What are chains of joined amino acids called?

Chains of joined amino acids are referred to as polypeptide chains. Amino acids are the building blocks of proteins, and when they link together through peptide bonds, they form a polypeptide. These polypeptides can further fold and combine to create functional proteins, which play essential roles in various biological processes.

Understanding this concept is vital in fields related to biology and cosmetology because proteins, including keratin, significantly affect hair structure and health. Keratin itself is a type of protein that plays a crucial role in the composition of hair, skin, and nails, but it is not a term used to describe the chain of amino acids directly. Hair follicles are structures in the skin from which hair grows, not chains of amino acids. Thus, while proteins and keratin relate to amino acids, the specific term for the chains of amino acids is polypeptide chains.