Ribosomes are non-membrane-bounded particles where protein synthesis occurs. The number of ribosomes in a cell varies depending on its functions. For example, pancreatic cells and those of other glands have many ribosomes because they produce secretions that contain proteins.
Though, simply, they are:
- tiny dot-like structures
- composed of RNA and protein
- they have two types; attached (to the rough ER) and free
- they function for protein synthesis