What is the Difference Between Fluid Mosaic Model and Sandwich Model?

The fluid mosaic model and the sandwich model are two different models that describe the structure of the cell membrane. The key differences between these two models are:

1. Protein arrangement: The fluid mosaic model states that large protein (glycoprotein) molecules are embedded partially or completely within the phospholipid bilayer. In contrast, the sandwich model proposes that a phospholipid bilayer is sandwiched between two layers of proteins.
2. Membrane structure: The sandwich model describes the cell membrane as a rigid and stable structure, while the fluid mosaic model describes it as a less rigid and dynamic structure.
3. Variability: The sandwich model does not explain the variability of the plasma membrane, whereas the fluid mosaic model does.
4. Lipid-protein ratio: The fluid mosaic model supports the lipid-protein ratio in the cell membrane, while the sandwich model does not.

The fluid mosaic model, proposed by G.L. Nicholson and S.L. Singer in 1972, is considered the most accurate model that explains the structure of the cell membrane. It describes the plasma membrane as a mosaic of phospholipids, cholesterol, proteins, and carbohydrates. The model also explains the transport of solutes and solvents through the biological membrane and the active and bulk transport of substances through the plasma membrane.

On the other hand, the sandwich model is a rejected model due to its various limitations. It did not explain the cell membrane's dynamic nature, repair capabilities, and variability among different biomembranes.

Comparative Table: Fluid Mosaic Model vs Sandwich Model

Here is a table comparing the Fluid Mosaic Model and the Sandwich Model:

The Fluid Mosaic Model, proposed by G.L. Nicholson and S.L. Singer in 1972, is the more accurate and widely accepted model of the cell membrane. It describes the plasma membrane as a mosaic of phospholipids, cholesterol, proteins, and carbohydrates, with proteins partially or completely embedded in the phospholipid bilayer. The Sandwich Model, proposed by Hugh Davson and James Danielli, is an older model that states a phospholipid bilayer is sandwiched between two layers of proteins.