Which is an optically inactive amino acid?

The secondary structure of a protein refers to

Which of the following statements is not correct?

Among the $\alpha$-amino acids - threonine,tyrosine,methionine,arginine and tryptophan,those which contain an aromatic group in their side chain are

Which amino acid from the following contains $-CH_3$ as a side chain?

The $pK_a$ values for the three ionizable groups $X, Y$ and $Z$ of glutamic acid are $4.3, 9.7$ and $2.2$ respectively. The structure is $HO_2C-CH_2-CH_2-CH(NH_3^+)-CO_2H$. The isoelectric point $(pI)$ for this amino acid is: