THE CYTOSKELETON AND CELL SURFACE
The cytoskeleton includes structures made of proteins, containing C, H, O, N and sometimes other elements such as sulfur (S).

Microtubules and microfilaments provide support to the cell. They are involved in organelle movement and cell division. Microtubules compose cilia, flagella, centrioles, and basal bodies.

Intermediate filaments provide added stability to the cell.

Centrioles also are made of proteins and are involved in animal cell division.

Cilia are short structures protruding from the cell surface. They are used for movement by certain unicellular organisms and for material transport across various tissues in multicellular organisms.

Flagella are long structures protruding from the cell surface. They are used for motility by certain unicellular organisms and sperm cells.

Plant cell walls are made of the polysaccharide cellulose, composed of C, H, and O. Bacterial and fungal cells also have cell walls made of peptidoglycan and chitin, respectively.