Final answer:
The terms 'polypeptide' or 'protein' are used for amino acid chains of more than fifty amino acids, and 'peptide' is used for shorter chains. Polypeptides and proteins can be made of one or more chains, and the shape and sequence of amino acids are critical for their function.
Step-by-step explanation:
The term polypeptide or protein is used for chains of more than fifty amino acids, while the term peptide is used for shorter chains. Amino acids are linked together by peptide bonds to form these chains. Shorter chains, which include dipeptides (two amino acids) and tripeptides (three amino acids), are referred to simply as peptides. Longer chains are referred to as polypeptides or proteins and are typically composed of 50 or more amino acids. These proteins can be made up of one or more polypeptide chains and have specific three-dimensional shapes that determine their function in physiological processes.