Which of the following are not secondary metabolites in plants ?

The correct answer is Amino acids, glucose.

In plants, metabolites are generally classified into two groups:

1. Primary metabolites – compounds required for the basic growth, development, and reproduction of the plant. They are directly involved in vital processes such as photosynthesis, respiration, and protein synthesis. Examples include sugars (e.g., glucose), amino acids, nucleotides, and fatty acids.

2. Secondary metabolites – compounds that are not essential for basic metabolic functions but often provide ecological advantages, such as defense against herbivores, pathogens, or competition, and attraction of pollinators. Typical secondary metabolites are alkaloids (e.g., morphine, codeine), terpenoids (e.g., vinblastine), phenolics (e.g., curcumin), and plant gums or latex.

Now examine each option:

Vinblastine, curcumin – Both are well‑known secondary metabolites: vinblastine is a terpene‑indole alkaloid used in chemotherapy, and curcumin is a phenolic compound responsible for the yellow colour of turmeric and has protective roles.

Rubber, gums – These are also secondary metabolites. Natural rubber is a polymer of isoprene units, and plant gums are polysaccharide exudates that protect wounds and deter herbivores.

Morphine, codeine – Classic alkaloid secondary metabolites derived from the phenylpropanoid pathway.

Amino acids, glucose – Both are fundamental building blocks of primary metabolism. Amino acids are the monomers of proteins, and glucose is a central sugar used in energy production and biosynthesis. They are required for the plant’s growth and are not classified as secondary metabolites.

Therefore, the pair that does **not** belong to the secondary‑metabolite category is amino acids and glucose.