| what is it | when mRNA forms a polypeptide ; the sequence of nucleotide bases along the length of mRNA is used to produce the sequence of amino acids in the polypeptide, process begins with the activation of amino acids that will make up the polypeptide |
| amino acid activation 1 | the amino acid first forms an intermidiate with ATP, muchg of the energy provided by ATP is conserved for peptide bond formation later |
| amino acid activation 2 | the intermediate then combines with transfer rna (tRNA) to form an amino acid trna complex named amino acyl tRNA, reaction is controlled by the enzyme amino-acyl tRNA synthetase |
| what is anticodon | sequence of 3 nucleotides located on one arm of a tRNA molecule, complementary to the codon in mRNA |
| amino acid activation 3 | tRNA molecule contains the sequence of bases, adenine - cytosine - cytosine, and it is to this end that the amino acid attatches, the tRNA anticodon sequence determines which amino acid is attatched to the tRNA molecule |
| starting polypeptide contruction (ribisome) | small subunit of the ribosomes become attatched to the end of an mRNA molecule (5' end). The large and small subunit of the ribosome come together to hold the mRNA molecule in place |
| starting polypeptide contruction (codon) | the starting point of translation on the mRNA is normally the triplet of bases (CODON) AUG (AUG often named the start codon) |
| starting polypeptide contruction (attacthment points) | 3 attatchment points on the large ribosome sub unit for tRNA. exit site (e site), peptidyl site (p site), aminoacyl site (a site) |
| starting polypeptide contruction (amino acyl trna) | amino acyl trna with the anticodon sequence UAC moves into the ribosome and attacthes to p site so it pairs with the AUG sequence on the mRNA by complementary base pairing |
| starting polypeptide contruction (first amino acid) | as the tRNA which pairs with the AUG sequence on the mRNA alaways carry methionine, the first aminoacid on the polypeptide chain is methionine. |
| making the polypeptide (second trna) | second tRNA molecule binds to the ribisome adjacentto tRNA in the A site and the anticodon bbinds to the complementary mRNA codon, bringing the 2 amino acids carried by the tRNA molecule close together, binded by a peptide bond due to an enzyme |
| making the polypeptide (3rd) | the ribosome movesw on to the thrid codon in the sequence of mRNA, so that the amino acids on the second and third TRNA molecule can be linked, as this happens the first tRNA is released from its aminoi acid (MET) and briefly occupies the E site on the ribosome before being released into the cytoplasm to collect another met molecule from the amino acid pool in the cell, continues until a chain is built up |
| what is a polysome | a group of ribosomes that make polypeptides at teh same time |
| when does the process stop | reaches a stop CODON, UGA, UAG, UAA and do not attract a tRNA. |
