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Translation - 100 NCERT

Translation is the process of synthesizing proteins from mRNA, involving a translational unit flanked by a start and stop codon, with untranslated regions (UTR) at both ends. The process consists of three main steps: initiation, elongation, and termination, requiring components like mRNA, ribosomes, tRNA, and specific enzymes. During elongation, amino acids are sequentially added to form a polypeptide, and termination occurs when a release factor binds to the stop codon, releasing the completed polypeptide.

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55 views2 pages

Translation - 100 NCERT

Translation is the process of synthesizing proteins from mRNA, involving a translational unit flanked by a start and stop codon, with untranslated regions (UTR) at both ends. The process consists of three main steps: initiation, elongation, and termination, requiring components like mRNA, ribosomes, tRNA, and specific enzymes. During elongation, amino acids are sequentially added to form a polypeptide, and termination occurs when a release factor binds to the stop codon, releasing the completed polypeptide.

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Translation – The process of synthesising proteins from mRNA is known as translation.

• A translational unit in mRNA is the sequence of RNA that is flanked by the start codon (AUG)
and the stop codon and codes for a polypeptide.
• An mRNA also has some additional sequences that are not translated and are referred as
untranslated regions (UTR).
• The UTRs are present at both 5' -end (before start codon) and at 3' -end (after stop codon).
They are required for efficient translation process.

Components required for Translation –

M RNA – Its acts as a template,

Ribosome – Prokaryotes [ 70 (50+30) ], Eukaryotes [80s(60+40)] it contain 80 protein

t RNA - it acts as adapter

ENZYMES – aminoacyl t RNA synthetase , Peptidyl transferase [ ribozyme ]

Translation consists of 3 steps –


Initiation –

Elongation

Termination

Initiation - 1. Charging of t RNA - tRNA is charged with its cognate amino acid and delivers it to
the ribosome.

• tRNAs are charged by enzymes called aminoacyl-tRNA synthetases in an energy dependent


process.

Amino acid + tRNA + ATP------------------→ aminoacyl-tRNA + AMP+ PP

2. The ribosome In its inactive state exists as two subunits; a large subunit and a small subunit.

• First, mRNA binds to the small subunit of the ribosome.


• Second, initiator tRNA [ contain met ] binds to the mRNA through base pairing between the
start codon [ AUG ] and the anticodon.
• Third, the large subunit of ribosome joins the initiation complex.

The large subunit of the ribose contain 3 sites , E , P and A .

• A (aminoacyl) site, which accepts the incoming aminoacylated tRNA; P (peptidyl) site, which
holds the tRNA with the nascent peptide chain; and E (exit) site,

There are two sites in the large subunit[ P and A ] for subsequent amino acids to bind to and thus, be
close enough to each other for the formation of a peptide bond.

Elongation – During this stage, complexes composed of an amino acid linked to tRNA, sequentially
bind to the appropriate codon in mRNA by forming complementary base pairs with the tRNA
anticodon at the A site .

PARIKSIT INC
1st Floor, In front of B/18, KOELNAGAR, Rourkela, Odisha 769014 ,Contact - 07008558336
• The Large subunit of ribosome also acts as a catalyst as it contain peptidyl transferase (23S
rRNA in bacteria is the enzyme- ribozyme and 28s r RNA in eukaryotes ) for the formation of
peptide bond.
• It transfer the amino acid from the t RNA of P site and forms a peptide bond with aminoacyl
t RNA of the A site .
• The ribosome moves from codon to codon along the mRNA. Amino acids are added one by
one, translated into Polypeptide sequences. [ This is dictated by DNA and represented by
mRNA ]

Termination –

At the end, a release factor binds to the stop codon, terminating translation and releasing the
complete polypeptide from the ribosome.

PARIKSIT INC
1st Floor, In front of B/18, KOELNAGAR, Rourkela, Odisha 769014 ,Contact - 07008558336

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