Cell membrane overview and fluid mosaic model

The cell membrane protects our cells from the harsh outside environment. Without it, life wouldn't be possible. The three main components of the cell membrane are:

Phospholipids
Cholesterol
Proteins

🧱 Phospholipids

Phospholipids make up the majority of the cell membrane.

Structure: Each phospholipid has a polar head group (phosphate group) and two fatty acid tails.
A phospholipid bilayer (or lipid bilayer) is formed by phospholipids packed closely together. It looks like a cross-section when cut in half.

🌡 Cholesterol

Cholesterol is important for the cell membrane.

Structure: Cholesterol has a lot of rings, which gives it a stable structure.
Function: Cholesterol inserts itself between phospholipids and acts like a buffer, maintaining the fluidity of the cell membrane.
- At lower temperatures, it increases fluidity.
- At higher temperatures, it decreases fluidity.

⚙ Proteins

Proteins are a big component, and some cells have a significant amount of protein in their membranes.

Types:
- Integral proteins (or transmembrane proteins): Cross the entire membrane.
- Peripheral proteins: Sit on top of the membrane or on another protein.
- Rare proteins: Can go halfway through the membrane or reside inside the bilayer between phospholipids.
Function: Proteins carry out nearly all membrane processes.
- Receptors: Proteins act as communication channels, telling the cell what's going on outside.
- Transporters: Transmembrane proteins help transport molecules in and out of the cell.
Lipid-bound proteins: Proteins stuck within the lipid bilayer are rare because they don't play a significant role in communication or transport.

🍬 Carbohydrates (Glyco-)

Carbohydrates, or glyco- molecules, bind to lipids or proteins, forming glycoproteins or glycolipids.

Function: They play a role in communication, allowing cells to recognize each other.
Location: Sugars mainly occur on the outside of the membrane, sticking out on proteins (glycoproteins) or lipids (glycolipids).

🖼 Fluid Mosaic Model

If viewing the cell membrane from the outside (top view):

You would see phospholipid head groups.
Cholesterol would be interspersed.
Larger proteins would be on top.
Glycoproteins and glycolipids would be attached to proteins and phospholipids.

This arrangement resembles a mosaic, with different pieces put together.

Fluidity: The components of the cell membrane (proteins and phospholipids) can move around, hence the term "fluid." This movement isn't just two-dimensional; it can occur in various directions.
Discovered in 1972: The fluid mosaic model was discovered relatively recently.