Translation in protein synthesis.

It is a process of formation of polypeptide chain of amino acids during protein synthesis as a result of information and direction present on m RNA.

It involves following steps-

A) Activation of amino acids:-

  The Amino acids are present in Cytoplasm in inactivated form which are activated with the help of ATP (Source of energy) and enzyme amino acyl synthetase.The enzyme amino acyl synthetase links with A.A.AMP to give A.A.AMP. Enzyme complex called as activated amino acid.

               

B)  Attachment of activated amino acid to t – RNA:-

The activated amino acid attaches itself with specific t – RNA molecule at 3’ end (CCA end). It forms amino acid t – RNA complex.

There is separate t – RNA for each amino acid.

C)  Formation of polypeptide Chain:-

It involves following steps.

I) Chain Initiation: a) the synthesis of polypeptide chain starts with the formation of initiation complex.

b) Its formation requires presence of initiation factors (IF) and GTP molecules.

c) The released mRNA binds itself to the site of protein synthesis i.e. r – RNA.

d) m-RNA attaches with the smaller subunit through 5’ end.

e) Smaller subunit attaches itself with larger subunit. Thus, initiation
        complex is formed.

II)     Chain elongation:

a) The addition of amino acids in a sequence to form a polypeptide chain is called as chain elongation.

b) The specific t – RNA molecule brings specific amino acids to the site of protein synthesis which link together with the help of peptide linkage (CONH bond)

c) The ribosomal unit moves along m– RNA strand. This shifting is called as translocation and it does not consume energy.

d) The process is continued till the last amino acid is added.

III) Termination & Release of Polypeptide Chain:-

a) The elongation of chain is terminated at right stage and the chain is released with the help of various releasing factors. (RF)

b) The process of termination takes place near 3 end of m – RNA strand.

c) It is brought about by any one of the three termination codons namely, UAA, UAG and UGA.

d) After termination of polypeptide chain no amino acid is added, process completely stops and the two ribosomal subunits detach.

Thus, polypeptide chain is synthesized.