CH 6
ch 6
ch 6
ch 6
ch 6
100
Which of the following is TRUE about enzymes?
Enzymes are often specific for the substrate they will bind
Enzymes typically act under mild (physiological) conditions of temperature and pH.
Enzymes can increase rates of reactions 108 to 1012 times greater than the uncatalyzed reaction.
Enzymes lower the overall delta G for a reaction.
Enzyme activities can often be regulated.
Enzymes are often specific for the substrate they will bind.
Enzymes typically act under mild (physiological) conditions of temperature and pH.
Enzymes can increase rates of reactions 108 to 1012 times greater than the uncatalyzed reaction.
Enzyme activities can often be regulated.
100
How does the addition of an enzyme to a chemical reaction affect each of the following parameters?
Standard free energy of the reaction
Activation energy of the reaction
Velocity of the reaction
Standard free energy of the reaction. No Effect
Activation energy of the reaction.Decrease
Velocity of Reaction. Increase
100
Which type of enzyme catalyzes the following reactions? (Isomerase or Lyase)
a = Isomerase
b = Lyase
100
Each of the following reactions is catalyzed by an enzyme. For each reaction, classify the enzyme according to one of the six main classes suggested by the International Union of Biochemistry. (Lyase, Ligase or Transferase)
A= Ly
B= Li
C= Tr
100
What effect does a catalyst have on the ΔG of a reaction?
It depends on the specific catalyst.
A catalyst has no effect on the ΔG.
A catalyst raises the ΔG.
A catalyst lowers the ΔG.
A catalyst has no effect on the ΔG.
200
Enzymes catalyze reactions by...
covalently modifying active-site residues
binding regulatory proteins
binding a specific substrate and converting it to product
remaining rigid upon the binding of the substrate
binding a specific substrate and converting it to product
200
All are distinctive features of enzymes EXCEPT:
ability to change ΔG.
specificity.
catalytic activity.
regulation.
ability to change ΔG.
200
All of the following are properties of a coenzyme EXCEPT:
They are organic.
They are usually actively involved in the catalytic reaction of the enzyme.
They may contain vitamins as part of their structure.
They are amino acids in the primary structure of the enzyme.
They are amino acids in the primary structure of the enzyme.
200
Which of the following is the most effective way to increase the rate of a biochemical reaction?
add a catalyst
increase or decrease the pH
increase the concentrations of the reactants
increase the temperature
add a catalyst
200
Chymotrypsin uses water to catalyze the hydrolysis of a peptide bond and is therefore categorized as a _____.
lyase
transferase
hydrolase
oxidoreductase
hydrolase
300
The ability for an enzyme to pick out one particular substrate from the myriad of molecules floating around its environment is an example of _____.
natural selection
processivity
specificity
high affinity
specificity
300
The highest point in a reaction coordinate diagram represents _____.
the transition state
the overall G for the reaction
the products in an endergonic reaction
an intermediate of the reaction pathway
the reactants in an exergonic reaction
the transition state
300
Which of the following amino acids would be most likely found in the active site of an enzyme that uses acid-base catalysis?
Trp
Met
Asn
Ser
His
His
300
What amino acid performs the nucleophilic attack during the chymotrypsin mechanism?
His
Cys
Ser
Lys
Ser
300
Of all the species that enzymes bind, they are thought to bind most tightly to _____.
transition states
substrates
products
all are bound very tightly
transition states
400
What amino acid residue present in the specificity pocket allows trypsin to bind to peptides containing Arg or Lys?
Asp
Ser
Lys
His
Asp
400
Which of these amino acid groups would not make a good nucleophilic catalyst in a covalent catalytic mechanism?
hydroxyl
methyl
amino
sulfhydryl
methyl
400
The model that best describes a conformational change in enzyme structure upon binding substrate is referred to as:
The lock-and-key model
The induced-fit model
Induced Fit
400
Each of the following reactions is catalyzed by an enzyme. For each reaction, classify the enzyme according to one of the six main classes suggested by the International Union of Biochemistry. (Hydrolase, Oxidoreductase, or Isomerase)
A=H
B=O
C=I
400
Select below all the amino acid residues that make up the catalytic triad of chymotrypsin.
Ser
His
Lys
Glu
Asp
Thr
Ser His Asp
500
How does an enzyme affect the overall G of an endergonic reaction?
the reaction becomes exergonic
it has no effect
the reaction has a G of zero
the reaction becomes more endergonic
it has no effect
500
How does a catalyst increase the rate of a reaction?
it allows reacting molecules to more easily form the transition state
it increases the temperature of the reaction
it makes the reaction more exergonic
it causes a localized increase in the concentration of reactants
it allows reacting molecules to more easily form the transition state
500
Research scientists are trying to clone a gene. To accomplish this task, they join two pieces of DNA using ATP as the energy source to do this. Which class of the enzymes below might accomplish this task?
oxidoreductase
ligase
lyase
isomerase
hydrolase
ligase
500
An enzyme that forms a covalent bond with its substrate during the course of a reaction is considered to undergo _____.
acid-base catalysis
electrophilic catalysis
metal ion catalysis
covalent catalysis
covalent catalysis
500
A negatively charged intermediate in an enzymatic reaction is stabilized by a Mg2+ in the active site. The enzyme is using which of the catalytic mechanisms?
Covalent Catalysis
Metal ion catalysis
It cannot be determined which type of catalysis the enzyme is using.
Acid/Base Catalysis
Metal ion catalysis