Enzymes belong to which class of compounds?

Which amino acid does not contain a chiral centre?

Which of the following compounds does not exist as a zwitterion?

Amino acids can be classified as $\alpha$,$\beta$,$\gamma$,$\delta$ and so on,depending upon the relative positions of the amino group with respect to the carboxyl group. Which type of amino acids form polypeptide chains in proteins?

The correct structure of the dipeptide gly-ala is

The number of cyclic tripeptides formed with $2$ amino acids $A$ and $B$ is: