Final answer:
The groups within a peptide that will retain their charge are the side chains, N-terminus, and C-terminus.
Step-by-step explanation:
The correct answer to the question "What 3 groups within a peptide will retain their charge?" is B) Side chains, N-terminus, C-terminus. In the structure of a peptide, the N-terminus has a free amino group which can be positively charged, while the C-terminus has a free carboxyl group which can be negatively charged. The side chains or R-groups can also retain charge depending on their nature – some side chains can be acidic or basic, hence carrying a negative or positive charge respectively.
A peptide is basically a chain of amino acids joined together by peptide bonds, and each individual amino acid is made up of an amine group, a carboxyl group, and an R-group or side chain attached to the central alpha carbon. These R-groups vary widely and can have different properties, including whether they can be charged or not.