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IB HL Biology 8.1 Metabolic Pathways (Enzyme Inhibition: molecule disrupts…
IB HL Biology 8.1 Metabolic Pathways
Metabolism: sum of all reactions that occur w/in organism to maintain life
Extension
Result from series of pathways w/ each step controlled by enzyme
Enzymes speed up rate of reaction by lowering activation energy by binding to substrate, stressing it, and destabilising bonds
Exergonic/catabolic: free energy released into system; energy released from broken bonds
Endergonic/anabolic: free energy lost to system; energy required to synthesize bonds
Pathways allow for greater regulation (change controlled by intermediates)
Enzyme Inhibition: molecule disrupts normal reaction pathway b/t enzyme and substrate
Normal
Substrate binds to active site forming enzyme-substrate complex (shape/properties of substrate and active site complementary → specificity)
Active site undergoes conformational change to interact optimally → induced fit
Destabilises chemical bonds w/in substrate, lowering EA → substrate converted into product at accelerated rate
Competitive Inhibition
Molecule other than substrate binds to active site (structurally/chemically similar to substrate)
Competitive inhibitor blocks active site, preventing substrate binding → effects can be reduced by increasing substrate []
Non-competitive Inhibition
Molecule binds to allosteric site causing conformational change to active site
No more specificity meaning substrate cannot bind → increasing substrate [] cannot mitigate inhibitor's effect
Example: cyanide - binds to allosteric site of carrier molecule on ETC → cytochrome oxidase can no longer pass e-'s to oxygen (final acceptor) therefore ETC cannot produce ATP via aerobic respiration
Feedback inhibition
Product of series of reactions binds to allosteric site to temporarily inactivate the enzyme → reaction sequence halted, rate of product formation decreased
Ensures levels of product are always regulated (if product levels build up, product inhibits reaction pathway and decreases rate of futher product formation; product levels drop, reaction pathway will proceed unhindered and rate of formation will increase)