The ribosome is a complex molecular machine found inside the living cells that make proteins from amino acids together in the process called protein synthesis or translation. Protein synthesis is the major task performed by living cells.


Ribosomes are special as they are found in both prokaryotes and eukaryotes cells. Every cell needs ribosomes to manufacture proteins.

It binds to a messenger ribonucleic acid (mRNA) and reads the information contained in the nucleotide sequence of the mRNA. The transfer RNAs (tRNAs) containing amino acids enter the ribosome in a special pocket is called the acceptor site.


A ribosome is made from complexes of RNAs and proteins and is, therefore, a ribonucleoprotein. It is made up of two parts, called subunits. The smaller subunit is where the mRNA binds and is decoded. While the larger subunit is where the amino acids get added. Both of the subunits are made up of both protein and ribonucleic acid components.

The two subunits are joined to each other by interactions between the rRNAs in one subunit and proteins in the other subunit.


Structure Of RibosomesFunction

Ribosomes are a cell structure that makes protein. Protein is needed for many cell functions such as repairing damage or directing chemical processes. Ribosomes can be found floating within the cytoplasm or attached to the endoplasmic reticulum.

Ribosome locations

Ribosomes are classified as being either free or membrane-bound. Both ribosomes differ only in their spatial distribution but are identical in structure.

Free Ribosomes: can move anywhere in the cytosol, but are excluded from the cell nucleus. Proteins that are formed are released into the cytosol and used within the cell.

Membrane-bound Ribosomes: when a ribosome begins to synthesize proteins that are needed in some organelles, the ribosome making this protein can become “membrane-bound”.

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Practise This Question

Which of the following isotopes would be useful in finding the path of translocation of food?