Tutorial Practice Questions - Week 9 Flashcards
Which of the following is not a function of an enzyme?
a) Accelerate the rate of a process
b) Lower the activation energy of a reaction
c) Shift the equilibrium between products and reactants
d) Speed up biological processes
e) Lower the energy of the transition state
c)
What is the active site of an enzyme?
a) Is the portion of the substrate that the enzyme binds to, initiating a chemical
reaction
b) Is a portion of the enzyme that allows the enzyme to diffuse through the
plasma membrane, allowing it to exit the cell
c) Is the portion of the enzyme that engulfs bacteria and other foreign particles
in the cell
d) Is the portion of the enzyme that substrates bind to, initiating a chemical
reaction
e) Is the portion of the enzyme that DNA binds to, initiating a chemical reaction
d)
An allosteric inhibitor 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
c)
With regards to the Michaelis-Menten equation, a molecule that has the effect of
increasing the V max of a reaction upon binding to an enzyme would be called what?
a) Competitive inhibitor
b) Non-competitive inhibitor
c) Uncompetitive inhibitor
d) Activator
d)
Potassium cyanide is a poison, which combines with cytochrome c to prevent binding of
oxygen to the enzyme without altering the KM . Which type of inhibition does this
represent?
a) Competitive inhibitor
b) Non-competitive inhibitor
c) Uncompetitive inhibitor
d) Activator
e) Irreversible inhibitor
b)
Estimate the V max and KM of the enzyme-catalyzed reaction for which the data in the table were obtained.
Which of the following is true regarding enzymes saturated with substrate?
a) An enzyme with lower KM is more easily saturated than an enzyme with high
KM
b) At saturating levels of substrate, a competitive inhibitor will affect the
reaction rate more than a non-competitive inhibitor
c) Any excess substrate will shift the equilibrium towards the product end of the
reaction
d) Increasing the substrate concentration will appreciably increase the reaction
rate
a
(The only thing that changes an equilibrium constant is a change of temperature. The position of equilibrium is changed if you change the concentration of something present in the mixture)
S-Adenosyl methionine (SAM) is a molecule utilised in various metabolic pathways to
transfer methyl groups from SAM to an acceptor. What is the proper designation of the complex of SAM and its enzyme together?
a) Prosthetic group
b) Coenzyme
c) Holoenzyme
d) Cofactor
c)
Which of the following is true concerning the induced fit model of enzyme catalysis?
a) The active site can be influenced by molecules binding elsewhere on an enzyme
b) The initial binding of enzyme and substrate is the most tightly bound
conformation
c) The binding of enzyme and substrate is weakest in the transition state
d) The induced fit must occur prior to the initial binding of enzyme and substrate in
order for the reaction to proceed
V max = 140 μM/min
KM = 10 μM
a)
In the induced fit model of enzyme action,
a) the substrate exactly fits multiple enzymes.
b) many substrates fit every enzyme.
c) the enzyme changes shape slightly to accommodate the substrate.
d) the enzyme doesn’t fit the substrate until it is induced by another substrate.
c)
An antibiotic that binds the active site of an enzyme but does not change its structure,
and when the antibiotic is removed, the enzyme returns to normal function. What kind of
interaction describes the action of the antibiotic in the enzyme?
a) Irreversible inhibitor
b) Uncompetitive inhibitor
c) Denaturation
d) Non-competitive inhibition
e) Competitive inhibition
e)
You are reading about the functions of a unique chemical compound. This compound
inhibits the activity of enzymes throughout the body by altering the shape of the enzyme
without blocking the active site. This compound functions via which mechanism?
a) Non-competitive inhibition
b) Competitive inhibition
c) Allosteric activation
d) Irreversible inhibition
a)
Which of the following factors influences the rate at which enzymes catalyse a reaction?
a) Concentration of substrate and enzyme
b) Temperature of environment
c) pH of environment
d) All of these factors have an effect on the rate at which enzymes catalyse a
reaction
d)
Consider the reaction: H2 CO 3 → CO2 + H 2 O
This reaction is catalysed by an enzyme called carbonic anhydrase. If the concentration of carbonic anhydrase is increased, which of the following statements is
true?
a) It will decrease the equilibrium constant
b) It will have no effect on the equilibrium constant
c) It will cause reaction to go slower
d) It will increase the equilibrium constant
b)
In physiological reactions there is an optimum temperature at which an enzyme
operates. Increasing the temperature beyond this will not increase enzyme activity or reaction rate. What explains this phenomenon?
a) Heat will shift the equilibrium to the left, favouring the reactant side
b) Increasing the temperature will decrease the activation energy
c) Increasing the temperature will increase the activation energy
d) High temperatures will change the shape and functionality of proteins
d)
