Question

Amino acids are classified as acidic, basic or neutral depending upon the relative number of amino and carboxyl groups in their molecule. Which of the following are acidic?

• A.
  
• B.
  
• C.
  
• D.
  

Answer 1

Answer: (B), (C)

$\text{Analysing the options}$

Options (A) and (C):

In options $\left(A\right)$ and $\left(C\right)$ the number of carboxyl groups is the same as the number of amino groups. Hence, these are neutral amino acids.

An amino acid having both amino and acidic group is neutralized in the zwitter ion form. The amino acid is neutral unless there is an extra acid or base group on the side chain.

If amino acids have more carboxyl group as compared to amino group, then they are classified as acidic but, in case amino acids have less carboxyl group as compared to amino group then they are classified as basic amino acids.

Options (B) and (D):

In options $\left(B\right)$ and $\left(D\right)$ the number of carboxyl groups is more than the number of amino groups. Hence these are acidic amino acids.

Hence, the correct answers are $\left(B\right)$ and $\left(D\right)$.