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Protein Synthesis. Making Proteins. Why do we need protein synthesis?. Cell Structure (80% of cell membrane is proteins) Transport Channels Cell Processing Hormones (signals) Enzymes What else?. What do we need for Protein Synthesis?. DNA - PowerPoint PPT Presentation
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Making Proteins
Protein Synthesis
Cell Structure(80% of cell membrane is proteins)Transport Channels
Cell ProcessingHormones (signals)Enzymes
What else?
Why do we need protein synthesis?
1. DNA• Is the template for making mRNA during
transcription
2. RNA mRNA =messenger RNA
Makes and takes copy DNA to cytoplasm
What do we need for Protein Synthesis?
tRNA = transfer RNA Matches with mRNA on ribosomes Carries Amino Acids
rRNA = ribosomal RNA Part of ribosome Reads mRNA Directs tRNA
3. RibosomeReads mRNADirects tRNACreates peptide bonds between AA’s
4. Amino Acids (AA’s)Building blocks of proteins (20 AAs essential)Protein = AA chain = polypeptide chain
ORDER MATTERS!
AA order determines f(x) of protein
Protein Synthesis Overview
http://www.columbia.edu/cu/biology/courses/c2005/images/animtransln.gif
TRANSCRIPTION: writing the message
DNAmRNA
STEPS:1. unwind DNA in nucleus with help of
enzyme2. DNA polymerase pairs RNA
nucleotides with DNA nucleotides =mRNA
* U replaces T in RNA *
2 main steps of Protein Synthesis
3 DNA nucleotides (triplet)
m RNA CODON
Codons
Start Codon
2 main steps of Protein Synthesis
TRANSLATION: mRNA tRNA Protein (AA chain)
Steps:1. mRNA leaves nucleus and binds
to ribosome 2. tRNA (anticodon) brings the
amino acid to the mRNA (codon) on ribosomes
3. Ribosomes move down mRNA to next codon
4. tRNA anticodon brings and attaches next AA with peptide bond
5. tRNA leaves ribosome once AA attached
6. Repeat above steps to add AA until STOP CODON to signal end of protein
UAG, UAA, or UGA7. Polypeptide chain releases from
ribosomes
A U G G G C U U A A A G C A G U G C A C G U U
This is a molecule of messenger RNA.
It was made in the nucleus by transcription from a DNA
molecule.
mRNA molecule
codon
A U G G G C U U A A A G C A G U G C A C G U U
A ribosome on the rough endoplasmic reticulum attaches to the mRNA
molecule.ribosome
A U G G G C U U A A A G C A G U G C A C G U U
It brings an amino acid to the first three bases (codon) on the mRNA.
Amino acid
tRNA molecule
anticodon
U A C
A transfer RNA molecule arrives.
The three unpaired bases (anticodon) on the tRNA link up with the codon.
A U G G G C U U A A A G C A G U G C A C G U U
Another tRNA molecule comes into place, bringing a second amino acid.
U A C C C G
Its anticodon links up with the second codon on the mRNA.
A U G G G C U U A A A G C A G U G C A C G U U
A peptide bond forms between the two amino acids.
Peptide bond
C C G U A C
A U G G G C U U A A A G C A G U G C A C G U U
The first tRNA molecule releases its amino acid and moves off into the cytoplasm.
C C G U A C
A U G G G C U U A A A G C A G U G C A C G U U C C G
The ribosome moves along the mRNA to the next codon.
A U G G G C U U A A A G C A G U G C A C G U U
Another tRNA molecule brings the next amino acid into place.
C C G
A A U
A U G G G C U U A A A G C A G U G C A C G U U
A peptide bond joins the second and third amino acids to form a polypeptide chain.
C C G C C G
A U G G G C U U A A A G C A G U G C A C G U U
The polypeptide chain gets longer.
G U C
A C G
The process continues.
This continues until a termination (stop) codon is reached.
The polypeptide is then complete.
Synthesis PracticeDNA : A=T and C=GRNA: A=U and C=G *So, when transcribing DNA into
RNA “T” is replaced with “U”Example:
Original DNA: ATCGComplementary DNA: TACG
Transcription example:Original DNA: ATCGMessenger RNA: UACG
(CODON)
Translation Example: Messenger RNA: UACG
(CODON)Transfer RNA: AUGC
(ANTICODON)
tRNA brings the AA so they can bond to make protein
Practice Continued
DNA(triplet)
mRNA (codon)
tRNA(anti-codon)
TAC
GGA
CCT
TAT
ACT
Synthesis Practice
AUG (start)
CCU
GGA
AUA
UGA (stop)
UAC
GGA
CCU
UAU
ACU
Use mRNA codon and use the Universal Genetic Code Chart.AUG (codon)
A = 1st base U = 2nd baseG = 3rd base
To determine the AA