The following is a list of these Amino Acids. Please check the reference below for more information on the extra 2.

The 20 to 22 amino acids that comprise proteins include: 

  • Alanine
  • Arginine
  • Asparagine
  • Aspartic Acid
  • Cysteine 
  • Glutamic acid
  • Glutamine 
  • Glycine
  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Proline
  • Serine 
  • Threonine
  • Tryptophan 
  • Tyrosine 
  • Valine
  • Selenocysteine
  • Pyrrolysine (not used in human protein synthesis)

Of these 20 amino acids, nine amino acids are essential: 

  • Phenylalanine
  • Valine
  • Tryptophan
  • Threonine
  • Isoleucine
  • Methionine
  • Histidine
  • Leucine
  • Lysine

A quote from the reference below –

“The non-essential, also known as dispensable amino acids, can be excluded from a diet. The human body can synthesize these amino acids using only the essential amino acids. For most physiological states in a healthy adult, the above nine amino acids are the only essential amino acids. However, amino acids like arginine and histidine may be considered conditionally essential because the body cannot synthesize them in sufficient quantities during certain physiological periods of growth, including pregnancy, adolescent growth, or recovery from trauma”

Reference

Lopez MJ, Mohiuddin SS. Biochemistry, Essential Amino Acids. [Updated 2023 Mar 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557845/