Chapter 6

An enzyme is a globular protein that inhibits the formation of chemical bonds within the enzyme's substrate(s) causing the rate of the reaction to slow down. A. True B. False

B. False

Which of the following is NOT a form of potential energy? A. food B. water in a dam C. a muscle contracting D. All of the choices are not potential energy.

C. a muscle contracting

The subunits from which ATP is made are: A. ADP and phosphate. B. FAD and NAD+. C. FAD and NADPH. D. ADP and FAD. E. ADP and NAD+.

A. ADP and phosphate

Identify the missing substrate in the reaction that will oxidize NAD+. NAD+ + 2e + _____ = NADH A. H+ B. 3H+ C. OH_ D. 2H+

A. H+

Feedback inhibition is the process that turns off an enzyme in a metabolic pathway as the result of inhibitory actions of a product of the pathway. A. True B. False

A. True

If the reaction graphed at right is coupled with D Picture E, then D Picture E is: A. exergonic B. endergonic C. spontaneous D. none of the above

B. endergonic If the reaction graphed at right is coupled with D-->E, then D-->E is endergonic, since the graphed reaction is exergonic. Endergonic and exergonic reactions are coupled.

Endergonic reactions: A. release energy. B. have a negative ΔG and occur spontaneously. C. can only occur if there is an input of energy. D. have products with less free energy than the reactants. E. All of the choices are correct.

C. can only occur if there is an input of energy.

Of the following, which process will not denature a protein? A. heating to temperatures above 100 C B. addition of strong acids C. addition of strong bases D. addition of distilled water

D. addition of distilled water

Energy coupling of endergonic and exergonic reactions within cells A. permits biological reactions to proceed at temperatures consistent with life. B. uses heat released by one reaction to fuel the other reaction. C. utilizes ATP to carry energy between the exergonic and endergonic reactions. D. All of the choices are correct.

D. all of the choices are correct

If a change in pH alters an allosteric site where an inhibitor binds, but doesn't change the active site for the intended substrate, it would be possible for an enzymatically controlled reaction to occur as normal. A. True B. False

A. True

Astrophysicists explain that eventually the sun will swell to become a red giant, engulf the earth and "burn out" with all forms of energy dispersing in a final "heat death." Compared with conditions today, the entropy of the universe then will A. have increased greatly. B. have decreased greatly. C. remain the same because energy cannot be created or destroyed.

A. have increased greatly

Which form of energy is NOT correctly associated with the related example? A. kinetic energy: fat molecules B. kinetic energy: movement of muscles C. chemical energy: glucose D. potential energy: water held behind a dam E. potential energy: ATP

A. kinetic energy: fat molecules

While we are sitting down to lunch we are consuming _______ energy which will then be converted into ______ energy as we work until dinner time. A. potential, kinetic B. kinetic, potential C.kinetic, free D. potential, stored

A. potential, kinetic

In this pathway, B Picture C is coupled with ADP Picture ATP. Categorize the reactions as endergonic or exergonic. A-->B-->C-->D-->E, F (B-->C = ADP-->up ATP) and (C-->D = ADP-->down ATP) A. B-->C is endergonic and ADP-->ATP is exergonic. B. ADP-->ATP is endergonic and B-->C is exergonic. C. Both B-->C and ADP-->ATP are endergonic. D. Both B-->C and ADP-->ATP are exergonic.

B. ADP-->ATP is endergonic and B-->C is exergonic.

Which best describes the first law of thermodynamics? A. Energy is changed from one form to another with a loss of usable energy. B. Energy is not created nor destroyed, but it can change from one energy form to another. C. Energy can be created from matter or used to produce matter. D. Some useful energy is lost as heat whenever an energy transfer occurs. E. Energy transfers are always 100% efficient in changing energy from one useful form to another.

B. Energy is not created nor destroyed, but it can change from one energy form to another.

Which of these statements is NOT a consequence of the second law of thermodynamics? A. While the total amount of energy is unchanged, the energy lost as heat is no longer useful to the cell in doing work. B. Reactions that occur spontaneously are those that increase the amount of useful energy in a system. C. The amount of disorder in the universe is always increasing. D. To maintain organization of a cell, a continual input of energy is required.

B. Reactions that occur spontaneously are those that increase the amount of useful energy in a system.

While eating a container of yogurt, you have to leave, so you store the yogurt in the refrigerator. A day later you return and find the surface of the yogurt is no longer smooth but has broken into several liquified products. You correctly guess that enzymes from your saliva, via the spoon, have continued digesting the yogurt in your absence. What will happen over time? A. The reaction will soon stop because the amount of saliva is small, and you would have to add more saliva to continue the degradation. B. The reaction will continue, since the enzyme is not denatured by the reaction. C. The reaction will continue until half is digested and then stop because the reaction between substrate and product will be balanced. D. Absolutely no degradation of the yogurt will occur naturally unless in the presence of this enzyme.

B. The reaction will continue, since the enzyme is not denatured by the reaction.

Coupling occurs when the energy released by an exergonic reaction is: A. used to drive another exergonic reaction. B. used to drive an endergonic reaction. C. lost as nonusable heat to the environment. D. used to decrease the entropy of the universe. E. All of the choices are correct.

B. used to drive an endergonic reaction.

__________ represents the first reactant of this metabolic pathway and ________ represents the endproduct (s) of the pathway? A-->B-->C-->D-->E, F A. A; E B. B; E and F C. A; E and F D. A and B; D and E

C. A;E and F

ATP is considered to be A. an enzyme used widely in all kinds of cells. B. a coenzyme used to inhibit or activate different enzymes. C. a molecule that carries a great deal of chemical energy in a chemical bond. D. the precursor of a high-energy membrane-bounded protein.

C. a molecule that carries a great deal of chemical energy in a chemical bond.

Which statement describes the currently accepted theory of how an enzyme and its substrate fit together? A. As the product is released, the enzyme breaks down. B. The enzyme is like a key that fits into the substrate, which is like a lock. C. The active site is permanently changed by its interaction with the substrate. D. As the substrate binds to the enzyme, the shape of the active site changes to accommodate the reaction.

D. As the substrate binds to the enzyme, the shape of the active site changes to accommodate the reaction.

Which best describes the second law of thermodynamics? A. Energy is not created nor destroyed, but it can change into matter. B. Energy is not created nor destroyed, but it can change from one energy form to another. C. Energy can be created from matter or used to produce matter. D. Some useful energy is lost as heat whenever an energy transfer occurs. E. Energy transfers are always 100% efficient in changing energy from one useful form to another.

D. Some useful energy is lost as heat whenever an energy transfer occurs.

A living organism represents stored energy in the form of chemical compounds. When an organism dies, what happens to this stored energy? A. All chemicals immediately lose their high-energy bonds. B. All molecules immediately degrade into basic elements. C. All energy immediately leaves, and that is one manifestation that the organism is dead. D. The chemical compounds in cells lose their organization over time because there is no longer an input of energy to maintain the organized state. E. The chemical compounds remain exactly intact and ready to start up again unless digested by a consumer or decay organism.

D. The chemical compounds in cells lose their organization over time because there is no longer an input of energy to maintain the organized state.

Which of the following is an example of potential energy? A. a snickers bar B. an apple growing on a tree C. a glass of milk D. all are examples of potential energy

D. all are examples of potential energy

In this reaction, the reactant (s) are _____________ and the coenzyme NAD is ____________. A+B-->C NAD, NADH A. reduced; oxidized B. oxidized; oxidized C. reduced; reduced D. oxidized; reduced

D. oxidized; reduced

The activity of an enzyme might be increased by all of the following except ________. A. increase in substrate concentration B. a vitamin C. a 2-4 degree increase in temperature D. the presence of lead

D. the presence of lead

Which statement is NOT true about enzyme inhibition? A. In competitive inhibition, the inhibitor binds to the active site of the enzyme. B. In noncompetitive inhibition, the inhibitor binds to the allosteric site of the substrate. C. In irreversible inhibition, a poison binds to the enzyme so that it can never work again. D. Most inhibitors act in a reversible fashion. E. All of the statements are true.

E. All of the statements are true.

All of the biochemical pathways in a cell constitute A. coupling reactions. B. free energy. C. endergonic reactions only. D. exergonic reactions only. E. metabolism.

E. metabolism