The organelle that synthesizes proteins is the ribosome. Ribosomes are essential to all cells, and they can either be found floating free in the cells' fluids or in eukaryotes embedded in a structure known as the endoplasmic reticulum.
Ribosomes synthesize proteins by assembling amino acids together in the proper sequences. They get the information for these sequences from RNA, which, in turn, receives the information from DNA. The proteins are used for many purposes, including as chemical catalysts and as structural units. Ribosomes floating in the cellular fluid make proteins for the cell itself, while ribosomes in the endoplasmic reticulum also make proteins for use outside of the cell.