Microfilaments are flexible, small protein strands that exist in a cell’s cytoplasm and are considered to be part of the cytoskeleton.

In the same way that microtubules are found throughout the cell, we also find microfilaments. The only problem with finding them is that they don’t always look the same in all cells.

They can appear lined up in straight lines in some cells and in others they look more like a spider web. To identify them, scientists have to put a dye in the cell that will turn the microfilaments a specific color.

The name “microfilament” is a description of what they are: “micro” means small and the Latin word for “thread” is filament; so they are small threads.

Microfilaments are really just a long protein string.

A good comparison might be to look at a strand of your hair. Your hair is a long string of the keratin proteins and when they are put together, they create your hair.

Microfilaments are made of a different kind of protein called “actin” and it takes two strands of the proteins wound together to make a microfilament.

However, there are thicker types of microfilaments that allow more strands to group together and these are held together with a different kind of protein.

So many small proteins

Cells are small and they make use of a lot of small proteins to create microfilaments.

Making them this way, instead of out of larger proteins gives the cell the ability to change both the location and the length of the microfilament whenever it wants.

In other words, it’s a lot more flexible and versatile. Cells need to change the shape and length of a microfilament as the cell changes and moves around.

The job of the microfilaments

Now that you know what microfilaments look like and what they are made up of, the next answer is to address what they do.

Microfilaments participate in a lot of areas where cells are needed to expand and contract.

They are involved in everything from the movement of a muscle to changing the shape of a cell in mitosis and meiosis.

Contracting Muscles

You don’t really think about the sophisticated processes involved when you reach over and pick something up.

You muscle arm contracts and becomes shorter so that it pulls on the bone and allows the bone to move. Anytime your muscles contract, all of the cells in the muscles have to contract as well.

You can thank microfilaments the next time you want to pick something up.

They line up together in the muscles right next to another filament type that is called “myosin.” The proteins in myosin have projections that stick out from the filament that are called “heads.”

The myosin heads latch onto and then pull on the microfilaments so that each myosin filament end is pulling on a different microfilament.

This pulls the two microfilaments closely together and as they get closer, they pull on the cell ends so that they are closer together as well.

The entire process makes the cell shorter and this, in turn, creates the contraction of the muscle. Kind of a lot of things going on there, just to pick something up!

Microfilaments help Cell Shape and Movement

Cells are constantly on the move and one of the ways that they accomplish movement is in changing the cell membrane shape so that it reaches in the direction that the cell wants to go.

Since microfilaments are made of small actin proteins they can be used for movement by the cell simply removing or adding actin proteins.

Cells have a lot of different shapes and many have protrusions, bumps, and little appendages.

When cells are stationary, the microfilaments help to keep all of these cells and their structures in shape and in the same place.

Microfilaments are Important in Mitosis

The process of mitosis is very complex and one of the jobs of microfilaments is to help at the end of the cell division process.

As soon as the cell is ready to split into two cells, microfilaments step in and create a kind of ring around the inside of the cells.

Myosin will then pull on the microfilament so that the ring becomes smaller and this pulls the cell membrane in along with it.

The ring gets pulled tighter and tighter until finally it creates the “pinch” in the middle that finishes with two cells.

 Facts about Microfilaments

  • Microfilament bundles often happen right under the surface of the cell. They can be aligned parallel to the cell and some can use the plasma membrane as an anchor.
  • Microfilaments also play a part in transporting material inside the cell and with the flow of cytoplasm to the cell’s organelles through a process called “cytoplasmic streaming.”
  • Of all of the filaments of the cytoskeleton, microfilaments are the thinnest. They have an average diameter of 6-7 nanometers.
  • Microfilaments can have quite a few shapes but many look long, thin, and stringy.
  • Microfilaments are sometimes found floating free and connected to other tubules and filaments.
  • Unlike microtubules, microfilaments are solid rods of actin protein.

Interesting Facts about Biology

  • The word “muscle” is found to be taken from the Latin word “musculus” which translates to “little mouse.” It’s thought that the name was given because a muscle moving under the skin appeared to look the same as a mouse moving around under a rug.
  • When you compare a muscle in relation to the job that it has to do, the strongest of the external muscles is the eye. It has to be about 100 times stronger than it needs to be in relation to its weight and size.
  • We use the term “muscle memory” as an explanation of the process of practicing over and over again so that the muscle is finely tuned to the task.
  • Muscle tissue is 15% denser than fat tissue and our muscles make up nearing half of the total body weight of a human.
  • Tendons connect our hard bones to our soft contracting muscles.
  • Skeletal muscles are divided into two unusual names for their types: fast twitch and slow twitch.

Microfilaments Quiz

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