ribosoom

Ribosoom is the molecular machine in cells that carries out protein synthesis. It translates genetic information encoded in messenger RNA into polypeptide chains, using transfer RNA to bring amino acids. Ribosooms consist of ribosomal RNA (rRNA) and ribosomal proteins and come in two main types: prokaryotic 70S ribosoom, formed from a 50S large subunit and a 30S small subunit, and eukaryotic 80S ribosoom, formed from a 60S large subunit and a 40S small subunit. Mitochondria and chloroplasts contain their own 70S-type ribosooms.

Ribosooms bind mRNA and tRNA at three tRNA binding sites: A, P, and E. During initiation, the ribosoom assembles on the mRNA at a start codon; during elongation, amino acids are added sequentially; termination occurs at a stop codon with release factors. The translation process uses energy from GTP hydrolysis and various elongation and initiation factors.

Ribosooms can be free in the cytosol or bound to the rough endoplasmic reticulum in eukaryotes, where they synthesize proteins destined for secretion or membranes. In eukaryotes, ribosoom biogenesis begins in the nucleolus, where rRNA genes are transcribed and processed, and ribosomal proteins imported from the cytoplasm assemble with rRNA to form subunits. The subunits are exported to the cytoplasm and can combine to form active ribosooms.

Clinical relevance: Many antibiotics target bacterial ribosooms, inhibiting protein synthesis. Abnormal ribosoom biogenesis or function is linked to disorders called ribosomopathies.