Proteins are synthesized and packaged within organelles known as ribosomes. Ribosomes are composed of RNA and proteins, and are located in a cell's liquid layer called the cytoplasm.
The nucleus of a cell contains the DNA that is responsible for the production of ribosomes. The nucleus utilizes RNA and proteins to create ribosomes before releasing them into the cytoplasm. Ribosomes are not bound within a membrane. Free ribosomes perform the function of proteins that function within a cell's cytoplasm, while bound ribosomes produce proteins intended for external release or to be used by the cell's membrane.
Ribosomes create proteins essential to cell function through a process of translation and transcription. During transcription, genetic information is transcribed from DNA onto RNA. The RNA in a ribosome is then used to form a chain of amino acids that eventually form into a protein. A cell typically contains a large variety of organelles responsible for biological function; however ribosomes are specifically programmed for protein production. Ribosomes transition from the nucleus to the rest of the cell within an area of a cell's inner membrane known as the endoplasmic reticulum. The ribosomes attach themselves to a piece of membrane known as the rough endoplasmic reticulum, which is pinched off from the area of production and then released into the cytoplasm to be used by the cell.