Question

Which of the following are correct with reference to amino acid?
a. Amphoteric in nature
b. Are substituted methane molecules.
c. Serine is an alcoholic amino acid.
d.Amino acids never exist in zwitterionic form at any stage in living cells.
e. A dipeptide comprises of two peptide bonds between amino acids.

• A. $a,b,c$
• B. $a,d,e$
• C. $b,c,d$
• D. $a,c,d,e$

Answer 1

The correct option is A $a,b,c$

Amino acids are the organic compounds that have a carboxyl group, an amino group, and an organic R-group. These are the building blocks of proteins.

A. Amino acids can act as an acid and as a base, so they are amphoteric in nature. The carboxyl group of an amino acid loses an electron and the amino group accepts that electron. so, there occurs a dipolar charge on the same molecule but the over all charge remains neutral. Such a molecule is called zwitter ion.

B. Amino acids are substituted methane molecules the four substituent groups attached on the alpha carbon provide the four valency positions.

C. Serine is an alcoholic amino acid.

D. Amino acids exist as zwitter ion at the pH ranging from 2 to 9 in living tissues.

E. A dipeptide is made up of two amino acids linked with each other through one peptide bond.

Hence, the correct answer is 'a,b,c'