Question

Which one of the following macromolecules function as energy storage compounds, components of cell membrane and can also provide insulation?
A) Proteins
B) Carbohydrates
C) Steroids
D) Lipids
E) Nucleic acids

Answer 1

Hint: Macromolecules are the large molecules which are composed of smaller units called monomers. A substance that is composed of many units i.e monomers is called a polymer. The common macromolecules in biochemistry are proteins, lipids, carbohydrates, etc.

Complete answer :
>Proteins : Proteins are the macromolecules which are composed of amino acids as monomeric units.Amino acids are joined with the help of peptide bonds to form protein molecules.There are 20 amino acids that are responsible for the formation of all types of proteins exist.Plasma membranes have some integral proteins and some peripheral proteins that act like membrane transporters.These proteins are loosely attached to the inside face or outside face of the cell membrane.
>Carbohydrates:Carbohydrates generally found on the outer surface of the cell membrane.They may be either bound to the proteins to form glycoproteins or bind to the lipids to form glycolipids.The carbohydrates are composed of glucose as monomeric units.They can be straight or can be branched.
>Steroids:Steroids are the derivatives of lipids.They are hydrophobic and insoluble in water.
Cholesterol is the main steroid present in the plasma membrane.Cholesterol is the precursor of Vitamin D, testosterone, Estrogen, progesterone, etc.Cholesterol in plasma membrane plays a role in structure and function of plasma membrane.
>Lipids:-The lipids that are present in the cell membrane are a kind of phospholipids.They are amphipathic which means that they have a polar or hydrophilic end and a no-polar or hydrophobic tail.
Membrane lipids organize into the bilayers with the polar ends oriented towards the outer surface and hydrophobic tail toward the inner surface of the membrane.Lipids act as storage molecules of the cell membrane.They can also provide insulation to the membrane due to its emphatic nature.
Nucleic acids:Nucleic acids are the genetic materials of all the living organisms. There are two types of nucleic acids present-
->DNA – Deoxyribo nucleic acid
-> RNA – Ribonucleic acid
 These molecules help in passing the characters from the parents to the offsprings.
Therefore, it has been clear from the above discussion that Lipids are the macromolecules that function as energy storage compounds, components of cell membranes and can also provide insulation.

Hence, option D is the correct answer.

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