Question

Which of the following is not present in the cell membrane?
A) Phospholipids
B) Glycolipids
C) Lignin
D) Cholesterol

Answer 1

Cell membrane is also called as the plasma membrane. It is the membrane found in all the cells. It separates the interior of the cell from the external environment of the cell. Cell membrane is a semi-permeable membrane which means that it allows the movement of selective molecules or ions across itself.
Complete answer:

Phospholipids :Phospholipids are the class of lipids that are present in the plasma membrane.They are amphoteric in nature which means that they have a polar or hydrophilic head and a no-polar or hydrophobic tail.Membrane phospholipids organize into the bilayers with the polar ends oriented towards the outer surface and hydrophobic tail toward the inner surface of the membrane.
Glycolipids :Glycolipids are found on the surface of the cell membranes.Glycolipids are the lipids that are attached to the carbohydrate molecule.They are attached to carbohydrate molecules by glycosidic linkage.The function of glycolipids is to maintain the stability of the cell membrane and to facilitate cellular recognition.
Lignin :Lignin is a complex organic molecule.It is the structural material which is present in the support tissues of the vascular plants and some algae.Lignins are important for the formation of cell walls especially in the wood and bark.They provide rigidity and do not rot easily.
Cholesterol : Cholesterol is the main steroid present in the plasma membrane.iT is the waxy, fat like substance which is found in all cells of the bodyCholesterol is the precursor of Vitamin D, testosterone, Estrogen, progesterone, etc.Cholesterol in plasma membrane play a role in structure and function of plasma membrane.
Therefore, it has been clear from the above discussion that Lignin is not present in the cell membrane.
Hence, option C is the correct answer.
Note: The plasma membrane consists of a lipid bilayer which includes cholesterol between phospholipids which maintain the fluidity of the membrane. The membrane also contains some integral proteins that act as membrane transporters. Plasma membranes perform various functions like osmosis, endocytosis, exocytosis, diffusion, etc.