
  2. Closure of the atrioventricular valves Correct answer.
  3. Opening of the atrioventricular valves
  4. Closure of the semilunar valves

Explanation

The first heart sound is produced by closure of the mitral and tricuspid valves at the onset of ventricular systole. The second heart sound results from closure of the aortic and pulmonary valves at the end of systole. Valve opening and atrial systole do not generate these audible sounds.

Question 8Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which enzyme catalyzes the rate-limiting step of glycolysis?

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

Explanation

Phosphofructokinase-1 catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, which is the committed and rate-limiting step of glycolysis. Hexokinase and pyruvate kinase are also regulated but not rate-limiting. Aldolase catalyzes a reversible cleavage step.

Question 9Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A patient has a lesion of the left recurrent laryngeal nerve. Which finding is expected?

  1. Right vocal cord paralysis
  2. Deviation of the tongue to the left
  3. Left vocal cord paralysis with hoarseness Correct answer.
  4. Loss of sensation over the chin

Explanation

The recurrent laryngeal nerve supplies most intrinsic laryngeal muscles, and a left-sided lesion causes left vocal cord paralysis with hoarseness. The left nerve is vulnerable because it loops under the aortic arch. Tongue deviation reflects hypoglossal nerve injury, and chin sensation is carried by the mental nerve.

Question 10Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Occlusion of the anterior interventricular artery most directly affects which region of the heart?

  1. Right atrium and right ventricle
  2. Posterior wall of the left ventricle
  3. Sinoatrial node in most people
  4. Anterior wall of the left ventricle and anterior two-thirds of the interventricular septum Correct answer.

Explanation

The anterior interventricular artery, a branch of the left coronary artery, supplies the anterior wall of both ventricles and the anterior two-thirds of the interventricular septum. Occlusion therefore produces an anterior myocardial infarction. The right atrium and posterior wall are supplied by other vessels.

Question 11Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which muscle both flexes the elbow and supinates the forearm?

  1. Biceps brachii Correct answer.
  2. Triceps brachii
  3. Pronator teres
  4. Brachioradialis

Explanation

The biceps brachii is a powerful elbow flexor and a strong supinator, especially when the elbow is flexed. Brachioradialis flexes the elbow but does not supinate. Pronator teres pronates, and the triceps extends the elbow.

Question 12Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Section of the dorsal roots of the spinal cord at a single level produces which effect?

  1. Spastic paralysis below the lesion
  2. Loss of motor power on the same side
  3. Loss of deep tendon reflexes only
  4. Loss of sensation in the corresponding dermatome Correct answer.

Explanation

Dorsal roots carry sensory fibers from the periphery to the spinal cord, so sectioning them abolishes sensation in the corresponding dermatome. Motor function is carried by ventral roots and remains intact. Reflex arcs may be affected, but the primary deficit is sensory loss.

Question 13Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which statement best describes the Frank-Starling relationship?

  1. Increased end-diastolic volume increases stroke volume within physiological limits Correct answer.
  2. Heart rate is directly proportional to stroke volume
  3. Contractility decreases as preload increases
  4. Cardiac output falls as venous return increases

Explanation

The Frank-Starling mechanism states that increased venous return raises end-diastolic volume and stretches cardiac muscle, increasing force of contraction and stroke volume. This occurs within physiological limits. It does not describe a fall in output with increased return, nor a direct relationship between heart rate and stroke volume.

Question 14Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which lung volume cannot be measured by simple spirometry?

  1. Tidal volume
  2. Expiratory reserve volume
  3. Inspiratory reserve volume
  4. Residual volume Correct answer.

Explanation

Residual volume is the air remaining in the lungs after maximal expiration and cannot be exhaled into a spirometer. It is measured indirectly by helium dilution, nitrogen washout, or body plethysmography. Tidal volume and the reserve volumes are all measurable by spirometry.

Question 15Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which hormone increases blood calcium by stimulating bone resorption and renal calcium reabsorption?

  1. Insulin
  2. Calcitonin
  3. Parathyroid hormone Correct answer.
  4. Aldosterone

Explanation

Parathyroid hormone raises serum calcium by stimulating osteoclastic bone resorption, increasing renal tubular calcium reabsorption, and promoting formation of active vitamin D. Calcitonin lowers serum calcium. Insulin and aldosterone do not primarily regulate calcium homeostasis.

Question 16Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A competitive inhibitor of an enzyme produces which kinetic change?

  1. Decreased both maximum velocity and Michaelis constant
  2. Decreased maximum velocity with unchanged Michaelis constant
  3. Increased Michaelis constant with unchanged maximum velocity Correct answer.
  4. Decreased Michaelis constant with unchanged maximum velocity

Explanation

A competitive inhibitor binds the active site reversibly, so higher substrate concentrations can overcome inhibition. This raises the apparent Michaelis constant while maximum velocity remains unchanged. Noncompetitive inhibition instead lowers maximum velocity.

Question 17Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which vitamin deficiency causes megaloblastic anemia with neurological symptoms?

  1. Vitamin B12 Correct answer.
  2. Folic acid
  3. Vitamin K
  4. Vitamin C

Explanation

Vitamin B12 deficiency impairs DNA synthesis and also causes demyelination of the spinal cord, producing megaloblastic anemia with neurological deficits. Folate deficiency causes megaloblastic anemia without neurological features. Vitamin C and K deficiencies do not cause megaloblastic anemia.

Question 18Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which enzyme is deficient in classic phenylketonuria?

  1. Phenylalanine hydroxylase Correct answer.
  2. Branched-chain ketoacid dehydrogenase
  3. Tyrosinase
  4. Homogentisate oxidase

Explanation

Classic phenylketonuria results from deficiency of phenylalanine hydroxylase, which converts phenylalanine to tyrosine. Phenylalanine accumulates and is transaminated to phenylpyruvate, causing intellectual disability if untreated. Tyrosinase deficiency causes albinism, and homogentisate oxidase deficiency causes alkaptonuria.

Question 19Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which structure lies immediately medial to the second part of the duodenum?

  1. Right kidney
  2. Common bile duct
  3. Head of the pancreas Correct answer.
  4. Transverse colon

Explanation

The head of the pancreas lies in the concavity of the duodenum, medial to its second part. The right kidney lies posterior and lateral. The transverse colon crosses anterior to the duodenum, and the common bile duct enters the second part posteromedially.

Question 20Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which condition results from a lesion of the right optic tract?

  1. Right monocular blindness
  2. Binasal hemianopia
  3. Left homonymous hemianopia Correct answer.
  4. Bitemporal hemianopia

Explanation

The right optic tract carries fibers from the temporal retina of the right eye and the nasal retina of the left eye, which correspond to the left visual field. A lesion therefore produces a left homonymous hemianopia. Monocular blindness follows optic nerve lesions, and bitemporal hemianopia follows optic chiasma lesions.

Question 21Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which molecule is the rate-limiting enzyme of cholesterol synthesis?

  1. Lipoprotein lipase
  2. HMG-CoA reductase Correct answer.
  3. Acetyl-CoA carboxylase
  4. Carnitine palmitoyltransferase I

Explanation

HMG-CoA reductase converts HMG-CoA to mevalonate and is the rate-limiting step of cholesterol synthesis. It is the target of statin drugs. Acetyl-CoA carboxylase regulates fatty acid synthesis, lipoprotein lipase hydrolyzes triglycerides, and carnitine palmitoyltransferase I controls fatty acid entry into mitochondria.

Question 22Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which nerve is most likely injured in a fracture of the midshaft of the humerus?

  1. Musculocutaneous nerve
  2. Radial nerve Correct answer.
  3. Ulnar nerve
  4. Median nerve

Explanation

The radial nerve runs in the spiral groove on the posterior surface of the humerus, making it vulnerable in midshaft fractures. Injury produces wrist drop and sensory loss over the dorsum of the hand. The median and ulnar nerves are more distally related to the elbow and forearm.

Question 23Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which of the following best explains why the left kidney is preferred for living donor nephrectomy?

  1. It has a shorter renal artery
  2. It has a longer renal vein Correct answer.
  3. It lacks a ureter
  4. It lies lower than the right kidney

Explanation

The left renal vein is longer because it crosses the aorta to reach the inferior vena cava, allowing easier anastomosis in transplantation. The left kidney lies slightly higher than the right, not lower. Both kidneys have a ureter and comparable arterial length.

Question 24Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A patient has metabolic acidosis with a normal anion gap. Which condition fits best?

  1. Lactic acidosis
  2. Methanol poisoning
  3. Diabetic ketoacidosis
  4. Renal tubular acidosis Correct answer.

Explanation

Renal tubular acidosis causes bicarbonate loss or impaired hydrogen ion excretion, producing hyperchloremic metabolic acidosis with a normal anion gap. Ketoacidosis, lactic acidosis, and methanol poisoning all accumulate unmeasured anions and widen the anion gap.

Question 25Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which of the following best describes the countercurrent multiplier mechanism in the loop of Henle?

  1. Water is actively transported out of the descending limb
  2. The descending limb is impermeable to water
  3. Solute is actively reabsorbed from the thick ascending limb, creating a hypertonic medullary interstitium Correct answer.
  4. The ascending limb is freely permeable to water

Explanation

The thick ascending limb actively transports sodium chloride into the interstitium while remaining impermeable to water, generating a hypertonic medullary gradient. The descending limb is permeable to water but not to solute. This arrangement allows concentration of urine under antidiuretic hormone.

Question 26Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which structure passes through the foramen ovale of the sphenoid bone?

  1. Middle meningeal artery
  2. Optic nerve
  3. Maxillary division of the trigeminal nerve
  4. Mandibular division of the trigeminal nerve Correct answer.

Explanation

The foramen ovale transmits the mandibular division of the trigeminal nerve along with the lesser petrosal nerve and accessory meningeal artery. The maxillary division instead traverses the foramen rotundum, and the middle meningeal artery enters through the foramen spinosum.

Question 27Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which type of epithelium lines the trachea?

  1. Pseudostratified ciliated columnar epithelium Correct answer.
  2. Stratified squamous epithelium
  3. Simple cuboidal epithelium
  4. Simple squamous epithelium

Explanation

The respiratory tract from the nasal cavity to the bronchi is lined by pseudostratified ciliated columnar epithelium with goblet cells, which moves mucus upward. Stratified squamous epithelium is found in the oral cavity and esophagus where abrasion occurs.

Question 28Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which ion is primarily responsible for the depolarization phase of the ventricular myocyte action potential?

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

Explanation

Rapid opening of voltage-gated sodium channels produces the steep phase 0 upstroke of the ventricular action potential. Calcium influx maintains the plateau, while potassium efflux drives repolarization.

Question 29Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which enzyme converts angiotensin I to angiotensin II?

  1. Renin
  2. Aldosterone synthase
  3. Neprilysin
  4. Angiotensin-converting enzyme Correct answer.

Explanation

Angiotensin-converting enzyme, located on pulmonary capillary endothelium, cleaves angiotensin I to the active octapeptide angiotensin II. Renin catalyzes the earlier step forming angiotensin I from angiotensinogen.

Question 30Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which vitamin deficiency causes night blindness and xerophthalmia?

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

Explanation

Vitamin A provides retinal, the chromophore of rhodopsin in rod photoreceptors, and maintains epithelial integrity. Deficiency therefore impairs dim-light vision and causes dry, keratinized conjunctiva and cornea.

Question 31Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which base pair is found in DNA but not in RNA?

  1. Adenine paired with uracil
  2. Adenine paired with thymine Correct answer.
  3. Guanine paired with cytosine
  4. Cytosine paired with guanine

Explanation

DNA contains thymine, which pairs with adenine through two hydrogen bonds. RNA substitutes uracil for thymine and therefore contains adenine-uracil pairs instead.

Question 32Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which cranial nerve supplies the muscles of mastication?

  1. Trigeminal nerve Correct answer.
  2. Glossopharyngeal nerve
  3. Hypoglossal nerve
  4. Facial nerve

Explanation

The motor root of the mandibular division of the trigeminal nerve innervates masseter, temporalis, and medial and lateral pterygoids. The facial nerve instead supplies the muscles of facial expression.

Question 33Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A red blood cell placed in a 0.45% sodium chloride solution will undergo which change?

  1. Sweeping
  2. Swelling followed by hemolysis Correct answer.
  3. Crenation
  4. No change in volume

Explanation

A 0.45% saline solution is hypotonic relative to plasma, so water enters the cell by osmosis. The erythrocyte swells and may eventually lyse, which is why such fluids are used cautiously.

Question 34Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A patient has elevated aldosterone with suppressed renin and hypertension. Which mechanism best explains the hypertension?

  1. Increased sodium reabsorption with volume expansion Correct answer.
  2. Reduced sympathetic outflow
  3. Decreased angiotensin II production
  4. Increased renal sodium excretion

Explanation

Primary aldosteronism drives sodium retention in the distal nephron, expanding extracellular fluid volume and raising blood pressure while suppressing renin. The volume expansion also causes hypertension with hypokalemia.

Question 35Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A competitive inhibitor is added to an enzyme reaction. Which parameter is unchanged?

  1. Apparent Km
  2. Maximal velocity (Vmax) Correct answer.
  3. Substrate affinity
  4. Michaelis constant (Km)

Explanation

A competitive inhibitor binds the active site reversibly, so a higher substrate concentration can still achieve the original maximal velocity. Vmax is therefore unchanged while the apparent Km increases.

Question 36Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A patient with chronic obstructive pulmonary disease has a prolonged expiration. Which change is expected?

  1. Decreased residual volume
  2. Increased vital capacity
  3. Increased residual volume Correct answer.
  4. Increased forced expiratory volume in one second

Explanation

Air trapping from airway obstruction leaves more gas in the lungs after maximal expiration, raising residual volume. The forced expiratory volume in one second falls and vital capacity is reduced.

Question 37Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which structure is most likely injured in a fracture of the surgical neck of the humerus?

  1. Axillary nerve Correct answer.
  2. Ulnar nerve
  3. Median nerve
  4. Radial nerve

Explanation

The axillary nerve winds around the surgical neck of the humerus and is at risk in fractures at this site, producing deltoid weakness and sensory loss over the lateral shoulder. The radial nerve is more associated with midshaft fractures.

Question 38Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A child presents with recurrent infections, absent thymic shadow, and low T lymphocytes. Which immune defect is most likely?

  1. X-linked agammaglobulinemia
  2. DiGeorge syndrome Correct answer.
  3. Chronic granulomatous disease
  4. Complement C3 deficiency

Explanation

DiGeorge syndrome results from failure of the third and fourth pharyngeal pouches, causing thymic hypoplasia with T-cell deficiency and hypocalcemia. Absent thymic shadow and defective cell-mediated immunity are characteristic.

Question 39Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which amino acid is the precursor of serotonin?

  1. Histidine
  2. Glutamate
  3. Tyrosine
  4. Tryptophan Correct answer.

Explanation

Tryptophan is hydroxylated and then decarboxylated to form serotonin, a biogenic amine neurotransmitter. Tyrosine is instead the precursor of catecholamines and thyroid hormone.

Question 40Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A patient has a lesion of the medial lemniscus. Which sensory modality is most affected?

  1. Pain and temperature from the contralateral body
  2. Taste from the anterior tongue
  3. Fine touch and vibration from the contralateral body Correct answer.
  4. Pain from the ipsilateral face

Explanation

The medial lemniscus carries proprioception, vibration, and fine touch fibers that crossed in the medulla to the contralateral side. Pain and temperature travel instead in the spinothalamic tract.

Question 41Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which hormone is released from the anterior pituitary and stimulates milk ejection?

  1. Follicle-stimulating hormone
  2. Prolactin
  3. Oxytocin Correct answer.
  4. Adrenocorticotropic hormone

Explanation

Oxytocin is released from the posterior pituitary and causes contraction of myoepithelial cells around alveoli, ejecting milk during suckling. Prolactin instead promotes milk synthesis.

Question 42Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A patient has a deficiency of pyruvate dehydrogenase. Which metabolic consequence is expected?

  1. Lactic acidosis with impaired acetyl-CoA formation Correct answer.
  2. Increased acetyl-CoA entry into the citric acid cycle
  3. Reduced glycolysis
  4. Enhanced gluconeogenesis from acetyl-CoA

Explanation

Pyruvate dehydrogenase converts pyruvate to acetyl-CoA, so deficiency causes pyruvate accumulation and conversion to lactate. Acetyl-CoA formation falls and the citric acid cycle is deprived of substrate.

Question 43Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A patient has a left-sided lesion of the optic chiasm. Which visual field defect is expected?

  1. Right homonymous hemianopia
  2. Binasal hemianopia
  3. Bitemporal hemianopia Correct answer.
  4. Left homonymous hemianopia

Explanation

The chiasm contains decussating fibers from the nasal retina of each eye, so a midline lesion interrupts both and produces loss of both temporal fields. This is classically associated with pituitary tumors.

Question 44Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which factor most increases oxygen unloading at the tissues?

  1. Decreased temperature
  2. Increased pH
  3. Increased carbon dioxide Correct answer.
  4. Decreased 2,3-bisphosphoglycerate

Explanation

Rising carbon dioxide lowers pH in tissue capillaries, shifting the oxygen dissociation curve to the right and reducing hemoglobin affinity. This Bohr effect enhances oxygen delivery to metabolically active tissue.

Question 45Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A patient with a cerebellar hemisphere lesion has which characteristic finding?

  1. Loss of vibration sense
  2. Contralateral spastic hemiplegia
  3. Intention tremor on the ipsilateral side Correct answer.
  4. Resting tremor with cogwheel rigidity

Explanation

The cerebellar hemispheres coordinate voluntary movement on the ipsilateral side, so lesions cause intention tremor, dysmetria, and ataxia. Resting tremor and rigidity point instead to basal ganglia disease.

Question 46Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which enzyme deficiency causes hereditary fructose intolerance?

  1. Fructokinase
  2. Glucokinase
  3. Fructose-1,6-bisphosphatase
  4. Aldolase B Correct answer.

Explanation

Aldolase B cleaves fructose-1-phosphate in the liver, and its deficiency causes fructose-1-phosphate accumulation with ATP depletion and hepatic dysfunction. Symptoms follow ingestion of fructose or sucrose.

Question 47Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which change in the pressure-volume loop occurs with increased arterial resistance?

  1. Increased end-systolic volume Correct answer.
  2. Decreased aortic pressure
  3. Decreased end-systolic volume
  4. Increased stroke volume

Explanation

Higher afterload opposes ejection, so the ventricle empties less completely and end-systolic volume rises. Stroke volume falls and myocardial oxygen demand increases as the ventricle works against greater resistance.

Question 48Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

A patient has a mutation causing loss of the sodium-potassium ATPase in the thick ascending limb. Which effect is expected?

  1. Increased potassium retention
  2. Reduced sodium chloride reabsorption with salt wasting Correct answer.
  3. Enhanced urine concentration
  4. Increased medullary concentration gradient

Explanation

The thick ascending limb Na-K-2Cl cotransporter depends on the basolateral sodium gradient generated by the Na-K ATPase. Loss of this pump reduces salt reabsorption and impairs the medullary gradient needed for concentration.

Question 49Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which statement best explains why the left ventricle has a thicker wall than the right ventricle?

  1. It has a larger end-diastolic volume
  2. It pumps against higher systemic vascular resistance Correct answer.
  3. It receives more coronary blood flow
  4. It contains more Purkinje fibers

Explanation

The left ventricle must generate pressures of about 120 mmHg to overcome systemic resistance, so chronic pressure load induces greater myocyte hypertrophy. The right ventricle pumps against low pulmonary resistance and needs less muscle mass.

Question 50Pre-clinical Sciences (Anatomy, Physiology, Biochemistry)

Which biochemical role is shared by biotin and pantothenic acid?

  1. Acting as coenzymes in carboxylation and acyl-transfer reactions Correct answer.
  2. Serving as antioxidants in membrane lipids
  3. Donating methyl groups in DNA methylation
  4. Functioning as intracellular calcium buffers

Explanation

Biotin is a coenzyme for carboxylase reactions, while pantothenic acid forms coenzyme A, which carries acyl groups into the citric acid cycle and fatty acid metabolism. Both are water-soluble vitamins acting as coenzyme precursors.