Cell Membranes - Video Tutorials & Practice Problems
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1
concept
Cell Membranes Concept 1
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50s
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We're gonna say here that a cell membrane separates the interior of the cell from the external environment. We're gonna say they're mainly composed of Glycerol phospho lipids as well as spinal lipids. They have what we call a selectively permeable membrane. So that means it controls what goes into and out of the cell. And we take a look here, we have what is called our lipid bilayer. This represents the exterior of the cell. This represents the interior of our cell. We're gonna say that we have our polar heads here, we have the nonpolar tails in the center and then we have polar heads. Again, this lipid bilayer will help to control the flow what goes into and out of our cell.
2
concept
Cell Membranes Concept 2
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2m
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Now, when it comes to our membrane structure, we follow what's called a fluid mosaic model. Here, this is a model for representing the general structure of a cell membrane. Now, when we say the word fluid, we're gonna say the lipid bilayer is not rigid but fluid and dynamic. We're gonna say here, phospho lipids in the lipid bilayer do not fit closely together due to kinks in the fatty acid chains. So here we have our phospholipid and we're gonna say that we have the polar heads orienting themselves on the externals. And then we have our hydrophobic tails on the interior of forming this lipid bilayer. Now, mosaic is basically the lipid bilayer also containing proteins, carbohydrates and cholesterol molecules. And we take a look here, we're going to say that these two structures at the top represent our carbohydrates side chains we have here, four fused rings together, which means it's a steroid and specifically it would be cholesterol. Next we have here, this is called an interval protein. And if we're talking about integral proteins, we're gonna say they extend through the entire bilayer and appear on both sides. We're gonna say next, we have our peripheral proteins, they're associated with our, with just one side, our peripheral protein will be this green blob right here. It doesn't cut all the way through to over here. Like the in integral proteins, would we have our carbohydrate side chains that we talked about up top these extend into the extra cellular fluid and they're responsible for self recognition and communication. Now, we talked about these four fused rings here representing a steroid but specifically cholesterol. So remember cholesterol here resides within a bilayer and increases membrane strength based on how much cholesterol we have there. And then in terms of this, remember we talked about this being the polar heads, we have our nonpolar tails, our hydrophobic tails in the inside and then we have our polar heads over here. This would give us a good description of what we mean by a fluid mosaic model.
3
example
Cell Membranes Example 1
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1m
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In this example question, it says which one of the following is not a component of cell membranes. Here, cholesterol, we've talked about cholesterol, which is represented by our four fused rings as being a key component of a cell membrane. And it helps with the membrane's strength based on the amount of cholesterol within it. So this is a part single myelins. We talked about our phospho lipids helping to create the lipid bilayer. A phospholipid can also be in the form of sphingomyelin. So, sphingomyelin are a type of phospholipid proteins. Now, we said that proteins are part of our cell membrane that can exist as intergral proteins which are found on both sides or they can be peripheral proteins that only are found on one side. The answer here would be waxes, waxes do not represent a component of a cell membrane. So here our final answer would be option D
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Problem
Problem
Which one of the following components of a cell membrane extends through its entire thickness?
A
Cholesterol
B
Peripheral proteins
C
Integral protein
D
Sphingomyelin
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Problem
Problem
Keeping in mind that unsaturated fatty acids form kinks in the phospholipid tails, what would happen if all of the unsaturated fatty acids in a lipid bilayer were replaced with saturated fatty acids?
A
It will become more fluid.
B
Its fluidity will be significantly reduced.
C
There will be no effect on its fluidity.
D
The lipid bilayer will become resistant to oxidation.