BCH4024 EXAM 1 QUESTIONS
WITH CORRECT DETAILED
ANSWERS GRADED A+
Chymotrypsin Reaction - Answer- - Digestive enzyme that breaks down proteins
(protease) in the small intestine
- Cleaves at the C-terminal of aromatic AA's
Michaelis-Menten equation - Answer- v = Vmax/1 + (Km/[S])
Michaelis Menten Explained - Answer- - At low [S], the velocity is linearly dependent on
[S] (pre-steady state phase)
- Steady State Phase: constant amount of product being formed (Rate of ES creation
equals ES breakdown)
-V max (maximal velocity) is the rate at which products are formed if every enzyme is
saturated with substrate; not a true constant because it depends on enzyme
concentration
- Km is the substrate concentration that gives a rate,V0,equal to half of Vmax
- Smaller Km value is better because takes less S to reach half max V
- Km and Vm are determined experimentally by testing the initial reaction rates for a
given number of enzymes at multiple concentrations of substrate
- Kcat is the limiting rate constant (turnover number; max number of substrate
molecules an enzyme can convert per unit time)
- Larger Kcat value is better because means enzyme can turnover more substrate
molecules per given time period, measures catalytic efficiency
- A true constant
- Kd is a measure of affinity, lower Kd means higher affinity
Competitive Inhibition (reversible) - Answer- - Inhibitor competes with substrate for
active site
- Km is increased because you need more substrate to reach the half max V
- Vm is constant because given enough substrate, you can overcome the effects of the
inhibitor (poor drug design), Vm is also constant because enzyme concentration stays
the same
Noncompetitive Inhibition (reversibile) - Answer- - Inhibitor binds to allosteric site
- Lowers Vm, Km is unchanged
- Km is a measure of affinity of the enzyme for its Substrate and this can only be
measure by an active enzyme
- Good drug design because it makes the enzyme inactive, so raising substrate
concentration won't fully overcome it
, - Taking away enzymes by making them inactive, lowers Vm, slower max rate if fewer
enzymes
- Enzyme already has an allosteric site for inhibitor to bind to, inhibitor can bind
independent of substrate (compare to uncompetitive)
Uncompetitive Inhibition (reversible) - Answer- - Rare form of inhibition
- These inhibitors bind only to the ES complex and essentially lock the substrate in the
enzyme, preventing its release
- Allosteric site for inhibitor to bind to is only present after the substrate binds
- Decreased Vm
-- Decrease in active enzyme concentration decreases the maximum velocity rate
Metabolism - Answer- totality of cellular processes that make and degrade chemical
substances
Anabolism - Answer- pathways that synthesize biomolecules from simpler precursor
metabolites
Allosteric regulation of enzymes - Answer- reversible binding of regulatory molecules
alters enzyme conformation & activity (µsec-to-msec timescale)
Reversible covalent modification of enzymes - Answer- - A group from a donor molecule
is transferred to a target enzyme to change its catalytic activity (msec timescale)
- This post-translational modification can be removed to reverse these effects (msec-to-
sec timescale)
Induction and repression of enzymes - Answer- - the concentration of enzyme is
controlled at the gene and/or mRNA level (1-1000 second timescale)
Bioenergetics and metabolism - Answer- is the systematic study of energy-transducing
processes to learn
- How cells extract energy from environment
- How they use this energy to synthesize biomolecules to drive energy-requiring
processes
- How the efficiency of biological pathways changes in disease or under metabolic
stress
1st law of thermodynamics - Answer- energy may change in form or be transported,
BUT it cannot be created or destroyed
2nd law of thermodynamics - Answer- the entropy (randomness) of the universe (i.e., a
system & its surroundings) always increases
Gibbs free energy equation - Answer- ΔG = ΔH - TΔS
WITH CORRECT DETAILED
ANSWERS GRADED A+
Chymotrypsin Reaction - Answer- - Digestive enzyme that breaks down proteins
(protease) in the small intestine
- Cleaves at the C-terminal of aromatic AA's
Michaelis-Menten equation - Answer- v = Vmax/1 + (Km/[S])
Michaelis Menten Explained - Answer- - At low [S], the velocity is linearly dependent on
[S] (pre-steady state phase)
- Steady State Phase: constant amount of product being formed (Rate of ES creation
equals ES breakdown)
-V max (maximal velocity) is the rate at which products are formed if every enzyme is
saturated with substrate; not a true constant because it depends on enzyme
concentration
- Km is the substrate concentration that gives a rate,V0,equal to half of Vmax
- Smaller Km value is better because takes less S to reach half max V
- Km and Vm are determined experimentally by testing the initial reaction rates for a
given number of enzymes at multiple concentrations of substrate
- Kcat is the limiting rate constant (turnover number; max number of substrate
molecules an enzyme can convert per unit time)
- Larger Kcat value is better because means enzyme can turnover more substrate
molecules per given time period, measures catalytic efficiency
- A true constant
- Kd is a measure of affinity, lower Kd means higher affinity
Competitive Inhibition (reversible) - Answer- - Inhibitor competes with substrate for
active site
- Km is increased because you need more substrate to reach the half max V
- Vm is constant because given enough substrate, you can overcome the effects of the
inhibitor (poor drug design), Vm is also constant because enzyme concentration stays
the same
Noncompetitive Inhibition (reversibile) - Answer- - Inhibitor binds to allosteric site
- Lowers Vm, Km is unchanged
- Km is a measure of affinity of the enzyme for its Substrate and this can only be
measure by an active enzyme
- Good drug design because it makes the enzyme inactive, so raising substrate
concentration won't fully overcome it
, - Taking away enzymes by making them inactive, lowers Vm, slower max rate if fewer
enzymes
- Enzyme already has an allosteric site for inhibitor to bind to, inhibitor can bind
independent of substrate (compare to uncompetitive)
Uncompetitive Inhibition (reversible) - Answer- - Rare form of inhibition
- These inhibitors bind only to the ES complex and essentially lock the substrate in the
enzyme, preventing its release
- Allosteric site for inhibitor to bind to is only present after the substrate binds
- Decreased Vm
-- Decrease in active enzyme concentration decreases the maximum velocity rate
Metabolism - Answer- totality of cellular processes that make and degrade chemical
substances
Anabolism - Answer- pathways that synthesize biomolecules from simpler precursor
metabolites
Allosteric regulation of enzymes - Answer- reversible binding of regulatory molecules
alters enzyme conformation & activity (µsec-to-msec timescale)
Reversible covalent modification of enzymes - Answer- - A group from a donor molecule
is transferred to a target enzyme to change its catalytic activity (msec timescale)
- This post-translational modification can be removed to reverse these effects (msec-to-
sec timescale)
Induction and repression of enzymes - Answer- - the concentration of enzyme is
controlled at the gene and/or mRNA level (1-1000 second timescale)
Bioenergetics and metabolism - Answer- is the systematic study of energy-transducing
processes to learn
- How cells extract energy from environment
- How they use this energy to synthesize biomolecules to drive energy-requiring
processes
- How the efficiency of biological pathways changes in disease or under metabolic
stress
1st law of thermodynamics - Answer- energy may change in form or be transported,
BUT it cannot be created or destroyed
2nd law of thermodynamics - Answer- the entropy (randomness) of the universe (i.e., a
system & its surroundings) always increases
Gibbs free energy equation - Answer- ΔG = ΔH - TΔS
