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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
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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
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Describe covalent modification (general)
Attachment and removal of chemical groups (eg. Phosphate and nucleotides)
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What are the patterns of regulation of allosteric metabolic pathways (just types)
- Feedback inhibition
- Positive regulation
- Regulatory Enzymes at branch point
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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)
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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)
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Describe regulatory enzymes at branch points in detail
- Catalyze IRREVERSIBLE reactions at metabolic branch points.
- Ensures that reactions proceed in a single direction
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Describe covalent modification in detail
- REVERSIBLE attachment of chemical groups to enzyme
- Acetyl groups, phosphate groups, methyl groups, adenyl groups, and uridyl groups
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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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