Plant-derived antimicrobials and drug testingEdexcel International A Level Biology: Mind map

Exam questions on Plant-derived antimicrobials and drug testing

1. A student investigates whether extracts from garlic and mint leaves kill bacteria. She spreads a non-pathogenic bacterium over the surface of sterile nutrient agar in a Petri dish and places on it small paper discs that have been soaked in garlic extract, mint extract or sterile distilled water. The dish is sealed and incubated at 25 °C for 48 hours.
   Explain how the results would show that garlic extract has antibacterial properties.2 marks
2. A school technician prepares agar plates for a class and transfers a broth culture of bacteria onto them. The technician uses aseptic technique throughout to avoid contamination of the cultures and to avoid growing pathogens.
   Explain two precautions in aseptic technique that prevent the cultures from being contaminated by microorganisms from the air or the bench.2 marks
3. In the 1780s the physician William Withering treated patients with dropsy using a mixture of foxglove (Digitalis) leaves, which he called digitalis soup. He adjusted the amount he gave each patient according to how they responded, and he recorded the outcomes in detail. Today a drug that is derived from a plant must go through a much more rigorous testing process before it is licensed.
   Suggest three reasons why Withering's testing of digitalis soup was less reliable than the testing of a modern drug.3 marks