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WorksheetsBIO 091: Enzymes
Total questions: 32
Worksheet time: 17mins
Enzymes
are very specific
are organic molecules
act as catalyst
mostly are fibrous protein
not consumed by the reaction
The active site of an enzyme
is where the coenzyme is located
is a specific bulge on an enzyme
is a groove in the structure of the enzyme
will react with only one substrate no matter how many molecules may resemble to the shape of the substrate
Enzymes function by
lowering the activation energy required for the reaction.
providing the activation energy to substrate molecules
increasing the production of substrate
increasing the temperature of the reaction
Which of the following is FALSE?
All enzymes work best at a neutral pH
Enzymes work well at any pH higher than optimum
At a lower pH, enzyme needs more kinetic energy to function
There is an optimum pH for each specific enzyme.
Substrate binds to enzymes at the
active site
regulatory site
allosteric site
substrate-enzyme complex
Enzymatic reactions can be controlled by
the amount of substrates available
the concentration of products
temperature
presence of inhibitors
An enzyme increases the rate of a reaction by
supplying the energy required to start the reaction
increasing the rate of random collisions of molecules
shifting the point of equilibrium of the reaction
aligning the reacting molecules precisely with each other
Which statement is true of all enzymes?
They are denatured at temperature above 60C
They catalyse the breakdown of large molecules into smaller ones.
They have active sites which can bind to only one kind of substrate.
They reduce the amount of energy required to start a reaction.
The specificity of enzymes is due to
their high molecular weight
their surface conformation
their hydrogen bonding
their pH sensitivity
Which of the following shows that enzymes are proteins?
Enzymes are denatured by high heat
Enzyme activity is not affected by increasing temperature
Enzymes have active sites for binding with substrates
The kinetic energy required to initiated a reaction is called the
activation energy
free energy
bond energy
heat energy
The main characteristic of a competitive inhibitor is its ability to
combine with a prosthetic group
occupy an active site
modify a substrate
occupy an allosteric site
Which statement is true for a non-competitive inhibitor of enzyme activity, but NOT for a competitive inhibitor?
Inhibitor molecules are similar to normal substrate molecule in size and shape
Inhibition can be reduced by increasing the concentration of substrate molecules
Large numbers of inhibitor molecules are needed for effective enzyme inhibition
The inhibitor binds to the enzyme molecules at a position away from the active site
The shape of an enzyme and consequently its activity can be reversibly altered from moment to moment by
heat
allosteric subunits
amino acids substitutions
sulphur substitutions
The active site of an enzyme is formed by a few of the enzyme's
R groups of the amino acids
carboxyl groups of the amino acids
the amino groups of the amino acids
exposed covalent bonds
What is meant by an induced fit?
The binding of the substrate is an energy-requiring process
The active site creates a microenvironment ideal for the reaction
The binding of the substrate changes the shape of the active site
Substrates are held in the active sites by hydrogen and ionic bonds
Zinc, an essential trace elements, may be bound to the active site of some enzymes. Such zinc ions function as?
coenzyme
cofactors
competitive inhibitors
allosteric activators
NAD+ and FAD are
coenzymes
electron acceptors
coenzymea and electron acceptors
coenzymes, electron acceptors and reduced forms
Allosteric inhibition is generally a result of
excees substrates
binding of regulatory molecules at another site
a lack of coenzymes
pH inhibition
How does a non-competitive inhibitor inhibit binding of a substrate to an enzyme?
It binds to the substrate
It binds to the active site
It changes the shape of the active site
It lowers the activation energy
An active site is the
part of the substrate that binds with the enzyme
part of the enzyme that binds with the substrate
site where enzymes are found in the cells
site where energy is added to an enzyme catalyst
Enzymes are highly sensitive to pH and temperature because
changes in the environment raise their activation energy
changes in pH and temperature readily break their hydrogen bonds
of their three-dimensional structure and side chain
coenzymes add chemical groups to the substrate at extreme temperature
All enzymes
are composed primarily of amino acids.
can react rapidly at extremely high temperature due to high kinetic energy.
need cofactors to work.
work well at all pH values
Enzymes can be inactivated by
removing the products as soon as they are formed.
affecting their active sites.
reducing the enzymes concentration by half.
adding coenzymes.
In the graph of reaction rate versus substrate concentration shown, the curve reaches a plateau. Reaction rate does not increase any further at higher substrate concentration because
the active sites of the enzyme molecules are saturated with substrates.
there is a competitive inhibitor present.
there is non-competitive inhibitor present.
all substrates have been converted to products.
What s the difference between the lock and key hypothesis and the induced fir hypothesis?
The configuration of the active site.
The composition of the enzyme.
The type of substrate.
The type of products formed.
Which of the following is true about coenzymes?
They are organic molecule
They transfer chemical groups, atoms or electrons
Are tightly bound to the enzyme,
Which of the following is true about the curves X, Y and Z?
X: competitive inhibitor; Y: non-competitive inhibitor; Z: normal activity
X: normal activity; Y: non-competitive inhibitor; Z: competitive inhibitor
X: non-competitive inhibitor; Y: competitive inhibitor ; Z: normal activity
X: normal activity; Y: competitive inhibitor; Z: non-competitive inhibitor
Enzymes which catalyse oxidation processes include
lipase
dehydrogenase
amylase
peptidase
How does an enzyme increase the rate of reaction?
By bringing the reactant molecules to he correct orientation.
By increasing the rate of random collision of molecules.
By shifting the equilibrium point of reaction.
By supplying the energy required to start the reaction.
The reaction below occurs in the human cell.
Which of the following enzymes catalyses the reaction?
Phosphorylase
Dehydrogenase
Decarboxylase
Kinase
The rate of reaction of salivary amylase on starch decreases when the concentration of chloride ion is reduced. Which of the following explains the role of chloride ion?
Prosthetic group
Coenzyme
Ion activator
Allosteric inhibitor
