Select incorrect statement for bacterial flagella :

Options

A. The filament is a hollow rigid cylindrical structure made of the protein called tubulin.
B. The filament measures about `20` nm in diameter and `1-70` nm in length.
C. The basal body is the most complex part of the flagellum and consists of four rings connected to a central rod in Gram-negative bacteria.
D. Filament rotate by `360^(@)` rather thane undulating back and forth like a whip.

Answer

**Step-by-Step Solution:**

1. **Understanding Bacterial Flagella**: Bacterial flagella are structures that aid in the locomotion of bacteria. They are thread-like and play a crucial role in the movement of these microorganisms.

2. **Analyzing the Statements**: We need to evaluate the given statements about bacterial flagella to identify the incorrect one.

3. **Statement 1**: "The filament is a hollow rigid cylindrical structure made up of protein called tubulin."
- **Evaluation**: This statement is incorrect. The filament of bacterial flagella is primarily made up of a protein called flagellin, not tubulin. Tubulin is a protein found in eukaryotic flagella, not in bacterial flagella.

4. **Statement 2**: "The filament measures about 20 nm in diameter and 1 to 70 nm in length."
- **Evaluation**: This statement is correct. The diameter of the filament is indeed around 20 nm, and its length can vary between 1 to 70 nm.

5. **Statement 3**: "The basal body is the most complex part of the flagellum and consists of four rings connected to a central rod."
- **Evaluation**: This statement is also correct. In Gram-negative bacteria, the basal body has four rings, which are essential for the flagellum's anchoring and rotation.

6. **Statement 4**: "Filament rotates by 360 degrees rather than moving back and forth like a whip."
- **Evaluation**: This statement is correct. The flagellum does rotate 360 degrees, allowing for efficient movement, unlike a whip that moves back and forth.

7. **Conclusion**: The incorrect statement about bacterial flagella is the first one regarding the composition of the filament.

**Final Answer**: The incorrect statement is: "The filament is hollow rigid cylindrical structure made up of protein called tubulin."

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