Question

What is the percentage of intrinsic proteins in the total proteins of plasma membrane?
a. 70%
b. 20%
c. 10%
d. 90%

Answer 1

The cytoplasm of the cell is bounded by a membrane which is known as the plasma membrane. The plasma membrane limits as well as separates the contents of the cell with its cytoplasm and other cell organelles. It performs several different functions.

Complete answer:
The plasma membrane or the cell membrane is the partially permeable membrane which surrounds the cell and encloses the different cell organelles as well as the cytoplasm and the nucleoplasm. The plasma membrane separates the cell from the external environment especially from the surrounding extracellular fluid.

The membrane of the cell consists of a bilayer made up of lipid which includes cholesterols. Cholesterols are lipids and it occurs between phospholipids which helps to maintain the fluid nature of the cytoplasm.

The plasma membrane consists of proteins which can be referred to as the membrane proteins. These proteins are present in the layer of the membrane of the cell and so are known as membrane proteins. The different types of membrane proteins are integral or intrinsic membrane protein, transmembrane proteins and peripheral membrane proteins.

Peripheral membrane proteins are temporarily attached to the lipid bilayer or to other types of protein while transmembrane proteins are present on the entirety of the cell membrane.

The integral membrane proteins are embedded into the lipid bilayer and they are anchored permanently. They form an important part of the cell membrane and are difficult to isolate from the membrane. The integral proteins are also known as intrinsic proteins. Some of the intrinsic proteins move in the entire span of the cell membrane as their one end contacts the exterior while the other end is connected with the interior of the cell. They represent about 70% of the total types of proteins that are present in the cell.

The exposed portion of intrinsic or integral proteins are hydrophilic in nature while the interior part is hydrophobic and is made up of non-polar amino acids.

Hence, the correct answer is option (A).

Note: The proteins that are present as embedded in the membrane of the cell are known as the membrane proteins. They appear in association with the lipid bilayer. The different types of proteins make up different percentages in the cell and the intrinsic or the integral proteins make up about 70% of the total proteins that are found to be present in the cell membrane.