Name: 迎接...細胞膜! (Meet... The Cell Membrane!)
Uploaded: 2021-01-14T06:32:26.000Z
Duration: 10 min 11 s
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>> Hi, everyone, and welcome to the Penguin Prof Channel.

to the wonderful world of cell membranes.

Okay, so if you ask people to draw a cell,

and most people don't really think too much

about the circle itself, but it's actually really important.

The circle really defines, you know, you versus everything else

in the universe that's not you, but it's more complicated

than that because inside the cell you're going

to produce wastes that need to get out, and there's going

to be food and good stuff that needs to get in.

What happens if you puncture this barrier and goodness

So the circle itself is actually worthy of our investigation.

So what the heck are these membranes like?

Are they sort of like a container or, you know, a bag?

I mean, that separates, you know, inside from outside.

I mean, if you get a hole in your barrier, that's not good.

The truth of the matter is that membranes really aren't

like any container or barrier that we're familiar

Membranes have to control what goes in and out of the cell.

They have to be free to move and signal and communicate

and repair and do all kinds of other things.

I mean, so much of what the cells do happens

at the cell membrane, but you always have this balance

One of the more amazing things I think that membranes do is

and if you puncture them, they reseal immediately.

The magic of cell membranes comes from the fact

that they're built from molecules called amphiphiles.

Now, that may not be a term that you're familiar with,

but it comes from the Greek, and there's a word

that you probably do know, and that's amphibian.

Amphis means both, so amphibians live both on land

and in the water, so that will help you to remember it.

In chemistry, we're talking about molecules

that have both a hydrophilic -- that is, a polar end --

and a hydrophobic -- that is, a nonpolar end.

There are actually amphiphiles that are present

in our regular life in the kitchen and so forth.

We use amphiphiles for detergents as well as for soaps.

This is a really cool little mnemonic device

So this little image can help you to remember that word.

it's in the amphipathic lipids that build cell membranes.

So we have on every molecule of a phospholipid a hydrophilic --

This polar head is comprised of a glycerol molecule,

a phosphate, and then there's the side chain in our group.

We'll see what those are here in a second.

And then there is a nonpolar end that's made

up of two fatty acids tails, and they are hydrophobic.

So you have this amazing, amphipathic molecule

that has one side that is polar and likes water and one side

We're going to see why that's such a great thing,

but before we do that, I said I would show you some

about phospholipids and also glycolipids.

If you need to know a little bit more detail about them,

probably one of the more common varieties

in animal cell membranes is this guy, phosphatidylcholine.

So these are the different options, and then the rest

of it, the, these are the fatty acids that are all trailing.

These are the hydrophobic parts of the beast, okay,

if you needed a little bit more detail there.

What you got to remember is that in chemistry, like likes like.

and nonpolar molecules stick together, but polar

You have seen this if you have poured oil in water.

Everybody knows that oil and water don't mix.

The reason is that water is polar and oil is nonpolar.

So you'll get this film of oil on top of water.

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迎接...細胞膜! (Meet... The Cell Membrane!)

structure

barrier

molecule

shape