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Taiwan Dentist Licensing Examination study materials
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Taiwan Dentist Licensing Examination practice questions

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Question 1Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which cranial nerve provides motor innervation to the muscles of mastication?

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

Explanation

The mandibular division of the trigeminal nerve supplies the four muscles of mastication (masseter, temporalis, medial and lateral pterygoids). The facial nerve supplies muscles of facial expression, not mastication.

Question 2Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which enzyme catalyzes the rate-limiting step of glycolysis?

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

Explanation

Phosphofructokinase-1 catalyzes the committed, rate-limiting step converting fructose-6-phosphate to fructose-1,6-bisphosphate and is the major regulatory point of glycolysis.

Question 3Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A patient has a lesion of the right hypoglossal nerve. On protrusion, the tongue deviates toward which side?

  1. Superiorly
  2. Right side Correct answer.
  3. Left side
  4. No deviation occurs

Explanation

The genioglossus protrudes the tongue; a unilateral hypoglossal lesion weakens that side, so the tongue deviates toward the side of the lesion on protrusion.

Question 4Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

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

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

Explanation

IgM is the first antibody isotype expressed during a primary humoral response, before class switching to IgG and other isotypes.

Question 5Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A drug that competitively antagonizes a receptor will characteristically produce which effect on the agonist dose-response curve?

  1. A parallel shift to the right with unchanged maximal response Correct answer.
  2. A downward shift of the maximal response
  3. No change in the curve
  4. A parallel shift to the left

Explanation

Competitive antagonism is surmountable: increasing agonist concentration overcomes the block, shifting the curve right without reducing the maximum. Noncompetitive antagonism lowers the maximal response instead.

Question 6Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which vitamin deficiency causes megaloblastic anemia with hypersegmented neutrophils?

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

Explanation

Vitamin B12 (and folate) deficiency impairs DNA synthesis, producing megaloblastic anemia with nuclear-cytoplasmic asynchrony and hypersegmented neutrophils.

Question 7Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

During the cardiac cycle, which event corresponds to the first heart sound?

  1. Opening of the mitral valve
  2. Closure of the semilunar valves
  3. Atrial contraction
  4. Closure of the atrioventricular valves Correct answer.

Explanation

The first heart sound (S1) results from closure of the mitral and tricuspid (atrioventricular) valves at the onset of ventricular systole.

Question 8Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which type of collagen predominates in the organic matrix of bone?

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

Explanation

Bone matrix is composed predominantly of type I collagen, which provides tensile strength for mineralization.

Question 9Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A lesion of the facial nerve within the facial canal proximal to the geniculate ganglion would most likely impair which function in addition to facial movement?

  1. Mastication
  2. Taste from the anterior two-thirds of the tongue Correct answer.
  3. Hearing acuity
  4. Taste from the posterior third of the tongue

Explanation

The chorda tympani branch of the facial nerve carries taste from the anterior two-thirds of the tongue; a lesion proximal to its origin impairs this taste along with facial motor function.

Question 10Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which process describes the movement of water across a semipermeable membrane from low to high solute concentration?

  1. Facilitated diffusion
  2. Active transport
  3. Osmosis Correct answer.
  4. Endocytosis

Explanation

Osmosis is the passive movement of water down its concentration gradient across a semipermeable membrane in response to solute concentration differences.

Question 11Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which organism is the most common cause of dental caries initiation?

  1. Staphylococcus aureus
  2. Streptococcus mutans Correct answer.
  3. Escherichia coli
  4. Candida albicans

Explanation

Streptococcus mutans adheres to enamel, ferments sucrose to produce acids, and is strongly implicated in caries initiation.

Question 12Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A patient with a duodenal ulcer tests positive for a urease-producing organism. Which organism is most likely?

  1. Helicobacter pylori Correct answer.
  2. Salmonella typhi
  3. Vibrio cholerae
  4. Campylobacter jejuni

Explanation

Helicobacter pylori colonizes the gastric mucosa, produces urease, and is strongly associated with peptic ulcer disease.

Question 13Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which phase of the cell cycle is the primary target of the spindle assembly checkpoint?

  1. Metaphase of mitosis Correct answer.
  2. G1 phase
  3. G2 phase
  4. S phase

Explanation

The spindle assembly checkpoint operates during metaphase to ensure all chromosomes are properly attached to the spindle before anaphase begins.

Question 14Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A 55-year-old man has hypertension and hypokalemia with an elevated aldosterone-to-renin ratio. Which is the most likely diagnosis?

  1. Renal artery stenosis
  2. Addison disease
  3. Primary hyperaldosteronism Correct answer.
  4. Pheochromocytoma

Explanation

Autonomous aldosterone secretion suppresses renin, producing a high aldosterone-to-renin ratio with hypertension and hypokalemia, typical of primary hyperaldosteronism.

Question 15Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which drug mechanism underlies the analgesic and antipyretic action of aspirin?

  1. Inhibition of voltage-gated sodium channels
  2. Activation of adenosine receptors
  3. Irreversible inhibition of cyclooxygenase Correct answer.
  4. Blockade of opioid receptors

Explanation

Aspirin irreversibly acetylates cyclooxygenase, reducing prostaglandin synthesis and thereby producing analgesia, antipyresis, and anti-inflammatory effects.

Question 16Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

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

  1. Mandibular nerve Correct answer.
  2. Maxillary nerve
  3. Optic nerve
  4. Facial nerve

Explanation

The mandibular division of the trigeminal nerve exits the skull through the foramen ovale, along with the lesser petrosal nerve and accessory meningeal artery.

Question 17Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A deficiency of pyruvate dehydrogenase would most directly impair the conversion of pyruvate to which product?

  1. Glucose
  2. Lactate
  3. Oxaloacetate
  4. Acetyl-CoA Correct answer.

Explanation

Pyruvate dehydrogenase catalyzes oxidative decarboxylation of pyruvate to acetyl-CoA, linking glycolysis to the citric acid cycle.

Question 18Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which type of hypersensitivity reaction mediates acute hemolytic transfusion reactions?

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

Explanation

Acute hemolytic transfusion reactions are type II (antibody-mediated cytotoxic) reactions in which preformed antibodies bind donor red cell antigens and trigger complement-mediated lysis.

Question 19Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

In a patient with chronic renal failure, which acid-base disturbance is most typical?

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

Explanation

Failing kidneys cannot adequately excrete hydrogen ions or regenerate bicarbonate, producing a normal-anion-gap or high-anion-gap metabolic acidosis.

Question 20Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which statement best distinguishes necrosis from apoptosis?

  1. Necrosis is always programmed and physiological
  2. Apoptosis triggers intense neutrophilic infiltration
  3. Necrosis is energy-dependent and non-inflammatory
  4. Apoptosis is energy-dependent and non-inflammatory Correct answer.

Explanation

Apoptosis is an ATP-dependent, programmed process that avoids inflammation by packaging cell remnants for phagocytosis. Necrosis is typically passive, injurious, and provokes inflammation.

Question 21Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A drug has a volume of distribution of 40 liters and a clearance of 4 L/hour. What is its elimination half-life?

  1. 7 hours Correct answer.
  2. 2 hours
  3. 40 hours
  4. 10 hours

Explanation

Half-life equals 0.693 times volume of distribution divided by clearance: 0.693 × 40 / 4 ≈ 6.93 hours, approximately 7 hours.

Question 22Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which mechanism best explains why local anesthetics fail to act in an acidic, inflamed tissue environment?

  1. Increased fraction of uncharged drug crossing the membrane
  2. Enhanced systemic absorption
  3. Reduced proportion of charged drug entering the axon Correct answer.
  4. Decreased binding to sodium channels

Explanation

Local anesthetics must cross the membrane in the uncharged form and then bind the channel in the charged form. In acidic tissue, more drug remains charged and cannot cross the membrane, reducing block.

Question 23Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which feature best characterizes a malignant tumor on histologic examination?

  1. Well-circumscribed borders with a capsule
  2. Uniform nuclei with low mitotic activity
  3. Absence of necrosis
  4. Invasion of the basement membrane Correct answer.

Explanation

Invasion through the basement membrane into underlying tissue is a defining feature of malignancy, distinguishing carcinoma in situ from invasive carcinoma.

Question 24Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A patient develops fever, rash, and hypotension minutes after a penicillin injection and has pre-existing IgE against penicillin. Which mediator is most responsible for the acute symptoms?

  1. Histamine released from mast cells Correct answer.
  2. Complement C3b opsonization
  3. Interferon-gamma from T cells
  4. IgG-mediated complement lysis

Explanation

Anaphylaxis is a type I IgE-mediated reaction in which antigen cross-links IgE on mast cells, triggering histamine release and vasodilation with bronchoconstriction.

Question 25Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which statement about the Bohr effect is correct?

  1. Increased pH shifts the oxygen dissociation curve to the right
  2. Increased carbon dioxide shifts the curve to the right Correct answer.
  3. Increased temperature decreases oxygen unloading
  4. Decreased 2,3-BPG increases oxygen unloading

Explanation

Rising CO2 lowers pH and increases carbamino formation, shifting the oxygen dissociation curve rightward and promoting oxygen unloading in tissues.

Question 26Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which nerve provides motor innervation to the muscles of mastication?

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

Explanation

The mandibular division (V3) of the trigeminal nerve carries branchial motor fibers to the muscles of mastication (masseter, temporalis, medial and lateral pterygoids), which derive from the first pharyngeal arch. The other branches listed serve sensory or different motor functions.

Question 27Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

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

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

Explanation

IgM is the first antibody isotype expressed during a primary immune response, appearing before class switching to IgG. IgG dominates the secondary response, while IgA and IgE serve mucosal and allergic roles.

Question 28Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which vitamin is a precursor for the coenzyme required by carboxylase enzymes such as pyruvate carboxylase?

  1. Thiamine
  2. Riboflavin
  3. Cobalamin
  4. Biotin Correct answer.

Explanation

Biotin is covalently attached to carboxylase enzymes and carries activated CO2 during carboxylation reactions, including those of pyruvate carboxylase and acetyl-CoA carboxylase. The other vitamins serve different coenzyme roles.

Question 29Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which class of drugs lowers blood pressure primarily by blocking the conversion of angiotensin I to angiotensin II?

  1. Angiotensin-converting enzyme inhibitors Correct answer.
  2. Thiazide diuretics
  3. Calcium channel blockers
  4. Beta-adrenergic antagonists

Explanation

ACE inhibitors block the enzyme that converts angiotensin I to angiotensin II, reducing vasoconstriction and aldosterone release. The other classes act through different mechanisms.

Question 30Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which type of epithelium lines the oral mucosa of the hard palate on its masticatory surface?

  1. Simple columnar epithelium
  2. Pseudostratified ciliated columnar epithelium
  3. Non-keratinized stratified squamous epithelium
  4. Keratinized stratified squamous epithelium Correct answer.

Explanation

Masticatory mucosa covering the hard palate and gingiva is subject to friction and is lined by keratinized stratified squamous epithelium. Lining mucosa elsewhere is typically non-keratinized.

Question 31Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which structure is the primary pacemaker of the heart?

  1. Purkinje fibers
  2. Bundle of His
  3. Sinoatrial node Correct answer.
  4. Atrioventricular node

Explanation

The sinoatrial node has the fastest spontaneous depolarization rate and therefore sets the normal sinus rhythm. The AV node and conduction system act as slower backup pacemakers.

Question 32Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which organism is a gram-positive coccus that grows in clusters and is a common cause of dental abscesses?

  1. Staphylococcus aureus Correct answer.
  2. Escherichia coli
  3. Streptococcus mutans
  4. Bacteroides fragilis

Explanation

Staphylococcus aureus is a gram-positive coccus arranged in clusters and is a frequent cause of suppurative dental and soft tissue infections. The other organisms differ in Gram stain, morphology, or oxygen tolerance.

Question 33Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A drug that competitively inhibits a receptor produces which type of pharmacologic effect when administered alone?

  1. It increases the potency of the agonist
  2. It shifts the agonist dose-response curve to the left
  3. It reduces the maximal response of the agonist without shifting the curve
  4. It shifts the agonist dose-response curve to the right without reducing maximal response Correct answer.

Explanation

Competitive (reversible) antagonists raise the agonist concentration needed to achieve a given effect, shifting the dose-response curve rightward while preserving maximal efficacy at high agonist concentrations. Noncompetitive antagonists instead reduce maximal response.

Question 34Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A patient has a lesion of the hypoglossal nerve on one side. Which finding is expected on examination?

  1. Loss of taste on the anterior two-thirds of the tongue
  2. Loss of sensation on the posterior one-third of the tongue
  3. Tongue deviation toward the side of the lesion on protrusion Correct answer.
  4. Tongue deviation away from the side of the lesion on protrusion

Explanation

The genioglossus muscle protrudes the tongue, so when it is weak the unopposed contralateral muscle pushes the tongue toward the weak (lesioned) side. Taste and general sensation are carried by other nerves.

Question 35Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

During a starvation state, which process provides glucose primarily for the brain from non-carbohydrate precursors?

  1. Muscle glycogenolysis
  2. Hepatic glycolysis
  3. Adipose lipogenesis
  4. Hepatic gluconeogenesis Correct answer.

Explanation

After glycogen stores are depleted, the liver synthesizes glucose from lactate, glycerol, and amino acids via gluconeogenesis to maintain blood glucose for the brain. Muscle glycogen lacks glucose-6-phosphatase and cannot release free glucose.

Question 36Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A tumor is described as having cells that infiltrate surrounding tissue and lack a basement membrane. Which term best describes this behavior?

  1. Metastasis
  2. Invasive growth Correct answer.
  3. Dysplasia
  4. Hypertrophy

Explanation

Invasion refers to direct extension of tumor cells through the basement membrane into adjacent tissues, a hallmark of malignancy. Metastasis specifically requires spread to distant sites, which is not described here.

Question 37Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which change in the oxygen-hemoglobin dissociation curve results from an increase in 2,3-bisphosphoglycerate?

  1. No change in curve position but reduced maximum capacity
  2. A leftward shift, increasing oxygen affinity
  3. A rightward shift, facilitating oxygen unloading in tissues Correct answer.
  4. A leftward shift caused by increased pH

Explanation

2,3-BPG binds deoxygenated hemoglobin and stabilizes the T state, decreasing oxygen affinity and shifting the curve rightward so oxygen is released more readily to tissues. pH effects are separate and described by the Bohr effect.

Question 38Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A patient taking a drug that inhibits cyclooxygenase-1 experiences gastric mucosal injury. Which mechanism best explains this effect?

  1. Blockade of muscarinic receptors on parietal cells
  2. Increased histamine release from mast cells
  3. Direct stimulation of gastric acid secretion by the drug
  4. Loss of prostaglandin-mediated protection of the gastric mucosa Correct answer.

Explanation

COX-1 generates prostaglandins that enhance mucus and bicarbonate secretion and maintain mucosal blood flow; inhibiting it removes this protective effect. The injury is not due to direct acid stimulation or receptor blockade.

Question 39Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which feature distinguishes a type IV hypersensitivity reaction from types I, II, and III?

  1. It is caused by immune complexes deposited in tissues
  2. It is mediated by T cells rather than by antibody Correct answer.
  3. It is mediated by IgE bound to mast cells
  4. It is caused by antibodies directed against cell surface antigens

Explanation

Type IV reactions are cell-mediated, involving sensitized T cells and macrophages, and typically peak 48 to 72 hours after exposure. Types I, II, and III are antibody-mediated.

Question 40Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which change in membrane potential is produced by opening ligand-gated chloride channels in a neuron?

  1. Depolarization
  2. Hyperpolarization Correct answer.
  3. No change in membrane potential
  4. Generation of an action potential

Explanation

Chloride influx makes the inside of the cell more negative, producing an inhibitory hyperpolarization (IPSP). Depolarization would require cation influx or chloride efflux.

Question 41Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A patient with chronic alcohol use presents with ataxia and ophthalmoplegia. Which vitamin deficiency is most likely responsible?

  1. Thiamine Correct answer.
  2. Vitamin C
  3. Folate
  4. Vitamin K

Explanation

Thiamine deficiency causes Wernicke encephalopathy, classically with the triad of ataxia, ophthalmoplegia, and confusion, due to impaired glucose metabolism in vulnerable brain regions. The other vitamins produce different deficiency syndromes.

Question 42Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which mechanism explains why a bactericidal antibiotic is more effective than a bacteriostatic one in an immunocompromised patient?

  1. It lowers the minimum inhibitory concentration of other drugs
  2. It prevents bacterial protein synthesis without killing the cells
  3. It increases the host antibody response
  4. It kills organisms directly, reducing reliance on host immune clearance Correct answer.

Explanation

Bactericidal agents kill bacteria, so resolution does not depend on phagocytic clearance, which is impaired in immunocompromised hosts. Bacteriostatic drugs only inhibit growth and require intact host defenses for eradication.

Question 43Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which structural feature allows a molecule to cross a lipid bilayer most readily by simple diffusion?

  1. High lipid solubility and small molecular size Correct answer.
  2. Binding to a plasma transport protein
  3. Large molecular size and high charge
  4. Presence of a specific carrier protein

Explanation

Simple diffusion depends on the concentration gradient and membrane permeability, which favors small, uncharged, lipophilic molecules. Charged or large molecules require channels or transporters.

Question 44Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which enzyme deficiency causes phenylketonuria?

  1. Branched-chain alpha-ketoacid dehydrogenase
  2. Galactose-1-phosphate uridyltransferase
  3. Homogentisate oxidase
  4. Phenylalanine hydroxylase Correct answer.

Explanation

Phenylketonuria results from deficient phenylalanine hydroxylase, causing phenylalanine accumulation and intellectual disability if untreated. The other enzymes are defective in different metabolic disorders.

Question 45Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A tissue sample shows a granuloma with caseous necrosis. Which process does this finding most directly indicate?

  1. Coagulative necrosis from ischemia
  2. Acute suppurative inflammation
  3. Apoptotic cell death
  4. Chronic granulomatous inflammation Correct answer.

Explanation

Granulomas composed of epithelioid macrophages with caseous necrosis reflect chronic granulomatous inflammation, classically from mycobacterial infection. Acute suppurative inflammation produces neutrophil-rich pus instead.

Question 46Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A drug is administered by continuous infusion and reaches steady state. Which relationship determines the steady-state plasma concentration?

  1. It equals the infusion rate multiplied by clearance
  2. It equals the volume of distribution divided by clearance
  3. It equals the elimination half-life divided by the dose
  4. It equals the infusion rate divided by clearance Correct answer.

Explanation

At steady state the rate of drug input equals the rate of elimination, so concentration equals infusion rate divided by clearance. Volume of distribution affects time to reach steady state, not the final concentration.

Question 47Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which mechanism best explains tissue damage in a type III hypersensitivity reaction?

  1. Antibody binding to cell surface receptors
  2. IgE cross-linking on mast cells
  3. Direct T-cell cytotoxicity against target cells
  4. Deposition of antigen-antibody complexes activating complement and neutrophils Correct answer.

Explanation

Type III reactions involve circulating immune complexes that deposit in tissues such as glomeruli and vessel walls, activating complement and recruiting neutrophils that cause injury. The other mechanisms describe types I, IV, and II.

Question 48Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A mutation in a proto-oncogene that converts it to an oncogene typically has which functional consequence?

  1. Deletion of both alleles with loss of protein expression
  2. Gain-of-function that promotes cell proliferation Correct answer.
  3. Silencing of the promoter by hypermethylation
  4. Loss-of-function that impairs DNA repair

Explanation

Oncogenes arise from proto-oncogenes by activating mutations that confer a gain of function, and a single altered allele can drive proliferation. Tumor suppressor genes instead typically require loss of both alleles.

Question 49Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

Which factor most directly increases oxygen delivery to tissues during exercise?

  1. Increased hemoglobin oxygen affinity
  2. Decreased cardiac output with a leftward shift of the dissociation curve
  3. Increased cardiac output with a rightward shift of the dissociation curve Correct answer.
  4. Reduced tissue carbon dioxide production

Explanation

Exercise raises cardiac output and, through increased CO2, hydrogen ions, and temperature, shifts the dissociation curve rightward so more oxygen is released. Increased affinity would impair unloading.

Question 50Basic medical and dental sciences (anatomy, physiology, biochemistry, pharmacology, microbiology/immunology, pathology)

A patient develops a severe reaction with fever, hypotension, and rash shortly after starting a new antibiotic. Which mechanism of hypersensitivity is most likely?

  1. T-cell-mediated delayed reaction
  2. Immune complex deposition in small vessels
  3. Complement-mediated lysis of red blood cells
  4. IgE-mediated mast cell degranulation Correct answer.

Explanation

An immediate reaction with urticaria, hypotension, and bronchospasm after drug exposure is characteristic of type I, IgE-mediated anaphylaxis. The other mechanisms produce different timing and clinical patterns.