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13 Cards in this Set
- Front
- Back
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What is the effect of enzymes on activation energy? On equilibrim of the reaction? On rate of the reaction?
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Descrease, no change, increase
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Describe the lock and key model of enzyme specificity.
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Active site (lock) copmlementary to spatial structure of substrate (key)
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Describe the induced fit model of enzyme specificity.
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Active site has flexibility of shape; when substrate comes into contact w/active site, conformation changes so it encloses substrate
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What is a cofactor?
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Non-protein molecule that some enzymes require to become active
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Describe the make up of a holoenzyme.
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Holoenzyme = apoenzyme (protein portion of enzyme) + cofactor
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How does a cofactor differ based on the forces holding it to the enzyme?
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if non-covalent = co-factor
if covalent = prosthetic group |
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What is the effect of concentration of substrate on enzyme kinetics?
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Increase [substrate]-->increase rate, but once Active Sites are saturated, reach Vmax
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Describe the Michaelis-Menten model of enzyme kinetics.
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E + S -->ES at a rate of K1
ES --> E + S at a rate of K2 ES-->P at a rate of K3 When reaction rate is half of Vmax, Km = [S]; i.e., it is the point at which 1/2 of the enzyme's active sites are filled |
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Accodring to M-M model, how does the effect of concentration of substrate change in relation to Km.
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When [S]<Km, increases in [S] greatly affect rxn rate; not true when Km,[S]
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What is the effect of temperature on enzyme kinetics?
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Increase in T causes increase in rate until optimatal temp reached, then enzymes denature (37 degrees in humans)
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What is the effect of pH on enzyme kinetics?
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Optimal pH varies from protein to protein
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Describe allosteric effects.
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Allosteric enzymes ahev 2 or more Asites; they oscillate between active and inactive confiurn
REGULATOR molecs can stabilize either state Allosteric INHS: stabilize inactive Allosteric ACTS: stabilize active (perhaps by increased substrate affinity, etc.) |
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Describe:
Feedback inhibition Reversible inhibition Irreversible inhibition |
Feedback: end product of sequence of rxns ebcomes allosteric modulator of preceding enzymes (as decrease endproduct, dec ihibition)
Rev: dissociates easily; can be competitive (competes with substrate by bidning to Asite) or noncompetitive (bindo ther sites and induce confrmal change so enzyme can't bind substrate) Irrev: permanent damage to Asite, prevent formn of ES |
