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Cytoskeleton: Structure & Function

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  • 0:01 What is a Cytoskeleton?
  • 1:55 Structure: Microtubules
  • 2:56 Structure:…
  • 3:56 Structure: Microfilaments
  • 4:44 Cytoskeleton Importance
  • 5:26 Lesson Summary
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Lesson Transcript
Instructor
Darla Reed

Darla has taught undergraduate Enzyme Kinetics and has a doctorate in Basic Medical Science

Expert Contributor
Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson you will discover what the cytoskeleton is, what it's composed of and the various things the cytoskeleton does for the cell. You will also discover a little bit about the importance of the cytoskeleton.

What is a Cytoskeleton?

Have you ever seen the scene in Harry Potter when the bone in Harry's arm is made to disappear? Without a bone, his arm starts bending and flapping around like rubber. That's because, without a skeleton, there's nothing to keep our shape intact.

Cells also need to have something to keep their shape intact, a cytoskeleton. In fact the word cyto means 'cell,' so the cytoskeleton is the cell's skeleton. Put another way, the cytoskeleton is the framework of the cell. It is highly organized and also flexible. It doesn't appear the same as our skeleton, but some parts of it can act like our bones, and some parts can act like our muscles.

Cytoskeleton Function

The cytoskeleton functions rather like our skeleton. It provides structural support so the cell can keep its shape, move around, and be protected from outside forces. The effect of outside forces on the cell is called mechanical stress.

What is mechanical stress? Imagine two people tugging on your arms in two different directions. The two people tugging on your arms create mechanical stress. You don't split in half because your muscles and skeleton prevent the force from doing so. Likewise, the cell can resist changes in shape because of its cytoskeleton.

The cytoskeleton has other functions as well. It gives support to the cell membrane, helps evenly split up chromosomes during cell division, and aids in recovery from any outside injury. It's also involved in organelle trafficking, which is the movement of cell components, like mitochondria, from one part of the cell to another.

Just as there is strength in numbers, the components of the cytoskeleton are not found single stranded but are composed of multiple strands of three main components. In addition to the three main components, there are accessory proteins that aid in cytoskeletal assembly, disassembly, stability, and cellular transport.

Cytoskeleton Structure: Microtubules

There are 206 bones in the human body. The cytoskeleton doesn't have bones per se, but it does have three main components: microtubules, intermediate filaments, and microfilaments.

Just as your bones are different sizes, the three main components of the cytoskeleton are also different sizes. The biggest are the microtubules. Microtubules resemble what their name implies. They look like small (micro), round, hollow tubes (tubules) and have a diameter of about 24 nanometers.

Microtubules are made up of a protein called tubulin. Interestingly, microtubules' lucky number seems to be 13. Thirteen tubulin connect to form the tube. Microtubules are very dynamic structures. This means they can easily change. They are constantly growing or shrinking, kind of like a rope raveling and unraveling at one end. Microtubules are involved in the transport of cellular materials and divvying chromosomes during cell division.

Cytoskeleton Structure: Intermediate Filaments

The middle or intermediate-sized components of the cytoskeleton are the intermediate filaments (IF). What is a filament? It's something that looks like a thin thread. IFs actually resemble thin threads. They are middle-sized, around ten nanometers in diameter, and are the meshwork that supports the cell rather like a net.

Interestingly, there are many different kinds of IF proteins, and not all cells have the same type of IF protein. In fact, some cells contain no IF whatsoever. One type of IF protein is called keratin. You may not have heard of it, but you will know what it forms. Keratin is what helps compose your fingernails and hair, and it aids in holding your skin together. IFs help protect the cell from mechanical stress. That is, they allow the cell to be stretched or parts of it to bend without being broken apart. They also act as a net to hold genetic material, like DNA, in the nucleus.

Cytoskeleton Structure: Microfilaments

The tiniest main component of the cytoskeleton is the microfilament. Microfilaments are three to six nanometers in diameter and are composed of the protein actin. For this reason they are often referred to as actin filaments. The actin filaments are twisted together like two pieces of thread.

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Additional Activities

Cytoskeleton Model

This activity will help your students visualize the difference between the different parts of the cytoskeleton by creating a model of each one. Offer students a variety of supplies to choose from such as pipe cleaners, beads, clay, or even tape and newspaper. The more different types of materials you have to offer, the more creative student products can be. For example, a student might include different colors of beads to make the tubulin dimers and then glue them together to form microtubules. Intermediate filaments might come together from pipe cleaners twisted together. Remind students of the relative sizes of the different parts of the cytoskeleton and what their component parts are if they are having trouble starting their models.

Directions

Now that you're familiar with the three parts of the cytoskeleton, you're going to be creating a model of each using craft supplies. When creating your model, you want to keep the following in mind:

  • There should be one model for each part of the cytoskeleton: microtubules, microfilaments and intermediate filaments
  • Each model should include the components of each part of the cytoskeleton
  • Each model should be an accurate size relative to the other models

After you create your models, answer the reflection questions.

Reflection Questions

  1. What materials did you use for each part of the cytoskeleton and why?
  2. Are there any materials that would be better suited to this project that you didn't have access to? Why or why not?
  3. Why do you think it's important for cells to have different parts of the cytoskeleton?

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