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2013-04-28 00:55:12

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  1. Levels of metabolic regulation and their rates
    • Transcription (gene expression): takes longer because translation still has to occur
    • Enzyme activity (protein): Allows for quick adaptation and coordination of pathways
    • -Allosteric and covalent
  2. Describe allosteric modification (general)
    • AKA noncovalent modification
    • Binding of effectors to allosteric enzymes in pathways
    • Allosteric enzymes have binding sites for substrate AND allosteric sites for effector molecules
    • Effectors can stimulate OR inhibit enzyme activity
    • Conformational change occurs in enzyme when effector binds to allosteric site
  3. Describe covalent modification (general)
    Attachment and removal of chemical groups (eg. Phosphate and nucleotides)
  4. What are the patterns of regulation of allosteric metabolic pathways (just types)
    • Feedback inhibition
    • Positive regulation
    • Regulatory Enzymes at branch point
  5. Describe Feedback inhibition in detail (types)
    • The end-product of a pathway negatively regulates a branch-point enzyme
    • Functions to prevent a buildup of product
    • Applies to both biosynthetic and catabolic pathways
    • Simple: involves linear biosynthetic pathway. 
    • Inhibited by a single end-product
    • Concerted: involves branched pathways (more than one product inhibits enzyme)
    • Both end products must bind simultaneously to achieve inhibition.
    • Cumulative: involves branched pathways (more than one product inhibits enzyme)
    • Enzyme is not completely inhibited by any single end product (each exerts partial inhibition)
    • Isoenzymes: Involves branched pathways
    • Have same catalytic sites (functions), but different effector sites (inhibitions)
  6. Describe positive regulation in detail (types)
    • 1: Pathway is positively regulated by intermediate in ANOTHER pathway
    • 2. Precursor activation: A precursor positively regulates an enzyme farther ahead in the pathway.
    • Ensures that reactions downstream match upstream (keeps rate constant)
  7. Describe regulatory enzymes at branch points in detail
    • Catalyze IRREVERSIBLE reactions at metabolic branch points.
    • Ensures that reactions proceed in a single direction
  8. Describe covalent modification in detail
    • REVERSIBLE attachment of chemical groups to enzyme
    • Acetyl groups, phosphate groups, methyl groups, adenyl groups, and uridyl groups
  9. Describe the kinetics of regulatory and nonregulatory enzymes
    • Nonregulatory enzymes: follow Michaelis-Menten kinetics
    • Low [substrate]
    • Rate of rxn is proportional to [substrate]
    • As [substrate] increases, rate approaches a maximum (Vmax) because enzyme becomes saturated
    • Not affected by product at all, occurs regardless
    • Regulatory enzymes: rarely follow Michaelis-Menten kinetics
    • Sensitive to small in changes in [effector]
    • Increase to positive effector: decreases Km (the [substrate] at half Vmax)
    • increases rate of reaction
    • Increase to negative effector: increases Km
    • Decreases rate of reaction
    • *see illustration in notebook

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