The organic molecule made up of a long chain of repeating units is called a polymer.

Here's a breakdown:

* Polymer: A large molecule composed of many smaller repeating structural units called monomers.

* Monomer: A small molecule that can join with other monomers to form a polymer.

Examples of polymers include:

* Proteins: Made of amino acid monomers.

* Carbohydrates: Made of sugar monomers (like glucose).

* Nucleic acids (DNA and RNA): Made of nucleotide monomers.

* Polysaccharides: Made of sugar monomers, like starch and cellulose.

* Plastics: These are synthetic polymers, often made from petroleum products.

Let me know if you want to learn more about any specific type of polymer!