Question

Naturally occurring amino acids have configuration:
(A) D
(B) L
(C) Either D or L
(D) Neither D nor L

Answer 1

Hint: As we know that amino acids that occur naturally as alpha-amino acids are optically active because the alpha-carbon in these amino acids is asymmetric. Also these amino acids exist in both configurations or forms as D as well as L.

Complete step-by-step answer:As we know that there are a total of twenty one amino acids which are basically those organic compounds that make up a protein by joining into short polymer chains which are normally called peptides or linger chains called polypeptides.
Now, we know that amino acids exist in two isomeric forms which are D- configurations as well as L-configurations. Among these the L-configuration possessing amino acids are most naturally occurring. In L-configuration of amino acids, the amino group is present on the left hand side and carboxylic group is present on the right hand side. For instance: L-alanine and D-alanine which we can show as below:

Glycine is the exceptional amino acids and it is also the simplest amino acid which possess no enantiomers as it has two hydrogen atoms which are attached to the alpha carbon or the central carbon atom and as we know that when all the four group attached to the central carbon atom are different then only the enantiomers are formed.

Therefore the correct answer is (B).

Note:Remember that also, only L-amino acids are manufactured in the cells and also only these amino acids are incorporated into proteins. And some D-configuration possessing amino acids are found in the cell walls of bacteria but these are not found in bacterial proteins.