UNIT 1 UNE CHEM 1005 EXAM QUESTIONS AND
ANSWERS
Hemoglobin binds oxygen with a greater affinity in the:
R state
Hemoglobin bound to heme is termed a holoprotein. The heme or porphoryin ring
is required for oxygen binding and it is termed a:
prosthetic group
Alpha helices and beta sheets are primarily stabilized by:
H bonding
Ligases are a class of enzymes characterized by their ability to:
synthesize bonds between carbon atoms and an additional atom that is involved in the
cleavage of a high energy bond.
An enzyme inhibitor that increases the Km but does not change the Vmax is
classified as:
competitive inhibitor
Cleavage of fructose 1, 6 bisphosphate to dihydroxyacetone and glyceraldehyde
3-phosphate is achieved by what class of enzymes:
lyase
Enzymes reduce the activation energy for a reaction. All enzymes do this by:
providing an active site most complementary the transition state, Enzymes help to
reduce the activation energy of a reaction by stabilizing high energy intermediates. By
have a flexible active site that is highly complementary to the transition state of a
substrate this is most readily achieved.
The activity of an enzyme is increased when the enzyme is phosphorylated on an
exposed tyrosine residue. Phosphorylation of this amino acid is classified as
which of the following?
covalent modification, Phosphorylation is a covlanet modification to an enzyme that can
increase or decrease the activity of an enzyme.
Under low energy conditions, AMP will bind to phosphofructokinase I and
glycogen phosphorylase. This is an example of which of the follow types of
enzyme regulation?
allosteric activation
Which of the following is an example of enzyme regulation through covalent
modification?
Phosphorylation of muscle glycogen phosphorylase
Movement of ammonia from an amino acid to an alpha-keto acid involves a family
of enzymes best categorized as:
Transferases
An alpha-helical arrangement of amino acids is considered to be part of what
level of protein structure?
secondary structure of the protein
An example of enzyme activation by cleavage is best illustrated by which of the
following?
activation of chymotrypsinogen to chymotrypsin
, Coenzymes are complex nonprotein molecules that participate in catalysis by
providing functional groups that form a covalent intermediate between the
enzyme and the substrate. Which of the following is an example of a coenzyme
that participates in an activation-transfer reaction?
Thiamaine pyrophosphate (TPP)
Motifs are common structural elements that retain a particular function within the
protien. Which of the following is an example of a protein motif?
An arrangment of β-strands connected by α - helicies (βαβαβ)
What is an allosteric activator?
a. binds and puts active site in optimal configuration which
favors substrate binding, higher efficiency
b. noncovalent, so reversible
c. also dependent on enzyme concentration
What is an allosteric inhibitor?
a. binds to enzyme and changes shape of active site so substrate cannot bind and
enzyme is turned off
b. binding through noncovalent interactions so are reversible
c. whether or not they bind to enzyme depends on concentration
d. the mechanism behind feedback inhibition
Competitive inhibitors?
Compete with substrate for binding at enzyme's substrate recognition site. This
increases Km because it increases the concentration of substrate needed to saturate
the enzyme, but no change to Vmax.
Noncompetitive inhibitor
Does not compete with substrate for binding at the enzyme's substrate recognition site.
Lowers concentration of active enzyme so Vmax decreases, but no change to Km.
Protein kinases phosphorylate proteins only at a certain hydroxyl groups on
amino acid side chains. All contain side chain hydroxyl groups:
Serine, Threonine, Tyrosine
Globular protein characteristics
Tertiary structure is formed by hydrophobic and electrostatic interactions between
amino acid side chains and by hydrogen bonds between the peptide bonds.
hydrophobic inside, hydrophilic outside.
T/F Heme is not a coenzyme
True
Competitive inhibitor competes with a substrate for binding at enzyme active site.
This interaction causes which of the following changes in enzyme activity?
Addition of competitive inhibitor will not impact Vmax of enzyme.
Enzymes facilitate reactions through this mechanism
Decrease activation energy
Allosteric activator will increase enzyme activity through this mechanism
Binding the enzyme and keeping it in R conformation.
Hemoglobin has the ability to display cooperative binding. The property of
cooperative binding is only displayed by proteins that have __________________
structure.
ANSWERS
Hemoglobin binds oxygen with a greater affinity in the:
R state
Hemoglobin bound to heme is termed a holoprotein. The heme or porphoryin ring
is required for oxygen binding and it is termed a:
prosthetic group
Alpha helices and beta sheets are primarily stabilized by:
H bonding
Ligases are a class of enzymes characterized by their ability to:
synthesize bonds between carbon atoms and an additional atom that is involved in the
cleavage of a high energy bond.
An enzyme inhibitor that increases the Km but does not change the Vmax is
classified as:
competitive inhibitor
Cleavage of fructose 1, 6 bisphosphate to dihydroxyacetone and glyceraldehyde
3-phosphate is achieved by what class of enzymes:
lyase
Enzymes reduce the activation energy for a reaction. All enzymes do this by:
providing an active site most complementary the transition state, Enzymes help to
reduce the activation energy of a reaction by stabilizing high energy intermediates. By
have a flexible active site that is highly complementary to the transition state of a
substrate this is most readily achieved.
The activity of an enzyme is increased when the enzyme is phosphorylated on an
exposed tyrosine residue. Phosphorylation of this amino acid is classified as
which of the following?
covalent modification, Phosphorylation is a covlanet modification to an enzyme that can
increase or decrease the activity of an enzyme.
Under low energy conditions, AMP will bind to phosphofructokinase I and
glycogen phosphorylase. This is an example of which of the follow types of
enzyme regulation?
allosteric activation
Which of the following is an example of enzyme regulation through covalent
modification?
Phosphorylation of muscle glycogen phosphorylase
Movement of ammonia from an amino acid to an alpha-keto acid involves a family
of enzymes best categorized as:
Transferases
An alpha-helical arrangement of amino acids is considered to be part of what
level of protein structure?
secondary structure of the protein
An example of enzyme activation by cleavage is best illustrated by which of the
following?
activation of chymotrypsinogen to chymotrypsin
, Coenzymes are complex nonprotein molecules that participate in catalysis by
providing functional groups that form a covalent intermediate between the
enzyme and the substrate. Which of the following is an example of a coenzyme
that participates in an activation-transfer reaction?
Thiamaine pyrophosphate (TPP)
Motifs are common structural elements that retain a particular function within the
protien. Which of the following is an example of a protein motif?
An arrangment of β-strands connected by α - helicies (βαβαβ)
What is an allosteric activator?
a. binds and puts active site in optimal configuration which
favors substrate binding, higher efficiency
b. noncovalent, so reversible
c. also dependent on enzyme concentration
What is an allosteric inhibitor?
a. binds to enzyme and changes shape of active site so substrate cannot bind and
enzyme is turned off
b. binding through noncovalent interactions so are reversible
c. whether or not they bind to enzyme depends on concentration
d. the mechanism behind feedback inhibition
Competitive inhibitors?
Compete with substrate for binding at enzyme's substrate recognition site. This
increases Km because it increases the concentration of substrate needed to saturate
the enzyme, but no change to Vmax.
Noncompetitive inhibitor
Does not compete with substrate for binding at the enzyme's substrate recognition site.
Lowers concentration of active enzyme so Vmax decreases, but no change to Km.
Protein kinases phosphorylate proteins only at a certain hydroxyl groups on
amino acid side chains. All contain side chain hydroxyl groups:
Serine, Threonine, Tyrosine
Globular protein characteristics
Tertiary structure is formed by hydrophobic and electrostatic interactions between
amino acid side chains and by hydrogen bonds between the peptide bonds.
hydrophobic inside, hydrophilic outside.
T/F Heme is not a coenzyme
True
Competitive inhibitor competes with a substrate for binding at enzyme active site.
This interaction causes which of the following changes in enzyme activity?
Addition of competitive inhibitor will not impact Vmax of enzyme.
Enzymes facilitate reactions through this mechanism
Decrease activation energy
Allosteric activator will increase enzyme activity through this mechanism
Binding the enzyme and keeping it in R conformation.
Hemoglobin has the ability to display cooperative binding. The property of
cooperative binding is only displayed by proteins that have __________________
structure.
