Answer: Antihistamines for allergies block H1 receptors, while acid secretion in the stomach is controlled mainly through H 2 receptors.
- A Antihistamines are broken down by stomach acid before they can act on any receptor in the gut lining
- B Antihistamines for allergies block H1 receptors, while acid secretion in the stomach is controlled mainly through H<sub>2</sub> receptors
- C H1 receptors are concentrated mainly in the brain, so antihistamines rarely reach the digestive tract in useful amounts
- D Acidity is regulated mainly by adrenaline receptors in the stomach, which respond poorly to histamine-based drugs
Correct answer: B. Antihistamines for allergies block H1 receptors, while acid secretion in the stomach is controlled mainly through H<sub>2</sub> receptors
Explanation: Histamine acts on different receptor subtypes for different effects; H1 receptors mediate allergic responses while H<sub>2</sub> receptors on stomach lining cells stimulate acid secretion, so a drug must target H<sub>2</sub> specifically to reduce acidity.
The hydrophobic hydrocarbon tail of each soap/detergent molecule dissolves into an oily dirt droplet, while the hydrophilic (ionic) head stays in the surrounding water - trapping the grease inside a micelle that rinses away with water.
Concept context
Drugs and how they interact with biological targets, chemicals in food, and cleansing agents (soaps and detergents) - chemistry applied directly to daily life and healthcare.