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Enzymes pp
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Enzymes All enzymes are proteins; not all proteins are enzymes.
Most enzymes have an –ase ending. ATPase amylase
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Enzymes enzyme -
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Enzymes Substrate – Enzymes which act on glucose will not act on galactose.
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Steps to Enzyme Reactions
Write out the 5 steps for an enzyme catalyzing a reaction
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Substrate Binding active site
Q: What part of AAs interact with substrate? A: R-groups also involved in the t - negative acid group is attracted to the positively charged part of substrate.
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Substrate Binding R-groups
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Enzymes activation energy EA Q: What is an enzyme?
A: Biological catalyst; speeds up reactions without being consumed (true for organic and inorganic catalysts) Let’s review the potential energy diagram: 1) Relative energy of reactants and products determine endothermic / exothermic 2) Difference between reactants and transition state = activation energy Q: How does an enzyme change the shape of a potential energy diagram? (refer back to the animation) A: Lowers EA so that more reactions can happen.
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Reaction Progression Reaction Progession
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Enzyme Energy Enzymes lower the activation energy (EA) of reactions.
Enzymes lower EA. Energy stored in the reactants and products don’t change. Therefore, free energy of a reaction does not change. (delta G)
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enzyme-substrate complex
Substrate Binding induced-fit model - enzyme-substrate complex Enzymes are not static.
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Substrate Binding Enzymes reduce EA by:
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Enzyme Limitations
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Enzyme Limitations
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Limitations of Enzymes
Why do enzymes operate at an optimal temperature and pH?
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Enzyme Limitations cofactors – coenzymes – An apoenzyme is
Enzymes don’t always act alone.
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Enzyme Inhibition competitive inhibitor – noncompetitive inhibitor –
Competitive: estrogen / tamoxifen / BPA example
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Enzyme Inhibition
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Enzyme Regulation allosteric site – allosteric activator – allosteric inhibitor –
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Allosteric Sites Note the two enzyme forms.
- identify various allosteric sites - note the different shapes between subunits
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Feedback Inhibition A, B, C and D are molecules along a metabolic pathway. E1, E2 and E3 are enzymes required for this metabolic pathway. D is an allosteric inhibitor of E1.
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