Here's why:

* Ribosomes are the protein synthesis machines of the cell. They read the genetic code from messenger RNA (mRNA) and use that information to assemble amino acids into proteins.

* Other organelles play supporting roles in protein synthesis:

* The nucleus contains the DNA that holds the genetic code.

* The endoplasmic reticulum provides a platform for ribosomes to attach and can further modify proteins.

* The Golgi apparatus packages and transports proteins to their final destinations.

So, while other organelles are involved, it's the ribosome that actually builds the protein molecules.