Nutritional İmportance

Further information: Protein in nutrition
Of the 20 standard proteinogenic amino acids, 8 are called essential amino acids because the human body cannot synthesize them from other compounds at the level needed for normal growth, so they must be obtained from food.[23] However, the situation is a little more complicated since cysteine, tyrosine, histidine and arginine are semiessential amino acids in children, because the metabolic pathways that synthesize these amino acids are not fully developed.[24] The amounts required also depend on the age and health of the individual, so it is hard to make general statements about the dietary requirement for some amino acids.

Several common mnemonics have evolved for remembering the ten amino acids often described as essential. PVT TIM HALL ("Private Tim Hall") uses the first letter of each of these amino acids.[27] Another mnemonic that frequently occurs in student practice materials beneath "TV TILL Past Midnight", which just includes the 8 essential amino acids, is "These ten valuable amino acids have long preserved life in man".[28]