- Ribosomes are the cellular structures responsible for translating mRNA into polypeptide chains, which fold to form functional proteins.
- This process is known as protein synthesis.
- Unlike lipids, nucleic acids, and carbohydrates, which are synthesized through different enzymatic pathways, ribosomes specifically assemble amino acids in the correct sequence dictated by the genetic code.

Thus, the macromolecule synthesized by ribosomes during cellular function is proteins.

Reference: Molecular Biology of the Cell, 6th Edition, Chapter 6