NEET 2019 · BiologyPrevious Year Question
What triggers activation of protoxin to active Bt toxin of Bacillus thuringiensis in boll worm? (NEET 2019)
Answer: (C) Alkaline pH of gut. Answer: (C) Alkaline pH of gut Solution: The Bt toxin exists in the bacterium as an inactive protoxin (crystal protein).
- A.Body temperature
- B.Moist surface of midgut
- C.Alkaline pH of gut✓
- D.Acidic pH of stomach
Correct Answer
(C) Alkaline pH of gut
Solution & Explanation
Answer: (C) Alkaline pH of gut Solution: The Bt toxin exists in the bacterium as an inactive protoxin (crystal protein). When an insect such as the bollworm ingests it, the alkaline pH of the insect gut solubilises the crystals and converts the protoxin into the active toxin, which then binds midgut epithelial cells, creating pores that cause cell lysis and death. NCERT Reference: Ch 10, p.179, line 046 — "of toxin due to the alkaline pH of the gut which solubilise the crystals."
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