Which of the following drugs is used to treat or prevent bacterial infections by inhibiting bacterial cell wall synthesis?

Correct Answer: A

Rationale: The correct answer is A: Penicillin. Penicillin is a beta-lactam antibiotic that works by inhibiting bacterial cell wall synthesis, leading to bacterial cell death. This mechanism makes penicillin effective against a wide range of bacterial infections. Azithromycin (B) and Ciprofloxacin (C) are antibiotics that work by inhibiting bacterial protein synthesis and DNA replication, respectively, not cell wall synthesis. Amoxicillin (D) is also a beta-lactam antibiotic like penicillin, but it is not the best choice here as penicillin is more commonly used for cell wall synthesis inhibition.

Correct Answer: B

Rationale: Rationale: 1. Enalapril is an ACE inhibitor. 2. ACE inhibitors block the conversion of angiotensin I to angiotensin II. 3. Angiotensin II is a potent vasoconstrictor. 4. By inhibiting its production, enalapril helps lower blood pressure. 5. Therefore, choice B is correct. Summary: A: Blocking angiotensin II directly is the mechanism of ARBs, not ACE inhibitors. C: Enalapril does not directly affect sodium excretion. D: Enalapril may actually increase potassium levels due to decreased aldosterone production.

Correct Answer: B

Rationale: The correct answer is B: Replacing deficient thyroid hormone. Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4). In hypothyroidism, the thyroid gland does not produce enough thyroid hormones, leading to various symptoms. By prescribing levothyroxine, we are supplying the body with the thyroid hormone it lacks, thereby replacing the deficient hormone and restoring normal thyroid function. Explanation of other choices: A: Increasing the production of thyroid-stimulating hormone (TSH) is incorrect because levothyroxine does not directly affect TSH production. C: Inhibiting thyroid hormone synthesis is incorrect because levothyroxine does not inhibit thyroid hormone production. D: Increasing the metabolism of thyroid hormones is incorrect because levothyroxine does not directly increase the metabolism of existing thyroid hormones; it simply replaces the deficient hormone.

Correct Answer: B

Rationale: The correct answer is B: Constipation. Opioid medications slow down the movement of the digestive system, leading to constipation. This is a well-known side effect of opioids due to their action on opioid receptors in the gut. Nausea and vomiting can also occur but are less common than constipation. Diarrhea is actually a less common side effect of opioids. Increased appetite is not a typical side effect of opioid medications.

Correct Answer: A

Rationale: The correct answer is A: Blocking beta-1 adrenergic receptors in the heart. Bisoprolol is a beta-blocker that specifically targets beta-1 adrenergic receptors in the heart, leading to reduced heart rate and blood pressure. This helps in managing hypertension. Choices B, C, and D are incorrect because bisoprolol does not target beta-2 adrenergic receptors in the lungs, does not affect sodium excretion in the kidneys, and does not inhibit the conversion of angiotensin I to angiotensin II. The mechanism of action of bisoprolol primarily involves its selective blockade of beta-1 adrenergic receptors in the heart, making choice A the correct answer.