Question

Who proposed the unit membrane model of the plasma membrane?
(a)Robertson
(b)Singer
(c)Danielli
(d)Robert Hook

Answer 1

Hint: He studied the ultrastructure of several biomembranes of the cell, example-plasma membrane, nuclear membrane, mitochondrial membrane, etc. and found that all these membranes are similar in their ultrastructure, except their thickness.

Complete answer:
Robertson proposed the unit membrane model of the plasma membrane in 1959 A.D. The Biomembrane model proposed by Robertson stated that these are made up of three layers and out of these three layers, two are protein layers and one is a phospholipid layer.
The unit membrane model has the following features:
1. A biomembrane is a lipoproteins (having fat and protein)structure and trilaminar (three layers).
2. Protein molecules are extended and not globular
3. Each phospholipid (two fatty acids, a phosphate group, and a glycerol molecule) is a polar molecule (attracting something) with a hydrophilic (water-loving) head of glycerol and hydrophobic (water-hating) tail of two fatty acid chain.
4. Heads of phospholipid molecules are directed in opposite directions while the tails of the two layers face each other.

Additional Information: -Both the Danielli and Davson model and Robertson’s model of the unit membrane are collectively called lamellar models.
-Although each of these membranes may serve different functions, they all share two common properties: they exhibit both a selective permeability to lipid solvents as well as a high electrical resistance.
So, the correct answer is, ‘Robertson.’

Note: As reported by Robertson, the average thickness of the biomembrane is somewhere between 75 to 100 angstrom in which each protein layer is around 20 to 30 angstrom while the phospholipid bilayer is around 35 to 40 angstrom.