Final answer:
Proteins composed of 12-20 amino acids are known as oligopeptides, which are short chains of amino acids. These small peptides play crucial roles in various biological functions and are differentiated from larger polypeptides or proteins based on their size and number of amino acids.
Step-by-step explanation:
Proteins composed of 12-20 amino acids are broadly categorized as peptides, specifically called oligopeptides. These are relatively small chains of amino acids compared to larger proteins or polypeptides, which may consist of fifty or more amino acids.
Proteins are essential macromolecules and are involved in various biological functions, including structural support, catalysis of biochemical reactions, and regulation of biological processes. They are made up of amino acids, which are the building blocks of proteins and the source of immense structural diversity in protein formation. The 20 different amino acids found in proteins are linked together in specific sequences to form protein molecules. The specific sequence and number of amino acids ultimately determine a protein's three-dimensional shape and function.