The fluid mosaic model proposes that the cell membrane is composed of a lipid bilayer with embedded proteins that move laterally within the bilayer. Phospholipids form a double layer with their hydrophobic tails pointed inward and hydrophilic heads outward. Proteins are embedded within or attached to either surface of the membrane. Cholesterol is also present within the phospholipid bilayer, where it helps to stabilize the structure. The fluid mosaic model provides a satisfactory structure of the cell membrane and was proposed by Singer and Nicolson in 1972.

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Ned
FLUID MOSAIC MODEL?
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Fluid Mosaic Model proposed by Singer and Nicolson in 1972. This model define the
satisfactory structure of cell membrane. Cell membrane consists with phospholipids and
protein molecules. The viscous fluid matrix present between the phospholipid bilayer. The
lipid and proteins are vary from one layer to another layer. Cholesterol is also present
within the phospholipid molecules.
In previous time their was no any accurate structure of cell membrane. Singer and
Nicolson study on cell membrane and proposed this model and named Fluid Mosaic
Model. In this they show us that, a cell membrane is composed with phospholipids,
proteins, cholesterol, fluid matrix and carbohydrate molecules.
1) Phospholipids molecules makes a layer by attached their head to each other. Their
is no space between them. Phospholipids are made up of two fatty acids and a
phosphate group. They have two parts, one is head part and other is tail part. Head part
is known as Hydrophilic end (water loving end) and the tail part is known as hydrophobic
end (water fearing end). Hydrophilic end are polar, they directed outward and the
hydrophobic end are non-polar, they directed inward. These layer only allow molecules to
pass through. The two layer of phospholipid arranged opposite to each other is known as
phospholipid bilayer. This arrangement forms water resistant barrier and also allow
stretching of cell when it need. Phospholipid bilayer is 35A thick.
2) Protein molecules present between the phospholipid molecules or on the surface of
hydrophilic head. Those protein molecule lie between the phospholipid molecules are
known as Integral protein molecule they are attached tightly. Protein present on the
hydrophilic surface known as peripheral protein molecule and they are not attached
tightly. In cell membrane their is big size protein molecule present between the
phospholipid bilayer and it called tunnel protein molecule. These proteins are act as

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carrier molecules. They carry the specific molecules and allow to transport inside or
outside of the cell. It provide a path for selective material exchange from cell to
extracellular fluid and also control the flow of material.
3) Cholesterol- these molecules present between the phospholipid molecules. A good
amount of cholesterol present in animal cell membrane. It helps to stabilize the cell
membrane.
4) Oligosaccharide (Carbohydrate molecule)- The branched shaped molecules
present on cell membrane is known as carbohydrate molecules. These are attached with
protein molecules and phospholipid molecule. The oligosaccharides attached with
peripheral protein molecule known as glycoprotein and if the oligosaccharide attached
with hydrophilic end is known as glycolipid. The glycoprotein is act as receptor.
This is the simple explanation of Fluid Mosaic Model.
Some Important Questions.
Q1) What is Tunnel protein molecule?
Ans. The largest protein molecule lie between the phospholipid bilayers are known as
tunnel protein.
Q2) Who proposed the Fluid Mosaic Model and when?
Ans. In 1972, Singer and Nicolson proposed the fluid mosaic model.
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