Which of the following organelles functions in making ribosomal subunits?

Question

nucleolus, nucleus, ribosomes, smooth ER, none of the above

Answer 1

The nucleolus.

http://en.wikipedia.org/wiki/Nucleolus

By strict definition, ribosomes are not organelles -- they are macromolecular structures. Organelles have a membrane, whereas ribosomes are composed of only protein and rRNA, not lipids. Sure the ribosomal proteins require a nucleus and a ribosome, but that brings up the whole "chicken or the egg" question -- which comes first?

One of the main functions of the nucleolus is to assemble ribosomes. That is the best answer.

Answer 2

ribosomal subunits are composed of rRNA AND specific proteins. the proteins that make up ribosomal subunits must be synthesized from other ribosomes =)  The rRNA is synthesized from an enzyme polymerase.

Answer 3

None of the above.  It's RNA

Answer 4

nucleolus