BIOS E-1a Lecture 06 092611 annotated

BIOS E-1a Lecture 06 092611 annotated - Lecture 6 Cellular...

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Lecture 6: Cellular Metabolism Reading: Chapter 6 (concepts 6.1-6.4) 1
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http://www.youtube.com/watch?v=CfRvmtBdZ9I FRAP fluorescence recovery after photobleaching 2 Allows for the measurement of the lateral movement of membrane proteins
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Recycling • Most large molecules exist for a relatively short period of time • Half-life: time it takes for 50% of the molecules to be broken down and recycled • All living organisms must efficiently use and recycle organic molecules 3
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• Expression of genome allows cells to respond to changes in their environment – RNA and proteins made when needed – Broken down when they are not • mRNA degradation important – Conserve energy by degrading mRNAs for proteins no longer required – Remove faulty copies of mRNA 4
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mRNA degradation • Exonucleases – Enzyme cleaves off nucleotides from end • Exosome – Multiprotein complex containing exonucleases 5
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A A Cap mRNA Poly A tail mRNA degradation in eukaryotic cells 6
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A A Cap mRNA Poly A tail Poly A tail is shortened. 7 mRNA degradation in eukaryotic cells
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A A Cap mRNA Poly A tail Poly A tail is shortened. 5´ cap is removed. 8 mRNA degradation in eukaryotic cells
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A A Exonuclease Cap mRNA Poly A tail Poly A tail is shortened. 5´ cap is removed. Nucleotides are recycled. RNA is degraded in the 5´ to 3´ direction via an exonuclease. 9 mRNA degradation in eukaryotic cells
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A A Exonuclease Cap mRNA Poly A tail Poly A tail is shortened. RNA is degraded in the 3´ to 5´ direction via the exosome. 5´ cap is removed. Nucleotides are recycled. RNA is degraded in the 5´ to 3´ direction via an exonuclease. Nucleotides are recycled. Exosome 10 mRNA degradation in eukaryotic cells
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A A Exonuclease Cap Exosome mRNA Poly A tail Poly A tail is shortened. RNA is degraded in the 3´ to 5´ direction via the exosome. 5´ cap is removed. Nucleotides are recycled. RNA is degraded in the 5´ to 3´ direction via an exonuclease. (a) 5´ (b) 3´ 5´ degradation by exosome Nucleotides are recycled. 3´ degradation by exonuclease 11 mRNA degradation in eukaryotic cells
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Proteins are degraded by the proteosome • Targets - misfolded proteins and proteins that need to be broken down rapidly • Ubiquitin is attached to proteins in first step – Enzymes attaching ubiquitin can recognize misfolded proteins • Protein directed to proteosome cap • Protein unfolded and threaded through proteosome • Protein degraded • Small peptides and amino acids released to cytosol 12
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Ubiquitin Target protein Stages of proteosome-mediated protein degradation 13
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Ubiquitin Target protein Stages of proteosome-mediated protein degradation 14
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Ubiquitin Target protein Stages of proteosome-mediated protein degradation 15
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Cap 1 2 3 4 Cap (a) Structure of the eukaryotic proteasome Core proteasome (4 rings) (b) Steps of protein degradation in eukaryotic cells Ubiquitin Target protein Stages of proteosome-mediated protein degradation 16
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This note was uploaded on 02/09/2012 for the course BIOLOGY 102 taught by Professor Anderson during the Spring '11 term at Harvard.

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BIOS E-1a Lecture 06 092611 annotated - Lecture 6 Cellular...

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