PROTEIN SYNTHESIS:-

GENE EXPRESSION 

           OR

PROTEIN SYNTHESIS:-

INTRODUCTION:-

•Protein are large complex compound.
•The one protein molecule is made up of 20- amino acid.
• The nature of protein is based on number and kind of amino acid.

SYNTHESIS :-

• The protein synthesis take placed under the direction of DNA in ribosome and following main steps are include in protein synthesis.

1)TRANSCRIPTION.

2) TRANSLATION.

1) TRANSCRIPTION:-

Definition:

  It is formation of messenger RNA molecule on DNA helix.

1) RNA POLYMERASE an enzyme attaches with helix DNA and brings about breaking of hydrogen bond between nitrogenous base. Thus, separation occurs between 2 helix.

2) Nucleotides of RNA line up next to the complementary DNA nucleotide .

3) The mRNA leaves nucleus through passes from nuclear membrane.

4) When enzyme arrives at a special STOP signal at the far edge of gene, it dis engage from DNA and releases the assembled RNA chain. This chain is complementary to DNA strand ,Thus it is called Primary RNA transcript or RNA transcript copy.

5) Messenger RNA molecule having coded message also.

2) TRANSLATION:-

Definition:

It is the process in which building of polypeptide chain occurs in ribosome's according to message of mRNA.

ATTACHMENT OF mRNA TO RIBOSOME:-

- mRNA is not read by one ribosome, many ribosome's are bind with mRNA.

  Transfer of amino acid to site if protein synthesis:-

- Activated tRNA brings amino acid to ribosomes, where mRNA resides.

- The inactive amino acid are activated by specific enzyme and ATP.

FORMATION OF PROTEIN:-

1) tRNA also has sequence of 3 nucleotide called Anti codons . This anti codons must be complementary with codons present on mRNA ,other wise attachment of tRNA to mRNA is not possible.

2)The first tRNA shifts its amino acid to second tRNA. Two amino acid make peptide bond.

3) The same process remains continue until desired polypeptide chain is prepared.

4) lastly, a stop codon present on mRNA stop this process and polypeptide chain set free in cytoplasm.