Molecular model, Molecular model of a ribosome, Molecular model of a bacterial ribosome showing the RNA and protein components in the form of ribbon models. In the large (50S) subunit the 23S RNA is shown in cyan, the 5S RNA in green and the associated proteins in purple. In the small (30S) subunit the 16S RNA is shown in yellow and the proteins in orange.
The three solid elements in the centre of the ribosome, coloured green, red and reddish brown are the transfer RNAs (tRNAs) in the A, P and E sites respectively. The anticodon loops of the tRNAs are buried in a cleft in the small subunit where they interact with mRNA.
The other ends of the tRNA, which carry the peptide and amino acid, are buried in the peptidyl transferase centre of the large subunit, where peptide bond formation occurs.
Ribosomes (from ribonucleic acid and “Greek: soma meaning body) are complexes of RNA and protein that are found in all cells. Prokaryotic ribosomes from archaea and bacteria are smaller than most of the ribosomes from eukaryotes such as plants and animals.
However, the ribosomes in the mitochondrion of eukaryotic cells resemble those in bacteria, reflecting the evolutionary origin of this organelle.
The function of ribosomes is the assembly of proteins, in a process called translation. Ribosomes do this by catalysing the assembly of individual amino acids into polypeptide chains; this involves binding a messenger RNA and then using this as a template to join together the correct sequence of amino acids.
This reaction uses adapters called transfer RNA molecules, which read the sequence of the messenger RNA and are attached to the amino acids.
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