Which Statement Is TRUE About the PK_a Values for Ionizable

Multiple Choice

Which statement is TRUE about the pK_a values for ionizable R-group of amino acids within a polypeptide?

A) The pK_a values for R-groups do not change from free amino acids.
B) The pK_a values for R-groups are 1 pH unit higher than free amino acids.
C) The pK_a values for R-groups are 1 pH unit lower than free amino acids.
D) The pK_a values for R-groups vary depending on the local environment of the side chain.
E) The pK_a values for R-groups depend on how close the R-group is to the N- or C-terminus of the polypeptide.