Q56 Match the secondary metabolites in Group-I with types of secondary metabolites in Group-II in CORRECT order.
| P. Myrcene | I. Sesquiterpene |
|---|---|
| Q. Quercetin | II. Cyanogenic glycoside |
| R. β-Farnesene | III. Flavonoid glycoside |
| S. Nicotine | IV. Alkaloid |
| T. Luteolin | V. Monoterpene |
Myrcene belongs to Group-I and matches with monoterpene (V) from Group-II, while β-Farnesene is a sesquiterpene (II). The correct matching is option (A): P-V, Q-II, R-IV, S-III, T-I.
Question Breakdown
Group-I lists four secondary metabolites: P. Myrcene, Q. β-Farnesene, R. Nicotine, S. Luteolin. Group-II provides types: I. Cyanogenic glycoside, II. Sesquiterpene, III. Flavonoid, IV. Alkaloid, V. Monoterpene. Secondary metabolites are plant compounds aiding defense, not essential for growth.
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Myrcene (P): Acyclic monoterpene (C10, two isoprene units) in plants like cannabis.
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β-Farnesene (Q): Sesquiterpene (C15, three isoprene units), an acyclic olefin in essential oils.
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Nicotine (R): Pyridine alkaloid from tobacco, nitrogen-containing base.
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Luteolin (S): Flavone flavonoid, phenolic with antioxidant roles.
Option Analysis
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(A) P-V, Q-II, R-IV, S-III: P (Myrcene)-V (Monoterpene), Q (β-Farnesene)-II (Sesquiterpene), R (Nicotine)-IV (Alkaloid), S (Luteolin)-III (Flavonoid). Matches exactly.
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(B) P-V, Q-I, R-IV, S-III: Q wrongly as cyanogenic glycoside (sugar-cyanohydrin, e.g., amygdalin); β-Farnesene is terpenoid.
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(C) P-I, Q-III, R-IV, S-V: P wrongly cyanogenic; Q as flavonoid (phenolics); S as monoterpene. Mismatches all except R.
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(D) P-V, Q-I, R-II, S-III: Q wrongly cyanogenic; R (alkaloid) as sesquiterpene (terpenoid).
Secondary metabolites matching CSIR NET questions test classifications like terpenoids, alkaloids, and phenolics. These plant defense compounds, absent in primary metabolism, include Myrcene (monoterpene hydrocarbon from MEP pathway), β-Farnesene (sesquiterpene from farnesyl diphosphate), Nicotine (pyridine alkaloid from ornithine), and Luteolin (flavone flavonoid via phenylpropanoid route).
Terpenoids: Myrcene and β-Farnesene
Terpenoids form via isoprenoid pathways (MEP for monoterpenes, MVA for sesquiterpenes).
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Myrcene: C10 monoterpene in mango, cannabis; volatile, anti-inflammatory.
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β-Farnesene: C15 sesquiterpene in peppermint; aphid repellent.
Alkaloids and Flavonoids: Nicotine and Luteolin
Nitrogenous alkaloids like Nicotine derive from amino acids, toxic to herbivores. Flavonoids like Luteolin (yellow pigment) offer UV protection, anti-inflammatory benefits.
| Metabolite | Class | Biosynthetic Origin | Key Function |
|---|---|---|---|
| Myrcene (P) | Monoterpene (V) | MEP pathway | Volatile oil, defense |
| β-Farnesene (Q) | Sesquiterpene (II) | MVA pathway | Insect repellent |
| Nicotine (R) | Alkaloid (IV) | Ornithine | Herbivore deterrent |
| Luteolin (S) | Flavonoid (III) | Phenylpropanoid | Antioxidant |
For CSIR NET Life Sciences, memorize: terpenoids by C-units (mono C10, sesqui C15), alkaloids N-based, flavonoids phenolic.
