Which of the following amino acids is an essential amino acid?

Which of the following molecules forms a Zwitter ion?

Which of the following statements are correct?
$A$) $\alpha$-amino acids present in proteins are $L$-amino acids.
$B$) Amino acids contain both $-NH_2$ and $-COOH$ groups.
$C$) The number of amino groups and carboxylic groups is always the same in amino acids.
$D$) Tyrosine was first obtained from cheese.
Choose the correct alternatives from below:

Among the following,the essential amino acid is

In which of the following amino acids is the $-OH$ group present?

$(A)$ Lysine	$(B)$ Serine
$(C)$ Tyrosine	$(D)$ Valine

Proteins do not respond to