Cytoskeletons in Animal Cells

Instructor: Gretchen Baumle
The word cytoskeleton literally means 'skeleton of the cell,' and just like the human skeleton provides the body with support and structure, the cytoskeleton does the same thing, plus a lot more, on a much smaller scale inside almost every single cell in the body!

Framework of the Animal Cell

While the human body uses the skeleton for support and muscles for movement, the microscopic cells inside our body don't have muscles, so cells use the cytoskeleton for both support and motility. This means that not only can things move around inside the cell using the cytoskeleton, but the entire cell itself can use it to move from one place to another! The cytoskeleton is actually a collective term for three separate structures inside an animal cell. Animal cytoskeletons consist of: microfilaments, intermediate filaments and microtubules . These are basically support structures, each made of many smaller proteins linked together. Each cytoskeletal component is made of a different type of protein and each has its own unique contribution to the cell.

Microfilaments are typically found just inside the cell. They're strong, yet flexible and are able to resist crushing forces from outside the cell. There's usually a thick tangle of microfilaments just under the cell membrane of most animal cells. In certain single-celled animals like an amoeba, microfilaments can also play a role in moving the entire cell by allowing it to continually change its shape. Microfilaments are made of a protein called actin, and in humans this filament is essential for muscle contraction, which allows us to move and to move things through our bodies like blood and food.

Intermediate filaments are a little larger than microfilaments (hence the name 'intermediate') and can be made of several types of proteins depending on the cell. Often, its composed of tough, durable proteins like keratin, the protein found in your hair and fingernails. That's because intermediate filaments are really strong and are used to protect really important parts of the cell, like the nucleus. Intermediate filaments are so durable in fact, that after being exposed to a powerful degrading chemical like bleach, sometimes the only thing remaining from the original cell is a bare cage-like structure of intermediate filaments--everything else would be broken down or destroyed.

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