MyCompetitiveExams Dynamic 180-question full-length simulator mixed dynamically from all 6 years for 2027 & 2026 aspirants.
The inactive form of Bt toxin is converted to the active form in the insect gut ___.
Insect Midgut = Alkaline pH (Solubilizes Crystals) -> Lytic Pores -> Death!
Bacillus thuringiensis produces intracellular protein crystals during sporulation containing toxic insecticidal Cry proteins. Because the crystals are insoluble at neutral/acidic pH, the protoxin remains non-toxic to the bacterium.
Susceptible insect larvae possess a strongly alkaline midgut environment (pH 9.0–10.5). Upon ingestion, the high alkaline pH solubilizes the crystal proteins into active monomers.
The activated toxin binds to cadherin receptors on the surface of midgut epithelial cells, inserting into the membrane to create open pores that cause osmotic swelling, cell lysis, gut paralysis, and death.
Diagnose every choice: Know exactly why the right option works and why distractors fail.
100% accurate. Canonical physiological trigger that solubilizes crystalline Bt protoxin in insect midgut.
Incorrect. Acidic pH stabilizes the insoluble crystal and prevents activation (as in human stomach).
Incorrect. Proteases cannot digest or activate the crystal until it is first solubilized by the alkaline pH.
Incorrect. Nucleases digest nucleic acids (DNA/RNA); Cry toxin is a protein.
Medical students frequently associate digestion with acid (HCl in human stomach). Insect midguts are alkaline, which is why Bt toxin is lethal to bollworms but safe for humans.
"Inactive Bt protoxin is converted into active toxin due to the alkaline pH of the insect midgut which solubilises the crystals."
Test your speed and accuracy in the authentic 180-minute timed NTA simulator.
Spotted a mistake in this solution? Report an error ([email protected])
Cover all 1,140 official NEET questions in 285 days at your own pace. Progress is saved on your device. No login needed.