The group that contains only molecules assembled from smaller organic compounds is macromolecules.

Here's why:

* Macromolecules are large polymers built from smaller repeating monomer subunits. These monomers are organic molecules themselves, meaning they contain carbon and hydrogen.

* Examples of macromolecules include:

* Carbohydrates: Made from simple sugars like glucose.

* Lipids (fats and oils): Assembled from glycerol and fatty acids.

* Proteins: Constructed from amino acids.

* Nucleic acids (DNA and RNA): Built from nucleotides.

Let me know if you have any other questions!