What is the full name of the chemical group represented by $NH_{2}$?

Molecules that bear charged groups of opposite polarity are known as $:-$

Glycine and alanine are different with respect to one substituent on the $\alpha$-carbon. What are the other common substituent groups?

Which group is present at the $N$-terminal of a polypeptide chain?

Which structure of a protein represents its three-dimensional form?

What type of amino acid is an $L-$amino acid?