Describe the role of a ribosome in the production of a polypeptide

mRNA from the nucleus binds to a ribosome which is either free in the cytoplasm or associated with the rough ER. The ribosome binds at the 5' end and scans to the start codon (AUG). The ribosome allows tRNA to associate with the mRNA by specific base pairing between codons and anti-codons. It then catalyses the formation of peptide bond between the amino acids bound to the tRNA molecules. The ribosome then moves along the mRNA allowing more amino acids to be added to the polypeptide, until a stop codon is encountered and translation is terminated.