Ch08_Lecture_enzymes and metabolism

Question 1

1) Which of the following is a statement of the first law of thermodynamics?
A) Energy cannot be created or destroyed.
B) The entropy of the universe is decreasing.
C) The entropy of the universe is constant.
D) Kinetic energy is stored energy that results from the specific arrangement of matter.
E) Energy cannot be transferred or transformed.

Answer 1

A) Energy cannot be created or destroyed.

Question 2

2) For living organisms, which of the following is an important consequence of the first
law of thermodynamics?
A) The energy content of an organism is constant.
B) The organism ultimately must obtain all of the necessary energy for life from its
environment.
C) The entropy of an organism decreases with time as the organism grows in
complexity.
D) Organisms grow by converting energy into organic matter.
E) Life does not obey the first law of thermodynamics.

Answer 2

B) The organism ultimately must obtain all of the necessary energy for life from its
environment.

Question 3

3) Living organisms increase in complexity as they grow, resulting in a decrease in the
entropy of an organism. How does this relate to the second law of thermodynamics?
A) Living organisms do not obey the second law of thermodynamics, which states that
entropy must increase with time.
B) Life obeys the second law of thermodynamics because the decrease in entropy as
the organism grows is exactly balanced by an increase in the entropy of the universe.
C) Living organisms do not follow the laws of thermodynamics.
D) As a consequence of growing, organisms cause a greater increase in entropy in their
environment than the decrease in entropy associated with their growth.
E) Living organisms are able to transform energy into entropy.

Answer 3

D) As a consequence of growing, organisms cause a greater increase in entropy in their
environment than the decrease in entropy associated with their growth.

Question 4

4) Whenever energy is transformed, there is always an increase in the \_\_\_\_\_\_\_\_. 
A) free energy of the system 
B) free energy of the universe 
C) entropy of the system 
D) entropy of the universe 
E) enthalpy of the universe

Answer 4

D) entropy of the universe

Question 5

5) Which of the following statements is a logical consequence of the second law of
thermodynamics?
A) If the entropy of a system increases, there must be a corresponding decrease in the
entropy of the universe.
B) If there is an increase in the energy of a system, there must be a corresponding
decrease in the energy of the rest of the universe.
C) Every energy transfer requires activation energy from the environment.
D) Every chemical reaction must increase the total entropy of the universe.
E) Energy can be transferred or transformed, but it cannot be created or destroyed.

Answer 5

D) Every chemical reaction must increase the total entropy of the universe.

Question 6

6) Which of the following statements is representative of the second law of
thermodynamics?
A) Conversion of energy from one form to another is always accompanied by some gain
of free energy.
B) Heat represents a form of energy that can be used by most organisms to do work.
C) Without an input of energy, organisms would tend toward decreasing entropy.
D) Cells require a constant input of energy to maintain their high level of organization.
E) Every energy transformation by a cell decreases the entropy of the universe.

Answer 6

D) Cells require a constant input of energy to maintain their high level of organization.

Question 7

7) Which of the following is an example of potential rather than kinetic energy?
A) the muscle contractions of a person mowing grass
B) water rushing over Niagara Falls
C) light flashes emitted by a firefly
D) a molecule of glucose
E) a crawling beetle foraging for food

Answer 7

D) a molecule of glucose

Question 7

7) Which of the following is an example of potential rather than kinetic energy?
A) the muscle contractions of a person mowing grass
B) water rushing over Niagara Falls
C) light flashes emitted by a firefly
D) a molecule of glucose
E) a crawling beetle foraging for food

Answer 7

D) a molecule of glucose

Question 8

8) The mathematical expression for the change in free energy of a system is ΔG =ΔH −
TΔS. Which of the following is (are) correct?
A) ΔS is the change in enthalpy, a measure of randomness.
B) ΔH is the change in entropy, the energy available to do work.
C) ΔG is the change in free energy.
D) T is the temperature in degrees Celsius.

Answer 8

C) ΔG is the change in free energy.

Question 9

9) A system at chemical equilibrium ________.
A) consumes energy at a steady rate
B) releases energy at a steady rate
C) consumes or releases energy, depending on whether it is exergonic or endergonic
D) has zero kinetic energy
E) can do no work

Answer 9

E) can do no work

Question 10

10) A chemical reaction that has a positive ΔG is best described as \_\_\_\_\_\_\_\_. 
A) endergonic 
B) entropic 
C) enthalpic 
D) spontaneous 
E) exergonic

Answer 10

A) endergonic

Question 10

10) A chemical reaction that has a positive ΔG is best described as \_\_\_\_\_\_\_\_. 
A) endergonic 
B) entropic 
C) enthalpic 
D) spontaneous 
E) exergonic

Answer 10

A) endergonic

Question 11

11) Enthalpy (H) is the \_\_\_\_\_\_\_\_. 
A) total kinetic energy of a system 
B) total energy in biological systems 
C) system's entropy 
D) cell's energy equilibrium 
E) condition of a cell that is not able to react

Answer 11

B) total energy in biological systems

Question 12

12) Biological evolution of life on Earth, from simple prokaryote-like cells to large,
multicellular eukaryotic organisms, ________.
A) has occurred in accordance with the laws of thermodynamics
B) has caused an increase in the entropy of the planet
C) has been made possible by expending Earth’s energy resources
D) has occurred in accordance with the laws of thermodynamics, by expending Earth’s
energy resources and causing an increase in the entropy of the planet
E) violates the laws of thermodynamics because Earth is a closed system

Answer 12

A) has occurred in accordance with the laws of thermodynamics

Question 13

13) Which of the following is TRUE for all exergonic reactions?
A) The products have more total energy than the reactants.
B) The reaction proceeds with a net release of free energy.
C) The reaction goes only in a forward direction: All reactants will be converted to
products, but no products will be converted to reactants.
D) A net input of energy from the surroundings is required for the reactions to proceed.
E) The reactions are rapid.

Answer 13

B) The reaction proceeds with a net release of free energy.

Question 14

14) Why is ATP an important molecule in metabolism?
A) Its hydrolysis provides an input of free energy for exergonic reactions.
B) It provides energy coupling between exergonic and endergonic reactions.
C) Its terminal phosphate group contains a strong covalent bond that, when hydrolyzed,
releases free energy.
D) Its terminal phosphate bond has higher energy than the other two phosphate bonds.
E) It is one of the four building blocks for DNA synthesis.

Answer 14

B) It provides energy coupling between exergonic and endergonic reactions.

Question 15

15) When 10,000 molecules of ATP are hydrolyzed to ADP and i in a test tube, about
half as much heat is liberated as when a cell hydrolyzes the same amount of ATP.
Which of the following is the best explanation for this observation?
A) Cells are open systems, but a test tube is an isolated system.
B) Cells are less efficient at heat production than nonliving systems.
C) The hydrolysis of ATP in a cell produces different chemical products than does the
reaction in a test tube.
D) The reaction in cells must be catalyzed by enzymes, but the reaction in a test tube
does not need enzymes.
E) Reactant and product concentrations in the test tube are different from those in the
cell.

Answer 15

E) Reactant and product concentrations in the test tube are different from those in the
cell.

Question 16

16) Catabolic pathways ________.
A) combine molecules into more energy-rich molecules
B) supply energy, primarily in the form of ATP, for the cell’s work
C) are endergonic
D) are spontaneous and do not need enzyme catalysis
E) build up complex molecules such as protein from simpler compounds

Answer 16

B) supply energy, primarily in the form of ATP, for the cell’s work

Question 17

17) When chemical, transport, or mechanical work is done by an organism, what
happens to the heat generated?
A) It is used to power yet more cellular work.
B) It is used to store energy as more ATP.
C) It is used to generate ADP from nucleotide precursors.
D) It is lost to the environment.

Answer 17

D) It is lost to the environment.

Question 18

18) Which of the following is the most correct interpretation of the accompanying figure?
A) Inorganic phosphate is created from organic phosphate.
B) Energy from catabolism can be used directly for performing cellular work.
C) ADP + Pi are a set of molecules that store energy for catabolism.
D) ATP is a molecule that acts as an intermediary to store energy for cellular work.
E) Pi acts as a shuttle molecule to move energy from ATP to ADP.

Answer 18

D) ATP is a molecule that acts as an intermediary to store energy for cellular work.

Question 19

19) How do cells use the ATP cycle shown in the figure?
A) Cells use the cycle to recycle ADP and phosphate.
B) Cells use the cycle to recycle energy released by ATP hydrolysis.
C) Cells use the cycle to recycle ADP, phosphate, and the energy released by ATP
hydrolysis.
D) Cells use the cycle to generate or consume water molecules as needed.
E) Cells use the cycle primarily to generate heat.

Answer 19

A) Cells use the cycle to recycle ADP and phosphate.

Question 20

20) Which of the following is TRUE when comparing an uncatalyzed reaction to the
same reaction with a catalyst?
A) The catalyzed reaction will be slower.
B) The catalyzed reaction will have the same ∆G.
C) The catalyzed reaction will have higher activation energy.
D) The catalyzed reaction will consume all of the catalyst.

Answer 20

B) The catalyzed reaction will have the same ∆G.

Question 21

21) You have discovered an enzyme that can catalyze two different chemical reactions.
Which of the following is most likely to be correct?
A) The enzyme contains α-helices and β-pleated sheets.
B) The enzyme is subject to competitive inhibition and allosteric regulation.
C) Two types of allosteric regulation occur: The binding of one molecule activates the
enzyme, while the binding of a different molecule inhibits it.
D) Either the enzyme has two distinct active sites or the reactants involved in the two
reactions are very similar in size and shape.

Answer 21

D) Either the enzyme has two distinct active sites or the reactants involved in the two
reactions are very similar in size and shape.

Question 22

22) Consider the HIV enzyme called protease. The amino acid residues at the active
site are highly hydrophobic. In designing a drug that would bind to the active site and
jam it, researchers should use a molecule that is ________.
A) hydrophobic
B) polar
C) charged
D) acidic

Answer 22

A) hydrophobic