Answer: Human cells get folic acid from the diet and lack the enzyme pathway that synthesises it from PABA, unlike bacteria.
- A Sulphonamides bind to bacterial ribosomes, a structure largely absent in human cells, rather than the folic acid pathway
- B Human cells get folic acid from the diet and lack the enzyme pathway that synthesises it from PABA, unlike bacteria
- C Human cells break down sulphonamides into harmless products before the drug can reach any enzyme target
- D Bacterial folic acid synthesis enzymes sit on the cell wall, where the drug accumulates more readily than inside human cells
Correct answer: B. Human cells get folic acid from the diet and lack the enzyme pathway that synthesises it from PABA, unlike bacteria
Explanation: Bacteria must synthesise their own folic acid from PABA, and sulphonamides block this by mimicking PABA; humans obtain folic acid from food and do not rely on this enzyme pathway, so they are largely unaffected.
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.