Ribosome Structure, Function, and Evolution

Ribosome definition and universal role

A ribosome is a ribonucleoprotein particle found in all cells that synthesizes proteins by translating the genetic information carried by messenger RNA (mRNA). During translation, ribosomes read mRNA codons in sequence and, with the help of transfer RNA (tRNA), link amino acids into a growing polypeptide chain. Each ribosome consists of a small and a large subunit made from ribosomal RNA (rRNA) and many ribosomal proteins. Although ribosomes vary in size, composition, and organization across bacteria, archaea, and eukaryotes, they share a conserved core structure that reflects a common evolutionary origin. Ribosomes are universal to life but differ among domains and organelles: bacteria and archaea use 70S ribosomes (30S and 50S subunits), while eukaryotic cytosol uses 80S ribosomes (40S and 60S subunits). Eukaryotes also have distinct ribosomes in mitochondria (mitoribosomes) and chloroplasts/plastids (plastoribosomes), which resemble bacterial ribosomes due to endosymbiotic origins. Functionally, ribosomes decode mRNA and catalyze peptide bond formation; the catalytic activity is performed by rRNA (with proteins mainly stabilizing the structure). Because bacterial and eukaryotic ribosomes differ in structure, some antibiotics can target bacterial ribosomes without strongly affecting human ribosomes.

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Translation decoding mRNA into polypeptides

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