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Skitty2004
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The Km is...
equal to the substrate concentration when the velocity is half its maximal value
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When substrate concentration is much greater than Km, the rate of catalysis approaches...
Vmax
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List the five major classes of enzymes (in order)
- oxidoreductase
- transferase
- hydrolase
- lyase
- ligase
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Be able to draw a Lineweaver-Burk plot. And label the x and y intercepts.
Do it.
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Define what the slope equates to in a Lineweaver-Burk plot.
slope = Km/Vmax
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In a biomolecular reaction, how would you carry out a kinetics experiment to determine Vmax for one of the reactants. Assume you desire pseudo-first order kinetics with respect to one of the reactants?
For pseudo-first order kinetics in this situation you would use a substrate concentration for one of the reactants that is probably at least 100 fold higher than the Km where change in substrate concentration for that substrate would not affect Vmax.
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The slope of a Lineweaver-Burk plot for an enzyme is found to be 1.88. Its maximal velocity is 3.45 umoles/min. What is the Km?
Km/Vmax=1.88; Vmas = 3.45 so Km/3.45 = 1.88Km = (3.45)(1.88) uM
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Formation of the ES complex results in an increase in entropy. [T/F]
F; decrease
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What are the three main types of catalysis?
Covalent catalysis;General acid-base catalysis;Metal ion catalysis
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In uncompetitive inhibition, the inhibitor can only bind to the ES complex to form an ESI complex. [T/F]
T
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Formation of the ES complex results in an increase in entropy. [T/F]
F; decrease
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In near-attack complexes, reacting atoms and catalytic groups are precisey positioned for their roles in catalysis (proximity and orientation). [T/F]
True
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Transition state analogs (TSAs) are stable molecules that are...
chemically similar to the transition state and structurally similar to the transition state
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Transition states are bound ______ than substrates.
More tightly
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What is K-cat?
substrate molecules converted to product per second
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Enzymes catalyze _____ favorable reactions.
thermodynamically
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Enzymes provide cells with the ability to exert....
kinetic control over thermodynamic potentiallity
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Living systems use enzymes to ____ and ____ of ______
- accelerate;
- control the rates;
- vitally important biochemical reactions
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Nearly every _______ is catalyzed.
biological reaction
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Enzymes are the ____ of ____.
agents; metabolic function
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What common macromolecule is often burned or oxidized by enzymes?
glucose
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Enyzmes lower _____.
delta G++
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The breakdown of glucose by ____ provides a prime example of a metabolic pathway.
glycolysis
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________ is the ratio of the enzyme-catalyzed rate of a reaction to the uncatalyzed rate.
catalytic power
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____ is the term used to define the selectivity of enzymes for their substrates.
specificity
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_____ of enzyme activity ensure that the rate of metabolic reactions is appropriate to cellular requirements.
regulation
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Coenzymes and cofactors are....
non-protein components essential to enzyme activity.
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_____ and ______ are non-protein components essential to enzyme activity.
coenzymes and cofactors
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Cofactors are usually _____.
metals
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Coenzyme usually refers to ____.
organic non-protein molecules
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Enzymes selectively recognize proper ___ over other molecules.
substrates (s)
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Enzymes produce ____ yields with ___ side products.
very high; no
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Specificity is controlled by _____.
structure
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_____ is controlled by structure.
specificity
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_____ and _____ of the substrate in the enzyme active site leads to catalysis.
proximity and orientation
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Main classification: 1
1: oxidoreductases
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Main classification: 2
2: transferases
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Main classification: 3
3: hydrolases
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Main classification: 4
4: lyases
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Main classification: 5
5: isomerases
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Main classification: 6
6: ligases
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____ is the branch of science concerned with the rates of reactions.
kinetics
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_____ seeks to determine the maximum reaction velocity (Vmax) that enzymes can attain and binding affinities for substrates and inhibitors.
enzyme kinetics
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What is the symbol for maximum reaction velocity?
Vmax
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What is the abbreviation for the binding affinities for substrates?
Km
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What is the abbreviation for the binding affinities for inhibitors?
Ki
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Analysis of enzyme rates yields insights into.....
enzyme mechanisms and metabolic pathways
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What is the term for the amount of product formed (or substrate consumed) per unit time?
rate or velocity
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What is the definition of the rate constant (k)?
a proportionality constant that predicts the velocity at different concentrations of substrate
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What is a rate law?
the actual mathematical relationship in a reaction
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What is that order of a reaction?
the exponent in the rate equation
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What is the molecularity of a reaction?
The number of molecules that must simultaneously interact
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What is the molecularity in: ?
A----> P
one
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Kinetics can prove a reaction mechanism. [T/F]
F
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What is the half-time in a reaction?
The time for one-half of the starting amount to disappear.
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A typical enzyme-catalyzed reaction must pass through a ____ ____.
transition state
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The reaction rate is proportional to.....
the concentration of reactant molecules with the transition-state energy
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The energy barrier of the transition state is known as ____.
the free energy of activiation (delta G++)
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What is the abbreviation for the free energy of activation?
delta G++
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Decreasing delta G++ _______ the reaction rate.
increases
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Decreasing ______ increases the reaction rate.
delta G++
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What is the difference between delta G and delta G++?
- free energy change for a reaction is related to the equilibrium constant
- the free energy of activation for a reaction is related to the rate constant
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Enzymes work by ___ the ____ by ____ with the ____, which promotes entry into the ____, ____ structure that promotes conversion to _____.
- lowering;
- free energy of activation;
- combining;
- reactants;
- reactive, transition state;
- product
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When S is low, the equation for rate is __ order in S
1st
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When S is high, the equation for rate is __ order in S.
0
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When S is high, even if you add more substrate, the rate would ____.
Thus v= ? at this point.
not increase; v=Vmax
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The Michaelis-Menten equation describes a....
rectangular hyperbolic dependence of v on S
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What is another name for Kcat?
The turnover number
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What is Kcat?
the number of substrate molecules converted to product per enzyme molecule per unit of time, when E is saturated with substrate
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What is the formula for catalytic efficiency?
Kcat/Km
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