Health, disease and the development of medicines study guide

Plants possess a wide array of physical and chemical adaptations to protect themselves from various threats, including pests and pathogens. Chemically, plants can produce a diverse range of compounds that act as deterrents or toxins. For instance, some plants produce nicotine, which is poisonous to many insects, while others produce tannins, which can make plant tissues unpalatable or indigestible. These chemical defences can target specific biological processes in pests, such as disrupting nerve function or inhibiting growth. Beyond direct toxicity, some plant chemicals can act as signalling molecules that attract beneficial insects (e.g., predators of herbivores) or warn other parts of the plant of an attack. Many of these plant-derived compounds have found applications in human medicine due to their specific biological activities, such as analgesic (pain-relieving), anti-inflammatory, or antimicrobial properties. Quinine, for example, derived from the Cinchona tree, is used to treat malaria, while salicylic acid, found in willow bark, is a precursor to aspirin, used for pain relief and reducing inflammation.

Plants, like all living organisms, are susceptible to attacks from pests and pathogens. To protect themselves, plants have developed a variety of defense mechanisms, including physical barriers. Two primary physical barriers are the leaf cuticle and the cell wall. The leaf cuticle is a waxy layer on the outer surface of leaves, acting as a waterproofing layer that prevents excessive water loss and forms a physical barrier against the entry of pathogens and the feeding of some pests. Plant cells also possess a rigid cell wall, primarily composed of cellulose, located outside the cell membrane. This cell wall provides structural support to the plant and forms a robust physical barrier that pathogens must overcome to infect the cell. Together, these structures play crucial roles in plant immunity by limiting entry points and providing structural integrity against threats.