A mother is nursing her infant. Of the 20 amino acids that exist, 9 would be considered essential for the mother. How many amino acids would be considered essential for her infant?

10

Explanation:

Proteins are polymers of amino acids. 20 different amino acids are present in various combinations in different proteins. Humans are incapable of synthesizing some amino acids. These are called the essential amino acids as they must be provided in the diet.

Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine are the nine amino acids that are not synthesized in the body of adult humans and therefore, are categorized as essential ones. Arginine is a non-essential amino acid for adult humans but is essential for adult humans. Therefore, for an infant, more than 9 amino acids are essential ones.