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Question 1Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

In Michaelis–Menten kinetics, what does the Km value represent?

  1. The rate constant for dissociation of the enzyme–product complex
  2. The enzyme concentration needed to achieve maximal velocity
  3. The substrate concentration at which velocity is half of Vmax Correct answer.
  4. The maximal velocity reached when the enzyme is saturated

Explanation

Km is the substrate concentration at which the reaction proceeds at one-half of Vmax, so it has units of concentration. A low Km indicates high apparent affinity of the enzyme for the substrate.

Question 2Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Beta-lactam antibiotics such as penicillin produce their antibacterial effect by interfering with which process?

  1. Cross-linking of peptidoglycan by transpeptidases Correct answer.
  2. Assembly of the 50S ribosomal subunit
  3. Conversion of para-aminobenzoic acid to tetrahydrofolate
  4. Supercoiling of bacterial DNA

Explanation

Beta-lactams acylate the active-site serine of penicillin-binding proteins, which are transpeptidases that cross-link peptidoglycan strands. Loss of cross-linking weakens the wall and leads to lysis of actively dividing bacteria.

Question 3Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which immunoglobulin class is transported across the placenta and supplies most of the newborn's passive humoral immunity?

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

Explanation

IgG is captured by the neonatal Fc receptor on syncytiotrophoblasts and actively transported into fetal circulation, peaking in the third trimester. This transfer gives the infant temporary protection against many systemic pathogens.

Question 4Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which route of administration is assumed by definition to give 100% bioavailability?

  1. Transdermal patch
  2. Intravenous bolus Correct answer.
  3. Oral tablet
  4. Rectal suppository

Explanation

Bioavailability is defined relative to the intravenous dose, because drug injected directly into the systemic circulation escapes absorption and first-pass hepatic metabolism. All extravascular routes yield a fraction less than one.

Question 5Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

In bacteria, which enzyme catalyzes synthesis of an RNA copy from a DNA template?

  1. RNA polymerase Correct answer.
  2. DNA polymerase III
  3. Reverse transcriptase
  4. Primase

Explanation

DNA-dependent RNA polymerase binds the promoter, unwinds DNA and polymerizes ribonucleotides complementary to the template strand. In prokaryotes the same core enzyme transcribes mRNA, tRNA and rRNA.

Question 6Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which excipient serves as a binder in a wet-granulated tablet formulation?

  1. Croscarmellose sodium
  2. Magnesium stearate
  3. Colloidal silicon dioxide
  4. Povidone Correct answer.

Explanation

Povidone is a hydrophilic polymer added as a granulating solution or dry powder to promote adhesion of particles within granules. It improves granule strength and tablet compactibility.

Question 7Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which vitamin is required as a cofactor for gamma-carboxylation of glutamate residues in clotting factors II, VII, IX and X?

  1. Folic acid
  2. Vitamin K Correct answer.
  3. Thiamine
  4. Ascorbic acid

Explanation

Vitamin K hydroquinone is the cofactor for the vitamin K-dependent carboxylase that converts specific glutamate residues to gamma-carboxyglutamate. These residues bind calcium and allow the factors to assemble on phospholipid membranes.

Question 8Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which organism appears as Gram-positive cocci in clusters and is catalase-positive?

  1. Staphylococcus aureus Correct answer.
  2. Neisseria meningitidis
  3. Streptococcus pyogenes
  4. Escherichia coli

Explanation

Staphylococci are Gram-positive cocci arranged in grape-like clusters and, unlike streptococci, produce catalase. This combination distinguishes them from the catalase-negative streptococci in chains.

Question 9Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A drug is eliminated by first-order kinetics with a half-life of 6 hours. Approximately what percentage of an intravenous dose remains in the body 24 hours after administration?

  1. 3.1%
  2. 25%
  3. 6.25% Correct answer.
  4. 12.5%

Explanation

Twenty-four hours corresponds to four half-lives, and the fraction remaining is (1/2)^4 = 1/16, or 6.25% of the dose. Each half-life halves whatever amount is present.

Question 10Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A 500 mg intravenous bolus of a drug produces an immediate plasma concentration of 25 mg/L before any elimination occurs. What is the apparent volume of distribution?

  1. 0.05 L
  2. 5 L
  3. 20 L Correct answer.
  4. 12,500 L

Explanation

Volume of distribution equals dose divided by the extrapolated initial concentration: 500 mg ÷ 25 mg/L = 20 L. The value is apparent because it assumes instantaneous and uniform distribution.

Question 11Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

When one molecule of glucose is converted to two molecules of pyruvate in glycolysis, what is the net yield of ATP?

  1. Zero
  2. One
  3. Two Correct answer.
  4. Four

Explanation

Four ATP molecules are generated at the phosphoglycerate kinase and pyruvate kinase steps, but two ATP are consumed by hexokinase and phosphofructokinase-1. The net yield is therefore two ATP per glucose.

Question 12Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which enzyme catalyzes the rate-limiting, committed step of the urea cycle?

  1. Ornithine transcarbamoylase
  2. Carbamoyl phosphate synthetase I Correct answer.
  3. Arginase
  4. Argininosuccinate lyase

Explanation

Carbamoyl phosphate synthetase I in the mitochondrial matrix forms carbamoyl phosphate from ammonia and bicarbonate and is activated by N-acetylglutamate. This step is both rate-limiting and committed, since carbamoyl phosphate enters essentially only this pathway.

Question 13Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Peptides derived from proteins synthesized inside a cell are displayed on the surface by which molecule, and recognized by which cell type?

  1. MHC class I, recognized by CD8+ T cells Correct answer.
  2. MHC class II, recognized by CD8+ T cells
  3. MHC class II, recognized by CD4+ T cells
  4. MHC class I, recognized by CD4+ T cells

Explanation

Endogenous cytosolic proteins are degraded by the proteasome, transported into the endoplasmic reticulum and loaded onto MHC class I molecules. The resulting complex is recognized by the CD8 coreceptor-bearing cytotoxic T cells.

Question 14Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which cytokine acts as the principal endogenous pyrogen in the febrile response?

  1. Transforming growth factor beta
  2. Interleukin-10
  3. Interleukin-4
  4. Interleukin-1 beta Correct answer.

Explanation

Interleukin-1 beta released by activated macrophages acts on the hypothalamus to raise the set point, largely through increased prostaglandin E2 synthesis. Interleukin-6 and TNF also contribute to fever.

Question 15Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

The minimum inhibitory concentration of an antimicrobial is defined as which of the following?

  1. The highest serum concentration tolerated without toxicity
  2. The lowest concentration that prevents visible growth Correct answer.
  3. The steady-state concentration reached after repeated dosing
  4. The lowest concentration that kills 99.9% of the inoculum

Explanation

The MIC is determined by broth or agar dilution and is the lowest drug concentration that suppresses visible turbidity after a defined incubation period. It is a measure of growth inhibition, not of killing.

Question 16Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Vancomycin interferes with bacterial cell wall assembly by which mechanism?

  1. Inhibiting DNA topoisomerase IV
  2. Acylating transpeptidases after ring opening
  3. Binding the D-alanyl-D-alanine terminus of peptidoglycan precursors Correct answer.
  4. Blocking translocation at the 50S ribosomal subunit

Explanation

Vancomycin is a glycopeptide that hydrogen-bonds to the D-Ala-D-Ala end of lipid-linked precursors, preventing their incorporation and cross-linking. Because it acts at the substrate rather than the enzyme, it is not hydrolyzed by beta-lactamases.

Question 17Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which statement describes zero-order elimination of a drug?

  1. A constant fraction of the drug in the body is removed per unit time
  2. The half-life is independent of the dose administered
  3. Clearance rises in proportion to plasma concentration
  4. A constant amount of drug is removed per unit time Correct answer.

Explanation

In zero-order kinetics the eliminating processes are saturated, so a fixed quantity is removed per unit time regardless of concentration. Because the amount removed is constant while the body burden falls, the half-life lengthens as concentration declines.

Question 18Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Under standard regulatory criteria, the 90% confidence interval for the ratio of AUC and Cmax of a generic product versus the reference product should fall within which range?

  1. 80% to 125% Correct answer.
  2. 90% to 110%
  3. 95% to 105%
  4. 70% to 143%

Explanation

Average bioequivalence requires the 90% confidence interval for the geometric mean ratios of AUC and Cmax to lie within 0.80 to 1.25. This range is a statistical decision rule intended to limit the risk that a truly bioinequivalent product is declared equivalent.

Question 19Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

In a standard polymerase chain reaction, what is the purpose of the annealing step?

  1. To extend primers with a thermostable polymerase
  2. To insert the product into a cloning vector
  3. To allow primers to bind complementary template sequences Correct answer.
  4. To separate double-stranded DNA into single strands

Explanation

After heat denaturation, the temperature is lowered so that short oligonucleotide primers hybridize to their complementary sequences flanking the target. The annealing temperature sets specificity and is usually a few degrees below the primer melting temperature.

Question 20Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Dideoxynucleotides that terminate chain elongation are central to which technique?

  1. Quantitative real-time PCR
  2. Southern blotting
  3. Western blotting
  4. Dideoxy DNA sequencing Correct answer.

Explanation

In Sanger sequencing, incorporation of a dideoxynucleotide lacking a 3'-hydroxyl group blocks further extension, generating a family of fragments ending at each base position. Size separation of these fragments reveals the sequence.

Question 21Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Classical phenylketonuria most often results from deficiency of which enzyme?

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

Explanation

Phenylalanine hydroxylase converts phenylalanine to tyrosine using tetrahydrobiopterin; when it is deficient, phenylalanine accumulates and is transaminated to phenylketones. Untreated accumulation causes intellectual disability, which is why newborn screening and a low-phenylalanine diet are used.

Question 22Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A drug has a hepatic extraction ratio of 0.9. Which statement about its disposition is most accurate?

  1. Its oral bioavailability is approximately 90%
  2. Its hepatic clearance is approximately equal to hepatic blood flow Correct answer.
  3. Doubling its intrinsic clearance will roughly double its hepatic clearance
  4. Its hepatic clearance is limited mainly by plasma protein binding

Explanation

For a drug with a high extraction ratio, the well-stirred model gives clearance close to liver blood flow, because the liver removes nearly all drug presented to it. Clearance is therefore flow-limited and relatively insensitive to changes in protein binding or intrinsic clearance, while oral bioavailability is only about 1 minus the extraction ratio, here 10%.

Question 23Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

According to the Noyes–Whitney relationship, which change would most increase the dissolution rate of a poorly water-soluble drug?

  1. Reducing the particle size of the powder Correct answer.
  2. Decreasing the saturation solubility of the drug
  3. Increasing the thickness of the diffusion layer
  4. Increasing the viscosity of the dissolution medium

Explanation

Dissolution rate is proportional to the surface area available and to the concentration gradient across the boundary layer. Milling or micronizing the powder raises surface area substantially, which increases the dissolution rate.

Question 24Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A young man develops acute hemolytic anemia after taking primaquine. Deficiency of which enzyme is most likely responsible, and through what immediate consequence?

  1. Hexokinase, causing impaired glucose trapping in erythrocytes
  2. Pyruvate kinase, causing impaired ATP generation
  3. Glucose-6-phosphatase, causing impaired gluconeogenesis
  4. Glucose-6-phosphate dehydrogenase, causing low NADPH and reduced glutathione Correct answer.

Explanation

Erythrocytes depend on the pentose phosphate pathway for NADPH, which keeps glutathione reduced and protects hemoglobin and membrane lipids from oxidation. In G6PD deficiency, oxidant drugs such as primaquine overwhelm these defenses and trigger intravascular hemolysis.

Question 25Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Methicillin resistance in Staphylococcus aureus arises primarily through which mechanism?

  1. Overexpression of a multidrug efflux pump
  2. Production of a plasmid-encoded beta-lactamase
  3. Mutation of the 30S ribosomal subunit
  4. Acquisition of mecA encoding an altered penicillin-binding protein Correct answer.

Explanation

The mecA gene encodes PBP2a, a transpeptidase with low affinity for essentially all beta-lactams, so cell wall cross-linking continues despite drug exposure. Because methicillin is already beta-lactamase stable, enzymatic hydrolysis cannot explain the resistance.

Question 26Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which enzyme catalyzes the rate-limiting, committed step of glycolysis?

  1. Pyruvate carboxylase
  2. Glucose-6-phosphate dehydrogenase
  3. Fructose-1,6-bisphosphatase
  4. Phosphofructokinase-1 Correct answer.

Explanation

Phosphofructokinase-1 converts fructose-6-phosphate to fructose-1,6-bisphosphate and is the committed, rate-limiting step of glycolysis. It is activated by AMP and fructose-2,6-bisphosphate and inhibited by ATP and citrate.

Question 27Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which reaction of the citric acid cycle generates GTP by substrate-level phosphorylation?

  1. Malate to oxaloacetate
  2. Citrate to isocitrate
  3. Isocitrate to alpha-ketoglutarate
  4. Succinyl-CoA to succinate Correct answer.

Explanation

Succinyl-CoA synthetase couples cleavage of the thioester in succinyl-CoA to phosphorylation of GDP (or ADP), yielding GTP (or ATP) directly. All other steps of the cycle produce reduced coenzymes or carbon dioxide rather than a nucleoside triphosphate.

Question 28Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Cyanide is rapidly lethal because it binds with high affinity to which component of the electron transport chain?

  1. Complex II
  2. ATP synthase
  3. Complex IV Correct answer.
  4. Complex I

Explanation

Cyanide binds the ferric heme iron of cytochrome c oxidase (Complex IV), blocking transfer of electrons to oxygen. Oxidative phosphorylation therefore stops and cells cannot regenerate ATP aerobically.

Question 29Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which coenzyme is required by aminotransferases during transamination reactions?

  1. Thiamine pyrophosphate
  2. Biotin
  3. Tetrahydrofolate
  4. Pyridoxal phosphate Correct answer.

Explanation

Aminotransferases use pyridoxal phosphate, the active form of vitamin B6, as a coenzyme that shuttles amino groups between amino acids and alpha-keto acids. Without it, transfer of nitrogen from amino acids to alpha-ketoglutarate cannot occur.

Question 30Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

During prolonged fasting the liver synthesizes ketone bodies but cannot use them for energy. Which statement best explains this?

  1. Hepatocytes lack acetyl-CoA carboxylase
  2. Hepatocytes lack carnitine palmitoyltransferase I
  3. Hepatocytes lack HMG-CoA synthase
  4. Hepatocytes lack thiophorase activity Correct answer.

Explanation

Peripheral tissues activate acetoacetate by transferring CoA from succinyl-CoA, a reaction catalyzed by thiophorase (succinyl-CoA:acetoacetate CoA transferase). The liver lacks this enzyme, so it exports ketone bodies instead of consuming them.

Question 31Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which enzyme catalyzes the rate-limiting step of de novo fatty acid synthesis?

  1. HMG-CoA reductase
  2. Fatty acid synthase
  3. Acetyl-CoA carboxylase Correct answer.
  4. Carnitine palmitoyltransferase I

Explanation

Acetyl-CoA carboxylase converts acetyl-CoA to malonyl-CoA, committing carbon to fatty acid synthesis; it is the regulated, rate-limiting enzyme. It is activated by citrate and inhibited by palmitoyl-CoA.

Question 32Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A neonate becomes lethargic and tachypneic after feeding. Plasma ammonia is markedly elevated, blood citrulline is low, and urinary orotic acid is high. Deficiency of which enzyme is most likely?

  1. Carbamoyl phosphate synthetase I
  2. Arginase
  3. Ornithine transcarbamylase Correct answer.
  4. Argininosuccinate lyase

Explanation

Ornithine transcarbamylase deficiency causes carbamoyl phosphate to accumulate and spill into pyrimidine synthesis, producing orotic aciduria with low citrulline and hyperammonemia. It is the most common inherited urea cycle defect and is X-linked.

Question 33Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which enzyme catalyzes the rate-limiting step of heme biosynthesis in hepatocytes?

  1. ALA synthase Correct answer.
  2. Ferrochelatase
  3. Porphobilinogen deaminase
  4. ALA dehydratase

Explanation

ALA synthase condenses glycine and succinyl-CoA to form delta-aminolevulinic acid and is the rate-limiting enzyme of heme synthesis. It requires pyridoxal phosphate and is feedback-inhibited by hemin.

Question 34Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

The Glu6Val substitution in the beta-globin chain of sickle hemoglobin is classified as which type of mutation?

  1. Missense Correct answer.
  2. Splice site
  3. Frameshift
  4. Nonsense

Explanation

A single base change alters one codon so that valine replaces glutamic acid, which is a missense mutation. The polypeptide length is unchanged, but the altered surface charge allows deoxygenated hemoglobin S to polymerize.

Question 35Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Fluoroquinolones act by inhibiting which bacterial enzyme?

  1. Primase
  2. DNA ligase
  3. DNA gyrase Correct answer.
  4. Helicase

Explanation

Fluoroquinolones trap the DNA gyrase (topoisomerase II) and topoisomerase IV complexes, preventing relief of supercoiling and blocking replication. The resulting double-strand breaks are lethal to the bacterium.

Question 36Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

In eukaryotic cells, which RNA polymerase synthesizes messenger RNA precursors?

  1. RNA polymerase II Correct answer.
  2. Reverse transcriptase
  3. RNA polymerase I
  4. RNA polymerase III

Explanation

RNA polymerase II transcribes protein-coding genes to produce heterogeneous nuclear RNA, which is processed into mRNA. It is selectively inhibited by alpha-amanitin.

Question 37Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A patient reports no analgesia after standard doses of codeine. Variation in which enzyme most likely explains this failure?

  1. N-acetyltransferase 2
  2. CYP2C9
  3. CYP3A4
  4. CYP2D6 Correct answer.

Explanation

Codeine is a prodrug that must be O-demethylated to morphine by CYP2D6. Poor metabolizers form little morphine and obtain poor analgesia, whereas ultrarapid metabolizers risk toxicity.

Question 38Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Adding a competitive inhibitor to an enzyme-catalyzed reaction produces which change in kinetic parameters?

  1. Both Km and Vmax are increased
  2. Km is unchanged but Vmax is reduced
  3. Km increases and Vmax is unchanged Correct answer.
  4. Both Km and Vmax are reduced

Explanation

A competitive inhibitor competes with substrate for the active site, so higher substrate concentrations are needed to reach half-maximal velocity. Because the block is surmountable at saturating substrate, Vmax is unchanged while the apparent Km rises.

Question 39Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A drug's volume of distribution is doubled while its systemic clearance remains unchanged. What happens to its elimination half-life?

  1. It is unchanged
  2. It is halved
  3. It is quartered
  4. It is doubled Correct answer.

Explanation

Half-life equals 0.693 times volume of distribution divided by clearance, so a twofold rise in Vd with constant clearance doubles the half-life. More extensive tissue distribution means a larger amount must be eliminated to lower the plasma concentration.

Question 40Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A 100 mg intravenous dose produces an AUC of 50 mg·h/L. What is the systemic clearance?

  1. 2 L/h Correct answer.
  2. 1 L/h
  3. 5 L/h
  4. 0.5 L/h

Explanation

For intravenous dosing, clearance equals dose divided by total AUC, giving 100 mg / 50 mg·h/L = 2 L/h. Clearance expresses the volume of plasma cleared of drug per unit time.

Question 41Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which dosage form avoids hepatic first-pass metabolism most completely?

  1. Sublingual tablet Correct answer.
  2. Oral solution
  3. Oral tablet
  4. Enteric-coated oral tablet

Explanation

Drug absorbed from the sublingual mucosa drains into the superior vena cava, entering the systemic circulation without passing through the portal vein and liver. All swallowed formulations are absorbed into mesenteric veins and therefore face first-pass extraction.

Question 42Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A drug with a half-life of 12 hours is given by constant intravenous infusion. When does the plasma concentration reach approximately steady state?

  1. Approximately 12 hours
  2. Approximately 48 to 60 hours Correct answer.
  3. Approximately 30 minutes
  4. Approximately 5 days

Explanation

Steady state is approached after about four to five half-lives regardless of dose rate. With a 12-hour half-life, this corresponds to roughly 48 to 60 hours.

Question 43Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which drug is a potent inducer of CYP3A4 that can lower plasma concentrations of oral contraceptives and many other drugs?

  1. Ketoconazole
  2. Erythromycin
  3. Cimetidine
  4. Rifampin Correct answer.

Explanation

Rifampin strongly induces hepatic and intestinal CYP3A4 and P-glycoprotein, accelerating metabolism of coadministered substrates and reducing their efficacy. Enzyme induction develops over days to weeks and resolves slowly after the inducer is stopped.

Question 44Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

A drug has a volume of distribution of 50 L and an oral bioavailability of 1.0. What loading dose gives a target plasma concentration of 2 mg/L?

  1. 200 mg
  2. 100 mg Correct answer.
  3. 25 mg
  4. 50 mg

Explanation

Loading dose equals volume of distribution multiplied by target concentration divided by bioavailability: 50 L × 2 mg/L ÷ 1.0 = 100 mg. A loading dose fills the apparent distribution volume rapidly, independent of clearance.

Question 45Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Aminoglycoside antibiotics exert their bactericidal effect by binding to which target?

  1. Penicillin-binding proteins
  2. Bacterial topoisomerase IV
  3. The 30S ribosomal subunit Correct answer.
  4. The 50S peptidyl transferase center

Explanation

Aminoglycosides bind the bacterial 30S subunit, distorting the decoding site so that incorrect amino acids are inserted and abnormal proteins are produced. Their action is concentration-dependent and requires oxygen-dependent uptake.

Question 46Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which immunoglobulin class crosses the placenta and provides passive humoral immunity to the fetus and newborn?

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

Explanation

IgG is actively transported across the placenta via the neonatal Fc receptor, giving the newborn circulating maternal antibody for the first months of life. It is also the predominant immunoglobulin in secondary immune responses.

Question 47Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which complement fragment acts as the principal opsonin that promotes phagocytosis of bacteria?

  1. C9
  2. C5a
  3. C3b Correct answer.
  4. C3a

Explanation

C3b covalently binds microbial surfaces and is recognized by complement receptors on phagocytes, greatly enhancing engulfment. This opsonization is a central effector function of the complement system.

Question 48Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which vaccine is contraindicated in a patient receiving high-dose systemic corticosteroids?

  1. Inactivated influenza vaccine
  2. Tetanus toxoid vaccine
  3. Live attenuated MMR vaccine Correct answer.
  4. Recombinant hepatitis B vaccine

Explanation

Live attenuated vaccines can replicate and cause disease when cell-mediated immunity is suppressed, so they are withheld in significant immunosuppression. Inactivated, toxoid, and subunit vaccines are safe because they cannot replicate.

Question 49Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which set of conditions describes standard steam sterilization under pressure in an autoclave?

  1. 160 °C dry heat for 2 hours
  2. 60 °C for 60 minutes
  3. 121 °C at 15 psi for 15 minutes Correct answer.
  4. 100 °C at atmospheric pressure for 30 minutes

Explanation

Saturated steam at 121 °C (250 °F) under about 15 psi for 15 minutes reliably kills vegetative bacteria and spores by denaturing proteins. Higher pressure raises the steam temperature above the boiling point of water.

Question 50Basic Biomedical and Pharmaceutical Sciences (biochemistry, microbiology, immunology, molecular biology, pharmaceutics, pharmacokinetics)

Which polymer is used as an enteric coating that remains intact in the stomach and dissolves at intestinal pH?

  1. Polyvinylpyrrolidone
  2. Cellulose acetate phthalate Correct answer.
  3. Hydroxypropyl methylcellulose
  4. Magnesium stearate

Explanation

Cellulose acetate phthalate carries weakly acidic phthalyl groups that remain unionized and insoluble at gastric pH but ionize and dissolve above about pH 6. Such coatings protect acid-labile drugs and prevent gastric irritation.