Chem4711(SlideSet8)

Chem4711(SlideSet8) - Metabolism Metabolism making and...

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Metabolism
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Metabolism – making and breaking stuff Catabolism Anabolism Common intermediates
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Ultimately, can only do reactions that have – G. Δ Photosynthesis – convert light energy into chemical energy Chemotrophs – convert chemical energy into waste products Picture 4 Picture 5 Picture 6
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General rules of metabolism 1. For interconversion of A and B, different pathways for A to B and B to A. All pathways must have G<0 Δ Inject energy in one direction 2. Metabolic pathways are highly regulated. Prevent accumulation of intermediates Levels of regulation Genetic regulation Allosteric regulation Exogenous – only use pathway when needed Product regulation – feedback inhibition Substrate level regulation Picture 2
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oordinate regulation Need to regulate multiple pathways simultaneously. . Metabolic pathways have a committed step. Committed step – psuedo-irreversible . In eukaryotes, metabolic pathways are located in specific places. Mitochondria – OxPhos, Citric acid cycle Golgi/ER – protein glycosylation Picture 2
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Living organisms – high G state Δ Organized – low S Δ High G compounds Δ Thus, need G to interact with environment. Δ G compounds in, garbage out. Δ There is a set of optimal concentrations for metabolites, proteins, hat a cell wants to maintain – steady-state. Perturb steady-state, cell responds.
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Enzymes that operate far from equilibrium Ideal for control Turn E on or off, and pathway immediately responds. Enzymes at equilibrium Immediately respond to changes in A or B by varying forward and reverse reactions. Reestablish equilibrium, little effect on overall rate. Picture 2
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Suppose a cell needs a reaction with G>0? Δ Direct coupling Ex. Ca +2 ATPase – pumps Ca +2 against concentration gradient . High [Ca +2 ] Low [Ca +2 ] ATP ADP + P i Rule – only hydrolyzes ATP when Ca +2 is pumped. Glucose import Picture 1
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ethods to elucidate metabolic pathways Radioactive precursors – 3 H, 14 C, 32 P, 35 S Emit particle (hot e β - from nucleus) Add labeled A and watch what happens. s A a precursor of C? Add A* to cells. Purify C, and ask if it is C* Chemically degrade C* to see where * ended up. oes NOT tell us the pathway, only that A can get to C. Picture 2
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nhibitors Inhibit a specific enzyme and look for effects on product formati and intermediate accumulation. an use specific small (or large) molecule inhibitors (drugs, toxins, an use genetic mutants (defective enzymes). epending on Keq, any species could accumulate. eed to inhibit each E to work out pathway.
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This note was uploaded on 02/23/2011 for the course CHEM 4711 at Colorado.

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Chem4711(SlideSet8) - Metabolism Metabolism making and...

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