Cilia and flagella are the motile appendages of eukaryotic cells

How are cilia and flagella similar?

Cilia and flagella are the motile appendages of eukaryotic cells. They are thick, flexible structures that exhibit a beating motion and project from the surfaces of many cells. A cell having one or a small number of appendages can be identified having flagella (singular, flagellum) if they are relatively long in proportion to the size of the cell. If the cell has many short appendages, they are called cilia (singular, cilium).

Cilia and flagela have the same internal structure, but differ in their length, the number occurring per cell, and mode of beating. They are axonemal in shape, formed by a main cylinder of tubules that are approximately 0.25 µm in diameter.

The axoneme has a pattern of "9 + 2" consisting of nine outer doublets of tubules and two additional central microtubules (the central pair). Cilia are about 2–10 µm long, while flagella are much longer, ranging from 1 µm to several millimeters, although they are most commonly 10–200 µm. They are both intracellular structures, bound by an extension of the plasma membrane. Both cilia and flagella are used by cells to move through watery environments or to move materials across cell surfaces.

How does the motion exhibited by cilia and flagella differ from one another?

Cilia move back-and-forth, causing their (Cilia) motion to be perpendicular to their axis of direction. Flagella undulate in a whip-like motion, moving in the same direction as their axis.

What are the largest and smallest organelles in a cell?

The largest organelle in a cell is the nucleus. The next largest organelle would be the chloroplast, which is substantially bigger than a mitochondrion. The smallest organelle in a cell is the ribosome.