Question

1. Answer the following about amino acids:

a. What is special about the 20 amino acids?

b. Why is the N-terminal amino acid always considered #1 and the C-terminal always “last”?

Answer 1

Solution:

Part A)

Amino acids are the organic compounds composed of amine (-NH₂) and carboxyl (-COOH) functional groups together with a side chain specific to each amino acid. Amino acids are the building blocks of proteins which play many critical roles in the body. Each of the 20 most common amino acids has its specific chemical characteristics and its unique role in a protein structure and function. They are needed for vital processes like the building of proteins and synthesis of hormones and neurotransmitters. They are categorized as essential, conditionally essential or nonessential depending on different factors.

Part B)

During the formation of a peptide, the amino acid residue which contains an amine group on the alpha carbon is called the N-terminal of the peptide. The amino acid residue on the other end has a carboxylic acid group, is called the C-terminal. By convention, peptide sequences are written from N-terminus to C-terminus. Thus, N terminal is considered 1 and C-terminal is last.