The net charge of a polypeptide at a particular pH can be determined by considering the pKa value of each ionizable group in the protein. For a linear polypeptide composed of 10 amino acids, how many (alpha-carboxyl plus alpha-amino) groups must be considered?
a) 10
b) 11
c) 12
d) 2
e) 8
We think the answer might be 2 because we're only counting the C-terminus and the N-terminus and because the question doesn't suggest to count the side chains. Is this correct?