Summary
Alkaloids, terpenoids and phenolics mediate defence and are the source of many drugs.
In depth
Alkaloids (caffeine, morphine, nicotine), terpenoids (menthol, taxol), phenolics (tannins, flavonoids). Not essential for basic growth but protect or attract. Many are drugs.
Synthesised through pathways such as the shikimate and mevalonate routes. Roles: deter herbivores, attract pollinators, allelopathy and UV protection. Humans use them as medicines, spices and dyes.
Common mistake: 'secondary' does not mean unimportant for survival.
They are made by pathways branching off primary metabolism: terpenes from isoprene units, phenolics from the shikimate pathway, and alkaloids from amino acids. Functions include defence, attracting pollinators and dispersers, UV protection, and signalling. They give humans medicines (aspirin from willow, quinine from cinchona, digoxin from foxglove, artemisinin from sweet wormwood, vincristine from periwinkle), flavours, dyes, and fragrances.
Most are stored in vacuoles or special structures such as latex ducts, glands and resin canals. Their levels vary with environment, and stress often increases them. Plant cell culture and synthetic biology in microbes are alternative production routes. Their evolution reflects arms races with herbivores.
Example: capsaicin in chilli deters mammals but not birds, which disperse seeds.
Frequently asked questions
What is Plant Secondary Metabolites?
Alkaloids, terpenoids and phenolics mediate defence and are the source of many drugs.
Which area of biology covers Plant Secondary Metabolites, and how advanced is it?
Plant Secondary Metabolites is one of the 56 topics in Plant Biology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Plant Defence Responses, Plant Hormones, Plant Tissue Culture.
Can you give an example of Plant Secondary Metabolites?
Aspirin was derived from willow bark salicin.
What should I learn before Plant Secondary Metabolites?
Work through the Beginner topics in Plant Biology first, such as Plant Kingdom, Photosynthesis, Chlorophyll, then return to Plant Secondary Metabolites. Advanced topics assume the Intermediate vocabulary.
What topics are related to Plant Secondary Metabolites?
The closest topics to Plant Secondary Metabolites are Plant Defence Responses, Plant Hormones, Plant Tissue Culture, Seed Dispersal. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Plant Secondary Metabolites?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Plant Secondary Metabolites. To practise the whole of Plant Biology, use the Plant Biology quiz.
How is Plant Secondary Metabolites different from Plant Defence Responses?
Plant Secondary Metabolites: Alkaloids, terpenoids and phenolics mediate defence and are the source of many drugs. Plant Defence Responses: Plants use thorns, toxins, jasmonate signalling and systemic acquired resistance against herbivores and pathogens. Read both side by side and note what each one explains.
What is a common mistake about Plant Secondary Metabolites?
'secondary' does not mean unimportant for survival.
How should I study Plant Secondary Metabolites step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Plant Defence Responses and explain the difference aloud. Finally, take the Plant Biology quiz and come back to this page for any question you miss.