7. Protein Synthesis and Translation
Download
Report
Transcript 7. Protein Synthesis and Translation
Chapter 21 Nucleic Acids and
Protein Synthesis
21.7
Protein Synthesis: Translation
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
1
tRNA Activation
The activation of tRNA
occurs when a
synthetase uses energy
from ATP hydrolysis to
attach an amino acid to a
specific tRNA
prepares each tRNA to
use a triplet called an
anticodon to complement
a codon on mRNA
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
2
Initiation of Protein Synthesis
For the initiation of protein synthesis,
an mRNA attaches to a ribosome
the start codon (AUG) binds to a tRNA with
methionine
the second codon attaches to a tRNA with the next
amino acid
a peptide bond forms between the adjacent amino
acids at the first and second codons
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
3
Translocation
During translocation,
the first tRNA detaches from the ribosome
the ribosome shifts to the adjacent codon on the
mRNA
a new tRNA/amino acid attaches to the open
binding site
a peptide bond forms, and the empty tRNA
detaches
the ribosome shifts down the mRNA to read the
next codon
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
4
Protein Synthesis
Translation
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
5
Termination of Protein Synthesis
The termination of protein synthesis occurs when
a polypeptide with all the amino acids for a protein
is synthesized
the ribosome reaches a “stop” codon: UGA, UAA,
or UAG
there is no tRNA with an anticodon for the “stop”
codons
the polypeptide detaches from the ribosome
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
6
Learning Check
Match the following:
1) activation
3) translocation
2) initiation
4) termination
A. Ribosomes move along mRNA, adding amino acids
to a growing peptide chain.
B. A completed peptide chain is released.
C. A tRNA attaches to its specific amino acid.
D. A tRNA binds to the AUG codon of the mRNA on the
ribosome.
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
7
Solution
Match the following:
1) activation
3) translocation
2) initiation
4) termination
3 A. Ribosomes move along mRNA, adding amino
acids to a growing peptide chain.
4 B. A completed peptide chain is released.
1 C. A tRNA attaches to its specific amino acid.
2 D. A tRNA binds to the AUG codon of the mRNA on
the ribosome.
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
8
Summary of Protein Synthesis
To summarize protein synthesis:
An mRNA attaches to a ribosome.
Molecules of tRNA bonded to specific amino acids
attach to the codons on mRNA.
Peptide bonds form between an amino acid and the
peptide chain.
The ribosome shifts to each codon on the mRNA
until it reaches the STOP codon.
The polypeptide chain detaches to function as an
active protein.
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
9
Overview of Protein Synthesis
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
10
Learning Check
The following section of DNA is used to build an mRNA
for a protein: 3′—GAA—CCC—TTT—5′
A. What is the corresponding mRNA sequence?
B. What are the anticodons on the tRNAs?
C. What is the amino acid order in the peptide?
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
11
Solution
The following section of DNA is used to build an mRNA
for a protein: 3′—GAA—CCC—TTT—5′
A. What is the corresponding mRNA sequence?
5′—CUU—GGG—AAA—3′ mRNA
B. What are the anticodons for the tRNAs?
mRNA codons: CUU GGG AAA
tRNA anticodons: GAA CCC UUU
C. What is the amino acid order in the peptide?
mRNA: 5′—CUU—GGG—AAA—3′
peptide: Leu — Gly — Lys
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
12