Transcript 5` cap Large subunit attaches

Central Dogma
DNA=genotype
Transcription
RNA=
the messenger
Translation
Polypeptide=
phenotype
Central Dogma
DNA
Transcription
RNA= the messenger
Translation
Polypeptide= phenotype
For translation to
happen, the
messenger RNA goes
to the cytoplasm
where it is attached to
a cellular structure
Translation :
Polypeptide
Amino Acid
AntiCODON
(tRNA)
CODON
(mRNA)
The structure of tRNA
Single strand of
RNA
Folded back upon
itself
Held together with
H-bonds
The structure of tRNA
Amino acid
attachment on
3” end
Anticodon couples
to the mRNA
Code Redundancy
• Third base in a codon
shows "wobble”.
• First two bases are the
most important in reading
the code and giving the
correct amino acid. The
third base often doesn’t
The structure of tRNA
coupling
a.acid to
the
enzyme
Enzyme
coupled
a. acid
joins
with P
Enzyme
•Phosphate
joins
to a.a.
Coupling
Enzyme
•Phosphate
joins to a.a.
by loosing 2
P
•tRNA bonds to
the amino acid
Coupling
Enzyme
•Phosphate
joins to a.a.
(for energy)
•tRNA bonds to
a.a.
•enzyme releases
“activated amino
acid”

TWO
subunits
to a
ribosome

3
Ribosome
Binding
Sites:
5’ cap
cap
•Large
The mRNA joins to the small ribosomal
unit at the 5' untranslated region. This
subunit
binds to a special binding site on the
attaches
small ribosomal subunit
5’ cap
•Large
The large ribosomal subunit attaches to
the small subunit such that the first
subunit
codon is aligned at the P binding site.
attaches
5’ cap
•Large
A tRNA carrrying the amino acid
methionine attaches to the start codon
subunit
(AUG) on the messenger RNA. This
inititates elongation.
attaches
5’ cap
Brings together:
• mRNA
Large
• tRNA carrying the 1st amino acid
subunit
• 2 subunits of the ribosome
attaches
5’ cap
•Large
Attachment of first amino acid carrying
tRNA to A binding site.
subunit
• A tRNA and its amino acid attaches to
attaches
the A binding site.
5’ cap
• Peptide bond formation between the met
Large
and the amino acid carried at the A
bindiung site. Our polypeptide chain is
subunit
now:
Met
-Thr
attaches
5’ cap
• Ribosome moves in the 3' direction down the
Large
messenger
RNA by three bases or one codon
shifting
the tRNA and polypeptide chain to the P
subunit
Binding
site.
The
A
binding
site
is
open
and
a
attaches
vacant tRNA is in the E binding site.
5’ cap
•
Large
tRNA
ejected from the E binding site.
subunit
attaches
5’ cap
•
•
Large
Repeat Elongation Step 1 - 4
subunit
attaches
until stop codon encountered..
5’ cap
•
•
Large
Elongation ends with:
subunit
attaches
* Old tRNA ejected from the E Binding site
Elongation of polypeptide chain:
Elongation of polypeptide chain:
Elongation of polypeptide chain:
Elongation of polypeptide chain:
Termination of Translation
Stop codon to
the A site.
QuickTime™ and a
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release factor (protein)
binds to A site -- offers a
water molecule (not a.a.)
5’ cap
•
Large
The polypeptide chain is at the P site. The stop
subunit
codon
at the A site.
attaches
•
Large
A Release factor protein binds to the stop
subunit
codon
at the A binding site.
attaches
•
Large
Separation of translation machinary.
subunit chain may go to cytoplasm for
Polypeptide
further
processing.
attaches
• Release factor protein initiates separation of
Large
polypeptide chain:
•
subunit
attaches
Met-Thr-His-Asp-Gly
Termination of Translation
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Termination of Translation
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
mRNA is translated
simultaneously by several
ribosomes in clusters
NOW WHAT?????? My head is going
to explode