Re: After proteins are made by the ribosomes, how do they leave the cell?

Both bacteria and eucaryotic cells use similar systems of protein secretion to allow proteins to leave the cell.

In the general secretion pathway, these proteins which are destined to be exported, are synthesized carrying a short 20-30 amino acid leader at the beginning of the protein. This signal (aptly termed the signal sequence ) is recognized by a cellular machinery which moves the protein across the membrane. The signal is then cleaved off of the protein after it crosses the membrane. The protein needs to be unfolded in order to be secreted. It then folds up after it leaves the cytoplasm.

This is the "major" system that is used by all cells, however there are also some specialized systems for specific proteins where the details change.

I hope this helps.