Chapter 8 BIO 114

What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways? A) feedback regulation B) bioenergetics C) energy coupling D) entropy E) cooperativity

c

Which of the following is most similar in structure to ATP? A) an anabolic steroid B) a DNA helix C) an RNA nucleotide D) an amino acid with three phosphate groups attached E) a phospholipid

c

Which of the following shows the correct changes in thermodynamic properties for a chemical reaction in which amino acids are linked to form a protein? A) + H, + S, + G B) + H, - S, - G C) + H, - S, + G D) - H, - S, + G E) - H, + S, + G

c

What must be the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in DNA and RNA? A) The sugar molecule is different. B) The nitrogen-containing base is different. C) The number of phosphates is three instead of one. D) The number of phosphates is three instead of two. E) There is no difference.

e

A chemical reaction that has a positive G is correctly described as A) endergonic. B) endothermic. C) enthalpic. D) spontaneous. E) exothermic.

A

The organization of organisms has become increasingly complex with time. This statement A) is consistent with the second law of thermodynamics. B) requires that due to evolution, the entropy of the universe increased. C) is based on the fact that organisms function as closed systems. D) A and B only E) A, B, and C

A

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.

A

Which of the following is considered an open system? A) an organism B) liquid in a corked bottle C) a sealed terrarium D) food cooking in a pressure cooker

A

Which of the following types of reactions would decrease the entropy within a cell? A) dehydration reactions B) hydrolysis C) respiration D) digestion E) catabolism

A

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 are unable to transform energy. E) Life does not obey the first law of thermodynamics.

B

Which of the following best describes enthalpy (H)? A) the total kinetic energy of a system B) the heat content of a chemical system C) the system s entropy D) the cell s energy equilibrium E) the condition of a cell that is not able to react

B

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) Some reactants will be converted to products. D) A net input of energy from the surroundings is required for the reactions to proceed. E) The reactions are nonspontaneous.

B

Which of the following statements is true concerning catabolic pathways? A) They combine molecules into more energy-rich molecules. B) They are usually coupled with anabolic pathways to which they supply energy in the form of ATP. C) They are endergonic. D) They are spontaneous and do not need enzyme catalysis. E) They build up complex molecules such as protein from simpler compounds.

B

Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose by the enzyme sucrase results in A) bringing glucose and fructose together to form sucrose. B) the release of water from sucrose as the bond between glucose and fructose is broken. C) breaking the bond between glucose and fructose and forming new bonds from the atoms of water. D) production of water from the sugar as bonds are broken between the glucose monomers. E) utilization of water as a covalent bond is formed between glucose and fructose to form sucrase.

C

The mathematical expression for the change in free energy of a system is G = H-T S. Which of the following is (are) correct? A) S is the change in enthalpy, a measure of randomness. B) H is the change in entropy, the energy available to do work. C) G is the change in free energy. D) T is the temperature in degrees Celsius.

C

Which of the following is (are) true for anabolic pathways? A) They do not depend on enzymes. B) They are usually highly spontaneous chemical reactions. C) They consume energy to build up polymers from monomers. D) They release energy as they degrade polymers to monomers.

C

Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell? A) a reaction in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium B) a chemical reaction in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell s surroundings C) an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment D) a chemical reaction in which both the reactants and products are only used in a metabolic pathway that is completely inactive E) There is no possibility of having chemical equilibrium in any living cell.

D

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 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 create more disorder in their environment than the decrease in entropy associated with their growth. E) Living organisms are able to transform energy into entropy.

D

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. E) It is transported to specific organs such as the brain.

D

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.

D

Which of the following is an example of potential rather than kinetic energy? A) a boy mowing grass B) water rushing over Niagara Falls C) a firefly using light flashes to attract a mate D) a food molecule made up of energy-rich macromolecules E) an insect foraging for food

D

Which of the following is true of metabolism in its entirety? A) Metabolism depends on a constant supply of energy from food B) Metabolism depends on an organism s adequate hydration C) Metabolism utilizes all of an organism s resources D) Metabolism is a property of organismal life E) Metabolism manages the increase of entropy in an organism

D

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.

D

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.

D

What is the change in free energy of a system at chemical equilibrium? A) slightly increasing B) greatly increasing C) slightly decreasing D) greatly decreasing E) no net change

E

When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice 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 a closed 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 are not the same

E

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones? A) catalysis B) metabolism C) anabolism D) dehydration E) catabolism

E

Which of the following statements is (are) true about enzyme-catalyzed reactions? A) The reaction is faster than the same reaction in the absence of the enzyme. B) The free energy change of the reaction is opposite from the reaction in the absence of the enzyme. C) The reaction always goes in the direction toward chemical equilibrium. D) A and B only E) A, B, and C

a

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the G for the new reaction? A) -40 kcal/mol B) -20 kcal/mol C) 0 kcal/mol D) +20 kcal/mol E) +40 kcal/mol

b

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction s A) entropy. B) activation energy. C) endothermic level. D) heat content. E) free-energy content.

b

The active site of an enzyme is the region that A) binds allosteric regulators of the enzyme. B) is involved in the catalytic reaction of the enzyme. C) binds the products of the catalytic reaction. D) is inhibited by the presence of a coenzyme or a cofactor.

b

When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free energy, total energy, and entropy are as follows: A) + G, + H, + S B) + G, + H, - S C) + G, - H, - S D) - G, + H, + S E) - G, - H, - S

b

Which of the following statements regarding enzymes is true? A) Enzymes decrease the free energy change of a reaction. B) Enzymes increase the rate of a reaction. C) Enzymes change the direction of chemical reactions. D) Enzymes are permanently altered by the reactions they catalyze. E) Enzymes prevent changes in substrate concentrations.

b

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. E) A, B, C, and D

b

A number of systems for pumping across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases although they don t often hydrolyze ATP unless they are simultaneously transporting ions. Small increases in calcium ions in the cytosol trigger a number of different intracellular reactions, so the cells must keep the calcium concentration quite low. Muscle cells also transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a muscle cell cytosol has a free calcium ion concentration of 10-7 in a resting cell, while the concentration in the SR can be 10-2, then how is the ATPase acting? A) The ATP must be powering an inflow of calcium from the outside of the cell into the SR. B) ATP must be transferring Pi to the SR to enable this to occur. C) ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient. D) The calcium ions must be diffusing back into the SR along the concentration gradient. E) The route of calcium ions must be from SR to the cytosol, to the cell s environment.

c

A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because A) the starch solution has less free energy than the sugar solution. B) the hydrolysis of starch to sugar is endergonic. C) the activation energy barrier for this reaction cannot be surmounted. D) starch cannot be hydrolyzed in the presence of so much water. E) starch hydrolysis is nonspontaneous.

c

According to the induced fit hypothesis of enzyme catalysis, which of the following is correct? A) The binding of the substrate depends on the shape of the active site. B) Some enzymes change their structure when activators bind to the enzyme. C) A competitive inhibitor can outcompete the substrate for the active site. D) The binding of the substrate changes the shape of the enzyme s active site. E) The active site creates a microenvironment ideal for the reaction

d

How can one increase the rate of a chemical reaction? A) Increase the activation energy needed. B) Cool the reactants. C) Decrease the concentration of the reactants. D) Add a catalyst. E) Increase the entropy of the reactants.

d

When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell? A) It is released as an excretory waste. B) It can only be used to regenerate more ATP. C) It can be added to water and excreted as a liquid. D) It can be added to other molecules in order to activate them. E) It can enter the nucleus to affect gene expression.

d