Name: Chromosomes, DNA and Genes
Uploaded: 2019-07-19
Duration: 5 min 50 s
Description: This informative video will help you learn about the structure of chromosomes and genes and the history behind DNA. Let's watch and learn more.

Question

The fluid mosaic model proposed by Singer and Nicolson has been replaced Sandwich model proposed by Danielli and Davson. Why?

Accepted Answer

The sandwich model proposed by Danielle and Davson suggests that the phospholipid bilayer lies between two layers of globular proteins. The lipid layer is sandwiched between two protein layers. This model has the following limitation.

This model assumed that the plasma membrane has a uniform thickness with constant lipid-protein ratio.

According to this model, all membranes have the symmetrical internal and external surface.

Membrane proteins were insoluble in water. Such proteins can not form a uniform and continuous layer.

It did not explain the permeability of substances.

To overcome these limitations, a new model was proposed by Singer and Nicolson in 1972, called the fluid mosaic model. According to this model, the cell membrane is made up of phospholipid bilayer, proteins, and a small amount of carbohydrate is also present. The proteins are embedded into the lipid bilayer. According to the model, proteins are like icebergs and lipid are like the sea. Due to the fluid nature of the plasma membrane, the lipids and proteins can change their position in the bilayer.

The fluid mosaic model proposed by Singer and Nicolson has been replaced Sandwich model proposed by Danielli and Davson. Why?

Important Questions on Cell Structure and Organization

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