Question

The integral protein, when removed from the plasma membrane, will show which of the following properties?
A. Soluble in aqueous solution
B. Insoluble in aqueous solution
C. Formation of bilayer in ${H_2O}$
D. Solubility will differ from protein to protein

Answer 1

The proteins that are embedded in the lipid bilayer have a very unique property – the outer surfaces of the proteins are made with hydrophilic amino acids and the inner surface is made up with hydrophobic amino acid. Hydro means water; philic means loving and phobic means fearing.
Step-by-step explanation:
The cell membrane is made up of proteins and lipids.
The lipid bilayer has heads on the outer surface and nonpolar tails on the inner side of the membrane.
Polar means hydrophilic and nonpolar means hydrophobic.
There are two types of proteins in the plasma membrane – 1. Integral membrane protein and 2. Peripheral membrane protein.
The peripheral proteins are attached on the outer surface with the lipid layer. They make a weak bond so it can be extracted easily.
The integral membrane proteins are embedded in the lipid bilayer and it spans the whole membrane. It is also called transmembrane protein. It attaches with the lipid with strong covalent bonds. Thus, it is very difficult to extract the integral proteins.
But when an integral protein is removed, it is soluble in aqueous solution as the outer surface of the protein is made up with hydrophilic amino acids and the inner surface has hydrophobic amino acids.

Hence, the correct answer is option A. Soluble in aqueous solution.

Note: The outer surface of the integral membrane protein is made up with hydrophilic amino acids such as lysine, tyrosine, serine, threonine etc. and inner surface is made up with hydrophobic amino acids such as valine, glycine, alanine, methionine, phenylalanine etc.