Q.63 Identify the CORRECT statements in plant secondary metabolism.
P. Tropane alkaloids in Atropa belladonna are synthesized from tyrosine
Q. Antioxidative food ingredient rosmarinic acid is obtained from cell suspension cultures of
Coleus blumei
R. Thiophenes are produced from hairy root cultures of Tagetes patula
S. Cyanidin, the principal anthocyanin responsible for red color in Rosa hybrida is
produced from cinnamaldehyde
(A) P, S (B) R, S (C) P, Q (D) Q, R
Q and R are correct statements about plant secondary metabolism.
Question Breakdown
This GATE Life Sciences question tests biosynthetic origins and biotechnological production of secondary metabolites. Secondary metabolism yields diverse compounds like alkaloids, phenolics, terpenoids from amino acid/polyketide pathways.
Statement Analysis
P: Tropane alkaloids in Atropa belladonna from tyrosine
FALSE. From ornithine → putrescine → N-methylputrescine → tropinone → tropine → hyoscyamine/atropine/scopolamine. Tyrosine for phenylpropanoids.
Q: Rosmarinic acid from Coleus blumei cell suspensions
TRUE. Coleus blumei (Plectranthus scutellarioides syn.) suspension cultures produce 8-11% dry weight rosmarinic acid (antioxidant, caffeoyl ester).
R: Thiophenes from Tagetes patula hairy root cultures
TRUE. Hairy roots accumulate bithienyls (α-terthienyl, BBT), interconvert thiophenes; light influences profiles.
S: Cyanidin in Rosa hybrida red color from cinnamaldehyde
FALSE. Anthocyanin cyanidin from phenylalanine → cinnamic acid → coumaroyl-CoA → flavonoids → dihydroquercetin → leucoanthocyanidin → cyanidin. Cinnamaldehyde intermediate, not direct precursor.
Correct Choice
(D) Q, R
Plant secondary metabolism correct statements highlight biotechnological production of rosmarinic acid and thiophenes for GATE Life Sciences prep.
Biosynthesis & Production Overview
-
Tropane: Ornithine-derived (Atropa); not tyrosine
-
Rosmarinic acid: Phenylalanine/tyrosine hybrid; Coleus suspensions >20% conversion
-
Thiophenes: Acetylenic polyynes; Tagetes hairy roots (BBT dominant)
-
Cyanidin: Phenylalanine → chalcone → anthocyanin; red rose pigment
Truth Table
| Statement | Content | Correct? | Key Fact |
|---|---|---|---|
| P | Tropane from tyrosine | No | Ornithine pathway |
| Q | Rosmarinic Coleus suspension | Yes | 8-11% DW |
| R | Thiophenes Tagetes hairy root | Yes | Bithienyls accumulated |
| S | Cyanidin from cinnamaldehyde | No | From dihydroquercetin |
GATE Exam Relevance
XL-Plant Physiology/Biotech PYQ tests pathways/production. Precursors: Alkaloids (Orn/Arg/Lys), phenolics (Phe/Tyr), terpenes (IPP). Bioreactors: Hairy roots (Ri T-DNA), suspensions for phenolics.
