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BIOCHEM Lecture 03
exam 1
| Question | Answer |
|---|---|
| thermodynamics | determines if a reaction will happen |
| kinetics | determines how fast a reaction will happen |
| free energy change | energy available to do work, G products - G reactants |
| if delta G is positive | endergonic, nonspontaneous, products have more free energy |
| if delta G is negative | exergonic, spontaneous, reactants have more free energy |
| if delta G equals 0 | equilibrium, same free energy in products and reactants |
| standard free energy change | temperature, pressure, concentration, pH, useful for comparisons |
| delta G equation | standard delta G + RT ln [C][D]/[A][B] |
| how do cells allow positve delta standard delta G to occur | alters concentrations of reactants and products |
| enzymes | catalysts that speed chemical reactions, made up of proteins |
| enzyme specificity | not permanently altered and highly specific for substrates |
| how do enzymes affect activation energy? | enzymes lower the activation energy to speed up the reaction |
| active site | portion of enzyme that the substrate binds |
| apoenzyme | inactive enzyme that requires cofactor for activation |
| cofactor | non protein molecule necessary to activate apoenzyme |
| what can be cofactors? | metals or coenzymes |
| holoenzyme | active enzyme made up of apoenzyme and cofactor |
| energy substrate interactions must be ___________ | sterically possible and energetically favorable |
| acid base catalysis | enzyme active sites donate or accept hydrogen ions from substrate |
| covalent catalysis | enzyme active site creates a temporary covalent bond with the substrate |
| metal ion catalysis | metal can stabilize ionic intermediates (transition state) |
| orientation catalysis | enzymes hold multiple substrates in the optimal position |
| oxidoreductase | transfer of electrons |
| transferase | transfer of functional groups |
| hydrolase | hydrolysis, cutting with water |
| lyase | removal of groups without hydrolysis |
| isomerase | rearrangement to make isomers |
| ligase | joining of two molecules |
| general kinetics | d[product]/dt |
| collision theory | more concentrated reactions have a faster reaction |
| zero order | rate is not affected by concentration of reactant |
| first order | only one reactant, doubling the concentration will double the rate |
| pseudo first order | two reactants present but only one affects the rate |
| second order reaction | two molecules of reactant |
| Michaleis-Menten model | [S] is similar to [E] |
| M-M enzymes | catalyst but not regulatory |
| michaelis constant Km | [S] at one half of V max |
| Vmax | max turnover of substrate when enzyme is saturated |
| lower Km | higher binding affinity |
| Kcat | number of substrate molecules converted to product per unit time |
| high Kcat | more efficient enzyme |
| Lineweaver-Burk Plot | y intercept = 1/Vmax |
| x intercept = -1/Km | |
| allosteric enzymes | catalysts and regulator of metabolic pathways |
| allosteric enzyme: allosteric site | effector binding (inhibitor and activation) |
| allosteric enzyme: active site | substrate binding |
| allosteric cooperativity | substrate binding changes affinity of other subunits |
| single headed arrow | irreversible, committed step |
| double headed arrow | reversible, not committed |
| allosteric enzyme catalysis | catalyze first committed step |
| negative feedback | accumulation of end product inhibits enzyme that catalyzes first committed step |
| positive feedback | accumulation of end product catalyzes enzyme for first committed step |
| allosteric enzyme repression | repressor binds to enzyme, changes active site conformation so that substrate cannot bind |
| allosteric enzyme activation | activator binds to enzyme and corrects active site conformation so that the substrate can bind |
| activators stabilize the ___ form | active |
| inhibitors stabilize ___ form | inactive |
| competitive inhibitors | compete with substrate for active site, can be overcome with high substrate |
| noncompetitive inhibitors | bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective, cannot be overcome with high substrate |
| uncompetitive inhibitors | bind to ES complexes and prevent product release, cannot be overcome with high substrate |
| Same Vmax, different Km | competitive inhibitor |
| Different Vmax, same Km | noncompetitive inhibitor |
| different Vmax, different Km | uncompetitive inhibitor |
| How do temperature and pH affect enzymes? | each enzyme has an optimum temperature and pH that allow it to be most active |
Created by:
r.logan6029
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