'Bt' toxin is

Options

A. Intracellular lipid
B. Intracellular crystalline protein
C. Extracellular crystalline protein
D. Lipid

Answer

**Step-by-Step Solution:**

1. **Understanding Bt Toxin**: Bt toxin is a biopesticide produced by the bacterium Bacillus thuringiensis. It is important to note that this toxin is associated with the life cycle of the bacteria.

2. **Nature of Bt Toxin**: The Bt toxin is produced in the form of crystalline proteins known as cryoproteins. These proteins are inactive in their crystalline form and are referred to as protoxins.

3. **Exclusion of Lipids**: Since the question provides options that include lipids, we can eliminate options that suggest the Bt toxin is a lipid. Therefore, options indicating 'intracellular lipid' and 'lipid' can be marked as incorrect.

4. **Activation of Toxin**: When insects ingest the protoxin, it is activated in their alkaline gut, leading to the formation of active toxins. These active toxins disrupt the midgut epithelial cells of the insects, causing cellular damage and ultimately leading to the death of the insect.

5. **Location of Production**: The Bt toxin is produced inside the bacterial cell, making it an intracellular protein. This rules out the option of it being an extracellular crystalline protein, as it is not secreted outside the bacterial cell.

6. **Conclusion**: Based on the above points, the correct answer is that Bt toxin is an intracellular crystalline protein.

**Final Answer**: Bt toxin is an intracellular crystalline protein.

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