Question

Keratin, a structural protein is present in?
A. Hair
B. Wool
C. Silk
D. All of these

Answer 1

Hint: Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication. Proteins differ from one another primarily in their sequence of amino acids.

Complete step by step answer:
Keratin is the primary fibrous structural protein component of hair, skin and nails Keratin is one of a family of fibrous structural proteins known as sclero-proteins. \[\alpha-keratin\] is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, horns, claws, hooves, calluses, and the outer layer of skin among vertebrates. Keratin also protects epithelial cells from damage or stress. Keratin is extremely insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong un-mineralized epidermal appendages found in reptiles, birds, amphibians, and mammals. Keratin intermediate filaments are also a cytoskeletal component of desmosome cellular junctions. Keratins are highly cross-linked proteins typically containing \[\alpha -helix\] and \[\beta -sheet\] motifs and are high in glycine and alanine content.
Hence, keratin is a structural protein present in hair, silk and wool

So, the correct answer is Option D.

Note: The four levels of protein structure are distinguished from one another by the degree of complexity in the polypeptide chain. A single protein molecule may contain one or more of the protein structure types: primary, secondary, tertiary, and quaternary structure.