Which is the most important structural component of the body?

Identify the structure of the amino acid shown in the image.

Amino acids that are synthesized in our body are called $.......$.

The simplest amino acid is .....

Given below are two statements:
Statement $I:$ Amino acids have a property of ionizable nature of $-NH_2$ and $-COOH$ groups,hence have different structures at different $pH$.
Statement $II:$ Amino acids can exist as Zwitterionic form at acidic and basic $pH$.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which protein is found in milk?