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6. The Membrane

Biological Membranes

6. The Membrane

Biological Membranes

1

concept

Biological Membranes

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in this video, we're going to begin our introduction to biological membranes. And so first we need to recall from our older lesson videos on lipids that Foss photo lipids are empty path IQ molecules and recall this word an type A thick just means that the fossil limits contained both water loving or hydro filic groups, as well as water fearing or hydrophobic groups, and also recall from our previous lesson. Videos that Foss follow Lipids are the major component of biological membranes. And so, if this information here does not ring a bell for you guys, then make sure to go back and check out those older lesson videos on lipids before you continue here with this video. Now that being said, a biological membrane can be defined as a phosphor, a lipid bi layer, because the fossil lipids will come together to form two layers. But biological membranes are more than just the fossil lipid bi layer, because biological membranes also have other embedded molecules as well, such as proteins and cholesterol, for instance, now biological membranes. They're also commonly referred to or called cell membranes or plasma membranes as well. And so really cell membranes. Plasma membranes and biological membranes are synonyms of each other now biological membranes. They're commonly described by the fluid mosaic model. And the reason for that is because the fluid mosaic model basically says that biological membranes are fluid. They're very, very fluid, which means that the molecules that are embedded inside of the membrane they're capable of shifting past each other and shifting around within the membrane. And so the molecules air not stuck in place that they are very, very fluid now. Also, biological membranes are a mosaic that are made up of lots of tiny pieces that come together to form the larger structure. And so they are a mosaic of these membrane embedded proteins. In fact, biological membranes can be comprised of anywhere between 20 to 80% protein by mass. And so what this goes to show is that there's quite a lot of proteins that air found inside of biological membranes. And once again these proteins they're still able to move laterally within the cell membrane or the biological membrane, which is once again why biological membranes are described as being fluid. So let's take a look at our image down below toe, clear up some of these ideas that we've talked about. So over here on the left hand side, notice that we're showing you a scanning electron Micrografx or an S e m of a biological membrane. And so notice here that this circle represents the biological membrane that's visualized using the scanning electron Micrografx. Now, notice here in this image on the right, we're zooming into this specific region of the biological membrane. And if we were to do that, it would look somewhat like what we see right here. And so notice that the major component of the biological membranes are these Foss follow lipids that we see, uh, in the membrane. Uh, just one of these circles here. One of these circles with the two tails here and here represents a single foss. Whoa, Lippett. And so all of these fossil lipids, they make up the major component of the biological membranes. As we indicated. Up above fossil lipids are the major component biological membranes. However, which you'll also notice just by looking at this image is that biological membranes they're more than just the fossil lipid, bi layer. They also have other embedded molecules as well. So just proteins in cholesterol. And so when you look at this image down below, notice that all of these purple structures that you see throughout the image represent proteins. And so there are quite a lot of proteins that are embedded in biological membranes. And once again, proteins by mass can make up somewhere between 20 to 80% of the mass of the biological membranes. So there are, ah lot of proteins embedded in the membrane, and the functions of these proteins can vary. And we'll get to talk more about the proteins that are embedded in the membranes as we move forward in our course. But once again, these members, these membrane proteins that you see here they are not stuck where you see them. They can actually shift around within the membrane laterally left and right, and so that makes the membrane very, very fluid like and also because all of these components are coming together to create the single structure. It makes the membrane a mosaic because it's made up of a bunch of smaller pieces that come together to create the single structure. Now also notice that we're labeling cholesterol molecules that air embedded within the membrane as well. And you'll also see that we have these greenest structures that air sticking up here. And these structures are supposed to represent carbo hydrates. And so, essentially, what we'll see is that biological membranes. They have lots of other embedded molecules as well. And so this here concludes our introduction to biological membranes, and we'll be able to get some practice applying these concepts as we move forward in our course, so I'll see you all in our next video.

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example

Biological Membranes Example 1

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All right. So here we have an example. Problem that's asking Membranes are a fluid mosaic of what major components. And we've got these four potential answer options down below. And so, of course, we know from our last lesson video that Foss follow lipids make up the major component of biological membranes. And so we would expect that one of the major components listed for the answer should be phosphor lipids. But when we take a look at answer option a notice that it has a lot of molecules listed, but no fossil lipids, which is the major component. And so option A is not gonna be the best answer option here and noticed that all of the other answer options do mention fossil lipids. So very nice. Now we have the major component considered in those three answer options. Now what we need to realize next is that new Clague acids are not going to be a major component of biological membranes. In fact, they're not really component biological membranes at all. And so for that reason, we could go ahead and eliminate answer option to see now when we take a look at option, be an option D, which will notice is the real difference between them is cholesterol or glucose. Now. Glucose, we did not mention, is going to be a major component of biological membranes. And in fact, it turns out that glucose is not a major component of biological membranes. But we did mention in our last lesson video that cholesterol is a major component of animal cell membranes or biological membranes, and so be here is going to be the correct answer. Fossil lipids, proteins and cholesterol are major components of cell membranes, and so we could go ahead and indicate that be Here is the correct answer for this example. And if we go back up to our image from our previous lesson video, you can see that proteins are certainly a major component of the membrane. Cholesterol is also a major component of the membrane, and once again, these little structures that we see here with the two tails. These are all fossil lipids, and so they're the major component of biological membranes. So once again, be here is the correct answer to this example, and that concludes this example. So I'll see you all in our next video

3

Problem

Problem

The fluid mosaic model of the membrane proposed that membranes:

A

Consist of a single layer of phospholipids and proteins.

B

Consist of a phospholipid bilayer composed of a variety of fatty acids.

C

Consist of protein molecules embedded in a dynamic bilayer of phospholipids.

D

Consist of a phospholipid bilayer between two layers of hydrophilic proteins.

Additional resources for Biological Membranes

PRACTICE PROBLEMS AND ACTIVITIES (5)