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