Question

The simplest amino acid is:
A. Glycine
B. Lysine
C. Tyrosine
D. Aspartic acid

Answer 1

The simplest amino acid will be that amino acid which will have only one amino group and one carboxyl group. It should not have any R or variable groups thus it will be considered as the simplest group among twenty naturally occurring amino acids.

Complete answer:
Amino Acids are the organic compounds generally made up of carbon, oxygen, hydrogen and nitrogen, having amino (-$N{H_2}$) and carboxyl (-COOH) functional group, a side chain (-R group), which differentiates each amino acid from each other.
The basic structure of an amino acid is:

Structure of amino acids differs from each other on the bases of the R-group of the amino acid.
In the given options, the structure of glycine is: Side chain of glycine is a single hydrogen atom.

Option ‘B’ is Lysine: Lysine is a long hydro-carbon chain having an amino group at the end of the chain. Thus, in lysine we have two amino groups and one carboxyl group.

Option ‘C’ is tyrosine: Tyrosine is a cyclic compound having one benzene ring, one -OH group, one amino group and one carboxyl group.

Option ‘D’ is aspartic acid: Aspartic acid is an amino acid in which the R-group is complex, having two carboxyl groups and one amino group. Its structure looks like this:

So, after discussing the structure of each given option we can conclude that option ‘A’ that is, Glycine is the correct answer, because of the simplest structure which has an R-group as only one hydrogen atom.

Thus, Option ‘A’ is the correct answer.

Note: Amino acids help in production of proteins inside the organisms. It helps in neurotransmission. They act as precursors for many compounds like glycine and act as a precursor for porphyrins, used in RBCs.