Use the figure below to compare the activities of glucokinase and hexokinase. Based on this information,
which of the following is a true statement?
Glucokinase has a higher Km than hexokinase.
As illustrated by the graph, hexokinase is able to reach Vmax at a much lower glucose concentration than
glucokinase. Km is defined at ½ the substrate concentration needed to reach Vmax therefore if you
compare the glucose concentration needed to reach Vmax in each case, glucokinase will have a much
greater Km when compared to hexokinase.
Children with cystinosis have growth delay and both renal and ocular issues due to accumulation of
cysteine in cellular lysosomes. The defect involves a specific lysosomal membrane receptor that
facilitates cystine removal from the cell. An effective therapy has been administration of a drug with a
similar structure to cystine. This therapy reflects the general principle that competitive inhibitors typically
resemble the structure of which of the following?
Substrates or ligands that bind the active site
Competitive inhibitors often look like the substrate and compete in the active site for binding. This is the
case in this scenario.
Which of the following is an example of enzyme regulation through covalent modification?
hosphorylation of muscle glycogen phosphorylase
Phosphorylation is a common covalent modification that can have various impacts on activity.
In the image below the blue line indicates enzyme kinetics with no inhibitor present. Based on this
information which of the following is true?
The green line shows enzyme kinetics with the addition of a noncompetitive inhibitor
There is no change in Km with the addition of the drug (as illustrated by the blue and green lines
originating on X axis at the same point). There is a change in Vmax as illustrated by the divergence of the
lines as they cross the X axis. This could be indicative of a noncompetitive inhibitor. Red line illustrates
addition of a competitive inhibitor when compared to control (blue line).
Which of the following best describes an enzyme inhibitor that increases the Km
but does not change the Vmax?
A competitive inhibitor
This the definition of a competitive inhibitor. The addition of a competitive inhibitor can be overcome the
addition of additional substrate therefore Vmax can be achieved but the affinity for the substrate is
reduced.
The following represents a series of reactions. As levels of B increase, this will decrease the conversion of
S3 to B. Which of the following best describes this type of regulation in a biosynthetic pathway?
a) feedback inhibition
, 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?
d) allosteric activation
An example of enzyme activation by cleavage is best illustrated by which of the following?
a) activation of chymotrypsinogen to chymotrypsin
Children with cystinosis have growth delay and renal issues to to accumulation of cysteine in cellular
lysosomes. The defect involves a specific lysosomal membrane receptor that facilitates cysteine removal
from the cell. An effective therapy involves administration of a drug with a similar structure to cysteine.
This therapy reflects the general principle that competitive inhibitors typically resemble the structure of
which of the following?
) substrates or ligands that bind the active site
If a mutation is made within the active site of an enzyme resulting in a decrease of it's Km value, which of
the following will be true with respect to enzyme kinetics?
d) the enzyme will require a lower substrate concentration to reach 1/2 Vmax
Movement of ammonia from an amino acid to an alpha-keto acid involves a family of enzymes best
categorized as:
a) transferases
Cleavage of fructose 1, 6 bisphosphate to dihydroxyacetone and glyceraldehyde 3-phosphate is achieved
by what class of enzymes?
b) lyase
An enzyme is participating in a general acid-base catalysis reaction with an optimal reaction pH of 6.0. If
acid is added to the environment reducing the pH to 3, what is the likely impact to the rate of reaction?
The rate of the reaction is likely to decrease as the pH is out of optimal catalytic range
General acid-base reactions are influenced by the surrounding pH changes. A change in pH from the
optimal pH range of 6.0, will reduce the overall reaction rate.
Covalent catalysis is used by many enzymes to cleave peptide bonds. Which of the following amino acids
would not facilitate this type of catalysis? (Think of the structure of the R-group of these amino acids)
Valine is a nonpolar amino acid and lacks a nucleophile to facilitate the generation of a catalyst- substrate
covalent bond.
Hemoglobin has the ability to display cooperative binding while myoglobin does not display this binding
kinetic pattern. Which of the following differences between the two protein accounts for this difference in
binding kinetics?
which of the following is a true statement?
Glucokinase has a higher Km than hexokinase.
As illustrated by the graph, hexokinase is able to reach Vmax at a much lower glucose concentration than
glucokinase. Km is defined at ½ the substrate concentration needed to reach Vmax therefore if you
compare the glucose concentration needed to reach Vmax in each case, glucokinase will have a much
greater Km when compared to hexokinase.
Children with cystinosis have growth delay and both renal and ocular issues due to accumulation of
cysteine in cellular lysosomes. The defect involves a specific lysosomal membrane receptor that
facilitates cystine removal from the cell. An effective therapy has been administration of a drug with a
similar structure to cystine. This therapy reflects the general principle that competitive inhibitors typically
resemble the structure of which of the following?
Substrates or ligands that bind the active site
Competitive inhibitors often look like the substrate and compete in the active site for binding. This is the
case in this scenario.
Which of the following is an example of enzyme regulation through covalent modification?
hosphorylation of muscle glycogen phosphorylase
Phosphorylation is a common covalent modification that can have various impacts on activity.
In the image below the blue line indicates enzyme kinetics with no inhibitor present. Based on this
information which of the following is true?
The green line shows enzyme kinetics with the addition of a noncompetitive inhibitor
There is no change in Km with the addition of the drug (as illustrated by the blue and green lines
originating on X axis at the same point). There is a change in Vmax as illustrated by the divergence of the
lines as they cross the X axis. This could be indicative of a noncompetitive inhibitor. Red line illustrates
addition of a competitive inhibitor when compared to control (blue line).
Which of the following best describes an enzyme inhibitor that increases the Km
but does not change the Vmax?
A competitive inhibitor
This the definition of a competitive inhibitor. The addition of a competitive inhibitor can be overcome the
addition of additional substrate therefore Vmax can be achieved but the affinity for the substrate is
reduced.
The following represents a series of reactions. As levels of B increase, this will decrease the conversion of
S3 to B. Which of the following best describes this type of regulation in a biosynthetic pathway?
a) feedback inhibition
, 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?
d) allosteric activation
An example of enzyme activation by cleavage is best illustrated by which of the following?
a) activation of chymotrypsinogen to chymotrypsin
Children with cystinosis have growth delay and renal issues to to accumulation of cysteine in cellular
lysosomes. The defect involves a specific lysosomal membrane receptor that facilitates cysteine removal
from the cell. An effective therapy involves administration of a drug with a similar structure to cysteine.
This therapy reflects the general principle that competitive inhibitors typically resemble the structure of
which of the following?
) substrates or ligands that bind the active site
If a mutation is made within the active site of an enzyme resulting in a decrease of it's Km value, which of
the following will be true with respect to enzyme kinetics?
d) the enzyme will require a lower substrate concentration to reach 1/2 Vmax
Movement of ammonia from an amino acid to an alpha-keto acid involves a family of enzymes best
categorized as:
a) transferases
Cleavage of fructose 1, 6 bisphosphate to dihydroxyacetone and glyceraldehyde 3-phosphate is achieved
by what class of enzymes?
b) lyase
An enzyme is participating in a general acid-base catalysis reaction with an optimal reaction pH of 6.0. If
acid is added to the environment reducing the pH to 3, what is the likely impact to the rate of reaction?
The rate of the reaction is likely to decrease as the pH is out of optimal catalytic range
General acid-base reactions are influenced by the surrounding pH changes. A change in pH from the
optimal pH range of 6.0, will reduce the overall reaction rate.
Covalent catalysis is used by many enzymes to cleave peptide bonds. Which of the following amino acids
would not facilitate this type of catalysis? (Think of the structure of the R-group of these amino acids)
Valine is a nonpolar amino acid and lacks a nucleophile to facilitate the generation of a catalyst- substrate
covalent bond.
Hemoglobin has the ability to display cooperative binding while myoglobin does not display this binding
kinetic pattern. Which of the following differences between the two protein accounts for this difference in
binding kinetics?
