Protein Synthesis The Story So Far The Sequence

Protein Synthesis

The Story So Far • The Sequence of Nitrogenous Bases in DNA (ATGC) contain information that directs protein synthesis (making of a protein). Where is DNA located? In the Nucleus • Proteins are assembled in the ribosomes • Where are the ribosomes located? In the cytoplasm or on the Endoplasmic Reticulum

The information must get from the Nucleus to the ribosomes • How? m. RNA • Three base pairs make a codon • Each Codon specifies a particular amino acid

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Now that the m. RNA is at the Ribosome Translation can occur

This is a molecule of messenger RNA. It was made in the nucleus by transcription from a DNA molecule. codon AUGGGCUUAAAG CAGUGCACGUU m. RNA molecule

A ribosome on the rough endoplasmic reticulum attaches to the m. RNA molecule. ribosome AUGGGCUUAAAG CAGUGCACGUU

Amino acid t. RNA molecule A transfer RNA molecule arrives. It brings an amino acid to the first three bases (codon) on the m. RNA. anticodon The three unpaired bases (anticodon) on the t. RNA link up with the codon. UAC AUGGGCUUAAAG CAGUGCACGUU

Another t. RNA molecule comes into place, bringing a second amino acid. Its anticodon links up with the second codon on the m. RNA. CC G UAC AUGGGCUUAAAG CAGUGCACGUU

Peptide bond A peptide bond forms between the two amino acids. U A CC C G AUGGGCUUAAAG CAGUGCACGUU

The first t. RNA molecule releases its amino acid and moves off into the cytoplasm. C A U CCG AUGGGCUUAAAG CAGUGCACGUU

The ribosome moves along the m. RNA to the next codon. CCG AUGGGCUUAAAG CAGUGCACGUU

Another t. RNA molecule brings the next amino acid into place. AA U CCG AUGGGCUUAAAG CAGUGCACGUU

A peptide bond joins the second and third amino acids to form a polypeptide chain. CCGCCG AUGGGCUUAAAG CAGUGCACGUU

The process continues. The polypeptide chain gets longer. This continues until a termination (stop) codon is reached. The polypeptide is then complete. AC G GUC AUGGGCUUAAAG CAGUGCACGUU

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End Codon