Transcription
The first molecule, well, the first things I want to point out on this slide for membrane structures or molecules that are involved with the membrane, well, we know the main one, and that is the phospholipid. So if I draw a circle around a single phospholipid there, it is. You can see the gray hydrophilic head and the two yellow hydrophobic tails, and there's another one down here that's mirroring it. You know, I can't draw it very well.
Um, so there's a whole bunch of those. Those are the phospholipid molecules that make up the majority of the bilayer. Also though, embedded in here, you can see this little guy, and there's several of them here. This is cholesterol. So it's the molecule that we met in unit number one, the steroid. The, the type of molecule we call it a lipid because it's, um, hydrophobic. It has no charges and it doesn't like water.
And so you can see it would make sense that it wouldn't like water and then it would be quite happy to hang out here in the membrane because this is the part of the membrane that's hydrophobic and is not touching any water. There's lots of water down here on the inside of the cell, and there's lots of water up here on the outside of the cell. But this hydrophobic cholesterol molecule is quite happy to hang out in this hydrophobic region of the membrane right here.
Its job, um, what its job is, is to maintain what we call the fluidity of the membrane. It's, it keeps everything kind of lined up, all these tails, and it keeps everything moving and wiggling kind of beside each other nicely. It's like lubrication in the membrane to keep the structures all lined up and the bilayer functioning correctly. So cholesterol, hydrophobic molecule, and it assists with keeping the membrane fluid and moving flexibly.