(A) Phytochelatin
(B) Calmodulin
(C) Tubulin
(D) Systemin
Plants synthesize phytochelatins to bind and detoxify heavy metals like cadmium. This article solves Q.50 with the correct answer and details all options for biology exam prep.
Correct Answer
The correct answer is (A) Phytochelatin.
Phytochelatins (PCs) are cysteine-rich peptides synthesized enzymatically from glutathione when plants face heavy metals such as cadmium or arsenic. PCs chelate these metals, forming stable complexes sequestered in vacuoles for safe storage and detoxification.
Option Breakdowns
(A) Phytochelatin
Phytochelatins feature repeating γ-Glu-Cys units with a C-terminal glycine, induced specifically by heavy metal exposure.
PC synthase catalyzes their rapid production, enabling tolerance and homeostasis in contaminated soils.
(B) Calmodulin
Calmodulin is a calcium-binding protein that regulates signaling pathways, enzyme activity, and stress responses.
It handles calcium signaling but plays no direct role in heavy metal chelation or detoxification.
(C) Tubulin
Tubulin forms microtubules essential for cell division, structure, and intracellular transport.
It supports cytoskeletal functions but does not bind or detoxify heavy metals.
(D) Systemin
Systemin is a peptide hormone that triggers systemic wound and defense responses, like jasmonic acid pathways.
It activates defenses against herbivores or pathogens, unrelated to heavy metal sequestration.
| Option | Function | Heavy Metal Detox Role | Matches Q.50? |
|---|---|---|---|
| (A) Phytochelatin | Metal-binding peptides | Chelates Cd, As for vacuolar storage | Yes |
| (B) Calmodulin | Ca²⁺ signaling | None | No |
| (C) Tubulin | Microtubule assembly | None | No |
| (D) Systemin | Wound signaling | None | No |
