Chapter 3—Thermodynamics of Biological Systems
MULTIPLE CHOICE
1. Thermodynamics does NOT:
a.
describe the flow and interchange of heat, energy, and matter.
b.
allow the determination of whether a reaction is spontaneous.
c.
provide information on the rate of a reaction.
d.
consider heat flow and entropy production.
e.
consider the effect of concentration on net free energy change of a reaction.
2. Living systems are:
a.
closed systems exchanging only energy with the surroundings.
b.
isolated systems that are totally contained.
c.
open systems exchanging only energy with the surroundings.
d.
open systems exchanging both energy and matter with their surroundings.
e.
none of the above.
3. Which statement pertaining to the three basic systems is true?
a.
The internal energy of an isolated system is mostly conserved.
b.
Open systems can exchange matter with other open systems.
c.
Open systems can exchange matter with a closed system.
d.
The internal energy of an open system is always constant.
e.
A closed system can accept heat from an isolated system.
4. Internal energy is all EXCEPT:
a.
includes all the energy that might be exchanged in physical or chemical processes.
b.
path dependent.
c.
referred to as a state function
d.
commonly designated E or U.
e.
none, all are true.
5. Enthalpy change, H, is:
a.
the sum of heat absorbed and work.
b.
not a thermodynamic state function.
c.
a measure of disorder in a system.
d.
determined by pressure change at a constant temperature.
e.
equal to the heat transferred at constant pressure and volume.
6. Calorimetry measures ____ by a biochemical process.
a.
heat absorbed or given off, H,
b.
pressure change inside calorimeter created
c.
water pressure created
d.
entropy change, S,
e.
volume change, V, created
7. An example of an open system would be:
a.
a chemical reaction taking place in a closed beaker.
b.
a steam radiator.
c.
an insulated bomb reactor.
d.
a pot of boiling water.
e.
contents of a calorimeter.
8. Which of the following statements is true for the Second Law of Thermodynamics?
a.
Systems tend to proceed from disordered states to ordered states.
b.
The entropy of the system plus its surroundings is unchanged by reversible processes
c.
The entropy of the system plus its surroundings decreases for irreversible processes.
d.
Naturally occurring processes never proceed toward equilibrium.
e.
All of the above are true
9. Entropy change, S, is
a.
the sum of heat absorbed and work.
b.
not a thermodynamic state function.
c.
a measure of disorder in a system.
d.
determined by pressure change at a constant temperature.
e.
equal to the heat transferred at constant pressure and volume.
10. Which example has the greatest increase in entropy, S?
a.
freezing water
b.
sublimation of CO2
c.
melting ice
d.
shattering glass
e.
boiling gasoline
11. Entropy, S, is exactly zero at:
a.
25C
b.
0C
c.
25K
d.
0K
e.
38C
12. Which equation defines a system at equilibrium?
a.
G > 0
b.
G = G
c.
G = 0
d.
G = 0
e.
G = RT ln ([products]/[reactants])
13. Given the following reaction, what can be said about the equilibrium concentrations of the components
of the reaction? (do not assume that concentrations began at standard conditions)
pyruvate + NADH + H+ lactate + NAD+
G = −25.2 kJ/mol
a.
[pyruvate] > [NADH]
b.
[pyruvate] < [NAD+]
c.
[NAD+] > [NADH]
d.
[pyruvate] > [lactate]
e.
cannot determine
14. All are true about G EXCEPT?
a.
A positive or negative G tells us which direction the reaction will proceed.
b.
G depends upon the concentration of the reactants and products.
c.
G is affected by temperature.
d.
G is affected by pressure and pH.
e.
G is negative for endergonic reactions.
15. An interaction between two subunits of a protein was determined to have a G = −57.05 kJ/mol.
What is the Keq for the reaction at 25C?
a.
1.02
b.
1.32
c.
10−10
d.
1010
e.
cannot determine from given information
16. The standard state free energy change, G, is:
a.
positive when the reaction is unfavorable.
b.
an expression of Keq.
c.
negative when the reaction is favorable.
d.
equal to H − TS.
e.
none of the above.
17. Thermodynamic parameters (entropy, enthalpy, free energy, and internal energy) are given for an
unknown enzyme. Explain which results would be expected for the breaking of hydrogen bonds and
the exposure of hydrophobic groups from the interior during the unfolding process of a protein.
a.
Entropy change, S, is zero
b.
Enthalpy change, H, is positive
c.
The reaction is spontaneous
d.
Enthalpy change, H, is negative
e.
Entropy change, S, is positive
18. For an endothermic reaction to be spontaneous, which of the following must be true?
a.
heat must be given off by the reaction
b.
energy must be added to the reaction
c.
the temperature must be very low
d.
the entropy must increase substantially
e.
none of the above are true
19. All describe modified standard state for a thermodynamic parameter EXCEPT:
a.
designated with a prime ( ) symbol.
b.
H+ ion of 10-7 M.
c.
10-6 M for solutions.
d.
1 atm. for gases.
e.
When the solvent is water at pH = 7.
20. To predict whether pairs of coupled reactions will proceed spontaneously:
a.
Subtract the smaller from the larger G.
b.
Sum the G values for each reaction.
c.
Add the S values for each reaction at constant temperature.
d.
The absolute value of the positive G must be larger than the value of the negative G.
e.
None are true.
21. Based upon the following reactions, what would be the G for the formation of ATP from
phosphoenolpyruvate and ADP?
ATP → ADP + Pi
G = −31.5 kJ/mol
phosphoenolpyruvate → pyruvate + Pi
G = −62.2 kJ/mol
a.
−93.7 kJ/mol
b.
−30.7 kJ/mol
c.
+30.7 kJ/mol
d.
+93.7 kJ/mol
e.
cannot determine from given information
22. Virtually all life on earth depends on energy ULTIMATELY from:
a.
the power company.
b.
batteries.
c.
the green-house effect.
d.
the sun.
e.
activation energy.
23. “High-energy” compounds exhibit large negative free energy of hydrolysis and include all EXCEPT:
a.
phosphate esters.
b.
enol phosphates.
c.
acyl phosphates.
d.
guanidino phosphates.
e.
thioesters.
24. ____ and ____ are a small family of universal biomolecules mediating the flow of energy from
exergonic reactions to the energy requiring processes of life.
a.
Reduced coenzymes, caffeine
b.
High-energy phosphate compounds, caffeine
c.
Chlorophyll, caffeine
d.
Hemoglobin, chlorophyll
e.
Reduced coenzymes, high-energy phosphate compounds
25. The metabolite with a lower G of hydrolysis than ATP is:
a.
acetyl phosphate.
b.
phosphoenol pyruvate (PEP).
c.
phosphocreatine.
d.
adenosine-5′-phosphate.
e.
pyrophosphate.
26. The hydrolysis of a phosphate from which of the following molecules is most thermodynamically
favorable?
a.
ADP
b.
glucose phosphate
c.
adenosine-5′-diphosphate
d.
phosphoenolpyruvate
e.
adenosine-5′-triphosphate
27. ATP can donate ____ and ____ to lower-energy molecules of metabolism.
a.
phosphates, energy
b.
reactants, products
c.
phosphates, water
d.
energy, G
e.
G, reactants
28. Biochemists define the group transfer potential as the ____ that occurs upon hydrolysis (i.e., transfer
of the particular group to water).
a.
G
b.
H
c.
S
d.
Cp
e.
E
29. ATP hydrolysis coupled reactions have equilibrium constants that are changed by a factor of:
a.
10
b.
100
c.
104
d.
106
e.
108
30. The chemical reasons for the large negative G for the hydrolysis of ____ include destabilization of
the reactant due to bond strain caused by electrostatic repulsion, stabilization of the products by
ionization and resonance, and entropy factors due to hydrolysis and subsequent ionization.
a.
AMP
b.
ATP
c.
PEP
d.
Phosphocreatine
e.
All of the above
31. Which of the following statements about ATP is NOT true?
a.
It is used for short-term energy in the cell.
b.
It has two phosphoanhydride bonds.
c.
The reason for the large −G values of hydrolysis reactions is due to stabilization of
products.
d.
ATP is usually complexed with Mn2+.
e.
ATP is a kinetically stable molecule.
32. Which statement MOST COMPLETELY EXPLAINS the large G for the hydrolysis of
phosphoenolpyruvate?
a.
Hydrolysis of the phosphate bond along with the conversion of the enol to the keto form of
pyruvate.
b.
The hydrolysis of the phosphoanhydride bond.
c.
Conversion from the enol to the keto form of pyruvate.
d.
Strong bond energy along with a change in the stereochemistry of the molecule.
e.
The large G of the phosphoester bond.
33. A widely used “consensus value” for G of ATP hydrolysis in biological systems is ____ kJ/mol.
a.
−21
b.
−30.5
c.
−7
d.
3
e.
21
34. The effects of ____ on the G of hydrolysis of ATP are much greater than the effects of ____ or
____ under physiological conditions.
a.
pH, concentration, metal ions
b.
metal ions, pH, concentration
c.
temperature, concentration, pH
d.
concentration, pH, metal ions
e.
none of the above.
35. Which of the following statements regarding ATP is true?
a.
the energy of hydrolysis is the same for all of the phosphate groups of the molecule
b.
despite the very exergonic nature of the hydrolysis, ATP does not hydrolyze
spontaneously due to a very high activation energy
c.
the G of hydrolysis within the cell is substantially greater than the G due to a higher
concentration of ATP with respect to ADP
d.
electrostatic attraction of the phosphate groups contributes to a more exergonic free energy
e.
both b and c are correct
36. The association of a protein and a fragment of DNA has a G of -57 kJ/mol. What is the equilibrium
constant at 25 ºC for the formation of this complex?
a.
d.
10-10
b.
e.
cannot be determined
c.
37. For the reaction of ATP + H2O -> ADP +Pi + H+, the biochemical standard state conditions would
include all of the following EXCEPT:
a.
d.
the concentration of water would be 1 M
b.
e.
all to the above are correct
c.
38. The conversion of glucose-6-phosphate to glucose-1-phosphate has a G of 8.4 kJ/mol. What can be
said about the value of Keq?
a.
c.
Keq < 1
b.
d.
cannot be determined
39. The reduction of pyruvate to lactate has an Eoof -0.185 V while the reduction of acetaldehyde to
ethanol has an Eoof -0.197 V. If these two reactions are coupled to produce a spontaneous reaction,
which of the following would be the reducing agent?
a.
d.
ethanol
b.
e.
cannot be determined from the given
information
c.