I have 2 multiple questions as attached. I have done those but have some doubts. The questions are in red and my answer is in black.
Need to get explanation why the option B in #61 is wrong (heavy references) and why option A in #53 is wrong (also references)
Basically I need to know why only 1 option is good for each question.
For the first question, the correct answer is alanine.
Gln doesn't have a free amino group. It has an amide group.
Arg doesn't have a free amino group either. It has a very complex functional group.
Ser has no NH2 group at all. The only NH2 group it has will be bound up in the peptide ...
The expert examines amino acid displaying a free amino group in the peptide. An explanation of these options are determined.