Metabolizing a test

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

A

According to the second law of thermodynamics, all of the following statements are true except that A) the synthesis of large molecules from small molecules is exergonic. B) life exists at the expense of greater energy than it contains. C) entropy increases in a closed system. D) every chemical transformed represents a loss of free energy. E) the Earth is an open system

A

The optimum temperatue for enzyme 1 (curve 1) is approximately? (in Celcius) A) 35 B) 45 C) 0 D) 75 E) Cannot be determined

A

When amino acids join to form a protein, the following energy and entropy changes apply: a. +△H, -△S, +△G b. +△H, +△S, -△G c. +△H, +△S, +△G d. -△H, +△S, +△G e. -△H, -△S, +△G

A

Which of the following bests describes the reaction? A) negative △G, spontaneous B) positive △G, nonspontaneous C) positive △G, exergonic D) negative △G, endergonic E) △G of zero, chemical equilibrium

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 most similar in structure to ATP? A) RNA nucleotides B) an amino acid with three phosphate groups attached. C) a phospholipid D) a double helix E) an anabolic steriod

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

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

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. Substance A functions as A) a coenzyme. B) an allosteric inhibitor. C) the substrate. D) an intermediate. E) a competitive inhibitor.

B

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

B

The inorganic non-protein components that participate in enzyme catalysis are known as a. coenzymes. b. cofactors. c. end-products. d. substrates. e. reactants.

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 represents the activation energy required for the enzyme-catalyzed reaction? A) a B) b C) c D) d E) e

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

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

Which of the following terms best describes the reaction? A) endergonic B) exergonic C) anabolic D) allosteric E) nonspontaneous

B

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. What is substance X? A) a coenzyme B) an allosteric inhibitor C) a substrate D) an intermediate E) the product

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

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following? A) denaturization of the enzyme B) allosteric inhibition C) competitive inhibition D) saturation of the enzyme activity E) insufficient cofactors

C

Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid. Based on this information, which of the following is correct? A) Succinate dehydrogenase is the enzyme, and fumarate is the substrate. B) Succinate dehydrogenase is the enzyme, and malonic acid is the substrate. C) Succinate is the substrate, and fumarate is the product. D) Fumarate is the product, and malonic acid is a noncompetitive inhibitor. E) Malonic acid is the product, and fumarate is a competitive inhibitor.

C

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

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 curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs at temperatures of 70°C or higher? A) curve 1 B) curve 2 C) curve 3 D) curve 4 E) curve 5

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. E) They consume energy to decrease the entropy of the organism and its environment.

C

Which of the following is true regarding catabolic pathways? a. they do not depend of enzymes b. they consume energy to build up polymers from monomers c. they release energy as they degrade polymers to monomers d. they lead to the synthesis of catabolic compounds e. both A and B

C

Which of the following represents the activation energy required for a noncatalyzed reaction? A) a B) b C) c D) d E) e

C

Which of these statements regarding enzymes is false? a. Enzymes are proteins that function as catalysts. b. Enzymes display specificity for certain molecules to which they attach. c. Enzymes provide activation energy for the reactions they catalyze. d. The activity of enzymes can be regulated by factors in their immediate environment. e. An enzyme may be used many times over for a specific reaction.

C

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

Assume that the reaction has a △G of -5.6 kcal/mol. Which of the following would be true? A) The reaction could be coupled to power an endergonic reaction with a △G of +6.2 kcal/mol. B) The reaction could be coupled to power an exergonic reaction with a △G of +8.8 kcal/mol. C) The reaction would result in a decrease in entropy (S) and an increase in the total energy content (H) of the system. D) The reaction would result in an increase in entropy (S) and a decrease in the total energy content (H) of the system. E) The reaction would result in products (C + D) with a greater free-energy content than in the initial reactants (A + B).

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

In an organism, the energy available to do work is called free energy because? a) it can be obtained with no cost to the system b) it can be spend with no cost to the universe c) the organism can live free of it if necessary d) it is available to do work e) it is equivalent to the systems total's energy

D

Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid? A) curve 1 B) curve 2 C) curve 3 D) curve 4 E) curve 5

D

Which of the following represents the difference between the free-energy content of the reaction and the free-energy content of the products? A) a B) b C) c D) d E) e

D

Which of the following represents the △G of the reaction? A) a B) b C) c D) d E) e

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 would be the same in an enzyme-catalyzed or noncatalyzed reaction? A) a B) b C) c D) d E) e

D

Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n) A) competitive inhibitor of the enzyme. B) noncompetitive inhibitor of the enzyme. C) allosteric activator of the enzyme. D) cofactor necessary for enzyme activity. E) coenzyme derived from a vitamin.

D

Metabolism is best described as a. synthesis of macromolecules b. breakdown of macromolecules c. control of enzyme activity d. A and B e. A, B, C

E

Which of the following is true of enzymes? a. Enzymes may require a nonprotein cofactor or ion for catalysis to take place. b. Enzyme function is reduced if the three-dimensional structure or conformation of an enzyme is altered. c. Enzyme function is influenced by physical and chemical environment factors such as pH and temperature. d. Enzymes increase the rate of chemical reaction by lowering activation energy barriers. e. All of the above are true.

E

Which of the following reactions would be coupled to the reaction ATP +H2O -> ADP + Pi (-7.3 kcal/mol)? A) A + Pi -> AP (+10 kcal/mol) B) B + Pi -> BP (+8 kcal/mol) C) CP -> C + Pi (-4 kcal/mol) D) DP -> D + Pi (-10 kcal/mol) E) E + Pi -> EP (+5 kcal/mol)

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