The passage of drug molecules from a region of high drug concentration to a region of low drug concentration is known as

Correct Answer: D

Rationale: Simple diffusion (D) is the passage of drug molecules from high to low concentration, a passive process driven by the gradient (e.g., ethanol across membranes), requiring no energy. Active transport (A) uses energy against the gradient. Bioavailability (B) is the fraction reaching systemic circulation. Biopharmaceutics (C) studies formulation effects. Pinocytosis (original E) involves vesicular uptake. Diffusion's lipid solubility dependence governs most drug absorption, a fundamental principle in pharmacokinetics, impacting onset and distribution rates.

Correct Answer: D

Rationale: The principle of superposition assumes early doses do not affect subsequent doses (D), valid in first-order kinetics where each dose's elimination is independent, summing linearly to predict steady-state (e.g., amoxicillin). Option A suggests nonlinearity (e.g., phenytoin). Option B is zero-order (e.g., ethanol). Option C overestimates; steady-state is ~4-5 half-lives. Option E (original) is unrelated. This linearity simplifies multiple-dose design, ensuring predictable accumulation, critical for maintaining therapeutic levels without toxicity.

Correct Answer: B

Rationale: A prosthetic group (B) is a cofactor firmly bound to an apoenzyme (e.g., heme in hemoglobin), forming a functional holoenzyme, unlike loosely bound coenzymes (C, e.g., NAD⁺). Holoenzyme (A) is the complete enzyme. Transferase (D) is an enzyme class. Heteropolysaccharide (original E) is unrelated. This tight binding enhances enzyme stability and activity, critical in drug metabolism (e.g., CYP450 with heme), influencing pharmacokinetics and therapeutic outcomes.

Correct Answer: C

Rationale: A declining growth rate occurs in the stationary phase (C), where bacterial growth slows as nutrients deplete and waste accumulates, balancing birth and death (e.g., E. coli in culture). Lag phase (A) is adaptation, exponential (B) is rapid growth, and death (D) is decline. No original E. This phase mimics chronic infections, influencing antibiotic efficacy (e.g., slower kill rates), critical in pharmacology for understanding bacterial persistence and treatment duration.

Correct Answer: D

Rationale: Cefazolin sodium (D) forms an alkaline solution, as its conjugate base (cefazolin anion) hydrolyzes water, raising pH (e.g., >7). Sodium chloride (A) is neutral. Benzalkonium chloride (B) and meperidine hydrochloride (C) are acidic from quaternary ammonium or protonated amines. Chlordiazepoxide hydrochloride (original E) is acidic. This basicity, from cephalosporin salts, affects compatibility in IV solutions, critical in pharmaceutical preparation and administration.