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Philippines PLE practice questions

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Question 1Anatomy and Physiology

A patient sustains a fracture through the surgical neck of the humerus. Which nerve is most likely injured because of its close relation to that region?

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

Explanation

The axillary nerve and posterior circumflex humeral artery wind around the surgical neck of the humerus, so a fracture at this site risks damaging the nerve and paralyzing the deltoid. The radial nerve lies in the spiral groove of the shaft, while the median and musculocutaneous nerves are not related to the surgical neck.

Question 2Anatomy and Physiology

Which heart valve prevents backflow of blood from the left ventricle into the left atrium during systole?

  1. Pulmonary valve
  2. Tricuspid valve
  3. Mitral valve Correct answer.
  4. Aortic valve

Explanation

The mitral (bicuspid) valve lies between the left atrium and left ventricle and closes during ventricular systole to prevent regurgitation into the atrium. The aortic valve guards the ventricular outflow, while the tricuspid and pulmonary valves belong to the right side of the heart.

Question 3Anatomy and Physiology

Which structure is the primary site of gas exchange in the lungs?

  1. Terminal bronchioles
  2. Alveoli Correct answer.
  3. Secondary bronchi
  4. Trachea

Explanation

Alveoli have thin walls and a rich capillary network, providing the large surface area needed for diffusion of oxygen and carbon dioxide. The conducting airways, including bronchi, bronchioles, and trachea, move air but do not perform meaningful gas exchange.

Question 4Anatomy and Physiology

Which hormone is released from the posterior pituitary?

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

Explanation

The posterior pituitary stores and releases antidiuretic hormone and oxytocin, both synthesized in the hypothalamus. ACTH, growth hormone, and prolactin are anterior pituitary hormones.

Question 5Anatomy and Physiology

Which type of muscle tissue is under voluntary control and shows striations?

  1. Cardiac muscle
  2. Myoepithelial tissue
  3. Skeletal muscle Correct answer.
  4. Smooth muscle

Explanation

Skeletal muscle is striated and innervated by somatic motor neurons, giving voluntary control. Cardiac and smooth muscle are involuntary, and myoepithelial tissue is a contractile epithelial derivative that is not voluntarily controlled.

Question 6Anatomy and Physiology

Which cranial nerve carries taste from the posterior third of the tongue?

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

Explanation

The glossopharyngeal nerve (CN IX) transmits taste from the posterior third of the tongue via its lingual branch. The facial nerve handles taste from the anterior two-thirds, while the hypoglossal and trigeminal nerves are motor and general sensory respectively.

Question 7Anatomy and Physiology

Which blood vessel is the main site of resistance to blood flow in the systemic circulation?

  1. Large veins
  2. Arterioles Correct answer.
  3. Large arteries
  4. Capillaries

Explanation

Arterioles have thick smooth muscle and small lumens, generating most peripheral resistance and regulating blood pressure distribution. Large arteries are elastic conduits, capillaries are exchange vessels, and veins are capacitance vessels.

Question 8Anatomy and Physiology

Which region of the nephron is the principal site of glucose reabsorption?

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

Explanation

The proximal convoluted tubule reabsorbs nearly all filtered glucose via sodium-coupled transporters. The descending limb is water-permeable but not a glucose reabsorption site, and the distal tubule and collecting duct handle fine-tuning of electrolytes and water under hormonal control.

Question 9Anatomy and Physiology

During a difficult delivery, a woman sustains a perineal tear that involves the muscle separating the urogenital and anal triangles. Which muscle is this?

  1. Bulbospongiosus
  2. External anal sphincter
  3. Levator ani
  4. Superficial transverse perineal muscle Correct answer.

Explanation

The superficial transverse perineal muscle runs across the perineal body and lies at the boundary between the urogenital and anal triangles. Bulbospongiosus and the external anal sphincter are located within their respective triangles, and levator ani forms the pelvic diaphragm above the perineum.

Question 10Anatomy and Physiology

A patient has a lesion of the upper trunk of the brachial plexus. Which posture of the limb is expected?

  1. Claw hand with preserved deltoid function
  2. Wrist drop with preserved shoulder abduction
  3. Arm abducted and externally rotated with the forearm supinated
  4. Arm adducted and internally rotated with the forearm pronated Correct answer.

Explanation

Upper trunk injury (Erb palsy) paralyzes supraspinatus, deltoid, biceps, and brachialis, producing the waiter's tip posture with adduction, internal rotation, and pronation. Wrist drop reflects radial nerve injury and claw hand reflects ulnar nerve injury.

Question 11Anatomy and Physiology

A patient with mitral stenosis develops pulmonary congestion. Which chamber is most immediately affected by the elevated pressure?

  1. Right ventricle
  2. Left atrium Correct answer.
  3. Inferior vena cava
  4. Aorta

Explanation

Mitral stenosis impedes flow from the left atrium to the left ventricle, raising left atrial pressure that is transmitted to the pulmonary veins. The aorta is downstream of the ventricle, and the right ventricle and vena cava are affected only after pulmonary hypertension develops.

Question 12Anatomy and Physiology

A patient has a lesion of the dorsal columns of the spinal cord. Which sensory modality is lost?

  1. Pain and temperature
  2. Crude touch and pressure
  3. Motor coordination of the contralateral limb
  4. Fine touch and vibration Correct answer.

Explanation

Dorsal columns carry fine touch, vibration, and conscious proprioception, which ascend ipsilaterally to the medulla. Pain and temperature travel in the spinothalamic tract, and motor coordination depends on cerebellar and corticospinal pathways.

Question 13Anatomy and Physiology

A patient with a thyroid tumor develops hoarseness due to involvement of a nerve in the tracheoesophageal groove. Which nerve is affected?

  1. Recurrent laryngeal nerve Correct answer.
  2. Superior laryngeal nerve
  3. Phrenic nerve
  4. Hypoglossal nerve

Explanation

The recurrent laryngeal nerve ascends in the tracheoesophageal groove and supplies most intrinsic laryngeal muscles, so injury causes vocal cord paresis and hoarseness. The superior laryngeal nerve is higher and supplies cricothyroid, while the hypoglossal and phrenic nerves serve the tongue and diaphragm.

Question 14Anatomy and Physiology

A patient's blood pressure is 120/80 mmHg. What is the approximate mean arterial pressure?

  1. 93 mmHg Correct answer.
  2. 120 mmHg
  3. 80 mmHg
  4. 100 mmHg

Explanation

Mean arterial pressure is estimated as diastolic pressure plus one-third of the pulse pressure, giving 80 + (40/3) ≈ 93 mmHg. The diastolic and systolic values themselves are endpoints, not the mean.

Question 15Anatomy and Physiology

A patient hyperventilates, lowering arterial CO2. What is the immediate effect on the oxygen-hemoglobin dissociation curve?

  1. Shift to the right with decreased hemoglobin oxygen affinity
  2. Shift to the right with decreased oxygen saturation at any given partial pressure
  3. No change because CO2 does not affect hemoglobin
  4. Shift to the left with increased hemoglobin oxygen affinity Correct answer.

Explanation

Hypocapnia raises blood pH, which shifts the oxygen-hemoglobin dissociation curve to the left (Bohr effect), increasing hemoglobin affinity for oxygen and reducing unloading at tissues. A rightward shift occurs with acidosis, hypercapnia, or raised temperature.

Question 16Anatomy and Physiology

A patient with chronic kidney disease has metabolic acidosis. Which compensatory response is expected in the respiratory system?

  1. Increased tidal volume with unchanged rate
  2. Hypoventilation to retain CO2
  3. Decreased oxygen affinity of hemoglobin
  4. Hyperventilation to lower arterial CO2 Correct answer.

Explanation

Metabolic acidosis stimulates peripheral chemoreceptors, producing hyperventilation that lowers arterial CO2 and raises pH toward normal (respiratory compensation). Hypoventilation would worsen the acidosis, and changes in hemoglobin affinity are not the primary respiratory compensation.

Question 17Anatomy and Physiology

A patient is unable to abduct the arm beyond 15 degrees and has weakness of shoulder abduction. Which muscle is most likely affected?

  1. Supraspinatus Correct answer.
  2. Pectoralis major
  3. Latissimus dorsi
  4. Teres major

Explanation

Supraspinatus initiates the first 15 degrees of abduction and is tested by resisting abduction with the arm at the side. Deltoid continues abduction beyond that range, while teres major, pectoralis major, and latissimus dorsi are adductors and medial rotators.

Question 18Anatomy and Physiology

A patient has a lesion of the facial nerve within the parotid gland. Which finding is expected?

  1. Contralateral loss of forehead wrinkling
  2. Ipsilateral loss of forehead wrinkling and mouth closure Correct answer.
  3. Ipsilateral loss of general sensation over the cheek
  4. Ipsilateral loss of taste from the posterior tongue

Explanation

A peripheral facial nerve lesion affects all ipsilateral facial muscles, including the frontalis, so both forehead wrinkling and mouth closure are lost. Central lesions spare the forehead because of bilateral cortical innervation, and taste and cheek sensation are served by other nerves.

Question 19Anatomy and Physiology

A patient has a lesion of the corticospinal tract above the decussation. Which side will show motor weakness?

  1. Contralateral side Correct answer.
  2. Ipsilateral side
  3. No weakness because of compensation
  4. Bilateral sides equally

Explanation

Corticospinal fibers decussate at the medullary pyramids, so a lesion above the decussation produces contralateral weakness. Lesions below the decussation produce ipsilateral deficits.

Question 20Anatomy and Physiology

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

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

Explanation

The left optic tract carries fibers from the temporal retina of the left eye and nasal retina of the right eye, representing the right visual field, so a lesion causes right homonymous hemianopia. Bitemporal defects arise at the optic chiasm, and quadrantanopia suggests a more distal radiation lesion.

Question 21Anatomy and Physiology

A patient has a stroke affecting the posterior limb of the internal capsule. Which artery is most likely involved?

  1. Posterior cerebral artery
  2. Anterior cerebral artery
  3. Lenticulostriate branches of the middle cerebral artery Correct answer.
  4. Vertebral artery

Explanation

The lenticulostriate arteries supply the internal capsule, and their occlusion commonly produces a dense contralateral hemiparesis. The anterior cerebral artery supplies the medial frontal cortex, the posterior cerebral artery the occipital lobe, and the vertebral artery the brainstem and cerebellum.

Question 22Anatomy and Physiology

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

  1. Loss of sensation over the left ear
  2. Hoarseness with the left vocal cord in a paramedian position Correct answer.
  3. Deviation of the tongue to the left
  4. Loss of taste from the anterior tongue

Explanation

The left recurrent laryngeal nerve loops under the aortic arch and supplies most intrinsic laryngeal muscles, so injury leaves the left cord paramedian and causes hoarseness. Taste, tongue movement, and ear sensation are served by other cranial nerves.

Question 23Anatomy and Physiology

Which change in the alveolar gas equation explains the lower arterial oxygen tension in a patient breathing room air at high altitude?

  1. Reduced inspired oxygen partial pressure Correct answer.
  2. Increased alveolar ventilation
  3. Increased oxygen consumption by tissues
  4. Reduced hemoglobin concentration

Explanation

At high altitude the barometric pressure falls, lowering the inspired oxygen partial pressure and alveolar oxygen tension, which lowers arterial oxygen tension. Hemoglobin concentration affects content rather than tension, and increased ventilation partially offsets but does not reverse the gradient.

Question 24Anatomy and Physiology

A patient with a lesion of the right phrenic nerve develops paradoxical movement of the right hemidiaphragm during inspiration. Which mechanism explains this?

  1. Increased sympathetic tone to the diaphragm
  2. Loss of motor innervation to the right hemidiaphragm with passive ascent during inspiration Correct answer.
  3. Compression of the right lung by the elevated diaphragm
  4. Loss of sensory innervation of the right pleura

Explanation

The phrenic nerve provides motor innervation to the diaphragm, and unilateral paralysis causes the affected hemidiaphragm to rise passively as intrathoracic pressure falls during inspiration. Sympathetic tone and pleural sensation do not drive diaphragmatic contraction.

Question 25Anatomy and Physiology

A patient with a lesion of the posterior column-medial lemniscus pathway has preserved pain sensation but impaired vibration sense. Which anatomical feature explains this dissociation?

  1. Vibration is transmitted by the corticospinal tract
  2. The dorsal columns carry vibration ipsilaterally before decussating in the medulla Correct answer.
  3. The spinothalamic tract carries vibration and pain together
  4. Pain fibers decussate in the medulla alongside the dorsal columns

Explanation

Dorsal column fibers ascend ipsilaterally and decussate in the medulla, whereas spinothalamic fibers decussate within the spinal cord and carry pain and temperature. This separation explains the dissociation between vibration and pain loss in partial cord lesions.

Question 26Anatomy and Physiology

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

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

Explanation

The foramen ovale transmits the mandibular division (V3) of the trigeminal nerve along with the lesser petrosal nerve and accessory meningeal artery. The maxillary division instead leaves through the foramen rotundum, while the optic nerve and facial nerve use entirely different foramina.

Question 27Anatomy and Physiology

Which type of cartilage forms the epiglottis?

  1. Hyaline cartilage
  2. Elastic cartilage Correct answer.
  3. Calcified hyaline cartilage
  4. Fibrocartilage

Explanation

The epiglottis is composed of elastic cartilage, whose abundant elastic fibers allow it to bend and spring back during swallowing. Hyaline cartilage forms most other laryngeal cartilages such as the thyroid and cricoid, while fibrocartilage is found in regions like the intervertebral discs.

Question 28Anatomy and Physiology

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

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

Explanation

IgM is the first antibody isotype synthesized in a primary immune response, appearing before class switching occurs. IgG dominates the secondary response, IgA guards mucosal surfaces, and IgE mediates type I hypersensitivity.

Question 29Anatomy and Physiology

A deficiency of which vitamin impairs the carboxylation of glutamate residues in clotting factors II, VII, IX, and X?

  1. Vitamin B12
  2. Vitamin K Correct answer.
  3. Vitamin C
  4. Vitamin B1

Explanation

Vitamin K is the cofactor for gamma-glutamyl carboxylase, which converts glutamate residues on factors II, VII, IX, and X into gamma-carboxyglutamate needed for calcium binding. Vitamin C supports collagen hydroxylation, B12 supports DNA synthesis and myelin, and B1 is a coenzyme in carbohydrate metabolism.

Question 30Anatomy and Physiology

A patient sustains a midshaft humeral fracture and develops wrist drop with loss of sensation over the dorsum of the hand between the first and second metacarpals. Which nerve is injured?

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

Explanation

The radial nerve spirals in the radial groove against the humeral shaft, so midshaft fractures commonly injure it. Loss produces weakness of wrist and finger extensors (wrist drop) plus sensory loss in the first dorsal web space, its autonomous zone.

Question 31Anatomy and Physiology

A patient has a lesion of the right oculomotor nerve. Which combination of findings is expected?

  1. Diplopia only on downward gaze with a normal pupil
  2. Ptosis, a medially deviated eye, and a constricted pupil
  3. Loss of abduction with preserved adduction
  4. Ptosis, a laterally deviated eye, and a dilated pupil Correct answer.

Explanation

The oculomotor nerve supplies the levator palpebrae superioris and all extraocular muscles except the superior oblique and lateral rectus. Its loss therefore causes ptosis, unopposed lateral rectus and superior oblique action (eye down and out), and parasympathetic pupillary dilation.

Question 32Anatomy and Physiology

Which lung volume cannot be measured by simple spirometry but requires body plethysmography or helium dilution?

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

Explanation

Residual volume is the air remaining after maximal expiration and cannot be exhaled into a spirometer, so it must be measured indirectly. Tidal volume and the inspiratory and expiratory reserve volumes are all directly measurable by spirometry.

Question 33Anatomy and Physiology

A patient has a tumor compressing the pituitary gland and develops bitemporal hemianopia. Which structure is being compressed?

  1. Optic tract
  2. Lateral geniculate body
  3. Optic radiation
  4. Optic chiasm Correct answer.

Explanation

The optic chiasm lies just above the sella turcica, so a pituitary mass compresses the crossing nasal fibers from each retina. Those fibers carry the temporal visual fields, producing the classic bitemporal hemianopia.

Question 34Anatomy and Physiology

A patient has an aldosterone-secreting adrenal adenoma. Which set of changes is expected?

  1. Hypernatremia with hyperkalemia
  2. Hyperkalemia with metabolic acidosis
  3. Hypokalemia with metabolic acidosis
  4. Hypokalemia with metabolic alkalosis Correct answer.

Explanation

Aldosterone increases sodium reabsorption and potassium and hydrogen secretion in the distal nephron. Excess aldosterone therefore drives potassium loss (hypokalemia) and hydrogen loss, generating a metabolic alkalosis with mild sodium retention.

Question 35Anatomy and Physiology

During the cardiac cycle, which event coincides with closure of the semilunar valves?

  1. Onset of ventricular systole
  2. End of ventricular systole Correct answer.
  3. Peak of the QRS complex
  4. Opening of the atrioventricular valves

Explanation

Semilunar valve closure marks the end of ventricular systole and produces the second heart sound. Atrioventricular valve closure occurs at the start of systole and produces the first heart sound.

Question 36Anatomy and Physiology

A patient with a lesion of the left cerebellar hemisphere is examined. Which finding is most likely?

  1. Resting tremor of both hands
  2. Loss of pain sensation on the right side
  3. Intention tremor of the left arm Correct answer.
  4. Spastic weakness of the right leg

Explanation

The cerebellar hemispheres coordinate the ipsilateral limbs, so a left hemisphere lesion produces left-sided limb ataxia with intention tremor and dysmetria. Spastic weakness and crossed sensory loss indicate corticospinal or spinothalamic tract involvement instead.

Question 37Anatomy and Physiology

A patient with severe diarrhea loses large amounts of bicarbonate-rich fluid. Which acid-base disturbance is expected?

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

Explanation

Gastrointestinal loss of bicarbonate removes the main extracellular buffer base, lowering plasma bicarbonate and producing a normal anion gap metabolic acidosis. The lungs compensate by increasing ventilation, which lowers arterial carbon dioxide.

Question 38Anatomy and Physiology

A patient has a mutation that abolishes the function of the Na+/K+ ATPase in skeletal muscle. Which immediate consequence is expected?

  1. Loss of the resting membrane potential gradient Correct answer.
  2. Failure of acetylcholine release from the motor terminal
  3. Inability of troponin to bind calcium
  4. Blockade of the ryanodine receptor calcium channel

Explanation

The Na+/K+ ATPase maintains the high intracellular potassium and high extracellular sodium that establish the resting membrane potential. Without it, ion gradients dissipate and the membrane depolarizes, eventually preventing excitability.

Question 39Anatomy and Physiology

A patient has a mutation in the gene for collagen type I. Which tissue abnormality is most directly explained?

  1. Defective cartilage at articular surfaces
  2. Absence of basement membrane anchoring fibrils
  3. Fragile bones with blue sclerae Correct answer.
  4. Disorganized elastic fibers in the aortic wall

Explanation

Type I collagen is the principal collagen of bone, skin, dentin, and tendon, so defective synthesis produces osteogenesis imperfecta with brittle bones and thin blue-appearing sclerae. Cartilage matrix depends mainly on type II collagen, elastic fibers on elastin, and anchoring fibrils on type VII collagen.

Question 40Anatomy and Physiology

A drug blocks the Na+/K+/2Cl- cotransporter in the thick ascending limb of the loop of Henle. Which change in tubular fluid composition is expected at the macula densa?

  1. Increased sodium and chloride delivery Correct answer.
  2. Decreased sodium and chloride delivery
  3. Increased potassium reabsorption
  4. Increased water permeability

Explanation

Loop diuretics inhibit the luminal Na+/K+/2Cl- cotransporter, so sodium and chloride remain in the tubular fluid and reach the macula densa in greater amounts. This increased distal delivery stimulates tubuloglomerular feedback and renin release.

Question 41Biochemistry and Nutrition

A 30-year-old man with a chronic alcohol use disorder is admitted with confusion and ataxia. Which enzyme is most directly impaired by thiamine deficiency in the pathogenesis of Wernicke encephalopathy?

  1. Lactate dehydrogenase
  2. Glutamate dehydrogenase
  3. Pyruvate carboxylase
  4. Pyruvate dehydrogenase complex Correct answer.

Explanation

Thiamine pyrophosphate is an essential cofactor for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase. Loss of pyruvate dehydrogenase activity impairs oxidative decarboxylation of pyruvate, reducing ATP production in glucose-dependent tissues such as brain. This energy failure underlies the classic triad of ophthalmoplegia, ataxia, and confusion.

Question 42Biochemistry and Nutrition

Which vitamin deficiency classically produces a macrocytic anemia with hypersegmented neutrophils and elevated serum methylmalonic acid?

  1. Vitamin B6 deficiency
  2. Iron deficiency
  3. Vitamin B12 deficiency Correct answer.
  4. Folate deficiency

Explanation

Vitamin B12 is required for the conversion of methylmalonyl-CoA to succinyl-CoA, so its deficiency raises methylmalonic acid. Folate deficiency produces the same macrocytic picture but methylmalonic acid stays normal because folate is not involved in that reaction. Elevated methylmalonic acid therefore points to B12.

Question 43Biochemistry and Nutrition

A newborn presents with poor feeding, vomiting, and hyperammonemia after starting protein feeds. Enzyme testing shows deficient ornithine transcarbamylase. Which metabolite pair is expected to be low in blood in this disorder?

  1. Aspartate and malate
  2. Citrulline and arginine Correct answer.
  3. Ornithine and glutamate
  4. Glutamine and alanine

Explanation

Ornithine transcarbamylase catalyzes the reaction of carbamoyl phosphate with ornithine to form citrulline. When this step is blocked, citrulline cannot be made, so both citrulline and its downstream product arginine fall. Ammonia instead accumulates and is buffered as glutamine.

Question 44Biochemistry and Nutrition

In the fasting state, which enzyme catalyzes the rate-limiting step of hepatic gluconeogenesis from lactate?

  1. Fructose-1,6-bisphosphatase Correct answer.
  2. Hexokinase
  3. Pyruvate kinase
  4. Phosphofructokinase-1

Explanation

Fructose-1,6-bisphosphatase catalyzes the hydrolysis of fructose-1,6-bisphosphate to fructose-6-phosphate, the key regulated and irreversible step of gluconeogenesis. It is activated by glucagon through reduced fructose-2,6-bisphosphate. The other listed enzymes catalyze glycolytic steps.

Question 45Biochemistry and Nutrition

A patient with severe abdominal pain, reddish urine, and neuropathy is found to have elevated delta-aminolevulinic acid and porphobilinogen. Which enzyme deficiency best fits acute intermittent porphyria?

  1. Protoporphyrinogen oxidase
  2. Porphobilinogen deaminase Correct answer.
  3. Uroporphyrinogen decarboxylase
  4. Ferrochelatase

Explanation

Acute intermittent porphyria results from deficiency of porphobilinogen deaminase, also called hydroxymethylbilane synthase. The block causes accumulation of the neurotoxic precursors delta-aminolevulinic acid and porphobilinogen. Urine darkens on standing as these precursors polymerize.

Question 46Biochemistry and Nutrition

A 45-year-old woman has fasting glucose of 118 mg/dL and a 2-hour glucose of 168 mg/dL on a 75-g oral glucose tolerance test. What is the most appropriate interpretation?

  1. Normal glucose tolerance
  2. Impaired glucose tolerance Correct answer.
  3. Diabetes mellitus
  4. Isolated impaired fasting glucose

Explanation

A 2-hour plasma glucose between 140 and 199 mg/dL on an oral glucose tolerance test defines impaired glucose tolerance. Her fasting value of 118 mg/dL also falls in the impaired fasting range of 100 to 125 mg/dL. Diabetes requires a 2-hour value of at least 200 mg/dL.

Question 47Biochemistry and Nutrition

Which lipoprotein particle is the primary carrier of endogenously synthesized triglycerides from the liver to peripheral tissues?

  1. Low-density lipoprotein
  2. Chylomicron
  3. High-density lipoprotein
  4. Very-low-density lipoprotein Correct answer.

Explanation

Very-low-density lipoprotein assembles in the liver and transports endogenous triglycerides to adipose and muscle tissue. Chylomicrons carry dietary fat instead. Low-density lipoprotein mainly delivers cholesterol, and high-density lipoprotein participates in reverse cholesterol transport.

Question 48Biochemistry and Nutrition

A child with poorly controlled type 1 diabetes presents with abdominal pain, Kussmaul breathing, and blood glucose of 480 mg/dL. Which laboratory pattern is most consistent with diabetic ketoacidosis?

  1. Metabolic alkalosis with hypochloremia
  2. Normal anion gap acidosis with hyperkalemia
  3. Respiratory alkalosis with low anion gap
  4. High anion gap metabolic acidosis with ketonemia Correct answer.

Explanation

Insulin deficiency drives lipolysis and hepatic ketogenesis, producing beta-hydroxybutyrate and acetoacetate. These ketoacids consume bicarbonate and generate an elevated anion gap metabolic acidosis. Kussmaul respirations represent compensatory respiratory alkalosis.

Question 49Biochemistry and Nutrition

Which enzyme is deficient in classic galactosemia, and which metabolite accumulates as a result?

  1. Galactose-1-phosphate uridyltransferase; galactose-1-phosphate Correct answer.
  2. Aldose reductase; galactitol
  3. Galactokinase; galactose
  4. UDP-galactose-4-epimerase; UDP-galactose

Explanation

Classic galactosemia is caused by deficiency of galactose-1-phosphate uridyltransferase, or GALT. Galactose-1-phosphate accumulates and is toxic to liver, brain, and lens. Affected infants develop jaundice, hepatomegaly, and cataracts after milk feeding.

Question 50Biochemistry and Nutrition

A 60-year-old man with chronic pancreatitis develops night blindness and dry eyes. Which biochemical role best explains his symptoms?

  1. Ascorbate is required for collagen hydroxylation
  2. Retinal is required for the visual cycle and epithelial integrity Correct answer.
  3. Phylloquinone is required for gamma-carboxylation of clotting factors
  4. Tocopherol acts as a cofactor for carboxylase enzymes

Explanation

Vitamin A deficiency impairs production of rhodopsin, the visual pigment needed for dim-light vision, causing night blindness. It also compromises epithelial differentiation, producing xerophthalmia and dry eyes. Fat malabsorption from chronic pancreatitis predisposes to this deficiency.