These subunits are attached to each other and together form the entire ribosome. When viewed through a light microscope the ribosomes appear as dots, they are very small and the subunits can not be seen. Function The only function of ribosomes is to build proteins. The plan for the protein in the form of mRNA passes through a groove in the ribosome. There are two kinds of ribosomes, those attached to the endoplasmic reticulum and those floating in the cell cytoplasm.
Free ribosomes make proteins that are used in the cytoplasm.
This is a complicated process beyond the scope of this document. Details Ribosomes are made in the nucleus of the cell. A ribosome can make the average protein in about one minute. Ribosomes often line up in clusters called polyribosomes, these are connected by the mRNA and all make the same protein. In this way the cell can make many copies of a protein very fast.