Irreversible precipitation of proteins is called

Which amino acid from the following is $NOT$ synthesized in our body?

Lysine $H_2N-(CH_2)_4-CH(NH_2)-COOH$ is:

$A$ tetrapeptide is made of naturally occurring alanine,serine,glycine,and valine. If the $C$-terminal amino acid is alanine and the $N$-terminal amino acid is chiral,the number of possible sequences of the tetrapeptide is $....$

Which one of the following structures represents the peptide chain?

The number of peptide bonds in the following compound is: