BMSC 200 Module 6 Exam Questions
with Correct Answers
How is the enzyme active site structured and why? - ANSWER-From weak
interactions between substrate and enzyme.
The enzyme active site is structured so that some of these weak interactions occur
preferentially in the reaction transition state, thus stabilizing the transition state.
What do additional catalytic mechanisms used by enzymes include? - ANSWER-It
can include covalent catalysis and acid-base catalysis
Most enzymes have certain kinetic properties in common. Describe the process of a
substrate binding to an enzyme and the kinetic relationship. - ANSWER-When
substrate is added to an enzyme, the reaction rapidly achieves a steady state in
which the rate the ES complex is formed balances the rate at which it breaks down.
As [S] increases, the activity increases in a hyperbolic fashion to approach a
characteristic maximal rate, Vmax, at which all the enzyme is saturated with
substrate.
Describe the Michaelis-Menten plots - ANSWER-Michaelis-Menten plots consider
the relationship between substrate concentration and velocity; they can be used to
determine the Km and Vmax of an enzyme.
What is Km? - ANSWER-Km is the concentration of substrate required for an
enzyme to function at half maximal velocity.
Describe the Michaelis-Menten equation - ANSWER-The Michaelis-Menten equation
relates initial velocity to [S] and Vmax through the constant Km.
Derivation of the Michaelis-Menten equation based on the steady-state assumption;
that rate of formation of the ES complex is equal to the rate of its breakdown.
Describe the Lineweaver-Burke plots - ANSWER-Lineweaver-Burke plots are double
reciprocal plots (1/V vs 1/[S]) that also consider the relationship between velocity and
substrate concentration; they can also be used to determine the Km and Vmax of an
enzyme and are more accurate than Michaelis-Menton plots
What are the three categories of reversible enzyme inhibition? - ANSWER-They are
competitive, uncompetitive or noncompetitive
Competitive Inhibitors - ANSWER-Competitive inhibitors bind only the free enzyme
(at the active site) to increase Km with no impact of Vmax.
,Uncompetitive Inhibitors - ANSWER-Uncompetitive inhibitors bind only the ES
complex to decrease both Vmax and Km
Noncompetitive Inhibitors - ANSWER-Noncompetitive inhibitors bind both the free
enzyme and the ES complex to Vmax without changing Km.
Irreversible inhibitors - ANSWER-Irreversible inhibitors bind permanently to an active
site by forming a covalent bond or a very stable non-covalent interaction.
Chymotrypsin - ANSWER-Chymotrypsin is a serine protease with a well-
understanding mechanism, featuring acid-base catalysis, covalent catalysis and
transition-state stabilization.
How are enzymatic pathways regulated? - ANSWER-Enzymatic pathways are often
regulated through feedback inhibition, the end product of a pathway inhibits the first
enzyme of that pathway.
The activity of allosteric enzymes is adjusted by what? - ANSWER-The activity of
allosteric enzymes is adjusted by reversible binding of a specific modulators, which
can be either activator or inhibitors, to regulatory allosteric sites.
Allosteric enzymes do not obtain Michaelis-Menton kinetics, instead they show
what? - ANSWER-They show a sigmoidal relationship between velocity and
substrate concentration.
The threshold effect - ANSWER-It refers to the sensitivity of allosteric enzymes to
changes in the concentration of substrate
Other regulatory enzymes are modulated by covalent modification through what? -
ANSWER-Through the reversible addition of a specific functional group to the
enzyme to regulate some aspect of its function.
What does life depend on? - ANSWER-Life depends on the ability to efficiently and
selectively catalyze chemical reactions
Most biomolecules are very stable with rates of uncatalyzed transformations that are
too slow to permit life
What do enzymes provide? - ANSWER-Enzymes provide a mechanism for
acceleration, regulation, and coordination of these reactions.
Some enzymes are information sensors as well as catalysts.
What is the most striking feature of life? - ANSWER-The most striking feature about
enzymes are their catalytic power and specificity
What must be avoided in chemical reactions in the body? - ANSWER-Side reactions
leading to useless or dangerous molecules must be avoided
, Describe vitalism - ANSWER-Originally biochemical reactions were believed to be
inseparable from life. It was the belief that these phonomems cannot be explained, it
is like "magic", this shows they thought life was too complex to explain. Vitalism is
the belief that living things are fundamentally different from non-living things; that
they contain some non-physical element and are governed by different principles
that inanimate objects. It had some famous supporters, such as Louis Pasteur
Who disproved vitalism and how? - ANSWER-Eduard Buchner demonstrated that
dead yeast still convert sugars into alcohol, indicating the reactions of life were
separate from life.
Enzymes mean "dead yeast"
Therefore, he proves it wasn't magic and that there is something in the yeast which
converts sugar into alcohol. There was a factor in yeast catalyzing the reaction
This work won Eduard Buchner the Nobel Prize, ten years before he was killed in
WWI.
Holoenzyme - ANSWER-Apoenzyme + Cofactor/Coenzyme makes this
Apoenzyme - ANSWER-Is a protein portion, polypeptide chain. It is inactive on its
own. It needs a coenzyme to become active.
Proteins are well suited to form what? - ANSWER-Proteins are well suited to form a
variety of complex three-dimensional structures that enable binding of a variety of
substrates.
For some enzymes, the protein component alone is fully active, however, some
enzymes required what? - ANSWER-Other enzymes require co-factors (inorganic
ions (Mg 2+, Fe 2+ , etc.)) or co-enzymes (complex organic molecules (vitamins)) for
activity.
What is a prosthetic group? What is the difference in these in? - ANSWER-A co-
enzyme or co-factor that is tightly associated with the enzyme is called a prosthetic
group
The difference is the degree of association
Enzymes will usually perform similar functions if? - ANSWER-If the different
enzymes that use the same coenzyme usually perform similar types of reactions.
Describe catalysts - ANSWER-• lower the amount of energy required for a reaction
to proceed.
• sped up attainment of equilibrium but do not change equilibrium.
• are unchanged by the reaction; recycled to participate in another reaction.
Enzymes offer incredible catalytic power in the rate enhancements they provide.
with Correct Answers
How is the enzyme active site structured and why? - ANSWER-From weak
interactions between substrate and enzyme.
The enzyme active site is structured so that some of these weak interactions occur
preferentially in the reaction transition state, thus stabilizing the transition state.
What do additional catalytic mechanisms used by enzymes include? - ANSWER-It
can include covalent catalysis and acid-base catalysis
Most enzymes have certain kinetic properties in common. Describe the process of a
substrate binding to an enzyme and the kinetic relationship. - ANSWER-When
substrate is added to an enzyme, the reaction rapidly achieves a steady state in
which the rate the ES complex is formed balances the rate at which it breaks down.
As [S] increases, the activity increases in a hyperbolic fashion to approach a
characteristic maximal rate, Vmax, at which all the enzyme is saturated with
substrate.
Describe the Michaelis-Menten plots - ANSWER-Michaelis-Menten plots consider
the relationship between substrate concentration and velocity; they can be used to
determine the Km and Vmax of an enzyme.
What is Km? - ANSWER-Km is the concentration of substrate required for an
enzyme to function at half maximal velocity.
Describe the Michaelis-Menten equation - ANSWER-The Michaelis-Menten equation
relates initial velocity to [S] and Vmax through the constant Km.
Derivation of the Michaelis-Menten equation based on the steady-state assumption;
that rate of formation of the ES complex is equal to the rate of its breakdown.
Describe the Lineweaver-Burke plots - ANSWER-Lineweaver-Burke plots are double
reciprocal plots (1/V vs 1/[S]) that also consider the relationship between velocity and
substrate concentration; they can also be used to determine the Km and Vmax of an
enzyme and are more accurate than Michaelis-Menton plots
What are the three categories of reversible enzyme inhibition? - ANSWER-They are
competitive, uncompetitive or noncompetitive
Competitive Inhibitors - ANSWER-Competitive inhibitors bind only the free enzyme
(at the active site) to increase Km with no impact of Vmax.
,Uncompetitive Inhibitors - ANSWER-Uncompetitive inhibitors bind only the ES
complex to decrease both Vmax and Km
Noncompetitive Inhibitors - ANSWER-Noncompetitive inhibitors bind both the free
enzyme and the ES complex to Vmax without changing Km.
Irreversible inhibitors - ANSWER-Irreversible inhibitors bind permanently to an active
site by forming a covalent bond or a very stable non-covalent interaction.
Chymotrypsin - ANSWER-Chymotrypsin is a serine protease with a well-
understanding mechanism, featuring acid-base catalysis, covalent catalysis and
transition-state stabilization.
How are enzymatic pathways regulated? - ANSWER-Enzymatic pathways are often
regulated through feedback inhibition, the end product of a pathway inhibits the first
enzyme of that pathway.
The activity of allosteric enzymes is adjusted by what? - ANSWER-The activity of
allosteric enzymes is adjusted by reversible binding of a specific modulators, which
can be either activator or inhibitors, to regulatory allosteric sites.
Allosteric enzymes do not obtain Michaelis-Menton kinetics, instead they show
what? - ANSWER-They show a sigmoidal relationship between velocity and
substrate concentration.
The threshold effect - ANSWER-It refers to the sensitivity of allosteric enzymes to
changes in the concentration of substrate
Other regulatory enzymes are modulated by covalent modification through what? -
ANSWER-Through the reversible addition of a specific functional group to the
enzyme to regulate some aspect of its function.
What does life depend on? - ANSWER-Life depends on the ability to efficiently and
selectively catalyze chemical reactions
Most biomolecules are very stable with rates of uncatalyzed transformations that are
too slow to permit life
What do enzymes provide? - ANSWER-Enzymes provide a mechanism for
acceleration, regulation, and coordination of these reactions.
Some enzymes are information sensors as well as catalysts.
What is the most striking feature of life? - ANSWER-The most striking feature about
enzymes are their catalytic power and specificity
What must be avoided in chemical reactions in the body? - ANSWER-Side reactions
leading to useless or dangerous molecules must be avoided
, Describe vitalism - ANSWER-Originally biochemical reactions were believed to be
inseparable from life. It was the belief that these phonomems cannot be explained, it
is like "magic", this shows they thought life was too complex to explain. Vitalism is
the belief that living things are fundamentally different from non-living things; that
they contain some non-physical element and are governed by different principles
that inanimate objects. It had some famous supporters, such as Louis Pasteur
Who disproved vitalism and how? - ANSWER-Eduard Buchner demonstrated that
dead yeast still convert sugars into alcohol, indicating the reactions of life were
separate from life.
Enzymes mean "dead yeast"
Therefore, he proves it wasn't magic and that there is something in the yeast which
converts sugar into alcohol. There was a factor in yeast catalyzing the reaction
This work won Eduard Buchner the Nobel Prize, ten years before he was killed in
WWI.
Holoenzyme - ANSWER-Apoenzyme + Cofactor/Coenzyme makes this
Apoenzyme - ANSWER-Is a protein portion, polypeptide chain. It is inactive on its
own. It needs a coenzyme to become active.
Proteins are well suited to form what? - ANSWER-Proteins are well suited to form a
variety of complex three-dimensional structures that enable binding of a variety of
substrates.
For some enzymes, the protein component alone is fully active, however, some
enzymes required what? - ANSWER-Other enzymes require co-factors (inorganic
ions (Mg 2+, Fe 2+ , etc.)) or co-enzymes (complex organic molecules (vitamins)) for
activity.
What is a prosthetic group? What is the difference in these in? - ANSWER-A co-
enzyme or co-factor that is tightly associated with the enzyme is called a prosthetic
group
The difference is the degree of association
Enzymes will usually perform similar functions if? - ANSWER-If the different
enzymes that use the same coenzyme usually perform similar types of reactions.
Describe catalysts - ANSWER-• lower the amount of energy required for a reaction
to proceed.
• sped up attainment of equilibrium but do not change equilibrium.
• are unchanged by the reaction; recycled to participate in another reaction.
Enzymes offer incredible catalytic power in the rate enhancements they provide.
