A proteinâs function is determined by the properties of its amino acids. Which replacement of one amino acid with another is least likely to affect the proteinâs function?

a. A hydrophilic amino acid is replaced by a hydrophobic amino acid. an amino acid with a C=O group is replaced by an amino acid with an O-H group.
b. A charged amino acid is replaced by an amino acid with a side chain consisting of a group with three C-H bonds.
c. A hydrophobic amino acid is replaced by a charged amino acid.
b. A negatively charged amino acid is replaced by a positively charged amino acid.

When an amino acid is substituted by another with opposite properties the replacement will modify the structure (and consequently also the function) of the resulting protein. For example, it is expected that the replacement of amino-acid residues with different solubility will alter the protein’s structure and this protein will establish different interactions with water, cell structures, or further segments of the protein. Therefore, in the cases above enumerated, only C-O and O-H groups have similar properties (i.e. they are hydrophilic and have polar bonds), and thereby it is expected that this replacement has no significant incidence on the protein’s structure and function.