Question

Which one is not a fibrillar protein?
A. Keratin
B. Collagen
C. Albumin
D. Elastin

Answer 1

Hint: Proteins are large-sized and big molecules so called macromolecules having one or more polypeptides (chains or polymers of amino acids linked by peptide bond). The term polypeptide is often used interchangeably with protein. Collagen is the most abundant protein in the animal world.

Complete answer:
Fibrillar proteins are those that are long molecules. These molecules are usually insoluble in water. These are rod shaped. Due to increase in size these molecules become less soluble.
Keratin:- the keratin protein is generally insoluble in water and they are large in size so they are fibrillar protein. They are rod shaped proteins and are structural in nature. They exhibit secondary structure of protein.
Collagen :- Collagen is the main protein in connective tissue. It is one of the long fibrous structural proteins, collagen has great tensile strength and is the main component of cartilage, ligaments, tendons, bone and teeth. It is the most abundant protein of the animal world.
Albumin :- some simple proteins are small and they are globular molecules. They are not soluble in water. As they have large size, they become less soluble and their heat coagulability increases. Thus this option is correct.
Elastin :- these kinds of proteins are present where elasticity occurs. These proteins are not soluble in water as they are very large in size. They exhibit beta pleated type of protein structure.

Our required answer is C) albumin.

Note: There are 20 types of amino acids, a protein is a heteropolymer and not a homopolymer. A homopolymer has only one type of monomer repeating 'n' number of times. Collagen is the most abundant and highest occurring protein in the animal world. It is the main component of connective tissue of animals. Ribulose bisphosphate carboxylase-oxygenase (RUBiSCO) is the most abundant protein in the whole of the biosphere.