The Plasma Membrane
The plasma membrane is made up of :
- Lipids.
- Proteins.
- Carbohydrates.
Lipids in the Plasma Membrane
The plasma membrane has phospholipids, which are the most abundant type of lipids in the plasma membrane (~75%).
Phospholipids have a polar (hydrophilic or water-loving) end and a nonpolar (hydrophobic or water-hating) end, forming the lipid bilayer.
The plasma membrane also contains cholesterol, which makes up ~25% of total lipids in the plasma membrane. Cholesterol maintains the structural integrity of the plasma membrane and regulates its fluidity.
Proteins in the Plasma Membrane
In the plasma membrane, proteins can be classified as integral or peripheral proteins.
Integral proteins are firmly embedded in the membrane and extend through the lipid bilayer.
Peripheral proteins are not as firmly embedded and are attached the polar heads of membrane phospholipids, or to integral proteins on the plasma membrane.