Why all proteins are containing only 20 amino acids?

Answer 1

Because all life in planet Earth comes from a common ancestor who early in the beginning used those 20 amino acids and the trait is conserved all the way up to this date.

Answer 2

The steps for creating proteins is this: DNA transcription to RNA, RNA translation to amino acids, and the amino acids connected together are called proteins. That is why amino acids not coded by DNA are not part of proteins. Of course you could manually create proteins from various amino acids, but that's another textbook.

Answer 3

tremendously much all animal proteins are finished proteins, together as maximum plant proteins are undesirable in some or the different aminoacids. Caesin i.e milk protein, egg and serum albumin and meat proteins are finished proteins potential that they incorporate all 20 amino acids. between plant life soy protein and the protein in beetle nut leaves has all 20 amino acids.

Answer 4

Its like the alphabet for cells; common components can combine in different ways to get multiple functional results. It would be hard for other parts of the cell to utilize protein made from "Chinese characters."