Biology · Biomolecules · NEET
Concanavalin A is a lectin. NCERT lists it as the example under the class 'Lectins' in the secondary metabolites table. It is not an alkaloid (those are nicotine, morphine, codeine), not an essential oil, and not a pigment. This exact fact was asked in NEET 2019.
Lectins are proteins. They are proteins that can bind to sugar molecules (carbohydrates). So a lectin is special because it is BOTH a protein and, in the NCERT chart, an example of a secondary metabolite. Remember this double nature for NEET matching questions.
In NCERT's chapter, lectins appear in the list of secondary metabolites (Table 9.3), along with alkaloids, toxins, terpenoids, drugs and pigments. This placement is what NEET tests, so treat 'lectin' as a secondary metabolite class in matching questions.
They are separate classes in the same secondary metabolite table. Lectin example = Concanavalin A. Toxin examples = Abrin, Ricin. Drug examples = Vinblastin, curcumin. A common NEET trap pairs 'Drugs - Ricin', which is WRONG because ricin is a toxin.
Lectins bind specifically to sugar groups on cell surfaces. Concanavalin A comes from the jack bean plant and binds glucose and mannose sugars. For NEET you mainly need the classification (it is a lectin), but knowing it is a sugar-binding protein helps you not confuse it with pigments or oils.
Concanavalin A is
Identify the incorrect pair.
Match List-I with List-II. List-I: (A) Terpenoids (B) Lectins (C) Alkaloids (D) Toxins. List-II: (I) Codeine (II) Diterpenes (III) Ricin (IV) Concanavalin A
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Concanavalin A is a lectin obtained from the jack bean plant. For NEET you mainly need to know its class (lectin), but its plant origin fits why NCERT puts lectins among plant secondary metabolites.
NCERT groups many odd plant molecules under 'secondary metabolites' by their role, not their chemistry. Lectins are proteins by structure but are placed in the secondary metabolite table, so for NEET both facts are true at once.
Always choose Lectin. Concanavalin A is the standard NCERT example for lectins and has appeared this way in NEET 2019, 2021, 2023 and 2026.
Ricin and abrin are toxins, while Concanavalin A is a lectin. They sit in different rows of the same NCERT secondary metabolite table, and NEET often mixes them to test you.
