Question

Keratin present in hair shows secondary structure known as (a) parallel \(\beta\)-sheet (b) antiparallel \(\beta\)-sheet (c) \(\alpha\)-helix (d) none of these.

Short answer

(c) \(\alpha\)-helix

Step-by-step solution

Identify the type of protein structure in keratin

Keratin, which is the structural protein in hair, primarily exhibits a specific type of secondary structure that gives it its strength and shape.

Recall the characteristics of the secondary structure in proteins

Proteins can fold into several types of secondary structures, including \(\beta\)-sheets, which can be parallel or antiparallel, and \(\alpha\)-helices. The \(\alpha\)-helix is characterized by its coiled shape which is stabilized by hydrogen bonds between the backbone atoms in the polypeptide chain.

Determine the correct secondary structure for keratin

Keratin is known for its coiled \(\alpha\)-helix structure that allows it to be both strong and flexible. This helical structure is important for the function and integrity of hair.

Key concepts

Keratin in Hair

Keratin is an essential protein found in hair, serving as a building block that gives hair its structure and resilience. This fibrous protein consists of long chains of amino acids that contribute to the strength and elasticity of hair. Keratin in the hair is highly packed into a compact formation, which defines the hair's texture and feel. Rigidity and resistance to stress are also notable characteristics imparted by keratin, which are crucial for protecting the delicate hair shaft from damage. Understanding the role of keratin is fundamental not only in biology but also in cosmetic science, as it explains how hair care products that aim to 'repair' or 'strengthen' hair work by interacting with keratin.

Alpha-Helix

The alpha-helix is a common motif in the secondary structure of proteins. An alpha-helix is a right-handed coil with amino acid residues positioned every 100 degrees in the helical structure, reflecting its tightly coiled nature. Each turn in the helix typically contains 3.6 amino acids, resulting in a compact and sturdy configuration. The alpha-helix is stabilized by hydrogen bonds that occur between the oxygen of the carbonyl group of one amino acid residue and the hydrogen of the amide group four residues earlier. This bonding pattern maintains the helical structure, which is pivotal in facilitating the protein's functional conformation and its interactions within the cell. The prevalence of the alpha-helix in proteins underscores its significance in protein stability and function.

Protein Folding

Protein folding is a complex process through which a polypeptide chain folds into its functional three-dimensional structure. It is a critical step in the journey from gene to functioning protein. During this process, the chain of amino acids adopts specific secondary structures, like alpha-helices and beta-sheets, before assembling into a final tertiary structure. The correct folding of proteins is necessary for their biological activity. Misfolding, however, can lead to dysfunctional proteins and is associated with various diseases, including Alzheimer's and Parkinson's. In the realm of biochemistry and molecular biology, understanding protein folding mechanisms is central to grasping how proteins attain their shape and how this shape determines their roles within living organisms.

Protein folding is not solely determined by the sequence of amino acids; it is also influenced by the cellular environment, including molecular chaperones that assist in the folding process. Innovative studies continue to explore the nuances of protein folding, employing advanced techniques like X-ray crystallography and cryo-electron microscopy to visualize the final, functional forms of these fascinating biomolecules.