Enzymes/III

Which of the designations listed below does not correspond to a major class of enzymes as outlined by the International Union of Biochemistry?
a.Hydrolases
b.Transferases
c.Carboxy lases
d.Isomerases

A particular oxidoreductase requires F AD as an essential component for its activity. The complete biological unit required for reaction is called a:
a.Holoenzyme
b.Cofactor
c.Coenzyme
d.Apoenzyme

Most coenzymes are derived from, or are:
a.Metal ions
b.Carbohydrates
c.Amino acids
d.Vitamins

Given the rate law, rate = k[A][B), the overall reaction order is:
a.Zero
b.One
c.Two
d.Cannot be determined

The Briggs and Haldane steady state assumption used in the derivation of the Michaeli!: Menten rate equation assumes that during this time period:
a.The product concentration does not change significantly.
b.The enzyme-substrate complex concentration does not change.
c.The substrate concentration is large and does not change significantly.
d.The free enzyme concentration is always in great excess to the concentration of the enzyme-substrate complex.

What statement is incorrect about coenzymes?
a.They can be metal ions such as Zn(II).
b.They are commonly derived from vitamins.
c.They bind to be active site region on specific enzymes.
d.NAD+, biotin, and FAD are examples of coenzymes.

Two inhibitors (a and B) of the enzyme beta-galactosidase were shown to be competitive. Inhibitor A has a Ki = I mM and inhibitor B has a Ki = 5 mM. What statement is correct?
a.The V max is less when inhibitor A is included in the assay than the uninhibited case.
b.Inhibitor B binds more tightly to the enzyme than inhibitor A.
c.Both inhibitors would decrease the velocity equally at a [inhibitor] = 2.5 mM.
d.None of lhe above is correct.

From the list of experiments below, which experiment would you need to perform to accurately determine the desired experimental value? You may assume that all the reactions were performed with a fixed amount of enzyme.

The value of the Michaelis-Menten combined rate constant Km.
a.Measure the velocity of the reaction at two temperatures.
b.Measure the velocity of the reaction at two or more pH values.
c.Measure the velocity of the reaction at two substrate concentrations.
d.Measure the concentration of product after the reaction has stopped.

The value of the activation energy of the reaction.
a.Measure the velocity of the reaction at two temperatures.
b.Measure the velocity of the reaction at two or more pH values.
c.Measure the velocity of the reaction at two substrate concentrations.
d.Measure the concentration of product after the reaction has stopped.

The value of the equilibrium constant Keq.
a.Measure the velocity of the reaction at two temperatures.
b.Measure the velocity of the reaction at two or more pH values.
c.Measure the velocity of the reaction at two substrate concentrations.
d.Measure the concentration of product after the reaction has stopped.

The value of the turnover number.
a.Measure the velocity of the reaction at two temperatures.
b.Measure the velocity of the reaction at two or more pH values.
c.Measure the velocity of the reaction at two substrate concentrations.
d.Measure the concentration of product after the reaction has stopped.

The action of hexokinase is best explained in terms of the:
a.Lock and key hypothesis
b.Proenzyme activation
c.Induced fit hypothesis
d.Post-translational modification model
e.None of the above

The concentration of the substrate for a specific enzyme in the cell is very often found to be:
a.Approximately equal to the km value.
b.Much less than the km value.
c.Much greater than the km value.
d.Equal to or greater than kcatlKm.

Which of the following is not expected to be characteristic of a homotetrameric allosteric enzyme?
a.Multisubunit enzyme
b.It has only one active site per enzyme.
c.Effector sites are non-overlapping with the active sites.
d.They exhibit sigmoidal kinetic profiles.

The slowest type of control influencing enzyme activity is:
a.Induction
b.Covalent modification
c.Interaction of an allosteric effector with the enzyme.
d.Conformational change in the subunits in an allosteric interaction.

The primary control in the clotting of blood is:
a.Induction
b.post-translational modification
c.Proteolytic cleavage of proenzymes
d.Association of subunits to form different isozymes.

The primary control on the activation of cAMP- dependent protein kinase is:
a. Induction of the transcription
b.Protein-protein interactions between the regulatory (R) and the catalytic © subunits
c.Substrate availability
d.Proteolytic cleavage of the proenzyme

Which of the following is not a characteristic of hemoglobin?
a.It is an allosteric enzyme.
b.It contains two different subunits.
c.It contains a prosthetic group.
d.Is a transport protein for molecular 02.

The positive effector in hemoglobin is:
a.Oxygen molecule
b.BPG
C. CO2
d.H+

If biophosphoglycerate is removed from the hemoglobin, the 02, sigmoidal saturatior binding curve for Hb is:
a.Unaffected
b.Shifted to higher 02 pressures
c.Shifted to lower 02 pressures
d.Changed to a hyperbolic curve.

The removal of bisphosphoglycerate from Hemoglobin will:
a.Decrease the 02 affinity.
b.Increase the 02 affinity.
c.Have no effect on 02 affinity.
d.Produce the same effect as lowering the pH.

Reaction of free heme with 02 in solution yields:
a.Oxygenated heme
b.Oxidized heme
c.No reaction
d.Positive cooperativity with other heroes

Which of the following is incorrect about the oxygen saturation curves of normal hemoglobin (HbA), fetal hemoglobin (HbF), and myoglobin (Mb)?
a.The Pso is smaller for HbF than for HbA
b.As the pH is decreased, the Pso for HbA is decreased.
c.The Pso is greater for HbA than for Mb.
d.The shape of the curve for normal hemoglobin is sigmoidal.

At high altitudes, the concentration of bisphosphoglycerate (BPG) in erythrocytes is higher than at low altitudes. Which of the following statements is logically correct?
a.The Psoof Hb at high altitudes is less than the Pso of Hb in erythrocytes at low altitude!
b.Hb adjusted to high altitudes will not show a Bohr effect.
c.The Pso of Hb increases as the concentration of BPG in erythrocytes Increases.
d.The Pso of myoglobin is increased as the concentration of BPG goes up in erythrocytE to high altitudes.

An interesting characteristic in the allosteric enzyme, ATCase, which is not found in hemoglobin, is:
a.Two different types of protein subunits in A Tease.
b.Allosteric effector sites are on both subunits types.
c.Binding of both positive and negative heterotropic effectors.
d.One subunit type binds only the substrate, while the other subunit type binds only heterotropic effectors.
e.None of the above.