What Are Ribosomes Composed Of?

A ribosome consists of two subunits: the large and small subunits. The materials that make up ribosomes are ribonucleic acid, or RNA, and proteins, with approximately 60 percent of a ribosome being made of ribosomal RNA and the other 40 percent consisting of proteins, according to Florida State University.

In eukaryotic organisms, the two ribosomal subunits are created and assembled inside the nucleolus. The units then exit through pores in the nucleus to perform protein synthesis. The proteins found in ribosomes have a positive charge to help them associate with the negatively charged messenger RNA, or mRNA, involved in genetic translation.

Ribosomes are cellular organelles involved in the production of proteins. Some of the proteins they synthesize remain inside the cell to perform intracellular functions, while other proteins exit the cell following their production.

Cells typically house several thousand ribosomes, although some types of cells contain a few million. Cells that play especially big roles in protein synthesis, such as brain and pancreas cells, tend to have greater quantities of ribosomes. The location of a cell's ribosomes is dependent on whether it is a plant, animal or bacterial cell, and ribosomes may be found attached to the nuclear envelope, bound to the endoplasmic reticulum or scattered around the cytoplasm.