Question

Which of the following is the latest model of cell membrane?
A. Unit membrane model
B. Fluid mosaic model
C. Danielli and Dovson’s model
D. Robertson’s model

Answer 1

Hint: The latest model of the cell membrane is actually very old. It was proposed by Singer and Nicolson in 1972. The evolution of the cell membrane models happened by adding more and crucial information to already existing models, to explain discrepancies in the model. So one can see a clear chronological order of each model establishing itself and paving the way to the next model.

Complete answer:
The latest model of cell membrane is the Fluid mosaic model. So the correct option is (B). This model was proposed by Singer and Nicolson in 1972. And this model could explain most of the properties of the cell membrane.
All the mentioned models are described and explained below :
Danielli and Dovson’s model was called a pauci-molecular theory. It was proposed in 1935. This theory was the first one to acknowledge the presence of proteins on the cellular membrane. The model was built on Gorter and Grendel in 1925, who had already proposed the lipid bilayer.
The unit membrane model was proposed by Robertson in 1959, building on Danielli and Dovson’s model. The confirmation of the plasma membrane by electron microscopy helped in the process of model building. As you can put together from the name, the model has suggested a unit membrane which has a similar structure and is present in all cell membranes. Both the pauci-molecular model and the unit membrane model predicted thin sheets of proteins surrounding the lipid bilayer. But this had inconsistencies with the observations of mainly globular proteins.
The fluid mosaic model was put forward to answer most of these irregularities. After what one can gather from the name, the membrane is a fluid of lipid bilayer and proteins are embedded like mosaics. They have proposed different types of membrane proteins (see below) , as opposed to the earlier models, which had just one thin layer of proteins.
Integral membrane proteins
Peripheral proteins
Lipid anchor proteins
Some additions and changes in the model are still going on. But the Fluid mosaic model is still the predominant model in this field.

Note: The unit membrane model and Robertson’s model are the same. Also, Robertson built on Danielli and Dovson’s proposed model. The fluid mosaic model of plasma membrane is the most widely accepted model. After the proposal of this structure by Singer and Nicolson, no other model is proposed yet because it has no limitations and drawbacks. So, it is the latest model of cell membrane.