Acidic drugs mainly bind to plasma

Correct Answer: A

Rationale: Acidic drugs mainly bind to albumin (A), the most abundant plasma protein, with sites for weak acids (e.g., warfarin, ibuprofen), affecting free drug levels. α₁-acid glycoprotein (B) binds basic drugs (e.g., lidocaine). Option C is incorrect as acidic drugs favor albumin. Option D is false. This binding, reversible and saturable, reduces free drug for distribution, prolonging action but risking displacement interactions (e.g., with aspirin), a key pharmacokinetic factor in dosing and toxicity.

Correct Answer: A

Rationale: The rate of blood flow to tissue (A) chiefly determines initial drug distribution, as perfusion delivers drug to organs (e.g., brain > fat), seen in anesthetics' rapid onset. GFR (B) affects excretion, not distribution. Stomach emptying (C) influences absorption. Tissue affinity (D) and plasma binding (original E) shape later distribution. Perfusion-limited kinetics prioritize highly vascular tissues, critical for acute therapies, with redistribution (e.g., thiopental) altering duration, a fundamental pharmacokinetic principle.

Correct Answer: D

Rationale: Maltose (D) is not a polysaccharide; it's a disaccharide (glucose-glucose), hydrolyzed to monosaccharides, unlike polysaccharides heparin (A, anticoagulant), starch (B, plant storage), and glycogen (C, animal storage), which are large, branched polymers. Cellulose (original E) is also a polysaccharide. Maltose's smaller size, formed during starch digestion, contrasts with polysaccharides' complexity, impacting absorption speed and therapeutic use (e.g., heparin's long-acting effects), key in carbohydrate pharmacology.

Correct Answer: B

Rationale: Thermophiles (B) grow at high temperatures (up to 55°C or more), thriving in hot environments (e.g., Thermus aquaticus). Psychrophiles (A) prefer cold. Mesophiles (C) grow at moderate (e.g., 37°C). Auxotrophs (D) require specific nutrients, unrelated to temperature. No original E. Thermophiles' heat-stable enzymes (e.g., Taq polymerase) revolutionized biotech, indirectly aiding pharmacology via PCR in drug development, distinct from human-pathogenic mesophiles.

Correct Answer: C

Rationale: A drug receptor can bind endogenous ligands to produce physiological activity (C), e.g., acetylcholine at nicotinic receptors for muscle contraction, a core pharmacodynamic principle. Option A is false; anesthetics act non-specifically on membranes. Option B is incorrect; receptors exist naturally. Option D is wrong; magnesium citrate's cathartic effect is osmotic, not receptor-based. Option E (original) about down-regulation is false; it desensitizes. Receptors' endogenous role enables drug mimicry or blockade, fundamental to therapeutic targeting.