Download LEQ: How does RNA help to make a protein?

Type of RNA that
functions as an
interpreter in
translation
 Each tRNA molecule
has a specific
anticodon and a site
of attachment for an
amino acid
 Each tRNA picks up a
specific amino acid
based on its
anticodon
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Anticodon – specific
sequence of 3
exposed nucleotides
found in tRNA;
complementary to
codon of mRNA
2 important sites
› Anticodon
› Point of attachment
to amino acid
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Type of RNA that,
together with
proteins, make up
ribosomes; most
abundant type of
RNA
Ribosome
composed of 2
subunits – small and
large
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Eukarytoic ribosomes are larger and of
different composition
Antibiotics can inactivate prokaryotic
ribosomes (but not the eukaryotic
ribosomes) can be used to treat
bacterial infections
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Initiation establishes exactly where translation
will begin
2 steps
› mRNA binds to small ribosomal subunit; initiator tRNA
binds to the start codon (AUG) of mRNA; tRNA UAC
carries Methionine
› Large ribosomal subunit binds to the small one
placing the initiator tRNA in the P site; A site is open for
the next tRNA
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P site – the ribosomal
binding site that holds
the tRNA carrying the
growing polypeptide
(peptidyl tRNA)
A site – the ribosomal
binding site that holds
the incoming tRNA
that holds the new
amino acid
E site – the ribosomal
release site for tRNA
molecules that release
the growing
polypeptide
Codon Recognition – incoming tRNA anticodon
pairs with mRNA codon in the A site bringing in a
new amino acid
 Peptide Bond Formation – peptide bond forms
between the amino acid in A site and the amino
acid in the P site; the tRNA in the P site releases
its amino acid once the bond is formed
 Translocation – ribosome moves so that the A
site tRNA is now in the P site; leaving the A site
open for a new tRNA
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Termination – when the ribosome reaches a
stop codon at the A site a release factor
binds to the mRNA this triggers the release
of the the polypeptide from the last tRNA;
mRNA is released from the ribosome and
the ribosome subunits separate