122. Which one of the following is a sulphur containing secondary metabolite in mustard plant derived from
glucose and an amino acid?
(1) Glucosinolates
(2) Phytoalexins
(3) Ecdysones
(4) Cyanogenic glycosides
Detailed Explanation:
Question:
Which one of the following is a sulfur-containing secondary metabolite in mustard plant derived from glucose and an amino acid?
✅ Correct Answer: (1) Glucosinolates
What are Glucosinolates?
Glucosinolates are a group of sulfur-containing secondary metabolites that are widely present in plants of the Brassicaceae family, including mustard, broccoli, cabbage, and rapeseed.
They are chemically derived from:
-
Glucose (a sugar molecule)
-
Amino acids (especially methionine, tryptophan, or phenylalanine)
This unique structure gives them their sulfur content and biological activity.
Functions of Glucosinolates in Plants:
-
Defense Compounds:
When plant tissue is damaged (e.g., by herbivores or pests), glucosinolates are broken down by the enzyme myrosinase into bioactive compounds like isothiocyanates, which deter insects and pathogens. -
Health Benefits for Humans:
Some breakdown products (like sulforaphane) have anti-cancer properties, which is why cruciferous vegetables are considered health-promoting.
Why the Other Options Are Incorrect:
-
(2) Phytoalexins:
These are antimicrobial compounds produced by plants in response to pathogen attack, but they do not contain sulfur and are not derived from glucose and amino acids in the same pathway. -
(3) Ecdysones:
These are insect molting hormones found in some plants, but they lack sulfur and have no relation to mustard plants. -
(4) Cyanogenic glycosides:
These are nitrogen-containing compounds that release hydrogen cyanide upon hydrolysis. They’re found in plants like cassava and do not contain sulfur.
Conclusion:
The correct answer is Glucosinolates, as they are the sulfur-containing secondary metabolites found in mustard plants and are derived from glucose and amino acids. Their role in plant defense and human health makes them particularly significant in both botany and nutrition.
