How many different amino acids are there used in protein synthesis?

In protein synthesis, the standard set of amino acids comprises 20 different amino acids. These amino acids are encoded by the genetic code, with codons in mRNA corresponding to specific amino acids during translation. Each of these 20 amino acids plays a unique role in the structure and function of proteins, ranging from contributing to the protein's shape to affecting its chemical properties and interactions.

While some sources might mention 22 amino acids, this generally refers to the fact that two additional amino acids—selenocysteine and pyrrolysine—are sometimes incorporated into proteins under specific circumstances. However, the primary and universally recognized set involved in protein synthesis remains 20. Options suggesting smaller numbers like twelve or larger numbers like sixty-four do not accurately represent the current understanding of amino acid diversity in standard protein synthesis processes.