This document discusses the process of translation. It begins by defining translation as the biosynthesis of a protein inside a living cell using the genetic code. It then describes the three main steps of translation - initiation, elongation, and termination. Initiation involves assembling the ribosome complex on prokaryotes and eukaryotes. Elongation is the process of amino acid chain elongation through tRNA and elongation factors. Termination occurs when a stop codon is reached, signaling the release of the polypeptide chain. The document also briefly mentions post-translational modifications that can occur after translation is complete.

2. CONTENTS
1.TRANSLATION – INTRODUCTION
2.COMPONENTS REQUIRED FOR TRANSLATION
3.PROKARYOTIC AND EUKARYOTIC TRANSLATION
4.THREE STEPS OF TRANSLATION
5.POST TRANSLATIONAL MODIFICATION

3. TRANSLATION – INTRODUCTION
1
• Translation: The Biosynthesis of a protein or a polypeptide
inside a living cell.
2
• In process of translation, the language of nucleotides sequence
on mRNA is translated into the language of Amino Acid
Sequence.
3
• The mRNA is translated from it’s 5’end to its 3’end,
producing a protein synthesised from its amino terminal end
to its carboxyl terminal end.

4. 4
• It occurs in cytoplasm, where ribosomes are located.
5
• Translation occurs in both Prokaryotes and Eukaryotes in
Unique Ways.

5. COMPONENTS REQUIRED FOR
TRANSLATION

6. RIBOSOMES
1
• Ribosomes are large complexes of protein and rRNA.
2
• They consist of two subunits – one large and one small whose relative sizes are
generally given in terms of their sedimentation coefficients or S (Svedberg) values.
3
• In Prokaryotes, it is 70S and in Eukaryotes, it is 80S Subunits.
4
• The Ribosomes has two binding sites for tRNA molecules, each of which extends over
such subunits. Together they cover the neighbouring codons.

7. 5
• During translation,
• The A Site binds an incoming Aminoacyl tRNA as directed
by the codon currently occupying the site. This codon
specifies the next Amino acid to be added to the growing
peptide chain.
• The P Site codon is occupied by the peptidyl-tRNA. This
tRNA carries the chain of Amino acids that has already
been synthesised.
• An E Site is also there that is occupied by the empty
tRNA that is about to exit the Ribosome.

8. STEPS OF PROTEIN SYNTHESIS
The Process of Protein Synthesis is divided into
THREE Stages. They are as follows:
Initiation
Elongation
Termination

9. INITIATION
1
• Prokaryotic Initiation require the large and small subunits, the mRNA, the initiator
tRNA and three initiation factors (IF-1, IF-2, IF-3) and GTP.
2
• IF-3 binds to the free 30s subunit, to prevent large subunit binding to it.
3
• IF-2 complexed with GTP and IF-1 binds to small subunit . It will assist the charged
initiator tRNA to bind.
4
• The initiator tRNA bind to the complex. At this point,IF3 can be released, as its role
in keeping the subunits apart are complete.

10. 5
• The 50s subunit can now bind, which displace IF1 and IF2. This complex is called
initiation complex.
6
• The assembled ribosome has two tRNA binding sites.
7
• These are called the A and P sites , for amino acyl and peptidyl sites and one site is
E (exit site) for empty tRNA.
8
• One major step of initiation is the placement of initiator tRNA in the P site.

12. EUKARYOTIC INITIATION
1
• Eukaryotic mRNAs do not contain a Shine-Dalgarnos sequence Instead, ribosomal
subunits recognize and bind to the 5’cap of Eukaryotic mRNAs.
2
• A ternary complex containing met-tRNA and eIF-2 bound to GTP attaches to 40s
ribosomal subunit. The presence of eIF-3 and eIF-1A stabilizes it.
3
• The eIF-4F(referred to as cap binding protein) binds to the cap of mRNA.
4
• Then eIF-4A and eIF-B binds to mRNA and reduces its complex structure. This mRNA
is then transferred to 43s complex. The ribosomal initiation complex scans the mRNA
for 5’-AUG initiation codon.

13. 5
• By the involvement of eIF-5, the 80s complex is formed.

14. ELONGATION
1
• It involves three elongation factors EF-Tu (Prokaryotes), eEF-1 alpha (Eukaryotes),
charged tRNA and the 70s initiation complex.
2
• Amino acyl tRNA delivery.
• EF-Tu and eEF1 alpha are required to deliver the amino acyl tRNA to A site.
3
• Peptide bond formation.
• The A and P sites are occupied with the two amino acids that are joined each
other with peptide bond.

15. 4
• Translocation
• The discharged tRNA is ejected from the P site, the peptidyl-tRNA is moved
from A site to P site. A new codon is now present in the vacant site. The
Uncharged tRNA is released through exit site.

16. TERMINATION
1
• Termination of translation happens when the A site of the ribosome faces a stop
codon (UUA,UGA or UGA).
2
• A releasing factor can recognize the stop codons and causes the release of polypeptide
chain
3
• In prokaryotes, three termination or release factor (RF1,RF2,RF3) contribute to the
hydrolysis of peptidyl-tRNA bond.
4
• Release the free polypeptide and last uncharged tRNA from P site.

17. 5
• The dissociation of the 70 s into 30s and 50s subunits.
6
• RF1 binds A site and release the polypeptide and uncharged tRNA.
7
• RF2 releases the RF1 from A site and release itself as well from translation binding
site(present on large subunit).
8
• RF3 function unknown.

18. 9
• Another factor called Ribosomal releasing factor causes the dissociation of 70s
complex.

19. EUKARYOTIC TERMINATION
1
• In eukaryotes eRF1 recognizes all the three stop codons, and eRF3 stimulate
the termination events.
2
• Once the release factor binds, the ribosome unit falls apart
•releasing the large and small subunits
•the tRNA carrying the polypeptide is also released, freeing up the
polypeptide product.

21. POST-TRANSLATIONAL MODIFICATION
1
• A Post-Translational Modification (PTM) is a biochemical modification that occurs
to amino acids on a protein after the protein has been translated by a ribosome.
2
• These modifications (PTMs) increase the diversity of the proteome by the covalent
addition of functional groups.
3
• Identifying and understanding PTMs is critical in the study of cell biology which
involves disease treatment and prevention.