How do molecules of cholesterol affect the structure of cell membranes?

Question

Accepted Answer

Hi, everyone. Welcome back. And let's take a look at our next question. Which statement is true regarding the effect of cholesterol on the structure of the cell membrane. So let's go through our answer choices. Here. We have A through C as statements about cholesterol and D as all of the above. So we can have all of our statements being correct. So we won't pick an answer until we get to the end choice. A says cholesterol decreases the membrane's permeability to small water soluble molecules by filling spaces between phospholipids. So recall that for small water soble molecules to get through the membrane, they would sort of make their way in between the phospholipid chains. But what is the structure of cholesterol? Cholesterol has a hydrophobic ring structure with one hydrophilic hydroxyl group. So it's quite a bit smaller than the phospholipids that make up the membrane which have these long fatty acid tails. So it is quite small but it can align with our phospholipids because that hydroxyl group can line up with the hydrophilic heads while the hydrophobic ring fits in with the tails being being hydrophobic. So being fairly small, it does pack in and fill in these gaps between the fossil lipids. So that would make mean that fewer of these small molecules can make their way through those spaces. So choice A is correct. We'll put a dot here rather than selecting it since, as we know, we have the possibility of more than one correct answer. Now, let's look at choice B cholesterol provides structural integrity and stability to the cell membrane, making it less susceptible to phase transitions and mechanical stress. Well, this is correct. So by filling in these spaces, cholesterol prevents excessive movement on the part of the phospholipids, so that restricts the movement and gives them more stability um under heated conditions or when under stress. So choice B also true. So we know by now since we have two correct answers that our correct answer must be choice d all of the above. But this is a practice problem. We want to be thorough. So let's look at our choice. C cholesterol modulates membrane fluidity by preventing the fascy acid chains of phospholipids from packing too closely in low temperatures. And this is also correct. Again, these little cholesterol molecules are wedged in there in between the phospholipids and their chains. So when the temperature lowers, you can't have that tight packing that would cause the membrane to become solid. So choice C also correct. So again, we have these statements about the effect of cholesterol on the structure of cell membranes. And we know that all of these statements are correct given the structure of cholesterol that it fills in gaps between phospholipids, prevents them from packing too closely and prevents excessive movement. So choice D all of the above is our correct answer. See you in the next video.

How do molecules of cholesterol affect the structure of cell membranes?

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Key Concepts

Cholesterol Structure and Function

Cell Membrane Composition

Membrane Fluidity