Plant-derived drugs and drug testing

Sample questions

Original practice questions written in the style of the exam.

1. Question 14 marks

   A new drug has passed pre-clinical testing. Describe the three phases of clinical trials it must go through before it can be approved.

   Mark scheme

   • Phase 1: a small number of healthy volunteers, to test safety / side effects and dosage (1)
   • Phase 2: a small number of patients with the disease, to test whether the drug works and find the best dose (1)
   • Phase 3: a large number of patients (1)
   • Phase 3 compares the drug with a placebo or the existing treatment in a randomised, double-blind trial (1)
2. Question 23 marks

   Paper discs soaked in two plant extracts were placed on an agar plate spread with bacteria. After incubation, the clear zones around the discs had these diameters:

   Extract	Diameter of clear zone / mm
   garlic	18
   mint	12

   Calculate how much larger, as a percentage, the area of the clear zone for garlic is than for mint.

   Mark scheme

   • Area for garlic $= \pi \times 9^2 = 254\,\text{mm}^2$ (1)
   • Area for mint $= \pi \times 6^2 = 113\,\text{mm}^2$ (1)
   • Percentage difference $= \dfrac{254 - 113}{113} \times 100 = 125\%$ (1)