Deck 3: Thermodynamics of Biological Systems

Question 1

Which equation defines a system at equilibrium?

A)DG > 0
B)DG° = DG
C)DG = 0
D)DG° = 0
E)DG = RT ln ([products]/[reactants])

Answer 1

C

Question 2

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] > [lactate][NAD?] [pyruvate] < [NAD?]
B)[pyruvate][NADH] < [lactate][NAD?]
C)[NADH] > [lactate]

Answer 2

[NADH] > [lactate]

Question 3

Which thermodynamic property of a biochemical process is measured by calorimetry?

A)heat absorbed or given off,?H
B)overall change in ?G°
C)entropy change,?S
D)volume change,?V

Answer 3

heat absorbed or given off,?H

Question 4

Which of the following is correct for a spontaneous endothermic reaction?

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.

Question 5

Which of the following best describes living systems?

A)They are closed systems exchanging only energy with the surroundings.
B)They are isolated systems that are totally contained.
C)They are open systems exchanging only energy with the surroundings.
D)They are open systems exchanging both energy and matter with their surroundings.

Question 6

Thermodynamic parameters (entropy,enthalpy,free energy,and internal energy)are given for an unknown enzyme.What result is 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,DS,is zero.
B)Enthalpy change,DH,is positive.
C)Entropy change,DS,is positive.
D)Enthalpy change,DH,is negative.

Question 7

Which of the following is NOT correct regarding DG?

A)DG depends upon the concentration of the reactants and products.
B)DG is affected by temperature.
C)DG is negative for endergonic reactions.
D)DG is affected by pressure and pH.

Question 8

Which of the following does NOT describe a modified standard state for a thermodynamic parameter?

A)designated with a prime ( ' )symbol
B)H⁺ ion of 1 M
C)1 M for solutions
D)when the solvent is water at pH = 7

Question 9

Which of the following is NOT a feature of thermodynamics?

A)It describes the flow and interchange of heat,energy,and matter.
B)It allows the determination of whether a reaction is spontaneous.
C)It provides information on the rate of a reaction.
D)It considers heat flow and entropy production.

Question 10

What defines enthalpy change,DH?

A)It is the sum of heat absorbed and work.
B)It is a measure of disorder in a system.
C)It is equal to the heat transferred at constant pressure and volume.
D)It is determined by pressure change at a constant temperature.

Question 11

Which of the following is an example of an open system?

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

Question 12

Which of the following is correct regarding basic systems?

A)The internal energy of an isolated system is mostly conserved.
B)Open systems can exchange matter with other open systems.
C)The internal energy of an open system is always constant.
D)A closed system can accept heat from an isolated system.

Question 13

How can pairs of spontaneously coupled reactions be predicted?

A)by subtracting the smaller from the larger ?G
B)by summing the ?G°s for each reaction
C)by adding the ?S values for each reaction at constant temperature
D)by determining if the absolute value of the positive ?G°' must be larger than the value of the negative ?G°'

Question 14

What defines entropy change,DS?

A)the sum of heat absorbed and work
B)equal to the heat transferred at constant pressure and volume
C)a measure of disorder in a system
D)pressure change at a constant temperature

Question 15

Which of the following is NOT a feature of the second law of thermodynamics?

A)Systems tend to proceed from ordered states to disordered states.
B)The entropy of the system plus surroundings is unchanged by reversible processes.
C)The entropy of the system plus surroundings increases for irreversible processes.
D)All naturally occurring processes proceed toward equilibrium.

Question 16

What defines the standard-state free energy change,DG?

A)positive when the reaction is unfavourable
B)an expression of Keq
C)negative when the reaction is favourable
D)equal to DH - TDS

Question 17

At what temperature is entropy,S,exactly zero?

A)0K
B)0°C
C)25K
D)25°C

Question 18

An interaction between 2 subunits of a protein was determined to have a ?G°'= -57.05 kJ/mol.What is the K?q for the reaction at 25°C?

A)10-10
B)1.02
C)1.32
D)10¹⁰

Question 19

Which of the following characteristics does NOT apply to internal energy?

A)It includes all the energy that might be exchanged in physical or chemical processes.
B)It is path dependent.
C)It is referred to as a state function.
D)It is commonly designated E or U.

Question 20

Which example has the greatest increase in entropy,DS?

A)freezing water
B)sublimation of CO₂
C)melting ice
D)boiling gasoline

Question 21

Which of these values is a widely used "consensus value" for DG°' of ATP hydrolysis in biological systems?

A)-2-30.5 kJ/mol
B)-2-21 kJ/mol
C)3 kJ/mol
D)21 kJ/mol

Question 22

"High-energy" compounds exhibit large negative free energy of hydrolysis.Which of the following are NOT "high-energy" compounds?

A)phosphate esters
B)enol phosphates and phosphate anhydrides
C)acyl phosphates
D)guanidino phosphates

Question 23

By which factor do equilibrium constants change for reactions coupled to ATP hydrolysis?

A)10²
B)10⁴
C)10⁶
D)10⁸

Question 24

Which of the following factors has the greatest effect on the DG°' of hydrolysis of ATP?

A)concentration
B)metal ions
C)temperature
D)pH

Question 25

Which statement best explains the large DG° for the hydrolysis of phosphoenolpyruvate?

A)hydrolysis of the phosphoanhydride 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

Question 26

From which of the following molecules is the hydrolysis of a phosphate most thermodynamically favourable?

A)adenosine-5'-triphosphate
B)glucose phosphate
C)adenosine-5'-diphosphate
D)phosphoenolpyruvate

Question 27

Which of the following is a characteristic of ATP?

A)The energy of hydrolysis is the same for all of the phosphate groups of the molecule.
B)ATP does not hydrolyze spontaneously due to a very high activation energy.
C)The DG of hydrolysis within the cell is substantially greater than the DG°¢ 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.

Question 28

Which thermodynamic property defines the group transfer potential that occurs upon hydrolysis (i.e.,transfer of the particular group to water)?

A)DG
B)DH
C)DS
D)DE

Question 29

Which energy source does virtually all life on earth depend on?

A)activation energy
B)batteries
C)the green-house effect
D)the sun

Question 30

Which of these metabolites has a lower DG°' of hydrolysis than ATP?

A)pyrophosphate
B)phosphoenol pyruvate (PEP)
C)phosphocreatine
D)adenosine-5'-phosphate

Question 31

Which of the following is NOT a chemical reason for the large negative DG°' for the hydrolysis of ATP?

A)destabilization of the reactant due to bond strain caused by electrostatic repulsion
B)the largely negative DS associated with it
C)stabilization of the products by ionization and resonance
D)entropy factors due to hydrolysis and subsequent ionization

Question 32

Which of the following is NOT a feature of ATP?

A)It is used for short-term energy in the cell.
B)It has 2 phosphoanhydride bonds.
C)It is usually complexed with Ca²⁺.
D)It is a kinetically stable molecule.

Question 33

Which pairs of biomolecules mediate the flow of energy from exergonic reactions to the energy-requiring processes of life?

A)reduced coenzymes and high-energy phosphate compounds
B)high-energy phosphate compounds and caffeine
C)chlorophyll and caffeine
D)hemoglobin and chlorophyll

Question 34

Which of the following can ADP accept from higher energy molecules,while ATP can donate to lower energy molecules of metabolism?

A)phosphates
B)reactants
C)products
D)energy

Question 35

Based upon the following reactions,what would be the Based upon the following Based upon the following ?G°¢ for the formation of ATP from phosphoenolpyruvate and ADP?
ATP? ADP + Pi ?G°' = -31.5 kJ/mol
Phosphoenolpyruvate? pyruvate + P??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