How Many Amino Acids Are There in Protein?
Proteins are made up of 20 standard amino acids. While over 500 amino acids exist in nature, only these 20 are commonly incorporated into proteins during the process of protein biosynthesis. These 20 amino acids are the building blocks that determine a protein's unique three-dimensional structure and, consequently, its function. [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
Although 20 is the standard number, it's important to note that two additional amino acids, selenocysteine and pyrrolysine, are sometimes incorporated into proteins through specialized mechanisms. [4, 8] However, they are not considered part of the standard 20.
- Amino Acids: These are organic compounds containing an amine group (-NH2) and a carboxyl group (-COOH). [1]
- Protein Synthesis: The process where cells assemble amino acids into protein chains following the instructions coded in genes. The sequence of amino acids dictates the final protein structure.
- Essential vs. Non-Essential Amino Acids: The human body can synthesize some amino acids (non-essential), while others (essential) must be obtained through diet. [5, 10] The classification can vary based on age and physiological needs.
- Sources of Amino Acids: Good sources include animal proteins (beef, poultry, eggs) and plant-based proteins (legumes). [2, 5, 10]
The Significance of the 20 Standard Amino Acids
The 20 standard amino acids provide the diversity needed to create the vast array of proteins with different functions. Each amino acid possesses unique chemical properties that affect how it interacts with other amino acids within a protein. These interactions determine the protein's folding pattern and, subsequently, its biological activity.
