Use the graph above for the following question(s).
47. The optimal pH for enzyme 1 is:
a.
2.
b.
3.
c.
4.
d.
5.
e.
6.
48. The optimal pH for enzyme 2 is:
a.
2.
b.
3.
c.
4.
d.
5.
e.
6.
49. If all three enzymes catalyze the same reaction and your conditions require a pH of 7, the best enzyme
to use would be:
a.
enzyme 1.
b.
enzyme 2.
c.
enzyme 3.
d.
either enzyme 2 or 3.
e.
both enzymes 2 and 3.
50. When an enzyme has an allosteric activator, it means that
a.
a product of the enzyme, or other downstream product, will bind to the enzyme at the
active site and inhibit enzyme activity.
b.
a product of the enzyme, or other downstream product, will bind to the enzyme at the
active site and stimulate enzyme activity.
c.
a product of the enzyme, or other downstream product, will bind to the enzyme at a site
other than the active site and inhibit enzyme activity.
d.
a product of the enzyme, or other downstream product, will bind to the enzyme at a site
other than the active site and stimulate enzyme activity.
e.
a product of a different pathway (not a direct or indirect product of the enzyme) will
stimulate the enzyme’s activity.
The above diagram of a metabolic pathway should be used for the following question(s). Solid arrows
represent enzyme-catalyzed reactions. The dashed arrow represents molecule R interacting with an
enzyme.
51. If the enzyme catalyzing the N to O reaction is inhibited, there will be a build-up of which compound?
a.
M
b.
N
c.
O
d.
P
e.
Q
52. If R inhibits the enzyme catalyzing the M to N reaction, we call this
a.
allosteric activation.
b.
allosteric inhibition.
c.
noncompetitive inhibition.
d.
competitive inhibition.
e.
either c or d, dependent on more information.
53. If the enzyme catalyzing the N to O reaction is allosterically stimulated, there will be a build-up of
which compound(s)?
a.
N
b.
O
c.
P
d.
Q
e.
P and Q
54. What type (or types) of reactions can a ribozyme catalyze?
a.
protein synthesis, but only with other proteins to assist in the process (like in a ribosome)
b.
protein synthesis in the absence of other proteins
c.
RNA splicing
d.
protein synthesis, but only with other proteins to assist in the process (like in a ribosome)
and RNA splicing
e.
protein synthesis in the absence of other proteins and RNA splicing
55. Is a ribozyme a true enzyme?
a.
Yes, because it is a catalyst.
b.
No, because it is not a protein.
c.
No, because it cannot catalyze a reaction.
d.
Yes, because it can synthesize a protein.
e.
No, because it doesn’t require cofactors.
56. Zhang and Cech’s experiments confirmed what feature of ribozyme activity?
a.
Ribozymes inhibit rates of biological
reactions.
d.
Ribozymes can link amino acids together
even if their proteins are removed.
b.
Ribozymes catalyze formation of the
fundamental linkage tying amino acids
together in proteins.
e.
Ribozymes provide the possible solution
of whether proteins or nucleic acids come
first in evolution.
c.
Ribozymes catalyze formation of the
fundamental linkage tying nucleic acids to
proteins.
57. Why is it useful to know the structure of a protein when trying to understand a protein’s function?
a.
Scientists still don’t know exactly what features of a protein’s structure determine how a
protein works. By gathering information about many different protein structures and
correlating them to their known functions, we can try to figure out this relationship.
b.
Since all proteins have enzymatic activity, we hope to learn what features of a protein
make an enzyme a catalyst.
c.
Since x-rays are used on protein crystals to determine the structure, this research can help
us understand the ways in which x-rays can be damaging to the proteins of living cells.
d.
The enzymatic activity of a protein cannot be measured unless we also have the structure
of that enzyme.
e.
We need to know which amino acids are essential for a cell to function. If we know the
structure of an enzyme, we can determine which amino acids are present and how they
work in the cell.
58. Why is it useful to know the structure of a ribozyme when trying to understand a particular ribozyme’s
function?
a.
The way the RNA folds determines the activity of the ribozyme. We need to understand
the structure in order to measure the rate of the reaction.
b.
It is not very useful at all; it is just a matter of curiosity.
c.
We need to know the structure in order to develop drugs that destroy that structure and
prevent HIV infection.
d.
We need to be able to determine if an RNA molecule is a ribozyme or not. The only way
to do that is to determine the structure.
e.
The way the RNA folds relates to the function of the ribozyme. If we can figure out the
relationship, we might be able to develop new ribozymes that act as therapeutic agents.
59. This molecule has two functions in a cell: encoding genetic information and using two additional
phosphates to transfer energy.
a.
glucose
b.
AMP
c.
glutamic acid
d.
aspartic acid
e.
fat
60. When an enzyme-catalyzed reaction reaches equilibrium
a.
the enzymes are now inhibited.
b.
the chemical reactions cease.
c.
the rate of the forward and reverse reactions are equal.
d.
the concentration of reactants equals the concentration of products.
e.
ATP is no longer required to drive the reaction.
61. Enzymes are
a.
protein catalysts.
b.
lipid catalysts.
c.
nucleic acid catalysts.
d.
inorganic catalysts.
e.
ionic catalysts.
62. Enzymes
a.
are catalytic lipids.
b.
are catalytic proteins.
c.
are RNA molecules that slow the rate of protein synthesis.
d.
are catalytic carbohydrates.
e.
are nonmacromolecule catalysts.
63. If a reaction in a cell requires an enzyme
a.
we know that the reaction must be endergonic.
b.
we know that the reaction must require ATP.
c.
we know that the reaction is subject to allosteric regulation.
d.
we know that the reaction is regulated by competitive inhibition.
e.
we know that the reaction occurs more readily with the enzyme than it would if there were
no enzyme.
64. The helix-turn-helix motif found in many regulatory proteins fits into the side of a DNA molecule. If a
newly discovered enzyme has a helix-turn-helix motif, you would predict that
a.
this enzyme has multiple peptide chain subunits.
b.
this enzyme is probably able to bind to RNA, too.
c.
this enzyme probably binds to DNA.
d.
this enzyme has an allosteric regulator.
e.
this enzyme is a polymerase that helps synthesize new DNA sequences.
95
65. You modify the primary sequence of an enzyme in a region that will be the active site when the protein
is properly folded. What is the predicted outcome of this change?
a.
The enzyme will not properly bind to the substrate.
b.
The enzyme will not be able to bind an allosteric inhibitor.
c.
The enzyme will have an increased rate of activity.
d.
There will be no change in the enzyme’s function.
e.
The enzyme will bind the substrate but not be able to release the products.
Select the Exception
66. Enzymes work with at least three mechanisms. Which of the following is not a mechanism by which
enzymes function?
a.
putting reactants in close proximity to each other
b.
altering the free energy (G) of the reaction
c.
altering the immediate environment of the reactants to promote reactant interactions
d.
orienting the reactants so they are positioned to favor the transition state
67. Which of the following does not impact an enzyme’s function?
a.
pH
b.
temperature
c.
absence of cofactors
d.
allosteric interactions
e.
excess product
MATCHING
Match each of the following terms with its correct definition.
a.
Primary coupling agent in cellular reactions
b.
The addition of a phosphate group to a target molecule
c.
The product of the reaction interacts with an enzyme in a noncompetitive way to inhibit or
enhance enzyme activity
d.
The linking of an exergonic reaction with an endergonic reaction that allows a cell to drive
a nonspontaneous reaction to completion
e.
A series of chemical reactions where the products of one reaction are the reactants for a
subsequent reaction
f.
A substance that facilitates a chemical reaction without itself being consumed by the
reaction
g.
The energy needed to start a reaction, be it endergonic or exergonic
h.
The portion of the enzyme that binds to a reactant or reactants
i.
A state in which the rate of the forward reaction equals the rate of the reverse reaction
j.
An RNA molecule that acts as a catalyst
k.
An intermediate arrangement of unstable bonds between atoms that can proceed towards
either the reactants or products of a reaction
96
l.
The reactant molecule that binds to an enzyme
68. coupled reaction
69. ATP
70. phosphorylation
71. equilibrium point
72. metabolic pathway
73. catalyst
74. activation energy
75. active site
76. substrate
77. transition state
78. allosteric regulation
79. ribozyme
Choice
For each of the following situations, choose the most appropriate term.
a.
endergonic
b.
exergonic
c.
equilibrium
80. a beaker of water sitting on a bench
81. folding laundry
82. protein synthesis
83. digestion of a candy bar
84. a toddler dumping boxes of toys
85. a dead cell
86. a reaction where G = 0
87. a reaction where G is positive
88. a reaction where G is negative
89. the rate of synthesis equals the rate of degradation
SHORT ANSWER
90. Define metabolism
91. What is the significance of activation energy?
92. Why is using heat to speed up biological reactions problematic?
93. Explain how temperature can impact enzyme activity.
94. How do ribozymes work?
MODIFIED TRUE/FALSE
If the statement is true, answer “T”. If the statement is false, answer “F” and make it correct by
changing the underlined word(s) and writing the correct word(s) in the answer blank(s).
95. AMP is the primary energy and phosphate source in coupled reactions.
96. At equilibrium, the concentration of the reactants equals the concentration of the products.
97. Reactions that reach an equilibrium point are reversible.
98. All true enzymes are proteins.
99. Activation energy is not required for nonspontaneous reactions.
100. Enzymes don’t change the G of a reaction.
101. Enzymes alter the equilibrium point of a reaction.
102. Enzyme activity is increased by falling temperatures.
ESSAY
103. Explain three ways in which other molecules regulate enzymes.
104. Explain how a cell can use catabolic reactions to drive anabolic reactions despite energy loss in the
form of entropy and heat.