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WorksheetsMCHAPTER 14
Total questions: 42
Worksheet time: 43mins
Which of the following statements regarding enzyme is TRUE
Enzyme decreases the free energy change of a reaction
Enzyme changes the direction of chemical reaction
Enzyme increase rate of reaction
Enzyme prevents changes in substrate concentration
An enzyme catalyses a reaction by …
lowering the energy of activation of a reaction
supplying the energy to speed up a reaction.
lowering the free energy of a reaction.
changing the equilibrium of a spontaneous reaction.
What is the active site of an enzyme?
A region that binds allosteric regulators of the enzyme
A region that binds the products of the catalytic reaction
A region that is inhibited by the presence of a coenzyme or a cofactor
A region that is involved in the catalytic reaction of the enzyme
Zinc, an essential trace element for most organisms, is present in the active site of enzyme carboxypeptidase. The zinc most likely functions as
a cofactor necessary for enzyme activity
a competitive inhibitor of the enzyme
a non-competitive inhibitor of the enzyme
a coenzyme derived from a vitamin
Watch the animation and identify the hypothesis involved
Lock and Key hypothesis
Induced Fit hypothesis
Enzyme-Substrate hypothesis
NAD+ is the example of
metal ion activator
coenzyme
prosthetic group
What reduces the productivity of enzymes by preventing substrates from entering active sites?
non competitive inhibitors
competitive inhibitors
coenzymes
cofactors
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
Denaturation of the enzyme
Non- competitive inhibition
Competitive inhibition
Saturation of enzyme activity
According to the induced fit hypothesis of enzyme catalysis, which of the following is CORRECT?
The binding of the substrate slightly changes the shape of the enzyme’s active site
The binding of the substrate depends on the shape of the active site
Some enzymes change their structure when activators bind to the enzyme
A competitive inhibitor can outcompete the substrate for the active site
A series of enzymes catalyze the reaction A --> B --> C --> D. Product D binds to the enzyme that converts A to B at a position other than its active site. This binding decreases the activity of the enzyme. What is substance A?
A substrate
A coenzyme
The product
An allosteric inhibitor
A series of enzymes catalyze the reaction A --> B --> C --> D. Product D binds to the enzyme that converts A to B at a position other than its active site. This binding decreases the activity of the enzyme. What is the function of substance D?
As a coenzyme
As a non-competitive inhibitor
As a competitive inhibitor
As a substrate
Which of these are NOT characteristics of an enzyme.?
Enzymes are highly specific
Can be denatured at high pH
Reusable
Can be denatured at extreme pH
Based on the graph, which of the following could be used to increase the reaction rate beyond point C?
Increase the amount of substrate
Add more water
Increase the temperature
Increase enzyme concentration
When a piece of liver is dropped into hydrogen peroxide, the hydrogen peroxide bubbles vigorously as a result of what reaction?
Hydogen peroxide being broken into water and oxygen
Hydogen peroxide is destroying germs in the liver
More hydogen peroxide is being created by the liver
Liver and hydogen peroxide are joining together to make a new protein
Hydrolases is one important class of enzyme that function to catalyze
conversion between isomers.
splitting of a molecule using water.
reaction in which double bonds are formed.
oxidation-reduction reactions.
Which of the following conclusions can be drawn from this graph?
The optimum pH of the enzyme is 6.6.
The optimum pH of the enzyme is 5.8
The enzyme’s activity increases as pH increases 5.0 to 9.0
The enzyme’s activity is greater around pH of 8.0 .
Only protease can catalyses the breakdown of protein. This shows that enzyme
is a biological catalyst
is highly specific in action
able to speed up chemical reaction
may catalyses reversibly
Enzyme that catalyses the transfer of functional group of atoms from one molecule to another. This enzyme is
Isomerases
Transferases
Oxidoreductase
Lyases
Enzymes in group Isomerases catalyse
the rearrangement of atoms
the transfer of functional group of atoms
the breaking of chemical bond
the formation of bonds
Enzymes function as catalysts because they
Increase the free energy of a chemical reaction
Lower the activation energy of a chemical reaction
Decrease the enthalpy of a chemical reaction
Supply the energy to start a chemical reaction
Cofactors for enzyme are
The protein substance
The inorganic substance
The protein and non-protein substances
The non-protein substance
How does an enzyme increase the rate of reaction?
By shifting the equilibrium point of reaction
By supplying the energy required to start the reaction
By increasing the rate of random collision of molecules
By bringing the reactant molecules to the correct orientation
What happens to an enzyme when it is denatured?
The activation energy is doubled
The activation energy is lowered
The optimal temperature for enzyme action is doubled
The shape of the enzyme molecule is change
In non-competitive inhibitor, the allosteric inhibitor
Binds to the active site, preventing the substrate from binding to the enzyme
Binds to the substrate, preventing it from binding to the active site
Binds to the enzyme at a site away from the active site, altering the shape of the enzyme
Changes the pH of the environment that the enzyme acts in
Transferases are enzymes that
Split chemical bonds by hydrolysis
Catalyse the transfer of an atom or group of atoms from one substrate to another
Rearrange atoms in a substrate
Form bonds with cleavage of ATP
Malonic acid could inhibit the action of succinic dehydrogenase on succinic acid because
Malonic acid could react with succinic acid
Malonic acid could bind at the active site of succinic dehydrogenase
Succinic acid could bind at the active site of succinic dehydrogenase
Succinic acid could not bind at the active site of succinic dehydrogenase
Some enzymes require the presence of a non-protein substance. Which of the following explain such substance in GENERAL?
prosthetic group
cofactor
inducer
co-enzyme
What term is used for a non-protein organic molecule that is required by some enzymes and bind loosely on the enzyme?
co-enzyme
cofactor
prosthetic group
inhibitor
Enzymes are important biological catalysts because they:
supply the energy to initiate a biochemical reaction
increase the free energy of a biochemical reaction
lower the entropy and enthalpy of a biochemical reaction
lower the activation energy of a biochemical reaction
The line on the graph labeled A represents the:
activation energy with an enzyme
activation energy without an enzyme
free energy of the reactants
change in entropy and enthalpy
Competitive inhibition can be overcome by _______________
increase the concentration of substrate
reduce the concentration of enzyme
increase the concentration of enzyme
reduce the concentration of substrate
If one continues to increase the temperature in an enzyme-catalyzed reaction, the rate of the reaction:
increases and then levels off
decreases and then levels off
increases and then decreases rapidly
decreases and then increases rapidly
The reaction rate of an enzyme catalyzed chemical reaction would likely be affected by:
pH
substrate concentration
temperature
all of these are correct
Consider the following: “Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid”.
Which of the following is correct?
Succinate dehydrogenase is the enzyme, and fumarate is the substrate
Succinate dehydrogenase is the enzyme, and malonic acid is the substrate
Succinate is the substrate, and fumarate is the product
Fumarate is the substrate, and malonic acid is a non-competitive inhibitor
What is an organic non-protein "helper" of an enzyme molecule called?
accessory enzyme
allosteric group
cofactor
functional group
The enzyme sucrase acts on
sucrose only
sucrose and starch
any disaccharide
any organic monomer
Which of these statements regarding enzymes is false?
Enzymes are proteins that function as catalysts
Enzymes display specificity for certain molecules with which they interact
Enzymes increase the activation energy for the reactions they catalyze
The activity of enzymes can be regulated by other molecule
The active site of an enzyme is the region that _________
binds allosteric regulators of the enzyme
is involved in the catalytic reaction of the enzyme
binds the product of the catalytic reaction
is inhibited by the presence of a coenzyme or a cofactor
Hydrogen cyanide binds to the active site of an enzyme that is part of the pathway that forms ATP in cells; in this way, it prevents the enzyme’s activity. Hence, hydrogen cyanide can best be described as a :
coenzyme
cofactor
competitive inhibitor
modulator
In which way the enzymatic reaction can be increased if the enzymes are saturated with the substrate?
add more enzymes
add more substrate
increase the temperature
add cofactor
Lyases are enzymes that _____
split chemical bonds by hydrolysis
catalyze the addition or removal of double bond
rearrangement atoms in a substrate
Form bonds with cleavage of ATP
Only a small amount of enzyme is needed for a large amount of substrate because _______
Enzymes do not change at the end of a reaction and as such can be reused
A small amount of enzyme can provide enough energy to continue the reaction
More enzymes are formed while reaction takes place
Enzymes act till completion of a reaction or not at all
