Characteristic of the cell membrane- Lipid bilayer No1

Before we proceed with the explanation, I wanted to confirm if you understand the difference between hydrophilicity and hydrophobicity?

I see. That's generally correct.

Here, it's sufficient to understand that hydrophilic substances dissolve easily in water, while hydrophobic substances do not dissolve in water, without delving too deeply into the matter.

And today's lecture will focus on lipids as hydrophobic substances.

Now let's get into the main topic.

Cellnosuke, do you remember from the previous explanation when we discussed how most cells reside in an aqueous environment called extracellular fluid?

I'm a bit suspicious, but let's proceed.

As an analogy, let's imagine that Cell's body was hydrophilic and could dissolve in water.

What do you think would happen if you jumped into the water with that body?

Do you think it would be able to move in that state?

That's right!

If the cell membrane that surrounds the cells were hydrophilic, most cells that live in the extracellular fluid, which is mostly composed of water, would dissolve.

In other words, it would be unable to sustain vital functions.

That's why the cell membrane is made of lipids, which are hydrophobic substances!

If you've understood this far, it's important to also note that the cell membrane is primarily composed of phospholipids, a type of lipid.

Let's now delve into a little analogy.

Let's imagine that Cellnosuke is living in a house with double doors.

That house had a flaw. The intercom was installed on the inside door.

Let's say Cellnosuke is living in such a house and decides to go shopping on Nyamazon

If both doors are closed, you would never notice the delivery person. In such a situation, if you want to securely receive your package, what would you do?

That's right!

When studying the lipid bilayer, it's important to understand that the outer door is open!

As mentioned earlier, most cells live in the extracellular fluid, which is a watery environment.

If the cell membrane is completely isolated from the external environment in that living condition...

It would become unable to exchange essential substances necessary for vital functions and would no longer be able to perceive changes in the extracellular fluid (internal environment).

You can understand that this is not very favorable, right?

So, the method that cells have found to survive is to have a double-layered cell membrane and keep the outer layer of the membrane open.

Therefore, the outside of the cell membrane has become hydrophilic.

Thanks to the outside being hydrophilic, it is able to perceive changes in the extracellular fluid (internal environment).

On the other hand, the inside is hydrophobic.

From the fact that the cell membrane has a dual structure of hydrophobicity on the inside and hydrophilicity on the outside

It is called a lipid bilayer.

I forgot to mention, but both hydrophilicity and hydrophobicity are formed by phospholipids.

Well, it has been a long lecture, but that concludes today's session.

You can see the continuation of this lecture by tapping here.

Let's try challenging the problem one last time!