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WorksheetsBiochem Exam 3
Total questions: 42
Worksheet time: 23mins
What is the first law of thermodynamics?
The entropy of an ordered system approaches zero as the temp approaches absolute zero (0 K)
The energy of an isolated system is conserved
The entropy of the universe is increasing
What is the second law of thermodynamics?
The entropy of an ordered system approaches zero as the temp approaches absolute zero (0 K)
The entropy of the universe is increasing
The energy of an isolated system is conserved
What is the third law of thermodynamics?
The entropy of an ordered system approaches zero as the temp approaches absolute zero (0 K)
The energy of an isolated system is conserved
The entropy of the universe is increasing
Define free energy (G: Gibbs)
the disorder of the system
the amount of heat required or transferred by the system
total energy of the system that is available for work
Define enthalpy (H)
the amount of heat required or transferred by the system
total energy of the system that is available for work
the disorder of the system
Define entropy (S)
the amount of heat required or transferred by the system
the disorder of the system
total energy of the system that is available for work
Gibbs free energy equation: Δ__= Δ__ - __Δ__
(a)
ΔG is equal to G(products) - G(reactants)
true
false
When ΔG > 0, the reaction is _________, requires energy to proceed.
endergonic
exergonic
endothermic
exothermic
When ΔG<0 the reaction is ___________, and will proceed spontaneously as written.
endergonic
exergonic
endothermic
exothermic
When ΔH > 0 the reaction is said to be _______________.
endothermic
exothermic
endergonic
exergonic
When ΔH < 0 the reaction is said to be _____________-
endergonic
exergonic
endothermic
exothermic
When ΔG = 0 the reaction is at equilibrium.
true
false
When ΔS < 0 the system chemical reaction is less disordered, when ΔS > 0 the chemical reaction is more disordered.
true
false
Which is the equation for the equilibrium constant?
Keq = [C][D]/[A][B]
Keq = [A][B]/[C][D]
Which is/are the equation(s) of standard free energy?
ΔG0' = -RT ln Keq
ΔG0' = RT ln Keq
ΔG0'= -RT ln ([C][D]/[A][B])
ΔG0'= RT ln ([C][D]/[A][B])
Define standard free energy (ΔG0')
Under standard conditions (reactants and products are at 1M concentration, 1 atm pressure and pH 7), relates to the equilibrium constant in the following way: ΔG0' = -RT ln Keq
Under standard conditions (reactants and products are at 2M concentration, 2 atm pressure and pH 7.2), relates to the equilibrium constant in the following way: ΔG0' = -RT ln Keq
Under standard conditions (reactants and products are at 3M concentration, 1 atm pressure and pH 7), relates to the equilibrium constant in the following way: ΔG0' = -RT ln Keq
Under standard conditions (reactants and products are at 1M concentration, 4 atm pressure and pH 7), relates to the equilibrium constant in the following way: ΔG0' = -RT ln Keq
All high energy molecules have ________ kJ/mol when hydrolyzed.
positive
negative
What is an enzyme?
biological molecule that catalyzes a chemical reaction
lowers the activation energy of the reaction
catalyzes reactions (in both directions) that would occur anyway
catalyzes reactions (reactants to products only) that would occur anyway
Enzymes:
enhance the rate of favorable reactions
make reactions happen that otherwise would not
specificity enhances yield
catalyze specific reactions
oxidoreductases:
transfer a functional group from one substance to another
formation of two products from a substrate by hydrolysis
catalyze oxidation/reduction reactions; transfer of H and O atoms or electrons from one substance to another
intramolecular rearrangement; ie isomerization changes within a single molecule
transferases:
intramolecular rearrangement; ie isomerization changes within a single molecule
formation of two products from a substrate by hydrolysis
catalyze oxidation/reduction reactions; transfer of H and O atoms or electrons from one substance to another
transfer a functional group from one substance to another
hydrolases:
transfer a functional group from one substance to another
formation of two products from a substrate by hydrolysis
join together two molecules by synthesis of new C-O, C-S, C-N, or C-C bonds with simultaneous breakdown of ATP
catalyze oxidation/reduction reactions; transfer of H and O atoms or electrons from one substance to another
Lyases:
transfer a functional group from one substance to another
non-hydrolytic addition or removal of groups from substrates. C-C, C-N, C-O, or C-S bonds may be cleaved
join together two molecules by synthesis of new C-O, C-S, C-N, or C-C bonds with simultaneous breakdown of ATP
formation of two products from a substrate by hydrolysis
Isomerases:
intramolecular rearrangement; ie isomerization changes within a single molecule
join together two molecules by synthesis of new C-O, C-S, C-N, or C-C bonds with simultaneous breakdown of ATP
non-hydrolytic addition or removal of groups from substrates. C-C, C-N, C-O, or C-S bonds may be cleaved
formation of two products from a substrate by hydrolysis
Ligases:
non-hydrolytic addition or removal of groups from substrates. C-C, C-N, C-O, or C-S bonds may be cleaved
intramolecular rearrangement; ie isomerization changes within a single molecule
formation of two products from a substrate by hydrolysis
join together two molecules by synthesis of new C-O, C-S, C-N, or C-C bonds with simultaneous breakdown of ATP
Metals in enzymes:
stabilizes negative charge or electron density of transition state
electrophilic catalyst
can provide strong nucleophile at neutral pH, resulting in deprotonation
Define metal-activated enzyme:
transient binding of metal, usually only during catalytic event
metal that binds to an enzyme to stop a reaction
What is Km?
relates the velocity of a reaction to the substrate concentration
number of substrate molecules converted to product per enzyme molecule per unit of time
the fastest a reaction will go
Define kcat:
number of substrate molecules converted to product per enzyme molecule per unit time
relates the velocity of a reaction to the substrate concentration
the fastest a reaction will go
Choose the 3 ways enzymes destabilize the substrate to prepare it for conversion to product:
Entropy reduction
Desolvation
Electrostatics
Increase time in transition state
Enzymes ________ transition state
destabilize
stabilize
Enzymes _______ activation energy
increase
decrease
Destabilization of the _________ drives the reaction to the transition state.
substrate
enzyme
product
Acid-Base Catalysis:
all enzyme reactions will involve some acid-base catalysis
H+ and OH- accelerate the reaction
proton donation or acceptance may come from buffer
the proton transfers in the transition state
Aspartic Proteases:
active at basic pH
active at acidic pH
utilize a catalytic dyad of aspartic acids for hydrolysis of peptide bond
homodimer with active site at cleft between domains
do not form covalent bonds with substrate
Define enzyme inhibition:
decrease in velocity of enzyme reaction in the presence of a second agent
decrease in velocity of enzyme reaction in the presence of a tertiary agent
Classify an inhibitor that interacts through non-covalent interactions
reversible
irreversible
competitive
noncompetitive
Classify an inhibitor that interacts via stable, covalent adducts to enzyme
reversible
irreversible
competitive
noncompetitive
Classify an inhibitor that binds at the active site
reversible
irreversible
competitive
noncompetitive
Classify an inhibitor that binds at a secondary site
reversible
irreversible
competitive
noncompetitive
Does dilution or dialysis of the enzyme release the inhibitor in irreversible inhibition?
yes
no
