Amino acids the human body cannot make and must obtain from food.
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Essential amino acids are those the human body cannot synthesise in sufficient amounts and must obtain from the diet. There are nine of them: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Non-essential amino acids can be made from metabolic intermediates through transamination and related pathways. Foods containing all nine in adequate proportions, such as meat, eggs and soy, are called complete proteins. Plant foods that are individually incomplete can be combined over a day to supply the full set.
Key ideas: Nine are essential for adults: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. The body cannot make their carbon skeletons, so they must come from diet. Complete proteins (meat, eggs, soy, quinoa) contain all nine in adequate amounts, while grains lack lysine and legumes lack methionine, so combining them fills gaps.
Common mistakes and connections: Essential does not mean more important, only not synthesized. Some, like arginine, are conditionally essential in growth. Students often think plant proteins are all incomplete. Links to protein quality scores, metabolism and nitrogen balance.
WHO estimated daily requirements of the nine essential amino acids in mg per kg body mass. Leucine is needed in the largest amount and tryptophan in the smallest. The interactive lesson shows this as a live animation or chart.
Rice and beans together supply all nine essential amino acids because each makes up for what the other lacks.
Amino acids the human body cannot make and must obtain from food.
Essential Amino Acids is a intermediate topic in Biochemistry, Environment & Industry. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Biochemistry, Environment & Industry first: Protein Structure Levels, Alpha Helix and Beta Sheet, Denaturation.
The next topics in Biochemistry, Environment & Industry are Enzymes and Active Site.
Yes. The interactive lesson includes a self-check question on Essential Amino Acids, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.
Essential Amino Acids is topic 11 of 127 in Biochemistry, Environment & Industry.
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