Proteins are composed of how many common amino acids in various proportions?

Proteins are composed of 20 common amino acids, which can be combined in various sequences and proportions to form the vast array of proteins found in living organisms. Each of these amino acids has a unique side chain that dictates its properties and how it interacts with other amino acids, influencing the protein's structure and function. The diversity and specificity of protein function in biological systems arise from the different combinations of these 20 amino acids. While there are other amino acids that can be found in certain biological processes, the foundational set that all proteins are built from strictly consists of these 20 common amino acids.