Life sciences · Reference
What is a ribosome?
A ribosome is the molecular machine that builds proteins by reading messenger RNA and joining amino acids in the order the genetic code specifies — the site where translation takes place in every living cell.
Structure
A ribosome is composed of two parts, a large subunit and a small subunit, each made from a combination of ribosomal RNA (rRNA) and proteins. The small subunit binds the messenger RNA and helps read its codons, while the large subunit catalyses the joining of amino acids. The rRNA is not merely structural: the catalytic core that forms peptide bonds is made of RNA, making the ribosome a ribozyme. Ribosomes can float freely in the cytoplasm or attach to internal membranes.
How it works
During translation, the two subunits assemble around an mRNA molecule. The ribosome moves along the mRNA three bases at a time, reading each codon.
Transfer RNAs deliver the amino acid matching each codon, and the ribosome links the amino acids with peptide bonds, building the protein chain from one end to the other until it reaches a stop codon and releases the finished protein.
Significance in research
Because ribosomes are central to making every protein, they are a major focus of molecular biology. Determining the detailed atomic structure of the ribosome was recognised with the 2009 Nobel Prize in Chemistry, awarded to Venkatraman Ramakrishnan, Thomas Steitz, and Ada Yonath. Ribosomes also differ enough between bacteria and other organisms that several antibiotics work by targeting bacterial ribosomes, a property studied extensively in the laboratory.
Key facts
At a glance
- Definition: the cellular machine that synthesises proteins
- Made of: ribosomal RNA (rRNA) and proteins
- Structure: a large subunit and a small subunit
- Function: carries out translation of mRNA
- Reads mRNA in: three-base codons
- Nobel Prize for structure: Chemistry, 2009
Common questions
FAQ
What does a ribosome do?+
A ribosome builds proteins. It reads a messenger RNA molecule three bases at a time and joins the matching amino acids into a chain, carrying out the process called translation.
What is a ribosome made of?+
A ribosome is made of ribosomal RNA (rRNA) and proteins, organised into two subunits — a large one and a small one. The rRNA forms the catalytic core that links amino acids together.
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