Lect11-KR - Regulatory mechanisms I PMB/MCB 112 September...

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Regulatory mechanisms I PMB/MCB 112 September 24, 2010
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All possible proteins encoded in the genome Proteins currently being synthesized Proteins currently active To respond appropriately and efficiently to environmental conditions, cells control 1) gene expression (which proteins are made) and 2) enzyme activity (which proteins are on/off)
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Regulation of enzyme activity determines which biochemical pathways are active- Respond to product levels Respond to substrate levels Feedback inhibition of a biosynthetic pathway Most efficient place to have feedback inhibition is at the first enzymatic step specific to that pathway and no others Enzyme activities change, but they still exist in the cell
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When the end product is depleted, the binding equilibrium shifts, the end product is released, and catalysis resumes. How is enzyme activity altered by the presence of a product many steps down the path? Allosteric regulation enzyme has two sites: active site binds the substrate and catalyzes reaction allosteric site binds the end product, which prevents catalysis at the active site
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Regulation of enzyme synthesis: transcriptional regulation
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Eukaryotic protein synthesis Transcription (tx) occurs in the nucleus Introns are removed Mature mRNA exported from the nucleus Translation (tl) occurs in the cytoplasm One protein per mRNA
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Prokaryotic protein synthesis Tx occurs in cytoplasm – no nuclear membrane Genes are organized in operons , creating polycistronic mRNAs Tl occurs in same compartment, coupled to tx Multiple genes on one RNA are translated separately
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This note was uploaded on 01/19/2011 for the course C 112 taught by Professor Ryan during the Fall '10 term at University of California, Berkeley.

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Lect11-KR - Regulatory mechanisms I PMB/MCB 112 September...

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