Deck 3: The Energetics of Life

Question 1

Which of the following would be considered a closed system?

A)a human living alone on a small island
B)the planet Earth
C)a fish living in a fish bowl
D)a bacteria living in the large intestine
E)a bacteria living in a Petri dish

Answer 1

B

Question 2

Which of the following represents an apparent violation of the second law of thermodynamics?

A)the organization of free amino acids into a protein
B)the tendency for dead cells to break down to smaller molecules
C)the hydrolysis of nucleic acids into nucleotides
D)the conversion of the polymer cellulose into glucose
E)the tendency for a professor's desk to become cluttered

Answer 2

A

Question 3

The formation of glucose-1-phosphate from glucose and orthophosphate has a $\Delta$ G ^$\circ$ ' of + 20.9 kJ/mol. If this reaction were coupled to another reaction in order to produce an exergonic reaction, which of the following would produce an overall endergonic reaction and therefore not be suitable for coupling?

A)creatine phosphate + H₂O $\rarr$ creatine + P_i
B)AMP + H₂O $\rarr$ adenosine + P_i
C)ATP + H₂O $\rarr$ AMP + PP_i
D)ATP + H₂O $\rarr$ ADP + P_i
E)1,3-bisphosphoglycerate + H₂O $\rarr$ 3-phosphoglycerate + P_i

Answer 3

AMP + H₂O $\rarr$ adenosine + P_i

Question 4

If the change in entropy for a process is much less than the change in enthalpy, why might the entropy change be the dominant factor in determining the overall free energy of the process?

A)biochemical reactions are performed at relatively constant pressure
B)biochemical reactions generally occur around 300 K.
C)biochemical reactions involve few reactants and products
D)biochemical reactions involve mixtures of molecules, never pure substances
E)all of the above

Question 5

The highly exergonic nature of ATP hydrolysis is explained by which of the following?

A)the resulting orthophosphate is stabilized by resonance
B)electrostatic repulsion occurs between phosphate groups and the adenine base of ATP
C)the resulting product undergoes tautomerization to the keto form of ADP
D)the bond that is hydrolyzed is considered an ester of phosphoric acid, making it highly unstable
E)all of the above

Question 6

Which of the following reactions, if coupled to the reduction of $\alpha$ -ketoglutarate, would give the most exergonic overall reaction? $\alpha$ -ketoglutarate + CO₂ + 2H⁺ + 2e^- $\rarr$ isocitrate (E ^$\circ$ ' = - 0.38 V)

A)ubiquinol $\rarr$ ubiquinone + 2H⁺ + 2e^- (E ^$\circ$ ' = - 0.04 V)
B)FADH₂ $\rarr$ FAD + 2H⁺ + 2e^- (E ^$\circ$ ' = + 0.22 V)
C)NADH $\rarr$ NAD⁺ + H⁺ + 2e^- (E ^$\circ$ ' = + 0.32 V)
D)H₂ $\rarr$ 2H⁺ + 2e^- (E ^$\circ$ ' = + 0.42 V)
E)pyruvate + CoA $\rarr$ acetyl CoA + CO₂ + H⁺ + 2e^- (E ^$\circ$ ' = + 0.48 V)

Question 7

Which of the following is a result of living cells not being at equilibrium?

A)the $\Delta$ G for all reactions will always be negative
B)all reactions proceed in only one direction
C)if the concentration of products is greater than the concentration of reactants, the reaction will always proceed in the reverse direction
D)the entropy of cells is always increasing
E)the direction in which most reactions will proceed depends upon concentrations of reactants and products

Question 8

Which of the following compounds contains a phosphate ester as its most energetically labile bond?

A)pyrophosphate
B)adenosine monophosphate
C)creatine phosphate
D)1,3-bisphosphoglycerate
E)acetyl phosphate

Question 9

Based on the half reactions given below, which of the following reactants is the strongest reducing agent?

A)NADH $\rarr$ NAD⁺ + H⁺ + 2e^- (E ^$\circ$ ' = + 0.32 V)
B)dihydrolipoic acid $\rarr$ lipoic acid + 2H⁺ + 2e^- (E ^$\circ$ ' = + 0.29 V)
C)FADH₂ $\rarr$ FAD + 2H⁺ + 2e^- (E ^$\circ$ ' = + 0.22 V)
D)lactate $\rarr$ pyruvate + 2H⁺ + 2e^- (E ^$\circ$ ' = + 0.18 V)
E)succinate $\rarr$ fumarate + 2H⁺ + 2e^- (E ^$\circ$ ' = - 0.03 V)

Question 10

Which of the following reactions would be a non-spontaneous process?

A)complete oxidation of glucose to carbon dioxide and water
B)formation of phosphoenolpyruvate from pyruvate and P_i
C)hydrolysis of ATP to ADP and P_i
D)the coupled reaction of phosphoenolpyruvate + ADP $\rarr$ pyruvate + ATP
E)all of the above

Question 11

Which of the following correctly relates the relative entropies?

A)sodium chloride crystals > sodium chloride dissolved in water
B)carbon dioxide in air > dry ice
C)carbon in a molecule of glucose > carbon in carbon dioxide gas
D)a solution of ATP > the same solution with ATP converted to ADP and P_i
E)ice made from pure water > ice made from salt water

Question 12

If the $\Delta$ G value for a given biochemical reaction is a relatively large, positive value, which of the following is true?

A)the reaction is said to be exergonic
B)the reaction is thermodynamically favorable
C)the reverse reaction is thermodynamically favorable
D)the reaction is freely reversible
E)the reaction is at equilibrium

Question 13

If the $\Delta$ G ^$\circ$ ' for ATP hydrolysis is -31 kJ/mol and the $\Delta$ G ^$\circ$ ' for phosphoenolpyruvate hydrolysis is -62 kJ/mol, what is the $\Delta$ G ^$\circ$ ' for the phosphorylation of ADP by phosphoenolpyruvate?

A)-93 kJ/mol
B)-31 kJ/mol
C)+31 kJ/mol
D)+93 kJ/mol
E)none of the above

Question 14

Which of the following best describes biochemical systems with respect to the first law of thermodynamics?

A)most biochemical systems operate at constant volume
B)most biochemical systems operate at constant temperature
C)most biochemical systems operate at constant pressure
D)most biochemical systems operate with a constant number of molecules
E)none of the above

Question 15

The conversion of glucose-6-phosphate to fructose-6-phosphate has a $\Delta$ G°´ of +1.7 kJ/mol but within a typical cell, the $\Delta$ G is -2.9 kJ/mol. What can be said about the value of K_eq and Q?

A)under standard conditions, K_eq > 1; in the cell, Q < 1
B)under standard conditions, K_eq < 1; in the cell, Q > 1
C)under standard conditions, K_eq > 1; in the cell, Q > 1
D)under standard conditions, K_eq < 1; in the cell, Q < 1
E)none of the above

Question 16

Which of the following best describes the relationship between the oxidation of glucose in a cell versus the oxidation of glucose in a bomb calorimeter?

A)both the reactions involved and the net enthalpy values are identical
B)both the reactions involved and the net enthalpy values are different
C)the reactions involved are identical but the net enthalpy values are different
D)the reactions involved are different but the net enthalpy values are identical
E)none of the above

Question 17

The biochemical standard state differs from standard state conditions in what way?

A)pH = 7.0
B)T = 298.15 K
C)activity of water = 0
D)ionic strength = 1
E)all of the above

Question 18

Which of the following is true regarding a spontaneous reaction?

A) $\Delta$ H must always be negative
B)the sign of $\Delta$ S does not matter since the entropy value is relatively small
C)if both $\Delta$ H and $\Delta$ S are positive, T $\Delta$ S must be larger than $\Delta$ H
D)if both $\Delta$ H and $\Delta$ S are negative, the reaction will only proceed at high temperature
E)the only scenario that always produces a spontaneous reaction, regardless of temperature, is when $\Delta$ H is positive and $\Delta$ S is negative

Question 19

Which of the following conditions will produce a non-spontaneous reaction?

A)positive $\Delta$ H, positive $\Delta$ S, low temperature
B)negative $\Delta$ H, positive $\Delta$ S, high temperature.
C)negative $\Delta$ H, negative, $\Delta$ S, low temperature
D)negative $\Delta$ H, positive.. $\Delta$ S, high temperature.
E)positive $\Delta$ H, positive . $\Delta$ S, high temperature

Question 20

In the study of thermodynamics, which of the following could be examined as a system?

A)an isolated mitochondria
B)a single muscle cell
C)an entire organism
D)the entire planet Earth
E)all of the above

Question 21

Calculate the $\Delta$ G ^$\circ$ 'for the oxidation of succinate to fumarate, a step in the citric acid cycle.
FAD + 2H⁺ + 2e^- $\rarr$ FADH₂ E ^$\circ$ ' = - 0.22 V
fumarate + 2H⁺ + 2e^- $\rarr$ succinate E ^$\circ$ ' = + 0.03 V

Question 22

In a resting muscle cell at 37 ^$\circ$ C, what is the $\Delta$ G for the phosphorylation of ADP by creatine phosphate (CP)given the following concentrations: CP, 25 mM; ATP, 5 mM; ADP, 0.1 mM and creatine, 1 mM? creatine phosphate + H₂O $\rarr$ creatine + P_i $\Delta$ G ^$\circ$ ' = -43.1 kJ/mol
ATP + H₂O $\rarr$ ADP + P_i $\Delta$ G ^$\circ$ ' = -30.5 kJ/mol

A)+14.4 kJ/mol
B)+10.8 kJ/mol
C)-10.8 kJ/mol
D)-14.4 kJ/mol
E)none of the above

Question 23

If acetyl phosphate is made from the combination of ATP and acetate, what is the $\Delta$ G ^$\circ$ '? How would this reaction proceed within a typical cell?
acetyl phosphate + H₂O $\rarr$ acetate + P_i + H⁺ $\Delta$ G ^$\circ$ '= -43.1 kJ/mol
ATP + H₂O $\rarr$ ADP + P_i + H⁺ $\Delta$ G ^$\circ$ ' = -30.5 kJ/mol

Question 24

The typical concentration of glucose-6-phosphate (G6P)in a cell is 1 mM. What concentration of glucose-1-phosphate (G1P)would be required to make the interconversion of G6P and G1P freely reversible at 37 ^$\circ$ C?
G1P + H₂O $\rarr$ glucose + P_i $\Delta$ G ^$\circ$ ' = -20.9 kJ/mol
G6P + H₂O $\rarr$ glucose + P_i $\Delta$ G ^$\circ$ = -13.8 kJ/mol

Question 25

What is the E ^$\circ$ ' for the spontaneous reaction that would result if the following reactions were coupled? NAD⁺ + H⁺ + 2e^- $\rarr$ NADH E ^$\circ$ ' = -0.32 V
Pyruvate + 2H⁺ + 2e^- $\rarr$ 0 lactate E ^$\circ$ ' = -0.19 V

A)-0.51 V
B)-0.13 V
C)+0.13 V
D)+0.51 V
E)none of the above