i can explain how the change in the structure of a molecular system may result in a change of the...
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Learning Targets
I can explain how the change in the structure of a molecular system may result in a change of the function of the system.
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Structure
Protein› Recall 4 levels of structure and bonds that
hold them in place Substrate-specific: the active site is
specifically shaped so only certain molecules fit on it
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Learning Targets
I can explain how the shape of enzymes, active sites and interaction with specific molecules are essential for basic functioning of the enzyme.› I can explain how for an enzyme-
mediated chemical reaction to occur, the substrate must be complementary to the surface properties (shape and charge of the active site). In other words, the substrate must fit into the enzyme’s active site.
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Induced Fit Shape of active site can change
slightly as substrate binds The active site is then molded into a
precise conformation--sort of like a hand in a glove
So, some enzymes can act on similar molecules, not just specific ones
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Enzyme-Substrate Interaction
How do the following relate to enzymes?› active site› substrate› induced fit› energy of
activation
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Activation Energy
How reactions work
How reactions work with enzymes
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Enzyme-Substrate Concentration
Enzymes act on one molecule at a time
Reach a saturation point when all enzymes are engaged in reaction› Reaction rate will
not change
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pH, Temperature, Salinity All enzymes have a specific range for
optimal performance Outside of that range denature
don’t function
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Denaturation Disruption of R-groups
at each level of structure› H-bonds at 2°› Disulfide bridges, ionic
bonds, hydrophobic interactions at 3°
› Disassociation of subunits at 4°
When structure changes, function changes
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Sometimes reversible, sometimes not
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Learning Target
› I can explain how cofactors and coenzymes affect enzyme function; this interaction relates to a structural change that alters the activity rate of the enzyme. The enzyme may only become active when all the appropriate cofactors or coenzymes are present and bind to the appropriate sites on the enzyme.
› I can explain how other molecules and the environment in which the enzyme acts can enhance or inhibit enzyme activity. Molecules can bind reversibly or irreversibly to the active or allosteric sites, changing the activity of the enzyme.
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Enhancing Factors
Help/Increase Enzyme Function
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Cofactors & Coenzymes Co-factors assist with
catalytic activities of enzyme› Can activate active
site, assist with substrate bonding
› Ex: iron, zinc, copper, magnesium, potassium
Co-enzyme is an organic co-factor› Ex: vitamins (ie: B, C)
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Allosteric Cooperativity
One substrate molecule primes an enzyme to receive more substrates readily
Ex: hemoglobin
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Inhibiting Factors
Prevent/Interfere with Enzyme Function
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Competitive Inhibition
Competitive inhibitor has same shape as substrate
(competes for active site)
Prevents substrate from binding to active site by binding to active site itself
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Allosteric Inhibition
Inhibitor binds to allosteric site of enzyme
Active site changes shape, no substrate binds
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Allosteric Activation
Change in the enzyme’s shape due to binding of activator at allosteric site
Enzyme is stabilized by activator
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Feedback Inhibition
The switching off of a biochemical pathway by the product of the pathway› Negative feedback› Conserve energy!
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Learning Targets
I can explain that the change in function of an enzyme can be interpreted from data regarding the concentrations of product or substrate as a function of time. These representations demonstrate the relationship between an enzyme’s activity, the disappearance of substrate, and/or presence of a competitive inhibitor.