A polymer that contains many different molecules of amino acids is called a protein.

Here's why:

* Amino Acids: The building blocks of proteins are amino acids. There are 20 different amino acids commonly found in proteins.

* Polymer: A polymer is a large molecule made up of many smaller repeating units.

* Protein Structure: Proteins are formed by linking amino acids together in long chains. The sequence of amino acids determines the protein's shape and function.

So, when you have a long chain of different amino acids linked together, you have a protein.