The number of essential and non-essential amino acids from the following list respectively is:
Val,Gly,Leu,Lys,Pro,Ser

Insulin is a .........

Which of the following amino acids is achiral?

Each polypeptide in a protein has amino acids linked with each other in a specific sequence. This sequence of amino acids is called . . . . . . structure of that protein.

Assertion $(A)$: An optically active amino acid can exist in three forms depending on the $pH$ of the solution.
Reason $(R)$: Amino acids contain both acidic and basic groups; they exist as a zwitterion in aqueous medium,anionic form in basic medium,and cationic form in acidic medium.

Find the isoelectric point $(pI)$ of the given amino acid: $HOOC-CH_2-CH_2-CH(NH_3^+)-COOH$. Given: $pK_{a1} = 2$,$pK_{a2} = 4$,$pK_{a3} = 9$.