AFAA Personal Trainer Certification Practice Exam 2026 - Free Personal Trainer Practice Questions and Study Guide

Protein is ultimately digested into amino acids, which are the building blocks of protein, and there are 20 standard amino acids that are used by the body to synthesize proteins. During digestion, proteins are broken down by enzymes into the individual amino acids that can then be absorbed into the bloodstream and used as needed for various physiological functions, such as tissue repair and building new proteins.

While the number of standard amino acids is 20, there are also two additional amino acids that are sometimes referenced in discussions about amino acids: selenocysteine and pyrrolysine, bringing the total to 22. However, in the context of basic human physiology and the most widely recognized types used in protein synthesis, the focus remains on the primary 20 amino acids.

In summary, proteins are digested into amino acids, primarily focusing on 20 standard types, though a broader understanding may include the additional two, resulting in 22 total recognized amino acids in a wider biological context. The distinction in daily nutrition typically revolves around the essential and non-essential amino acids that fall within the primary 20.