How many amino acids make up protein?

• A. 20
• B. 10
• C. 22
• D. 12

Answer: (A)

Proteins are built from amino acids joined in chains, and the sequence of these amino acids determines how the protein folds and functions. In almost all organisms, there is a defined, canonical set of amino acids that are used to assemble proteins by the genetic code. This fixed set serves as the standard toolkit for creating the wide variety of proteins necessary for life. While some organisms incorporate a few unusual amino acids into specific proteins, those cases don’t change the basic pool of amino acids typically used to construct the majority of proteins. So, the option that reflects this standard repertoire is the best choice. The other numbers refer to counts that don’t match the usual assembly pool for protein construction.