Flagellum

Definition

A flagellum is a long, whip-like structure that protrudes from the cell body of certain prokaryotic cells, enabling them to move through liquid environments. This organelle is essential for motility, allowing bacteria and archaea to navigate toward nutrients or away from harmful substances. Flagella can vary in number and arrangement, impacting the movement style of the organism.

5 Must Know Facts For Your Next Test

1. Flagella are composed of a protein called flagellin, which forms a helical structure that can rotate to propel the cell forward.
2. In bacteria, flagella can be arranged in various patterns, including monotrichous (single), lophotrichous (tufts), and peritrichous (surrounding the entire cell).
3. Flagella operate like tiny motors; the rotation of the flagellum is driven by proton motive force generated by the cell's membrane.
4. Some archaea possess flagella that differ in structure and composition from those found in bacteria, highlighting evolutionary diversity.
5. Flagellar movement is crucial for processes such as colonization, infection, and survival in changing environments.

Review Questions

• How do flagella contribute to the motility of prokaryotic cells, and what are some different arrangements of flagella found in bacteria?
  • Flagella enable prokaryotic cells to swim through liquid environments by rotating like a propeller. Different arrangements of flagella, such as monotrichous, lophotrichous, and peritrichous, affect how the organism moves. Monotrichous bacteria have a single flagellum at one end, while lophotrichous bacteria have multiple flagella at one end, and peritrichous bacteria have flagella distributed around the cell surface.
• Discuss the differences between bacterial and archaeal flagella in terms of structure and function.
  • Bacterial and archaeal flagella differ significantly in structure and composition. Bacterial flagella are made primarily of flagellin proteins and have a distinct helical shape, while archaeal flagella are composed of different proteins and have a thinner diameter. Functionally, both types of flagella serve to provide motility; however, their mechanisms of rotation and assembly also exhibit differences that reflect their unique evolutionary paths.
• Evaluate the role of flagella in ecological interactions and human health, considering their importance in disease-causing bacteria.
  • Flagella play a significant role in ecological interactions by allowing bacteria to move toward nutrients or away from harmful substances through chemotaxis. This motility is crucial for colonization and infection in host organisms. In human health, pathogenic bacteria with flagella can reach target tissues more effectively, making them more virulent. Understanding how flagella function can help develop strategies to combat infections caused by these mobile pathogens.

Related terms

Cilium: A short, hair-like structure that covers the surface of some eukaryotic cells, used for movement and feeding.

Chemotaxis: The movement of an organism in response to a chemical stimulus, which can be positive (toward) or negative (away from) a chemical.

Basal Body: The structure that anchors a flagellum or cilium to the cell membrane and acts as a motor for rotation.