Question

The latest model of the cell membrane is the
A. Unit membrane model
B. Fluid mosaic model
C. Danielli and Davson model
D. Robertson’s model

Answer 1

Hint:Cell membrane is also called plasma membrane. The cell membrane is found around the cytoplasm and it is also found surrounding some cell organelles.
The cell membrane is semi-permeable. It protects the cell and also determines the shape and permeability of the cell. It is made of phospholipids and protein.

Complete answer:
For the structure of cell membranes, many models were given by many scientists. But the accepted model is a fluid mosaic model.
The fluid mosaic model was given by two scientists Singer and Nicolson. According to this model, the unit membrane is made of lipids and proteins.
Lipid molecules provide fluidity to the membrane and there are two layers of lipid molecules. Protein molecules are embedded in the bilayer.
Some protein molecules are embedded partially (30 percent protein) that are called extrinsic proteins or peripheral proteins. These act as enzymes.
Some protein molecules are embedded completely that are called intrinsic proteins. These protein molecules act as carriers.
The lipid bilayer is polar by nature because glycolipids and phospholipids are found in them. It has both hydrophobic and hydrophilic parts.
Lipid and protein arrangement provides flexibility to the cell membrane.

Therefore the correct answer is option B. Fluid mosaic model.

Note: Cell membrane permeability depends on the carrier proteins.
Lipid has a hydrophobic part so charged molecules cannot pass through this. Protein molecules act as carriers and charged molecules are passed through this. Lipid soluble molecules are passed through lipid layers which are not charged.