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Enzymes
Food Analysis Final Exam
What is the equation for an enzyme reaction? | E + S --> <-- ES --> E + P |
Name three functions of enzymes in foods. | Used to measure specific compounds, processing aid, sample preparation for other assays, indicator of quality/adequacy of processing |
Why are enzymes kinetics important? | Can be used to control rates of enzyme-catalyzed reactions. |
Define initial velocity. | The slope of the curve during the steady-state period in an enzyme reaction. |
Define maximum velocity. | The velocity of the reaction at very large substrate concentration. |
Define the Michaelis constant. | The substrate concentration at half maximum velocity; indicates bind affinity of enzyme. |
What is the Michaelis-Menten equation. | v0=vm[S]/Km+[S] |
T or F: Km is affected by the concentration of the enzyme. | False |
Name three factors which affect both the Michaelis constant and maximum velocity. | Nature of enzyme/substrate, pH, temperature, inhibitors. |
When [S] << Km, the rate of the reaction is ____ order with respect to [S]. | first |
[S] << Km is used to measure _____. | substrates |
When [S] >> Km, the rate of the reaction is ____ order with respect to [S] and _____ order with respect to [E]. | zero, first |
[S] >> Km is used to measure ______. | enzyme activity |
The slope of the Lineweaver-Burk plot is equal to what? | slope = Km/Vm |
Name three effects of pH on reaction rate. | Enzyme stability, substrate to product conversion, ionization of the substrate. |
Name two enzyme activators. | prosthetic groups, coenzymes |
Define prosthetic groups. | Nonprotein portions of an enzyme, nearly irreversibly associated with enzyme; essential part of active site. |
Define coenzyme. | Dissociable nonprotein parts |
What are the three types of reversible inhibitors? | Competitive, noncompetitive, uncompetitive |
Describe competitive inhibitors. | Inhibitor binds to the active site, preventing the substrate from binding. |
Describe noncompetitive inhibitors. | Inhibitor binds equally well to the enzyme whether or not there is a substrate attached to it. |
Describe uncompetitive inhibitors. | Inhibitor binds to the enzyme only when substrate is already bound. |
T or F: The dissociation constant for an irreversible inhibitor is very large. | False |
Name four methods which can be used to measure an enzyme reaction. | Absorbance spectrometry, titration, viscosity, isotope measurement, fluorimetry, manometric methods. |
In a coupled enzyme reaction, the ____ enzyme must not be rate limiting. Enzyme ___ must be greater than enzyme ____. | 2, 2, 1 |
_____ determination can be used in a coupled enzyme reaction to determine metabolites. | Ethanol |
Ethanol determination of a couple enzyme reaction involves which two enzymes? | alcohol dehydrogenase, aldehyde dehydrogenase |
What two methods can be used to measure the amount of substrate in an enzyme reaction? | [S] << Km, endpoint method |
What method can be used to measure the amount of enzyme in an enzyme reaction? | [S] >> Km - near vm |
A _____ has a biological sensing element (enzyme) coupled to a _____ (optical, electrochemical). | biosensor, transducer |
Alkaline phosphatase or rennet can be used to measure quality of _____ products. | dairy |
alpha-amylase can be used to measure quality of _____ products. | cereal |
Pectin methylesterase can be used to measure quality of _____ products. | juice |
Peroxidase can be used to measure quality of _____ products. | vegetable |