The building blocks of proteins are called amino acids. There are 20 different amino acids that combine in various sequences to form proteins, each playing a unique role in the body's biological processes. Amino acids are categorized as essential, which must be obtained through diet, and non-essential, which the body can synthesize. The sequence and arrangement of amino acids determine the protein's structure and function, influencing everything from muscle growth and repair to enzyme production and hormone regulation. Some proteins serve as antibodies, while others are involved in transport, signaling, and regulatory functions essential for life.