Which of the following is an essential amino acid?

Find the correct option for the sequence given below:
$(1)$ Alanine $\rightarrow$ Valine
$(2)$ Asparagine $\rightarrow$ . . . . . .
$(3)$ Aspartic acid $\rightarrow$ Glutamic acid
$(4)$ Arginine $\rightarrow$ Histidine

Which of the following is polymerized to form proteins?

What is a protein formed by different amino acids called?

Lysine is an essential amino acid because

Proteins are primarily essential for which of the following needs of the body?