Blog / Composition And Function Of Cilia And Flagella

Composition and function of cilia and flagella

Written by Cindy Ma on Feb 13, 2020

Flagella and cilia are used to help move the entire cell or substances along the outer surface of the cell.

Flagella (singular = flagellum) are long, hair-like structures that extend from the plasma membrane and are used to move an entire cell. A well known example of a cell with a flagellum is sperm. When present, the cell has just one flagellum or a few flagella.

When cilia (singular = cilium) are present, however, many of them extend along the entire surface of the plasma membrane. They are short, hair-like structures that are used to move entire cells or substances along the outer surface of the cells. An example of cilia in the human body is the cilia lining of the respiratory tract that trap particulate matter and move it toward your nostrils for exit from the body.

Despite their differences in length and number, flagella and cilia share a common structural arrangement of microtubules called a “9 + 2 array.” This is an appropriate name because a single flagellum or cilium is made of a ring of nine microtubule doublets surrounding a single microtubule doublet in the center.

Key Points

  • Flagella are long, hair-like structures that extend from the plasma membrane and are used to move an entire cell.
  • Cilia are short, hair-like structures that are used to move entire cells or substances along the outer surface of the cell

Key Terms

  • flagellum: a lash-like appendage that protrudes from the cell body of certain prokaryotic and eukaryotic cells that help move the entire cell
  • cilia: short, hair-like structures that are used to move entire cells or substances along the outer surface of the cell
  • microtubule: small tubes made of protein that help cells with movement and resist compression


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