Deck 4: Energy

Question 1

The course of chemical reactions is determined by three factors. These are enthalpy, entropy, and

A) Heat of reaction
B) Free energy
C) States of matter
D) Bond energy
E) Both A and B are correct

Answer 1

B

Question 2

Which of the following statements is true of an open system?

A) There is an exchange of energy only with the surroundings
B) There is an exchange of matter only with the surroundings
C) There is an exchange of both matter and energy with the surroundings
D) In an open system either matter or energy, but not both may be exchanged with the surroundings
E) Energy flows only into the system: matter flows out of the system

Answer 2

C

Question 3

Which of the following statements is true of a closed system?

A) There is an exchange of energy only with the surroundings
B) There is an exchange of matter only with the surroundings
C) There is an exchange of both matter and energy with the surroundings
D) In a closed system either matter or energy, but not both may be exchanged with the surroundings
E) Energy flows only into the system: matter flows out of the system

Answer 3

A

Question 4

Which of the following thermodynamic properties is a state function?

A) Work
B) Heat
C) Enthalpy
D) Entropy
E) Both C and D are correct

Question 5

The first law of thermodynamics is described by which of the following equations?

A) $\Delta$ E = Q+W
B) $\Delta$ Q = E-W
C) $\Delta$ W = Q-W
D) Both B and C are correct
E) All of the above are correct

Question 6

Which of the following statements is not true of a spontaneous process?

A) The enthalpy value is negative
B) The entropy value is negative
C) The free energy value is positive
D) The work value is negative
E) The enthalpy value is positive

Question 7

Which of the following is not a standard condition for standard free energy?

A) 25 ⁰C
B) 1 Atm. pressure
C) Concentration of reactants = 1 molar
D) Concentration of products = 1 molar
E) pH = 7

Question 8

The ionization constant of acetic acid is 1x10^-5. What is $\Delta$ G^o for the reaction?

A) -6500 cal/mol
B) 3250 cal/mol
C) 6500 cal/mol
D) 6000 cal/mol
E) 1624 cal/mol

Question 9

Under standard conditions is the ionization of a carboxylic acid spontaneous or not? A typical carboxylic acid has a pK_a of 4.

A) It is spontaneous
B) It is not spontaneous
C) Not enough information is provided

Question 10

In order for two reactions to be coupled what conditions must be met?

A) They must both be spontaneous
B) One of the reactions must be spontaneous
C) A product of one of the reactions must be a reactant in the second reaction
D) They both must have ATP as a reactant
E) Both B and C must be true

Question 11

When water and hydrophobic molecules are mixed all of the following are true except:

A) The hydrophobic molecules aggregate
B) The free energy of dissolving molecules is unfavorable
C) -T $\Delta$ S becomes negative
D) Water's hydrogen-bonded interactions are disrupted
E) All of the above are true

Question 12

The oxidation of food molecules to form CO₂ and H₂O is a (n) _______ process.

A) Exergonic
B) Endergonic
C) Isothermic
D) Lithotropic
E) Spontaneous

Question 13

The most important direct source of the energy that drives reactions in the body is:

A) ATP
B) ADP
C) GTP
D) Glucose
E) Fatty acids

Question 14

The law of the conservation of energy states that

A) The total energy of the universe is constant
B) Entropy of a system increases
C) There are three laws of thermodynamics
D) The work that can be performed by a system is a constant
E) The energy of a system's surroundings is constant

Question 15

Which of the following is a low quality energy source

A) Electromagnetic radiation
B) Heat
C) Electrical Energy
D) Chemical Energy
E) B and C

Question 16

Which of the following statements regarding free energy changes is true?

A) At equilibrium $\Delta$ G⁰ = O
B) For the reaction to be spontaneous $\Delta$ G^o must be positive
C) Free energy is a state function
D) Both A and C are true
E) All of the above are true

Question 17

Which of the following compounds would liberate the most free energy on hydrolysis?

A) ATP
B) Phosphoenolpyruvate
C) PP_i
D) ADP
E) GTP

Question 18

Which of the following thermodynamic properties is the most useful criterion of spontaneity?

A) Entropy
B) Free energy
C) Standard free energy
D) Enthalpy
E) Change in temperature

Question 19

For a reaction to be spontaneous which of the following statements must be true?

A) $\Delta$ S_univ= O
B) $\Delta$ S_univ = positive
C) $\Delta$ S_iniv = negative
D) A or B
E) Entropy has no effect on the spontaneity of a process

Question 20

Which of the following processes are driven by the hydrolysis of ATP?

A) Biosynthesis of biomolecules
B) Active transport of substances across membranes
C) Mechanical work such as muscle contraction
D) Both A and B are correct
E) All of the above are correct

Question 21

The study of reaction rates is called ___________.

A) Reactions
B) Thermodynamics
C) Kinetics
D) Mechanics
E) Entropics

Question 22

Which of the following is described by the first law of thermodynamics?

A) EnthalpY
B) Entropy
C) Free energy
D) A and B
E) A, B and

Question 23

Which of the following is described by the second law of thermodynamics?

A) Enthalpy
B) Entropy
C) Free energy
D) A and B
E) A, B, and C

Question 24

What type of bond is being cleaved during the conversion of ATP to ADP?

A) Ester
B) Ether
C) Hydrogen
D) Anhydride
E) Amide

Question 25

The tendency of ATP to undergo hydrolysis is called __________.

A) Free energy of hydrolysis
B) Cleavage rate
C) Phosphoryl group transfer potential
D) High energy bond potential
E) None of the above is correct

Question 26

The products of the hydrolysis of ATP are more stable than ATP itself. This circumstance is due to __________.

A) pH effects
B) Relief of charge-charge repulsions
C) Resonance stabilization of the products
D) Relief of steric strain
E) Both B and C are correct

Question 27

A living organism is what type of thermodynamic system?

A) Closed
B) Open
C) A system at equilibrium
D) A system with negative entropy
E) Both C and D are correct

Question 28

Which of the following thermodynamic properties is pathway dependent?

A) Free energy
B) Entropy
C) Enthalpy
D) Work
E) Both B and C are correct

Question 29

A Kelvin is _________.

A) A unit of temperature measurement
B) A unit of entropy measurement
C) A measurement of the density of a system
D) An index of the spontaneity of a reaction
E) A unit of heat

Question 30

The rate of a reaction can be determined from which of the following?

A) Free energy
B) Enthalpy
C) Entropy
D) All of the above are correct
E) None of the above is correct

Question 31

To maintain a system far from equilibrium a constant input of _______ is required.

A) Entropy
B) Energy
C) Only systems at equilibrium are stable
D) Disorganized energy
E) Both A and B are correct

Question 32

Systems far from equilibrium are referred to as _________ systems.

A) Spontaneous
B) Dissipative
C) Critical
D) Entropic
E) Heterotropic

Question 33

An organism at equilibrium is said to be __________.

A) At rest
B) Dissipative
C) Organized
D) Dead
E) Dormant

Question 34

The following statement is made by which law of thermodynamics?
"At absolute zero the disorder of a perfect crystal approaches zero".

A) First Law
B) Second Law
C) Third Law
D) A and B
E) All make this statement

Question 35

A measure of a system's internal energy is

A) Enthalpy
B) Entropy
C) Free energy
D) Work
E) Heat

Question 36

In living organisms where does the increase in entropy takes place?

A) Cell
B) Surroundings
C) Either A or B
D) Entropy does not change
E) Entropy does not apply to living things

Question 37

How many molecules of oxygen are required to completely oxidize one mole of stearic acid, (C₁₇H₃₅COOH)?

A) 18
B) 9
C) 34
D) 45
E) 53

Question 38

Given the following $\Delta$ H values, calculate the $\Delta$ H for the complete combustion of stearic acid.
$\begin{array}{ll}\Delta \mathrm{H}(\mathrm{Kcal} / \mathrm{mol} .) & \text { Compound } \\-211.4 & \mathrm{C}_{17} \mathrm{H}_{35} \mathrm{COOH} \\0 & \text { Oxygen } \\-94 & \text { Carbon dioxide } \\-68.4 & \text { Water }\end{array}$

A) -49 Kcal
B) -2096.2 Kcal
C) -2711.8 Kcal
D) 0 Kcal
E) 3071.8 Kcal

Question 39

Magnesium ion (Mg⁺⁺) forms complexes with ATP. What would happen to the stability of ATP if the magnesium was removed?

A) There would be no change in stability
B) The ATP would be more stable
C) The ATP would be less stable
D) The effect on stability would depend on specific conditions
E) Either A or B is correct

Question 40

Choose the molecule with the highest phosphate transfer potential.

A) Phosphoenolpyruvate
B) ATP
C) PP_i
D) Glucose-1-phosphate
E) Carbamoyl phosphate

Question 41

Biogeochemical cycles are pathways driven by which of the following?

A) Nuclear
B) Solar
C) Geothermal energy
D) Tectonic movements
E) B and C

Question 42

Which of the following moves through a system in a biogeochemical cycle?

A) Chemical compounds
B) Heat
C) Light
D) Energy
E) All of the above

Question 43

In classical thermodynamics which of the following is true?

A) All systems are at or near equilibrium
B) All materials are at low concentration
C) The system is far from equilibrium
D) The systems are always open
E) A and B

Question 44

A Benard cell is an example of:

A) A classical thermodynamic system
B) A system at equilibrium
C) A dissipative system
D) A system at uniform temperature
E) B and C

Question 45

The evolution of living organisms is driven by:

A) Size of the energy gradient to be dissipated
B) First law of thermodynamics
C) Second law of thermodynamics
D) Attainment of equilibrium
E) A and C

Question 46

A process is spontaneous when

A) $\Delta$ G⁰ = 0
B) $\Delta$ G⁰ > 0
C) $\Delta$ G⁰ < 0
D) Energy is absorbed
E) Entropy is negative

Question 47

Explain why entropy is a state function.

Question 48

What is a chemolithotrophe?

Question 49

Define the thermodynamic term work. Provide two physiological examples of work.

Question 50

At what temperature is $\Delta$ G^0' = $\Delta$ H for all conditions?

Question 51

In some biochemical processes a reaction will not occur by itself unless its product is a reactant in a more favorable reaction. What principle is involved in this phenomenon?

Question 52

Describe why ATP, the molecule that serves as the energy currency for the body, has an intermediate phosphoryl group transfer potential.

Question 53

Magnesium ion (Mg⁺⁺) forms complexes with the negative charges of the phosphate in ATP. In the absence of Mg⁺⁺ would ATP have more, less or the same stability as when the ion is present?

Question 54

What factor makes the hydrolysis of AMP less energetic than the hydrolysis of ATP or ADP?

Question 55

The law of the conservation of energy is an alternate statement of which law of thermodynamics?

Question 56

Frequently when salts dissolve in water, the solution becomes warm. Such a process is exothermic. When other salts, such as ammonium chloride, dissolve in water, the solution becomes cold, indicating an endothermic process. Because endothermic processes are generally not spontaneous, why does ammonium chloride dissolve in water?

Question 57

What is a biogeochemical cycle?

Question 58

Why is free energy a better measure of the spontaneity of a reaction than any of the three laws?

Question 59

Reactions that occur only if there is sufficient energy available to the system are said to be __________________.

Question 60

What conditions are necessary for two reactions to be coupled?

Question 61

What two processes are involved in the exchange of energy between a system and its surroundings?

Question 62

What happens when the energy flow in a living organism reaches equilibrium?

Question 63

What is meant by the term endergonic reaction?

Question 64

What is an isothermic process?

Question 65

What are the energy currency molecules in cells?

Question 66

What two categories of reactions provide the energy to drive metabolic processes?

Question 67

In order for the carbon cycle to function there must also be a silica cycle. Explain.

Question 68

All of the energy captured by living organisms is stored as redox energy. Explain in reference to photosynthesis and cell respiration.

Question 69

The total energy of an isolated system is constant. Explain.

Question 70

The first law of thermodynamics states that $\Delta$ H = $\Delta$ E + P $\Delta$ V + V $\Delta$ P . In living systems P $\Delta$ V and V $\Delta$ P are negligible. Explain.

Question 71

According to the first law of thermodynamics, it is theoretically possible for CO₂ and H₂O to spontaneously react to form a hydrocarbon. Explain why this process is not observed.

Question 72

In a living cell $\Delta$ S is always positive, whereas in a dead cell $\Delta$ S is zero. Explain.

Question 73

Of the three thermodynamic quantities $\Delta$ H, $\Delta$ G and $\Delta$ S which provides the most useful criterion of spontaneity in a reaction. Explain.

Question 74

In chemical reactions it is possible to have conditions where $\Delta$ E or $\Delta$ H = 0. Is it ever possible to have a condition where $\Delta$ S = 0?

Question 75

Phosphoenolpyruvate has a very high free energy of hydrolysis but only one phosphate group. Why does it have such a high free energy value?

Question 76

What are the first and second laws of thermodynamics and what are their defining equations?

Question 77

The K_a for the ionization of formic acid is 1.8 X 10^-4. Calculate $\Delta$ G^o for this reaction.

Question 78

The equilibrium constant for the ionization of acetic acid is 1.8X10^-5. Calculate $\Delta$ G^o for this reaction.

Question 79

Consider the following reaction
Glucose-1-phosphate $\rightarrow$ Glucose-6-phosphate
$\Delta$ G^o' = -7.1 kJ/mol
What is the equilibrium constant for this reaction at 25 ^oC

Question 80

Pyruvate oxidation to form carbon dioxide and water liberates energy at the rate of 1142.2 kJ/mol. If pyruvate is oxidized by cell respiration approximately 12.5 ATP molecules per mole are produced. The free energy of hydrolysis of ATP is -30.5 kJ/mol. What is the apparent efficiency of ATP production?