Translation

Requires:

The twenty different amino acids that are used in proteins

mRNA which carries the information about the order in which amino acids must be added, in the form of a string of 3-base codons

tRNAs that carry the individual amino acids based on the anticodon for each tRNA

ribosomes, where the actual synthesis takes place

assorted accessory proteins, GTP and ATP

Steps

mRNA is synthesised

tRNAs are 'charged' with the appropriate amino acids

mRNA binds to 30S subunit of the ribosome

tRNA carrying fmet binds to initator codon (AUG)

50S subunit attaches to form active ribosome with tRNA/fmet in P site

tRNA with anticodon that matches the second codon in the message enters the A site

amino group of amino acid attached to second tRNA reacts with carboxyl group of fmet to link the two together via a peptide bond. fmet disconnects from its tRNA

ribosome moves three bases (translocation), so first tRNA is pushed out. Second tRNA carrying both amino acids moves from A site to P site

• tRNA with anticodon that matches the next codon in the message enters the A site

• its amino acid forms peptide bond with carboxyl end of existing chain

• translocation moves latest tRNA+ peptide chain to P site.

these steps (•) repeat until the last codon ( a STOP signal) attracts termination proteins which cause release of the protein and disassembly of the complex