Cytoskeleton and intracellular motility

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Cytoskeleton and intracellular motility


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Cytoskeleton and intracellular motility

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Investigators are examining the structure of cilia found on the respiratory epithelium. Which of the following is true about the structure of cilia?  

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cytoskeleton p. 46

Cytokeratin p. 220

cytoskeletal element p. 46


cytoskeletal elements p. 46

Cytoskeletal elements p. 46

Intermediate filaments

cytoskeletal element p. 46

Microfilaments (cytoskeleton) p. 46

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The cell is the basic unit of life, that can replicate on its own.

The human body alone has over 200 different cell types - from long skinny neurons that can grow over 1 meter long to myocytes or heart muscle cells that contract to let you to flex your muscles.

But despite their differences, they share many features, including the cytoskeleton.

The cytoskeleton is a network of proteins within the cell.

The cytoskeleton gives each cell its shape and anchors organelles in place - keeping everything sturdy - a bit like the frame for a house.

But it’s also a dynamic network, which can change shape when the cell wants to move, contract, divide, or pull in or push out molecules. Imagine if your house could do that - perhaps it would get up and walk away during an earthquake!

So the cytoskeleton is pretty special and it’s made up of three proteins: actin filaments, intermediate filaments, and microtubules.

Actin filaments are the thinnest of the three proteins, so they’re also called microfilaments.

They’re made up of two strands of actin proteins arranged in a long twisting chain like a twisted necklace.

The actin filaments connect to one another to form a network - like a spider's web - that’s located just below the cell membrane.

The actin filaments slide closer together and further apart, allowing the cell to change shape during muscle contraction.

Not surprisingly, muscle cells have plenty of actin, as well as another protein called myosin.

Myosin filaments bind to actin filaments, and that’s what allows the actin to slide closer together and further apart.

And ultimately, that makes the muscle cells shrink and stretch during muscle contraction and relaxation.

Similarly, sometimes these networks change their shape and that allows cells to move.

White blood cells like neutrophils use extensions called pseudopodia, or false feet, to crawl in and out of blood vessels - a process called diapedesis.

The way that works is that the neutrophil’s actin filaments grow rapidly through the polymerization of many actin monomers in one direction, to push out the cell membrane and create a foot.

This newly created foot wedges between the endothelial cells that make up the blood vessels.

The neutrophil then begins to squeeze through, until it reaches the other side.


The cytoskeleton is a mesh-like structure that spans the entire cell and provides structural support. It is made of three main protein filaments: microtubules, actin filaments, and intermediate filaments. These filaments can assemble and disassemble to allow the cell to change shape and move.

The cytoskeleton is responsible for many cellular processes, including intracellular motility (the movement of organelles within the cell). This motility is accomplished through the actions of motor proteins, which bind to the cytoskeleton and use it as a track to move along. This movement allows cells to respond quickly to their environment and carry out essential functions like replication and division.


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