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1
.
The process of cellular respiration, which converts simple
sugars such as glucose into CO2 and water, is an example of:
a catabolic pathway
6
.
an energy-releasing pathway
The free energy of the enzyme is greater than the free
energy of the substrate, which attracts the substrate to
the enzyme.
a pathway in which the entropy of the system increases
A positive charge on the substrate is attracted to a
negative charge in the active site of the enzyme.
The first and second choices are correct.
The enzyme has the ability to change its configuration
in response to the substrate binding.
The first, second, and third choices are correct.
2
.
Which of the following statements about the combustion of
glucose with oxygen to form water and carbon dioxide
(C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is incorrect?
This reaction is spontaneous with the release of free
energy.
A hydrophobic group on the substrate interacts with
several hydrophobic amino acids on the enzyme.
7
.
Binding of the substrate to the active site can stretch
bonds in the substrate that need to be broken.
The free energy lost in this combustion is greater than
the energy that appears as heat.
The active site of the enzyme can provide a
microenvironment with a different pH that facilitates the
reaction.
The binding of two substrates in the active site provides
the correct orientation for them to react to form a
product.
The reverse reaction, making glucose from water and
carbon dioxide, must be an endergonic reaction.
All of the above are ways that enzymes can speed up the
rate of a chemical reaction.
Which of the following statements about equilibrium of
chemical reactions is correct? (Concept 8.3
) [Hint]
Reactions can only go in the direction toward
equilibrium.
8
.
Most reactions in a living cell are close to equilibrium.
A reaction that is at equilibrium is not capable of doing
any work.
The compound causes a cofactor to be lost from the
enzyme.
None of the statements above correctly describes some
aspect of equilibrium.
The first and second choices are correct.
Which of the following statements about ATP (adenosine
triphosphate) is incorrect? (Concept 8.3 ) [Hint]
The hydrolysis of ATP is an endergonic process that can
supply needed energy for anabolic pathways.
The cycling between ATP and ADP + Pi provides an
energy coupling between catabolic and anabolic
pathways.
The energy release on hydrolysis of ATP is the result of
breaking a high-energy bond.
Much of the free energy released on the hydrolysis of
ATP is available to do cellular work.
In many cases, ATP makes energy available to other
reactions by transferring its phosphate group to the
substrate for another energy-requiring reaction.
5
.
The binding of a compound to an enzyme is observed to slow
down or stop the rate of the reaction catalyzed by the
enzyme. Which of the following could account for this
observation? (Concept 8.4 ) [Hint]
The compound is a competitive inhibitor.
The compound is a negative allosteric regulator.
The equilibrium point of a reaction represents the least
stable configuration for that reaction.
4
.
Which of the following is not a way in which an enzyme can
speed up the reaction that it catalyzes?
The active site can provide heat from the environment
that raises the energy content of the substrate.
The entropy of the products is greater than the entropy
of the reactants.
The entropy of the universe increases as the result of
this reaction.
3
.
Which of the following would be unlikely to contribute to the
substrate specificity of an enzyme? (Concept 8.4 ) [Hint]
A similar shape exists between a pocket on the surface
of the enzyme and a functional group on the substrate.
Enzymes are described as catalysts, which means that they
are proteins
provide activation energy for the reactions they
facilitate
increase the rate of a reaction without being consumed
by the reaction
can alter the free energy change (ΔG) for a chemical
reaction
increase the free energy of the reactants in order to
make the reaction go faster
The first three choices are correct.
9
.
Which of the following statements about feedback regulation
of a metabolic pathway is incorrect? (Concept 8.5 ) [Hint]
The final product of a metabolic pathway is the
compound that regulates the pathway.
The products of the pathway become the reactants for a
different reaction, and thus products are unable to
accumulate.
The enzyme that is regulated by feedback inhibition is
usually the first enzyme in the metabolic pathway.
The compound that regulates the pathway acts as a noncompetitive inhibitor or a negative allosteric regulator.
Accumulation of the product of the pathway will tend to
slow down further formation of that product.
Catabolism vs. Anabolism
Examples?
Laws of Thermodynamics
1. Conserve E
a. Potential
b. kinetic
2. Increase Entropy
Energy Flow in Rxns
High to low or require E input
Free energy (delta G)
Exergonic
Endergonic
Depends on Concentration of reactants
Coupled Rxns
ATP
Enzymes
Catalyst
What does this mean?
What changes?
Transition state
Intermediate
Energy of Activation
Regulate Rxn
How?
Inhibitors and Activators
Competitive inhibition
Noncompetitive inhibition
Cooperative allosteric activation and inhibition
Feedback Inhibition
Redox Reaction