BIOMOLECULES AND ENZYMES

Detailed explanation-1: -Substitutions: Arginine is a positively charged, polar amino acid. It thus most prefers to substitute for the other positively charged amino acid Lysine, though in some circumstances it will also tolerate a change to other polar amino acids.

Detailed explanation-2: -Alanine has a non-polar side chain.

Detailed explanation-3: -Arginine is often considered to be the most hydrophilic of the 20 natural amino acids. Its side chain contains a large guanidinium moiety that has the capacity for up to six hydrogen bonds (Fig. 1).

Detailed explanation-4: -Six amino acids have side chains that are polar but not charged. These are serine (Ser), threonine (Thr), cysteine (Cys), asparagine (Asn), glutamine (Gln), and tyrosine (Tyr).