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

Which of the following combine to form proteins?

How many disulfide bonds connect the $A$ and $B$ chains of human insulin to each other?

Describe the primary, secondary, and tertiary structures of proteins. $OR$ Describe the structure of proteins.

Which amino acid is not essential for the human body?

$A$: Tertiary structure of protein molecules makes them biologically active.
$R$: It is the native configuration of protein molecules maintained by multiple covalent bonds only.