B.Pharm. Bachelor of Pharmacy Bachelor of Pharmacy (B.Pharm.) Pharmaceutical Chemistry 5 — Questions and Answers
Question 1: What is the significance of the Henderson-Hasselbalch equation in pharmacy?
- It calculates drug bioavailability from plasma concentration
- It predicts the ratio of ionized to unionized drug at a given pH based on pKa (Correct answer)
- It determines the rate of drug elimination from the body
- It describes the relationship between drug dose and receptor response
Correct answer: It predicts the ratio of ionized to unionized drug at a given pH based on pKa
The Henderson-Hasselbalch equation (pH = pKa + log([A⁻]/[HA])) predicts drug ionization state, which governs membrane permeability and absorption.
Question 2: Which type of isomerism exists between glucose and fructose?
- Enantiomerism
- Constitutional (structural) isomerism (Correct answer)
- Geometric isomerism
- Conformational isomerism
Correct answer: Constitutional (structural) isomerism
Glucose and fructose are constitutional isomers — both have the molecular formula C₆H₁₂O₆ but differ in the position of their carbonyl group (aldehyde vs. ketone).
Question 3: In pharmaceutical quality control, what does the term 'limit test for heavy metals' primarily detect?
- Residual solvents exceeding ICH thresholds
- Trace amounts of lead and other toxic metals in drug substances (Correct answer)
- Microbiological contamination by metallic organisms
- Metallic impurities from packaging only
Correct answer: Trace amounts of lead and other toxic metals in drug substances
The limit test for heavy metals detects trace toxic metals (primarily lead) in drug substances using precipitation with hydrogen sulfide or sodium sulfide.
Question 4: What is the chemical basis of chelation therapy using EDTA (ethylenediaminetetraacetic acid)?
- EDTA oxidizes heavy metal ions to non-toxic forms
- EDTA forms stable, water-soluble complexes with metal ions, facilitating their excretion (Correct answer)
- EDTA precipitates metals as insoluble salts in tissues
- EDTA blocks metal ion receptor sites on enzymes permanently
Correct answer: EDTA forms stable, water-soluble complexes with metal ions, facilitating their excretion
EDTA is a hexadentate chelating agent that forms stable, water-soluble coordination complexes with metal ions, enabling renal elimination.
Question 5: Which pharmacokinetic parameter describes the volume of plasma cleared of drug per unit time?
- Volume of distribution (Vd)
- Clearance (CL) (Correct answer)
- Area under the curve (AUC)
- Half-life (t½)
Correct answer: Clearance (CL)
Clearance (CL) represents the volume of plasma from which a drug is completely removed per unit time, reflecting the efficiency of drug elimination.
Question 6: What is the role of a preservative such as benzalkonium chloride in ophthalmic pharmaceutical preparations?
- To enhance drug absorption across the cornea
- To prevent microbial contamination and maintain sterility during use (Correct answer)
- To adjust the osmolarity of eye drops
- To increase the viscosity of the formulation
Correct answer: To prevent microbial contamination and maintain sterility during use
Benzalkonium chloride is a quaternary ammonium preservative that disrupts microbial cell membranes, preventing contamination in multi-dose ophthalmic products.
Question 7: Which reaction type is involved when an amino acid forms a peptide bond with another amino acid?
- Electrophilic addition
- Condensation (dehydration) reaction (Correct answer)
- Radical substitution
- Nucleophilic aromatic substitution
Correct answer: Condensation (dehydration) reaction
Peptide bond formation is a condensation reaction where the carboxyl group of one amino acid reacts with the amino group of another, releasing water.
B.Pharm. Bachelor of Pharmacy Bachelor of Pharmacy (B.Pharm.) Pharmaceutical Chemistry 5
What is the significance of the Henderson-Hasselbalch equation in pharmacy?