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Ribosomes are defined as tiny molecules in cells that help the cell make proteins.  When you look at a picture of a cell, ribosomes look like little dots that float around the cell or are attached to some of the organelles.  Making proteins is one of the most important jobs in a cell.  In fact, ribosomes are found in every kind of cell, including animal cells and plant cells.

Cartoon image showing the subunits of ribosomes


Cartoon image of ribosomes attached to endoplasmic reticulum

Ribosomes attached to the rough endoplasmic reticulum (rough ER)

Ribosomes in the Cell

There are lots of different places in a cell where you can find ribosomes. For example, in bacteria cells they are found floating around in the cytoplasm. In animal and plant cells, they can be found attached to the nucleus and an organelle called the endoplasmic reticulum.

Ribosomes are found in so many parts of the cell, but where do they come from?  They are made in the nucleolus, which is a part of the cell’s nucleus.  Ribosomes are made out of a special material called rRNA and they have two parts: a small subunit and a large subunit. Try to find the small and large subunits on the diagram at the top of this page.


Ribosomes and Protein Synthesis

Cartoon image showing ribosome translation

The complicated process of making a protein out of amino acids

The main job of a ribosome is to help the cell make proteins. To do this, they work together with lots of other parts of the cell, including the nucleus.  The picture below shows the process of making proteins called “translation.”   Translation is a long and complicated process, so you don’t need to memorize all the different parts.

As you can see in the picture above, the protein is made out of tiny building blocks called amino acids. The ribosome help put all the amino acids together in the right order to make the protein. To know the right order, the ribosome read “instructions” for making the protein called mRNA. Can you find the mRNA and amino acids in the picture?

There are lots and lots of ribosomes in each of your cells helping to make protein. In fact, one animal cell, like the cells inside of you, can have 10 million ribosomes in it!



Written by: Leah Tolby