This page explains that amino acids, the building blocks of proteins, come in 20 types. Each has a unique "R" group affecting its properties, with nine essential amino acids required from the diet, in...This page explains that amino acids, the building blocks of proteins, come in 20 types. Each has a unique "R" group affecting its properties, with nine essential amino acids required from the diet, including histidine and leucine. It highlights the importance for vegetarians to ensure sufficient intake of lysine and tryptophan, which are commonly deficient in plant proteins.