Which amino acid does not contain a chiral centre?

Denaturation of proteins is caused by $.......$.

Total number of tripeptides possible by mixing of valine and proline is $............$.

The artificial sweetener aspartame $(A)$,$H_3N^{+}-CH(CH_2COO^{-})-CONH-CH(CH_2Ph)-COOCH_3$,is converted to . . . . . . on storage for extended periods of time in aqueous solution:

Which among the following amino acids has the lowest molecular mass?

Which statement correctly completes the statement?
Except for glycine,which is achiral,all the amino acids present in proteins ......