TUTORIAL 13 QUESTIONS! Flashcards
An allosteric activator does which of the following?
a) Binds to an enzyme away from the active site and changes the conformation of the active site, increasing its
affinity for substrate binding.
b) Binds to the active site and blocks it from binding substrate.
c) Binds to an enzyme away from the active site and changes the conformation of the active site, decreasing its
affinity for the substrate.
d) Binds directly to the active site and mimics the substrate
a
With regards to the Michaelis-Menten equation, a molecule that has the effect of decreasing the Vmax of a reaction upon binding to an enzyme would be called what?
a) Competitive inhibitor
b) Non-competitive inhibitor
c) Uncompetitive inhibitor
d) Activator
b, c
If the ΔG’0 of the reaction A → B is -40 kJ/mol, under standard conditions the reaction
a) is at equilibrium.
b) will proceed spontaneously from left to right.
c) will proceed spontaneously from right to left.
d) will never reach equilibrium.
e) will proceed at a rapid rate.
b
Which of the following is the best way to judge the relative activation energies between two given chemical
reactions?
a) Compare the ΔG values between the two reactions.
b) Compare their reaction rates.
c) Compare their ideal environmental conditions.
d) Compare the spontaneity between the two reactions
b
A biochemical reaction (A +B -> C+ D) has a positive ΔG0 value. Which statement(s) is (are) true about this reaction
a) The reaction is at equilibrium
b) The equilibrium constant, Keq, is > 1
c) The equilibrium constant, Keq, is < 1
d) In standard conditions, the reverse reaction is favoured
e) In standard conditions, the forward reaction is favoured
c, d
Which of the following is (are) true about enzymes:
a) They increase ΔG of reactions.
b) They are usually made of amino acids.
c) They lower the activation energy of chemical reactions.
d) They are specific to the particular substrate(s) to which they binds.
b, c, d
Estimate the Vmax and KM of the enzyme-catalyzed reaction for which the data in the table were obtained.
In the Michaelis-Menten plot (V0 versus [S]), why does the curve flatten out?
The curve flattens because all the enzyme’s active site is
saturated with substrate
Biological oxidation-reduction reactions always involve ________________ .
a) transfer of electron(s)
b) direct participation of oxygen
c) mitochondria.
d) formation of water.
e) transfer of hydrogens.
a
Enzymes that catalyse oxidation-reduction reactions:
a) often use NADH and NADPH as coenzymes
b) are classified as transferases because they transfer electrons
c) are classified as oxidoreductases
d) are classified as hydrolases because they use water as a reagent
e) always break covalent bonds
a, c
Rapid fine control of enzyme activity is important to regulate metabolic pathways, select two ways to achieve that:
a. Covalent modification via phosphorylation/dephosphorylation
b. Hormonal regulation
c. Allosteric regulation via feedback inhibition
d. Synthesis of more enzyme via gene expression
a, c
Slow coarse control of enzyme activity is important to regulate metabolic pathways, name two ways to achieve that:
a. Changes in substrate concentration
b. Changes in energy status
c. Synthesis of regulatory enzymes via gene expression
d. Spatial segregation of enzymes/substrates via compartmentation
c
Anabolic pathways often:
a. Are oxidative
b. Synthesise ATP
c. Consume ATP
d. Are reductive
e. Involve the synthesis of larger molecules
f. Involve the degradation of macromolecules to smaller molecules
c, d, e
- Which enzyme exerts the most control on gluconeogenesis?
a. Hexokinase
b. Fructose 1,6 biphosphatase-1
c. Glucose-6-phosphatase
d. Pyruvate carboxylase
b
