Transcript Proteins – where do they come from?

Dna and protein
synthesis
Proteins – where do
they come from?
Genetic transcription,
translation and
regulation.
Proteins
• You learned about these back in
September – remember
chemistry? (Ugh!!!!!)
• Macromolecules
• Made of amino acids
• Peptide bonds join 50 – 3000 amino
acids
We get proteins from:
• Plants make proteins by using materials made in
photosynthesis
• Animals eat those proteins to get the amino acids
they need to make their own proteins. Or we eat
animals that ate the plants (Whopper, please!)
Amino acids
These are amino acids with two different
R-Groups
R
R
Production of a
polypeptide chain
• Amino acid 1 is added to amino acid 2 by
forming a peptide bond between them.
• This continues at the ribosome until all the
amino acids of a polypeptide are placed in
the right order.
Aa-1
Aa-2
Remember the pathway for making
proteins in the cell?
Two major steps of
protein synthesis
RNA and DNA Nucleotides
Transcription - Dna
codes for RNA
transcription
translation
Central dogma
-
-
-
If the Dna code is this:
TACGAGtTACATAAA
what is the RNA code?
AUGCUCAAUGUAUUU
DNA codes for RNA codons,
RNA codes for the protein
Translation occurs at the ribosome when the
tRNA brings the amino acid in the proper
order as determined by the mRNA
Mrna codons for the amino acids
Removal of the introns (not needed)
and splicing of the exons (expressed)
part of the code
A tRNA molecule showing its anticodon which
complements mRNA’s codon and the amino acid attached
to its opposite end
Polysomes – many ribosomes moving along and
reading the same mRNA molecule – they all
make the same protein
Ribosome structure with mRNA passing
through and causing the creation of an amino
acid chain (protein)
The tRNA with the growing polypeptide
chain is at the P site, while the next amino
acid is brought to the A site by another tRNA.
Initiation
elongation
termination
• Occurs when the stop codon is reached.
• The polypeptide chain is complete
• The mRNA is either read by another
ribosome or it is recycled so its nucleotides
can be used again.
• The ribosome large and small subunit falls
apart from each other
Transcription – DNA codes for
RNA
RNA processing
Translation Initiation
Translation - Elongation
Translation - Termination
Entire Translation Procedure
Now the protein passes
from the ribosome and
moves into the rough
endoplasmic reticulum.
Do you remember what
happens to it next?
You should now understand this diagram. If you don’t, then
you need to come in after school and go through this
presentation on you own at your own speed.