Texas State Manicurist Written Practice Exam

Which structure helps in the motility of bacterial cells?

1. Cilia

2. Flagella

3. Pili

4. Capsules

The correct answer is: Flagella

Flagella are long, whip-like structures that play a critical role in the motility of bacterial cells. These appendages allow bacteria to move through their environment by rotating and propelling the cell forward. Unlike cilia, which are shorter and often occur in large numbers on eukaryotic cells, flagella are typically singular or present in small numbers on bacteria. This unique structure, combined with its movement mechanism, allows for various forms of locomotion, including swimming or "tumbling." Pili and capsules do not primarily aid in motility. Pili are hair-like structures that can help with adhesion to surfaces or in bacterial conjugation (a process of genetic exchange). Capsules are protective layers surrounding some bacteria, helping them evade the immune system, but they do not contribute directly to movement. Therefore, the function of flagella in enabling bacterial motility is distinct and well-established, making it the correct answer.