LIFE SCIENCE

Detailed explanation-1: -Disulfide bridges, covalent bonds formed between two cysteine residues, further reinforce the shape of a protein. Disulfide bridges form when the sulfhydryl groups of two cysteine residues come into close contact because of protein folding. Covalent bonds are not a weak interaction.

Detailed explanation-2: -The quaternary structure of proteins is stabilized by noncovalent bonds between complementary surface hydrophobic and hydrophilic regions on the polypeptide subunits, additionally, acidic and basic side chains can form salt linkages.

Detailed explanation-3: -Disulfide bonds function to stabilize the tertiary and/or quaternary structures of proteins and may be intra-protein (i.e., stabilizing the folding of a single polypeptide chain) or inter-protein (i.e., multi-subunit proteins such as antibodies or the A and B chains of insulin).

Detailed explanation-4: -Positively charged amino acids (arginine and lysine) are found to stabilize the secondary structure, while the zwitterionic amino acid glycine has no significant effect.