Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What structure on bacterial cells is primarily used for movement?

1. Pili

2. Cell Wall

3. Nucleus

4. Cell Membrane

The correct answer is: Pili

The primary structure on bacterial cells that is used for movement is the pili, which are hair-like appendages found on the surface of many bacteria. While pili can have several functions, such as adhering to surfaces or exchanging genetic material through a process called conjugation, certain types of pili, specifically called "flagella," are specialized for movement. Flagella are long, whip-like structures that rotate to propel the bacterial cell through its environment, facilitating locomotion. This mobility is crucial for bacteria to navigate toward nutrients or away from harmful substances. The pili's structural role in movement underscores the adaptability and versatility of bacteria in various environments. In contrast, the cell wall provides structure and protection to the bacterial cell, but it does not aid in movement. The nucleus is not a structure found in bacterial cells, as bacteria are prokaryotic organisms and lack a defined nucleus. The cell membrane, while essential for maintaining the integrity of the cell and controlling the entry and exit of substances, does not directly facilitate movement.