Which of the following vitamins can be also synthesized from a dietary precursor?

Correct Answer: B

Rationale: The correct answer is B: Vitamin A. Vitamin A can be synthesized from a dietary precursor beta-carotene, which is found in various fruits and vegetables. The body converts beta-carotene into active Vitamin A as needed. Vitamin C (A) cannot be synthesized from a dietary precursor and must be obtained directly from the diet. Vitamin B1 (C) and Vitamin B6 (D) are water-soluble vitamins that cannot be synthesized from dietary precursors.

Correct Answer: C

Rationale: Step-by-step rationale for why Choice C: Gemfibrozil (Loprol) is correct: 1. Gemfibrozil is a fibric acid derivative known to increase HDL levels. 2. It works by activating lipoprotein lipase, which increases the breakdown of triglycerides and raises HDL levels. 3. Cholestyramine (A) is a bile acid sequestrant that does not affect HDL levels. 4. Lovastatin (B) is a statin that primarily lowers LDL levels. 5. Probucol (D) is an antioxidant that mainly lowers LDL levels and does not significantly impact HDL levels.

Correct Answer: A

Rationale: Step-by-step rationale for why choice A is correct: 1. Etidronate is a biphosphonate drug used to reduce osteoclast activity in conditions like Paget's disease. 2. It inhibits bone resorption by osteoclasts without significantly affecting osteoblasts. 3. Monitoring serum phosphorus levels daily (choice B) is not necessary for etidronate. 4. Etidronate is a first-generation biphosphonate, not a 2nd generation (choice C). 5. Bioavailability of etidronate is poor and decreases with increasing doses, so choice D is incorrect.

Correct Answer: B

Rationale: Step 1: Furosemide is a loop diuretic, which acts on the ascending loop of Henle to inhibit sodium and chloride reabsorption, leading to potent diuresis. Step 2: Loop diuretics like Furosemide are more potent compared to other diuretics like thiazides (Hydrochlorothiazide) or potassium-sparing diuretics (Amiloride). Step 3: Acetazolamide is a carbonic anhydrase inhibitor that works in the proximal tubule and has a different mechanism of action, making it less potent than loop diuretics. Step 4: Therefore, the correct answer is B, Furosemide, as it is a potent diuretic acting on the loop of Henle. Other choices are less potent due to their mechanisms of action and sites of action.

Correct Answer: D

Rationale: Step-by-step rationale for Answer D being correct: 1. Aminoglycosides are primarily effective against aerobic Gram-negative bacteria. 2. They are broad-spectrum antibiotics but not effective against anaerobic microorganisms. 3. Aminoglycosides do not have antiviral properties. 4. Therefore, Answer D is correct as it accurately states their spectrum of activity. Summary of why other choices are incorrect: A: Incorrect because aminoglycosides are not effective against Gram-positive microorganisms, anaerobic microorganisms, or spirochetes. B: Incorrect because aminoglycosides are not effective against Pseudomonas aeruginosa. C: Incorrect because aminoglycosides are primarily effective against aerobic Gram-negative bacteria, not anaerobic microorganisms.