BCH4024 EXAM 1 QUESTIONS
WITH 100% COMPLETE
SOLUTIONS
What is the difference between the concerted model and the sequential model? -
Answer-The concerted model regulates subunit availability while the sequential model
regulates ligand affinity
Explain the Sequential Model - Answer-- The binding of O2 to one subunit causes the
other subunits to change into R-state
- Affinity increases with each O2 molecule that binds
CO and the Concerted Model - Answer-- CO binds 200x tighter than O2; O2 bound to
Hb in the presence of CO binds more tightly and cannot be released to the tissues
- Hyperbolic curve in the presence of CO ONLY explained by Concerted Model
-- Binding of CO drives Hb into R state, because each subunit has the same affinity, CO
is likely to bind
Enzyme key facts!!! - Answer-- They increase reactivity (reaction rate) without altering
equilibrium (doesn't alter amount of products or reactants)
- Increases forward and reverse reaction rate equally
- They can be regulated
- Exhibit substrate specificity (prevents unwanted reactions from taking place)
- Most are proteins (more flexible than RNA, though some are still left over from early
evolution)
-Optimizes nucleophile-electrophile orbital alignment (position groups in best/most
efficient way possible)
- Changes conformation during catalysis, but always returns back to its original form
after each round
- Stabilizes oxy-anion and other unstable intermediates (ex: chymotrypsin)
- Reduces energetic barrier (lowers amount of activation energy needed)
- Desolvation: removes water to reactivate nucleophilic reactions
What are the six classes of enzymes and the unofficial seventh class? - Answer-1.
Oxidoreductases
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases
7. Ergases (unofficial)
, Oxidoreductase function and example - Answer-- Catalyzes oxidation reduction
reactions (transfer electrons)
Ex) Ethanol + NAD → Acetaldehyde + NADH + H
Transferases function and example - Answer-- Catalyzes transfer of functional groups
(group transfer)
Ex) Glucose + ATP → Glucose 6P + ADP
Hydrolases function and example - Answer-- Catalyzes hydrolysis of covalent bonds
(add water to break things)
Ex) Glucose 6P + H2O → Glucose + Pi
Lyases function and example - Answer-- Catalyzes elimination/addition of a functional
group (biological scissors)
Ex) Malate → H2O + Fumarate
Isomerases function and example - Answer-- Catalyzes intramolecular rearrangement
(same molecular formula)
Ex) Glucose 6P → Fructose 6P
Ligases function and example - Answer-- Catalyzes joining of molecules (biological
tape/glue)
Ex) Glutamate + NH3 + ATP → Glutamine + ADP + Pi
Ergases function and example - Answer-- Converts chemical bond energy into
mechanical energy
Ex) ATP + Myosin at Position 1 → Myosin at Position 2 + ADP + Pi
The ____ is found at the highest energy point on a reaction coordinate? - Answer-
Transition state
Lock and Key mechanism - Answer-Originally thought to be the correct mechanism, but
if the active site were complementary to the substrate, it would be stuck in the ES
complex because it's so stable
equilibrium constant - Answer-Keq = [P]/[S]
- Concentrations of substrates and products at equilibrium
If Keq > 1 in the Equilibrium Constant, - Answer-more products are at equilibrium
If Keq < 1 in the Equilibrium Constant, - Answer-more reactants are at equilibrium
What does the equilibrium constant tell us? - Answer-which direction the reaction is
occurring in
WITH 100% COMPLETE
SOLUTIONS
What is the difference between the concerted model and the sequential model? -
Answer-The concerted model regulates subunit availability while the sequential model
regulates ligand affinity
Explain the Sequential Model - Answer-- The binding of O2 to one subunit causes the
other subunits to change into R-state
- Affinity increases with each O2 molecule that binds
CO and the Concerted Model - Answer-- CO binds 200x tighter than O2; O2 bound to
Hb in the presence of CO binds more tightly and cannot be released to the tissues
- Hyperbolic curve in the presence of CO ONLY explained by Concerted Model
-- Binding of CO drives Hb into R state, because each subunit has the same affinity, CO
is likely to bind
Enzyme key facts!!! - Answer-- They increase reactivity (reaction rate) without altering
equilibrium (doesn't alter amount of products or reactants)
- Increases forward and reverse reaction rate equally
- They can be regulated
- Exhibit substrate specificity (prevents unwanted reactions from taking place)
- Most are proteins (more flexible than RNA, though some are still left over from early
evolution)
-Optimizes nucleophile-electrophile orbital alignment (position groups in best/most
efficient way possible)
- Changes conformation during catalysis, but always returns back to its original form
after each round
- Stabilizes oxy-anion and other unstable intermediates (ex: chymotrypsin)
- Reduces energetic barrier (lowers amount of activation energy needed)
- Desolvation: removes water to reactivate nucleophilic reactions
What are the six classes of enzymes and the unofficial seventh class? - Answer-1.
Oxidoreductases
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases
7. Ergases (unofficial)
, Oxidoreductase function and example - Answer-- Catalyzes oxidation reduction
reactions (transfer electrons)
Ex) Ethanol + NAD → Acetaldehyde + NADH + H
Transferases function and example - Answer-- Catalyzes transfer of functional groups
(group transfer)
Ex) Glucose + ATP → Glucose 6P + ADP
Hydrolases function and example - Answer-- Catalyzes hydrolysis of covalent bonds
(add water to break things)
Ex) Glucose 6P + H2O → Glucose + Pi
Lyases function and example - Answer-- Catalyzes elimination/addition of a functional
group (biological scissors)
Ex) Malate → H2O + Fumarate
Isomerases function and example - Answer-- Catalyzes intramolecular rearrangement
(same molecular formula)
Ex) Glucose 6P → Fructose 6P
Ligases function and example - Answer-- Catalyzes joining of molecules (biological
tape/glue)
Ex) Glutamate + NH3 + ATP → Glutamine + ADP + Pi
Ergases function and example - Answer-- Converts chemical bond energy into
mechanical energy
Ex) ATP + Myosin at Position 1 → Myosin at Position 2 + ADP + Pi
The ____ is found at the highest energy point on a reaction coordinate? - Answer-
Transition state
Lock and Key mechanism - Answer-Originally thought to be the correct mechanism, but
if the active site were complementary to the substrate, it would be stuck in the ES
complex because it's so stable
equilibrium constant - Answer-Keq = [P]/[S]
- Concentrations of substrates and products at equilibrium
If Keq > 1 in the Equilibrium Constant, - Answer-more products are at equilibrium
If Keq < 1 in the Equilibrium Constant, - Answer-more reactants are at equilibrium
What does the equilibrium constant tell us? - Answer-which direction the reaction is
occurring in
