What is Cell Ribosome | Definition, Function, Formation, Role

Ribosomes are like tiny factories in cells. They make proteins that perform all kinds of functions for cell functioning.

Where are ribosomes located inside the cell?

The ribosomes are either located in the fluid inside the cell called the cytoplasm or are attached to the membrane. They are found in both prokaryotic, (bacteria) and eukaryotic (animal and plant) cells.

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Ribosomes are a type of organelle. Organelles are structures that perform specific functions for the cell. The role of the ribosome is to make proteins. Other organelles include the nucleus and mitochondria.

Ribosome Structure

The ribosome has two main components known as the large subunit and the small subunit. These two units come together when the ribosome is ready to make a new protein. Both subunits are made up of different strands of RNA and proteins.

Large Subunit – The large subunit contains the site for making new bonds during protein formation. It is called “60S” in eukaryotic cells and “50S” in prokaryotic cells.

Small Subunit – The small subunit is actually not that small, just slightly smaller than the large subunit. It is responsible for the flow of information during protein synthesis. It is called “40S” in eukaryotic cells and “50S” in prokaryotic cells.

The “S” in the subunit name is a unit of measure and represents the Svedberg unit.

Protein Synthesis

The main job of the ribosome is to make proteins for the cell. There can be hundreds of proteins that need to be made for the cell, so the ribosome needs specific instructions on how to make each protein. These instructions come from the nucleus in the form of messenger RNA. The messenger RNA contains specific codes that act as a recipe for telling the ribosome how to make proteins.

There are two main steps in making proteins: transcription and translation. The ribosome performs the translation step. You can go here to learn more about protein.


Translation is the process of taking instructions from messenger RNA and turning it into a protein. Here are the steps the ribosome takes to make proteins:

The two subunits are joined together by messenger RNA.

Ribosomes that find the right starting position on RNA are called codons.

The ribosome moves down the RNA, reading instructions for the amino acids to attach to the protein. Every three letters on RNA represents a new amino acid.

Ribosomes repair the amino acids that make up proteins.

It stops building proteins when it reaches the “stop” code in the RNA that tells it the protein is ready.

Interesting Facts about the Ribosome

The ribosome’s “ribs” come from ribonucleic acid (RNA) that provides instructions for making proteins.
They are produced inside the nucleolus of the nucleus. When they are ready, they are sent to the outside of the nucleus through the pores of the nuclear membrane.

Ribosomes differ from most organelles in that they are not enclosed by a protective membrane.

Ribosomes were discovered in 1974 by Albert Claude, Christian de Duve and George Emil Palade. They won the Nobel Prize for their discovery.