The cell membrane, also called the plasma membrane, plays a very important role in keeping the cell healthy. It helps control what goes in and out of the cell.

Key Parts of the Cell Membrane:

1. Phospholipid Bilayer:

   • The membrane is made of two layers of special fats called phospholipids.
   • The heads of these fats like water, so they face outside. The tails do not like water, so they point inward.
   • This setup means that only tiny, nonpolar molecules, like oxygen and carbon dioxide, can easily pass through. Water-soluble substances have a hard time getting through.

2. Proteins:

   • About half of the cell membrane is made up of proteins.
   • There are two types: integral (which go all the way through the membrane) and peripheral (which sit on the surface).
   • These proteins help move specific ions (like sodium, potassium, and chloride) and molecules (like glucose and amino acids) in and out of the cell, either passively (without using energy) or actively (using energy).

3. Cholesterol:

   • Cholesterol makes up about 30% of the fats in the membrane.
   • It helps keep the membrane flexible and stable so it works properly, no matter the temperature.

4. Carbohydrates:

   • These are often attached to proteins (called glycoproteins) or fats (called glycolipids).
   • They help the cell recognize other cells and communicate with them.

This organized structure of the cell membrane helps keep the cell balanced. It allows essential things to enter while keeping harmful substances out.