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The Structure of Cells

Author(s): Center for Educational Outreach

Cytoskeleton

The cytoskeleton is composed of several parts. Microtubules help to maintain cell shape. Centrioles are composed of nine sets of triplet microtubules, arranged in a ring. Cilia and flagella consist of nine doublets of microtubules, arranged in a ring with two single microtubules in the center. Microfilaments are fibrous proteins that hold organelles in place, and also form the cellular cortex.

Cilia beat in a back-and-forth motion. Flagella are normally found one per cell and have an undulating, or snakelike, motion.