The ribosome is the site of translation

The ribosome is the site of translation - o The P site...

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The ribosome is the site of translation. Ribosomes facilitate the specific coupling of the tRNA anticodons with mRNA codons during protein synthesis. o Each ribosome is made up of a large and a small subunit. o The subunits are composed of proteins and ribosomal RNA (rRNA) . In eukaryotes, the subunits are made in the nucleolus. o After rRNA genes are transcribed to rRNA in the nucleus, the rRNA and proteins are assembled to form the subunits with proteins from the cytoplasm. o The subunits exit the nucleus via nuclear pores. In both eukaryotic and prokaryotic cells, the large and small subunits join to form a functional ribosome only when they attach to an mRNA molecule. Though similar in structure and function, prokaryotic and eukaryotic ribosomes have enough differences that certain antibiotic drugs (like tetracycline and streptomycin) can inactivate prokaryotic ribosomes without inhibiting eukaryotic ribosomes. Each ribosome has a binding site for mRNA and three binding sites for tRNA molecules.
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Unformatted text preview: o The P site (peptidyl-tRNA site) holds the tRNA carrying the growing polypeptide chain. o The A site (aminoacyl-tRNA site) holds the tRNA with the next amino acid to be added to the chain. o Discharged tRNAs leave the ribosome at the E (exit) site. The ribosome holds the tRNA and mRNA in close proximity and positions the new amino acid for addition to the carboxyl end of the growing polypeptide. The ribosome then catalyzes the formation of the peptide bond. As the polypeptide becomes longer, it passes through an exit tunnel in the ribosomes large unit and is released to the cytosol. Recent advances in our understanding of the structure of the ribosome strongly support the hypothesis that rRNA, not protein, is responsible for the ribosomes structure and function. o rRNA is the main constituent at the interface between the two subunits and of the A and P sites, and it is the catalyst for peptide bond formation. o A ribosome can be regarded as one colossal ribozyme....
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