If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:6:53

Video transcript

when we first learn about cells because of the visualizations that we often see in textbooks or even some of the the micrographs we might see from microscopes we kind of imagine cells as these little balloons of fluid with things floating around in them so this right over here this is a fairly common textbook visualization of a cross-section of the cell and we see all of these important parts we see the nucleus we see the endoplasmic reticulum we see the we see the Golgi apparatus we see mitochondria here and the way that this is drawn it looks like they're just floating it looks like they're just floating in the cytosol and it is true that there is a lot of water in cells in fact you are mostly water and most of that water that makes up you is found in cells but it turns out that these types of drawings are missing a very crucial aspect of the structure of cells they are missing the cytoskeleton saito cytoskeleton and this is still something that we we are trying to understand better of what how does the cytoskeleton work and how does it help the cell have its structure and move things around and give it its shape so cytoskeleton it's one word but I've written the different parts of the words and the different parts of the word in different colors here because this literally means cell skeleton so if I were to actually try to visualize the cytoskeleton here I have all sorts of these structures just in a different color and have all sorts of these structures Criss crossing the cell in different ways that have proteins bound to them and they're even moving in they're growing in there they can help the cell move around or they can help transport things within the cell and other things could be lodged in them and so it's a much much much more complex thing that we're talking about than what was depicted in this in this in this visualization before I had my chance to to scribble on it and to help us visualize and I found this picture it's public domain picture and I found it fascinating because it really helps you think about the complexity that is going on in even one of your cells so let's look at some of the structures over here so this these this thing that I'm kind of that I'm kind of tracing that I'm kind of tracing right over here this is called a micro filament this is a micro filament so let me write that that's a micro microfilament and just to get a sense of the scale its diameter so this diameter is going to be about six or seven nanometers so approximately six to seven nanometers six to seven billionth of a meter and have just got a sense of that relative to the cell itself a typical cell could be it could be six to seven micrometers in diameter or larger so this is essentially one thousandth of the diameter of the cell so these these things that I'm drawing right over here these actually would not be that far off in terms of scale in fact I'd probably want to draw it even thinner and that's why you often won't see in these diagrams because you'd have to draw it you would have to draw it so thin the diameter of one of these filaments is one is roughly or to remand to mm of the diameter of a of a fairly typical cell but these things are incredibly important they help give the structure of the cell they're made up of they're made up of actin proteins so you can see there's kind of these two actin these two actin you can kind of visualize them as ropes wrapped around each other and so this the protein involved here let me do this I'm using that color too much the protein involved in these microfilaments is actin this is actin and what's neat about these microfilaments I sell they as I said they help give structure they help do all sorts of things they can actually be dynamically kind of destroyed and created their lengths can be changed this can help a cell actually move and even more you can use them you can transport things along them where you could pull and tug on them and there's actually a fascinating interaction between actin and what you see over here this this right over here this is made up of myosin this is myosin my let me write this and it's hard to see that is myosin myosin and the relationship with actin myosin myosin can act as kind of this thing that kicks along the myosin and can they can move relative to each other this is essential for muscles contracting it's fascinating to see that even things like proteins which are just made up of a bunch of amino acids they can interact and the fairly complex ways that you can have these myosin things kick along and move and tug on on the actin so that's myosin right over there we see we see ribosomes these ribosomes are the ribosomes that are not attached to the endoplasmic reticulum so these are free ribosomes around here so you can see it's incredibly incredibly complex you might say okay I see I see these micro filaments made up of made up of actin I see one the one I outlined there's others over here I see another one right over here I see one up over here but what are these big what are these big tube-like structures that we also see so for example what is this what are these tube-like structures well these are called micro tubules so micro micro tubules and they look massive compared to the microfilaments but they're still really small on a cellular scale this is about 25 nanometers 25 nanometers and once again these play a huge role in the structure of cells and they allow things to be organized and things to be transported and these are also dynamic pieces of the cell they can be constructed and they can be destroyed and they can change the shape of the actual cells and in animal cells the things I've just described are found in most cells but in animal cells you will also find things called intermediate filaments that are actually in between these two in size which also help maintain shape and do other things so the whole point of this video is to just give you even more appreciation hopefully all the other videos we had on cells I've given you appreciation for how much beauty and how much complexity there are and things that a lot of times on an everyday level we think of is something as simple as a cell but there's all this beauty and complexity to its structure that's often not even depicted in the drawings of the cells that you might find in your textbooks and to get a better appreciation here some public domain images I found of cells where you can see the cytoskeleton actually colored in and what you see in this picture in particular in this yellowish green color those this is actually cow lung cells right over here this yellowish green structure these these yellow screen lines you see those are the microtubules and what you see in this pinkish or oranges color these are the microfilaments oh you get a appreciation for how complex and and and structured these things that you used to think we're just big blobs actually are
Biology is brought to you with support from the Amgen Foundation