Ribosomes are the protein-synthesizing machines of the cell.

They translate the information encoded in messenger RNA (mRNA) into a polypeptide.

Link to a description of the process

Ribosomes are In eukaryotes,
The ribosomes of bacteria, eukaryotes, and mitochondria differ in many details of their structure.

This table gives some of the data. (S values are the sedimentation coefficient: a measure of the rate at which the particles are spun down in the ultracentrifuge. S values are not additive. nts = nucleotides.)

Comparison of Ribosome Structure in Bacteria, Eukaryotes, and Human Mitochondria
  Bacterial (70S) Eukaryotic (80S) Mitochondrial (55S)
Large Subunit 50S 60S 39S
(1 of each)
23S (2904 nts) 28S (4700 nts) 16S (1560 nts)
5S (120 nts) 5S (120 nts)  
  5.8S (160 nts)
Proteins 35 47 50
Small Subunit 30S 40S 28S
rRNA 16S (1542 nts) 18S (1900 nts) 12S (950 nts)
Proteins 20 33 30

But despite these differences, the basic operations of bacterial, eukaryotic, and mitochondrial ribosomes are very similar.

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7 May 2015