Transcript Biochem Practice Questions

Biochem (Test 1)
11. Which of the following statements most directly supports
the claim that different species of organisms use different
metabolic strategies to meet their energy requirements for
growth, reproduction, and homeostasis?
a. During cold periods pond-dwelling animals can increase the
number of unsaturated fatty acids in their cell membranes while
some plants make antifreeze proteins to prevent ice crystal
formation in tissue.
b. Bacteria lack introns while many eukaryotic genes contain many
of these intervening sequences.
c. Carnivores have more teeth that are specialized for ripping food
while herbivores have more teeth that are specialized for grinding
food.
d. Plants generally use starch molecules for storage while animals use
glycogen and fats for storage.
Biochem (Test 1)
20. Sickle-cell anemia results from a point mutation in the HBB
gene. The mutation results in the replacement of an amino acid
that has a hydrophilic R-group with an amino acid that has a
hydrophobic R-group on the exterior of the hemoglobin
protein. Such a mutation would most likely result in altered:
a. properties of the molecule as a result of abnormal interactions
between adjacent hemoglobin molecules.
b. DNA structure as a result of abnormal hydrogen bonding
between nitrogenous bases.
c. Fatty acid structure as a result of changes in ionic interactions
between adjacent fatty acid chains.
d. Protein secondary structure as a result of abnormal hydrophobic
interactions between R-groups in the backbone of the protein.
Biochem (Test 1)
22. Testosterone oxido-reductase is a liver enzyme that
regulates testosterone levels in alligators. One study
compared testosterone oxido-reductase activity between
male and female alligators from Lake Woodruff, a
relatively pristine environment and from Lake Apopka,
an area that has suffered severe contamination. The
graph below depicts the findings of that study. The data
in the graph best support which of the following claims?
a. Environmental contamination elevates total testosterone
oxido-reductase activity in females.
b. Environmental contamination reduces total testosterone
oxido-reductase activity in females.
c. Environmental contamination elevates total testosterone
oxido-reductase activity in males.
d. Environmental contaminations reduces total testosterone
oxido-reductase activity in males.
Bioshem(Test 1)
33-35. Both myoglobin and hemoglobin are proteins that
bind reversibly with molecular oxygen. The graph below
shows the oxygen binding saturation of each protein at
different concentrations of oxygen.
33. Which of the following statements is correct>
a. At 10 mmHg partial pressure, hemoglobin binds to oxygen
but myoglobin does not.
b. At 20 mmHg partial pressure, myoglobin and hemoglobin
bind oxygen in equal amounts.
c. At 40 mmHg partial pressure, myoglobin has a greater
affinity for oxygen than hemoglobin has.
d. At 80 mmHg partial pressure, myoglobin binds twice as
much oxygen as hemoglobin does.
34. Strenuous exercise lowers the blood pH, causing
the curves for both hemoglobin and myoglobin to
shift to the right. This shift results in:
a. an unloading of O2 at higher partial pressures.
b. an increase in the number of O2 binding sites.
c. the capture of more O2 by hemoglobin.
d. The capture of more O2 by myoglobin.
35. Which of the following best describes the physiological
significance of the different oxygen-binding capabilities of
hemoglobin and myoglobin?
a. They prevent muscles from depleting oxygen levels in the
b blood.
b. They cause muscles to become anaerobic.
c. They prevent glycogen depletion in muscles.
d. They enhance movement of oxygen from the blood into
the muscles.
Biochem (Test 2)
51. Enzymes are globular proteins that have either tertiary or
quarternary structure. This structure gives them a particular shape
that is maintained as long as the environment of the enzyme
remains stable. For an enzyme to be a productive catalyst for
reactions, which of the following is required?
a. A substrate that can be forced to fit into an allosteric site on the
enzyme.
b. A substrate that closely resembles the active site of the enzyme.
c. An allosteric site that can be modified so that the substrate will
fit into it.
d. An enzyme with tertiary structure that closely resembles that of
a different enzyme.
Biochem (Test 2)
52. Many enzymes require cofactors or coenzymes in order to
catalyze reactions. Some like the metals copper, zinc, or iron and
many vitamins act to speed the enzymatic activity. What do these
cofactors and coenzymes contribute to the enzymatic process?
a. Most cofactors and coenzyme modify the active site so that the
substrate fits better and many cofactors and coenzymes
contribute atoms to the reaction.
b. Cofactors and coenzymes contribute to reactions by breaking
hydrogen bonds of the substrate.
c. An induced fit is encouraged by the participation of cofactors
and coenzymes and their attachment to an allosteric site.
d. Cofactors and coenzymes inhibit the reaction catalyzed by the
enzyme by negative feedback.
Biochem (Test 2)
53. Enzyme structure and the shape of its active site are extremely
important for the reaction that the enzyme catalyzes. Which of
these choices is a method used to modify the shape of the active site,
rendering the enzyme inactive?
a. The product of the reactions binds to the active site on the
enzyme causing the active site to be unavailable as a form of
noncompetitive inhibition.
b. The product of the reaction bind to an allosteric site on the
enzyme causing a change to the shape of the active site as a form
of competitive inhibition.
c. The product of the reaction returns to the active site and
changes the site as a form of positive feedback, inhibiting further
reactions.
d. The product of the reaction binds to an allosteric site on the
enzyme causing a change to the shape of the active site as a form
o f noncompetitive inhibition.
Biochem (Test 2)
54. A group of students designed an enzyme catalysis experiment.
In the experiment, the enzyme, catalase, was used to decompose
hydrogen peroxide over a time course. The results are presented
below.
a.
Time (s)
5
10
15
20
25
30
H2O2
decomposed
(mL)
2
4
6
8
8
8
This data is useful to show the concentration of the product of the
catalyzed reaction.
b. This data is useful to show the concentration of the substrate the enzyme
decomposed.
c. This data shows the presence of a competitive inhibitor.
d. This data is useful in the determination of the rate of the enzymatic
reaction
Biochem (Test 2)
55. A further experiment by the same group of students found that a
small increase in the temperature of the enzyme catalase and the
substrate H2O2 produced a significant increase in the amount of
substrate degraded. Which of these possible explanations is the
most likely reason for the increased enzymatic activity?
a. The increased temperature has caused the enzyme to become
denatured.
b. The increased temperature removed a noncompetitive inhibitor
from the enzyme.
c. Evaporation due to the increased temperature increased the
concentration of the solutions and as a result increased the
reaction rate.
d. The increased temperature caused the enzyme and the substrate
to move faster and collide more frequently.