Match the entries of column I with appropriate entries of column II and choose the correct option out of the four options given.

(a)-(r), (b)-(s), (c)-(p), (d)-(q)

The correct answer is option 3. (a)-(r), (b)-(s), (c)-(p), (d)-(q). 

Let us delve into each matched option:

(a) α-Keratin → (r) Structural protein:

α-Keratin: This is a fibrous protein primarily found in epithelial cells, forming the main structural component of hair, nails, horns, feathers, and the outer layer of the skin (epidermis).

Structure and Function: α-Keratin proteins have a coiled-coil structure, formed by two α-helix chains twisted around each other. This structure provides strength, elasticity, and resilience to the tissues in which it is found. For example, in hair and nails, α-keratin provides structural support, protecting them from damage and environmental stressors.

Toughness and Water Resistance: The structure of α-keratin proteins allows for strong interactions between adjacent molecules, contributing to the toughness of tissues like hair and nails. Additionally, the hydrophobic nature of α-keratin makes these tissues resistant to water and moisture.

Function in Skin: In the skin, α-keratin proteins contribute to the barrier function, protecting underlying tissues from physical trauma, pathogens, and dehydration. They also play a role in wound healing by forming the initial scaffold for tissue regeneration.

(b) Gammaglobulins → (s) Antibodies:

Gammaglobulins: These are a class of proteins found in blood plasma and tissue fluids, collectively referred to as immunoglobulins (Ig). They are produced by specialized white blood cells called plasma cells (mature B lymphocytes).

Structure and Diversity: Gammaglobulins have a Y-shaped structure composed of four polypeptide chains—two heavy chains and two light chains—linked by disulfide bonds. The variable regions of the antibody, located at the tips of the Y arms, contain antigen-binding sites with high specificity for recognizing and binding to foreign molecules (antigens).

Role in Immune Response: Antibodies play a critical role in the immune system's humoral response, where they recognize and neutralize pathogens such as bacteria, viruses, and toxins. They do this by binding to antigens on the surface of pathogens, marking them for destruction by other components of the immune system, such as phagocytes or complement proteins.

Functions: Antibodies can function in various ways, including neutralization of pathogens, opsonization (marking pathogens for phagocytosis), activation of the complement system (leading to pathogen lysis), and facilitating agglutination (clumping) of pathogens to enhance their clearance.

(c) Nucleoproteins → (p) Constituents of genes:

Nucleoproteins: These are complexes formed by the association of proteins with nucleic acids, primarily DNA or RNA.

Structure and Function: Nucleoproteins play essential roles in the packaging, organization, and regulation of genetic material within cells. For example, in eukaryotic cells, DNA is wrapped around histone proteins to form nucleosomes, which are the basic units of chromatin. This condensed chromatin structure helps regulate gene expression by controlling access to DNA.

Gene Expression Regulation: Nucleoproteins also participate in the regulation of gene expression by influencing the accessibility of DNA to transcription factors and RNA polymerases. Post-translational modifications of histone proteins, such as acetylation, methylation, and phosphorylation, can alter chromatin structure and gene activity.

DNA Packaging and Compaction: Nucleoproteins are involved in the compaction of DNA into the nucleus, allowing the storage of large amounts of genetic information in a relatively small space. This compaction helps protect DNA from damage and facilitates its segregation during cell division.

(d) Insulin → (q) Protein hormone:

Insulin: Insulin is a peptide hormone produced by the beta cells of the pancreas.

Regulation of Blood Glucose: Insulin plays a central role in regulating blood glucose levels by promoting the uptake of glucose into cells, particularly muscle and adipose (fat) cells. It stimulates the translocation of glucose transporter proteins (GLUT4) to the cell membrane, facilitating glucose entry into the cell.

Anabolic Effects: Insulin also has anabolic effects, promoting the storage of glucose as glycogen in the liver and muscle cells, and facilitating the synthesis of proteins and lipids. It suppresses the breakdown of glycogen (glycogenolysis) and inhibits gluconeogenesis, the production of glucose from non-carbohydrate sources.

Role in Metabolism: Insulin helps regulate energy metabolism and nutrient storage, ensuring that cells have an adequate supply of glucose for energy production and other metabolic processes. Dysregulation of insulin secretion or signaling can lead to metabolic disorders such as diabetes mellitus.

In summary, each matched entry represents a specific protein and its corresponding function or role in biological processes. These proteins are essential for maintaining the structure, function, and regulation of cells and organisms.