Question

Who gave the lamellar or sandwich model of cell membrane?
A. Singer and Nicolson
B. Danielli and Davson
C. J. Robertson
D. None of the above

Answer 1

Hint:This model was proposed to explain the detailed structure of cell membrane. This model shows a lipid bimolecular layer sandwiched between two protein layers (globular proteins). Lipid bilayer has heads outside and tails inner side.

Complete step by step answer:Electron microscope studies showed the following details of cell membrane –
The lipid bilayer is held together by electrostatic interactions.
The heads of lipids are hydrophilic and face towards the positive charged protein layer and hydrophobic tails faces away.
This layer is capable of distinguishing molecules of different sizes and solubility.
The thickness of lipid bilayer is about 6nm and each protein layer is about 1nm thick. Thus, total thickness becomes about 7.5nm.
Electron microscope shows the protein layer as two dark lines outside and a light colored region inside.
The membrane proteins are insoluble in water and do not form a uniform layer but have pores inside it.
This model is well supported by experimental evidence.
The correct answer is option B i.e., Danielli and Davson.

                   SANDWICH MODEL

The correct answer is option B i.e., Danielli and Davson.
Additional information:There are some limitations of this model. These include - Membrane proteins are not fixed in place and they are mobile. The membrane proteins have an inner rough irregular surface.
Note:These layers are selectively permeable and do not allow some molecules to pass which are not recognized by hydrophilic pores. The structure of these layers can be written as P-L-L-P. Here, P stands for protein layer and L stands for lipid bilayer.