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31 Cards in this Set
- Front
- Back
What are the 4 physical properties that we identify in enzymes?
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1. Composition
2. Cofactors used 3. Isoenzyme forms 4. Binding sites |
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What are enzymes composed of?
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Proteins, organic components of C, H, O, N, S,.
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What is a catalyst?
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Substance that increases a reaction rate without being changed or consumed.
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What are cofactors?
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Nonproteins that optimize an enzyme's catalytic activity.
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What is a
-holoenzyme? -apoenzyme? |
Holo = whole enzyme+cofactor
Apo = enzyme w/out cofactor |
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What are
-Coenzymes? -Activators? -Prosthetic groups? |
Coenzyme: loose bound organic cofactor.
Activator: loose inorganic ion Prosth. Grp: titely bound cofactor |
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What are characteristics of isoenzymes?
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Different forms that catalyze same reaction; unstable; differentiate w/ electrophoresis
-CK and LD are examples |
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What are the catalytic properties of enzymes?
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1. Effective in small amounts
2. Unchanged by the reaction 3. Decrease activation energy 4. Specific 5. Can lose enzyme activity |
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What causes an enzyme to irreversibly lose its activity?
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Denaturation
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4 types of enzyme specificity:
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1. Absolute
2. Group 3. Bond 4. Stereo |
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What are the 2 types of enzyme classifciations?
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1. Substrate based
2. IUB systematic |
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How are enzymes classified in the old Substrate based method?
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Based on the type of SUBSTRATE the enzyme acts upon
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How are enzymes classified in the new IUB systematic method?
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Based on the catalyzed REACTION
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List the 6 enzyme classes in the IUB systematic method:
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1. Oxidoreductases
2. Transferases 3. Hydrolases 4. Lyases 5. Isomerases 6. Ligases |
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-Cite an oxidoreductase:
-Cite 4 transferases: -Cite 3 hydrolases |
Oxidored: LD
Transfer: CK, AST, ALT, GGT Hydrolas: Acid phosphatase, amylase, urease |
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What are the 3 phases of an enzyme reaction?
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1. Lag phase
2. Linear phase 3. Substrate depletion phase |
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What occurs in the lag phase?
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Mixing and temp/kinetic equilibrium establishment.
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What occurs in the linear phase?
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Constant reaction; the change in absorbance is constant per unit time - this is where we assay.
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What occurs in the substrate depletion phase?
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little change in absorbance/time
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What substrate concentration is seen in 1st vs. Zero order reactions?
How does the reaction rate relate to each order? |
1st order: low [S] - rate is proportional to amt of substrate
Zero order: high [S] - rate is independent of substrate |
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Why is zero order reaction rate preferred to first order?
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Because the zero order reaction will produce a linear graph of the reaction and allow measurement of the enzyme.
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What is the definition of the michaelis menton constant?
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The [S] that gives 1/2Vmax.
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What is the substrate concentration used in clinical assays?
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10Km
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How does that Substrate conc. affect the Velocity? What order is the reaction? What happens to the Vmax?
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-Velocity approaches Vmax.
-Order is Zero -Vmax becomes indepenent of [S] |
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So what is the resulting rate of clinical, zero-order assays?
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>90% Vmax!
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What is the optimum pH for biologic reactions?
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7.8-8.2
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What temp are clinical enzymes measured at?
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Biological, 37
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On a lineweaver-burk plot:
-What is the y-intercept? -What is the slope? |
Y-intercept = 1/Vmax
Slope = Km/Vmax |
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So if a Km is increased but Vmax is unchanged, what happens to the plot?
-What type of inhibition is this? |
The slope increases but the y-intercept stays the same.
-Competitive inhibition |
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If the Km is unchanged but the Vmax is decreased what happens to the plot?
-What type of inhibition is this? |
Slope increases AND the y-intercept increases.
-Noncompetitive inhibition |
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What happens to a lineweaver burke plot when Vmax AND Km are decreased?
-What type of inhibition is this? |
The Y-intercept decreases but the slope stays the same.
-Uncompetitive inhibition |