Which statement is TRUE about the p K a values for ionizable R-group of amino acids within a polypeptide?
A.
The p K a values for R-groups do not change from free amino acids.
B.
The p K a values for R-groups are 1 pH unit higher than free amino acids.
C.
The p K a values for R-groups are 1 pH unit lower than free amino acids.
D.
The p K a values for R-groups vary depending on the local environment of the side chain.
E.
The p K a values for R-groups depend on how close the R-group is to the N- or C-terminus of the polypeptide.