which of the 20 amino acids are essential：Among them, 8 kinds of amino acids, lysine, threonine, leucine, isoleucine, valine, methionine, tryptophan, and phenylalanine, cannot be produced by the human body. We call them essential amino acids. Need to be provided by food. Factory supply.

The 20 amino acids in the body can be divided into 4 groups according to their physical and chemical properties:
① Non-polar, hydrophobic amino acids: glycine, alanine, valine, leucine, isoleucine, phenylalanine and proline.
②Polar and neutral amino acids: tryptophan, serine, tyrosine, cysteine, methionine, asparagine, glutamine and threonine.
③ Acidic amino acids: aspartic acid and glutamic acid.
④Basic amino acids: lysine, arginine and histidine