Bt toxin kills insects by

Options

A. inhibiting protein synthesis
B. generating excessive heat
C. creating pores in the midgut epithelial cells, leading to cell swelling and lysis
D. obstructing a biosynthetic pathway

Answer

**Step-by-Step Solution:**

1. **Understanding Bt Toxin:**
- Bt toxin is a protein produced by the bacterium *Bacillus thuringiensis*. It is known for its insecticidal properties, particularly against certain pests that damage crops.

2. **Nature of the Toxin:**
- The toxin exists in an inactive form known as protoxin within the bacterium. This form does not harm the bacterium itself.

3. **Activation of the Toxin:**
- When the protoxin is ingested by an insect, it becomes activated. This activation occurs due to the alkaline pH found in the insect's gut.

4. **Mechanism of Action:**
- Once activated, the Bt toxin binds to the surface of the midgut epithelial cells of the insect.
- This binding leads to the formation of pores in the cell membranes of these epithelial cells.

5. **Consequences of Pore Formation:**
- The creation of pores results in cell swelling (due to the influx of fluids) and lysis (the breaking down of the cell membrane).
- Ultimately, this process leads to the death of the insect.

6. **Conclusion:**
- Based on the mechanism described, the correct answer to the question "Bt toxin kills insects by" is that it creates pores in the midgut epithelial cells, leading to cell swelling and lysis.

**Final Answer:**
- Bt toxin kills insects by creating pores in the midgut epithelial cells, leading to cell swelling and lysis.

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