Model of cell membrane

Let us learn about cell membrane,

Phospholipids are amphipathic, and have hydrophilic and hydrophobic character in the same molecule. Interactions with water cause the phospholipids to form a bilayer, with hydrophobic fatty acid tails inside the bilayer and hydrophilic groups exposed to water.

This basic structure makes the membrane a barrier to hydrophilic molecules. The interior of the membrane is fluid, with a viscosity about equal to olive oil. Cholesterol in membranes alters fluidity.

Proteins :

Proteins of membranes are divided into two general classes:

Integral membrane proteins penetrate or are embedded in the phospholipid bilayer. Some membrane proteins have one or more alpha-helical regions that can span the bilayer multiple times. Peripheral membrane proteins lack hydrophobic regions, and they frequently associate with integral membrane proteins or hydrophilic surfaces of the bilayer.

Transport of polar molecules through the cell membrane usually requires channels made up of proteins that span the lipid bilayer. Thus, we associate the majority of functional properties of cell membranes with the membrane proteins. The lipid is predominately a barrier. Later we shall see that both lipids and proteins of membranes can function in cell signaling.
Hope the above explanation was helpful.