Exhibit 4A The following question(s) refer to this peptide:
Cys-Ala-Gly-Arg-Gln-Met
Refer to Exhibit 4A. The overall, net ionic charge on this peptide at pH = 7 would be:
A) +2
B) +1
C) 0
D) − 1
E) − 2

Question

Quizplus · Accepted Answer

At pH 7, the amino (N-terminus) and carboxyl (C-terminus) groups are ionized, giving a +1 and -1 charge, respectively. The side chains of the amino acids in the peptide also contribute to the overall charge. Cysteine (Cys) has a neutral charge at pH 7. Alanine (Ala) and Glycine (Gly) are also neutral. Arginine (Arg) has a positively charged side chain, and Glutamine (Gln) and Methionine (Met) are neutral at pH 7. Therefore, the overall charge is +1 from the N-terminus plus +1 from Arginine, minus 1 from the C-terminus, resulting in a net charge of +1.

Exhibit 4A the Following Question(s) Refer to This Peptide