Pharmacy Pharmaceutical Chemistry 2 — Questions and Answers
Question 1: Which functional group is responsible for the acidic character of aspirin (acetylsalicylic acid)?
- Ester group
- Carboxylic acid group (Correct answer)
- Hydroxyl group
- Carbonyl group
Correct answer: Carboxylic acid group
The carboxylic acid (-COOH) group in aspirin donates a proton, giving it its acidic character with a pKa of ~3.5.
Question 2: The Henderson-Hasselbalch equation is primarily used in pharmacy to:
- Predict drug metabolism rates
- Calculate the ratio of ionized to unionized drug forms at a given pH (Correct answer)
- Determine drug solubility in lipids
- Measure drug receptor binding affinity
Correct answer: Calculate the ratio of ionized to unionized drug forms at a given pH
Henderson-Hasselbalch (pH = pKa + log[A⁻]/[HA]) calculates the ionization ratio of weak acids/bases at physiological pH, which affects absorption.
Question 3: Which stereochemical descriptor system is used to unambiguously name chiral centers in drug molecules?
- D/L system
- R/S (Cahn-Ingold-Prelog) system (Correct answer)
- +/- optical rotation system
- cis/trans system
Correct answer: R/S (Cahn-Ingold-Prelog) system
The R/S (Cahn-Ingold-Prelog) system assigns priority to substituents by atomic number and unambiguously designates absolute configuration at chiral centers.
Question 4: Prodrugs are compounds that:
- Are pharmacologically active as administered
- Require biotransformation in the body to become active (Correct answer)
- Have shorter half-lives than parent drugs
- Cannot cross the blood-brain barrier
Correct answer: Require biotransformation in the body to become active
Prodrugs are pharmacologically inactive precursors converted in vivo (typically by enzymes) to the active drug form to improve bioavailability or reduce toxicity.
Question 5: What is the primary mechanism by which beta-lactam antibiotics exert their antibacterial effect?
- Inhibiting bacterial DNA gyrase
- Inhibiting bacterial cell wall transpeptidase (PBPs) (Correct answer)
- Disrupting the bacterial cell membrane
- Inhibiting bacterial protein synthesis at the 30S ribosome
Correct answer: Inhibiting bacterial cell wall transpeptidase (PBPs)
Beta-lactam antibiotics irreversibly acylate and inhibit penicillin-binding proteins (transpeptidases), blocking cross-linking of peptidoglycan in bacterial cell walls.
Question 6: Optical rotation is measured using a:
- Spectrophotometer
- Polarimeter (Correct answer)
- Refractometer
- Viscometer
Correct answer: Polarimeter
A polarimeter measures the angle of rotation of plane-polarized light by a chiral compound, expressed as specific rotation [α].
Question 7: Which type of isomerism involves compounds with the same molecular formula but different spatial arrangements that are non-superimposable mirror images?
- Constitutional isomerism
- Geometric isomerism
- Enantiomerism (Correct answer)
- Conformational isomerism
Correct answer: Enantiomerism
Enantiomers are non-superimposable mirror images of each other, differing only in the configuration at one or more chiral centers.
Pharmacy Pharmaceutical Chemistry 2
Which functional group is responsible for the acidic character of aspirin (acetylsalicylic acid)?