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36 Cards in this Set
- Front
- Back
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What two things do enzymes do?
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1) speed up slow reactions
2) catalyze otherwise impossible reactions |
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What binds a small molecule to a Protein?
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-H-bonds
-Ionic bonds -Hydrophobic interaction -Van der Waals forces (very sensitive to interatomic distance) |
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What are 6 classes of enzymes?
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1) oxidoreductases
2) transferases 3) hydrolases 4) lyases 5) Isomerases 6) Ligases |
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What reaction type is: oxidoreductases?
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-Oxidation-Reduction
ex; Lactate Dehydrogenase |
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What reaction type is: Transferases?
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-Group Transfer
ex; nucleoside monophosphate kinase (NMP Kinase) |
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What reaction type is: Hydrolases?
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Hydrolysis
ex; Chymotrypsin |
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What reaction type is: Lyases?
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Addition or removal of groups to form double bonds
ex; fumarase |
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What reaction type is: Isomerases?
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-Intramolecular group transfer
ex; Triose phosphate isomerase |
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What reaction type is: Ligases
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-Ligation of two substrates at the expense of ATP
ex; Aminoacyl-tRNA synthetase |
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What does alcholol dehydrogenase do?
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-Catalyze the reduction of Acetaldehyde to ethanol
-Systematic name is EC 1.1.1.1 |
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What does NMP kinase do?
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-It transfers a phosphoryl group from ATP to NMP to form NDP, hence it is a transferase-group 2
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How do you calculate velocity for a linear plot of kinetic data?
What is this called? |
Vo= (Vmax[S])/(Km + [S]
OR 1/Vo= (Km/Vmax)x(1/[S])+(1/Vmax) *Called the Michaelis-Menton Equation |
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What is the name of the plot one would use for a Uni-Uni enzyme?
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-double reciprocal plot OR
-Lineweaver-Burk Plot |
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What are 5 reasons for finding Km?
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-Km comparisons
-different substrates -Ligand induced changes in Km -intracellular [S] -Enzyme assay |
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What is Aspariginase used for?
What variation is there? |
-Leukemia treatment
-aspariginases with high or low Km's were ineffective |
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Where is hexokinase found?
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-In the muscles of man and animals
-also in the liver (along with glucokinase |
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What is the main difference between hexokinase and glucokinase in terms of what they use?
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-hexokinase (low Km of 37uM)will work with many hexoses, whereas glucokinase only uses glucose (high Km of 10mM)
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How does hexokinase work in muscle?
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-works as fast as it can, near Vmax
-any glucose or hexose taken up by muscle is phosphorylated and locked into the muscle |
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How does hexokinase work in the liver?
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-hexokinase can not respond to blood glucose increase, but it can work with glucose in the liver for catabolic needs (of liver)
-after a meal, liver imports more glucose to store as glycogen |
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Where is lactate dehydrogenase found?
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-in muscles (and therefor the heart)
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How does muscle LDH work?
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-muscle LDH has a high Km for pyruvate. As pyruvate increases, more lactate is formed and fatigue results
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How does heart LDH work?
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-since heart shouldn't get fatigued, LDH has a low Km for pyruvate in the heart:
-can't respond to increased pyruvate -high pyruvate completely inhibits LDH in heart |
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What are enzyme inhibitors used for?
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-establish nature of reactants
-establish nature of binding sites -stablish the specificity of the enzyme -determine the reaction mechanism |
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What is the basis for rational pharmacology and chemotherapy?
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-Drugs work as selective inhibitors by natural (or synthetic) compounds
-Inhibition of enzymes lies at the root of the mode of action of many drugs |
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What are the two classes of inhibitor classes?
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-reversible
-irreversible |
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What happens to Vmax and Km in an irreversible inhibitor reacton?
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Vmax goes down and Km is unchanged
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What affect do heavy metals have on proteins?
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-since this is in the inhibitor section, it inhibits it!
-to be precise, metals inactivate proteins |
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What is a benefit of irreversible inhibitors?
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-can identify imprtant groups in the enzyme
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What is an example of how an irreversible inhibitor is used?
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-Iodoacetate treatment of RNAase at pH 5.5 inactivates an enzyme
-Look for alkylation on His 12 or 119 -If there, these histidines are important in the active site of the enzyme |
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What is Acetylcholine Esterase?
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-an enzymatic catalyst that is the site of action of organophosphate nerve gasses
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How does a competitive inhibitor work?
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-When inhibitor is added, reaction is pulled to the left, increasing Km (dissociation constant)
-If you add enough S to push all the enzymes to ES, you can get product still and Vmax is unchanged |
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What are the different types of reversible enzyme inhibitors?
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-competetive
-nonclassical competitive -uncompetetive -noncompetitive |
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Where do the lines intersect for each type of reversible inhibitor
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-Competative: Y-axis
-uncompetitive: parallel -noncompetative: X-axis -mixed/nonclassical: intersect anywhere but the x or y axis |
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How does a Noncompetitive inhibitor work?
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-no effect on binding of S so Km is unchanged
-can not force all of enzyme to ES, so Vmax is decreased |
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How does an Uncompetitive Inhibitor work?
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-Pulls equation to the right, so Km decreases
-Can not drive all enzyme to ES, so Vmax decreases |
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How does a mixed type inhibitor work?
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-effects binding site, so Km increased
-If I is present, you will always have ESI, hence Vmax decreased |
