Q&A Hero

Q: The reduction of pyruvate to lactate has an Eo' of -0.185 V while the reduction of acetaldehyde to ethanol has an Eo' of -0.197 V. If these two reactions are coupled to produce a spontaneous reaction, which of the following would be the reducing agent?a. pyruvate d. ethanolb. lactate e. cannot be determined from the given informationc. acetaldehyde

Q: The conversion of glucose-6-phosphate to glucose-1-phosphate has a G°'of 8.4 kJ/mol. What can be said about the value of Keq?a. Keq > 1 b. Keq = 1 c. Keq < 1d. cannot be determined

Q: For the reaction of ATP + H2O -> ADP +Pi + H+, the biochemical standard state conditions would include all of the following EXCEPT:a. the concentration of ATP would be 1 M b. the temperature would be 25C c. the concentration of protons would be 10-7 Md. the concentration of water would be 1 Me. all to the above are correct

Q: The association of a protein and a fragment of DNA has a G°'of -57 kJ/mol. What is the equilibrium constant at 25 C for the formation of this complex?a. 1 b. -1 c. 1010d. 10-10e. cannot be determined

Q: Which of the following statements regarding ATP is true?a. the energy of hydrolysis is the same for all of the phosphate groups of the moleculeb. despite the very exergonic nature of the hydrolysis, ATP does not hydrolyze spontaneously due to a very high activation energyc. the G of hydrolysis within the cell is substantially greater than the G°' due to a higher concentration of ATP with respect to ADPd. electrostatic attraction of the phosphate groups contributes to a more exergonic free energye. both b and c are correct

Q: The effects of ____ on the G°'of hydrolysis of ATP are much greater than the effects of ____ or ____ under physiological conditions.a. pH, concentration, metal ionsb. metal ions, pH, concentrationc. temperature, concentration, pHd. concentration, pH, metal ionse. none of the above.

Q: A widely used "consensus value" for G°'of ATP hydrolysis in biological systems is ____ kJ/mol.a. -21b. -30.5c. -7d. 3e. 21

Q: Which statement MOST COMPLETELY EXPLAINSthe large G°for the hydrolysis of phosphoenolpyruvate?a. Hydrolysis of the phosphate bond along with the conversion of the enol to the keto form of pyruvate.b. The hydrolysis of the phosphoanhydride bond.c. Conversion from the enol to the keto form of pyruvate.d. Strong bond energy along with a change in the stereochemistry of the molecule.e. The large G° of the phosphoester bond.

Q: Which of the following statements about ATP is NOTtrue?a. It is used for short-term energy in the cell.b. It has two phosphoanhydride bonds.c. The reason for the large -G° values of hydrolysis reactions is due to stabilization of products.d. ATP is usually complexed with Mn2+.e. ATP is a kinetically stable molecule.

Q: The chemical reasons for the large negative ΔG°'for the hydrolysis of ____ include destabilization of the reactant due to bond strain caused by electrostatic repulsion, stabilization of the products by ionization and resonance, and entropy factors due to hydrolysis and subsequent ionization.a. AMPb. ATPc. PEPd. Phosphocreatinee. All of the above

Q: ATP hydrolysis coupled reactions have equilibrium constants that are changed by a factor of: a. 10 b. 100 c. 104 d. 106 e. 108

Q: Biochemists define the group transfer potential as the ____ that occurs upon hydrolysis (i.e., transfer of the particular group to water).a. Gb. Hc. Sd. Cpe. E

Q: ATP can donate ____ and ____ to lower-energy molecules of metabolism.a. phosphates, energyb. reactants, productsc. phosphates, waterd. energy, Ge. G, reactants

Q: The hydrolysis of a phosphate from which of the following molecules is most thermodynamically favorable? a. ADP b. glucose phosphate c. adenosine-5'-diphosphate d. phosphoenolpyruvate e. adenosine-5'-triphosphate

Q: The metabolite with a lower G°'of hydrolysis than ATP is:a. acetyl phosphate.b. phosphoenol pyruvate (PEP).c. phosphocreatine.d. adenosine-5'-phosphate.e. pyrophosphate.

Q: ____ and ____ are a small family of universal biomolecules mediating the flow of energy from exergonic reactions to the energy requiring processes of life. a. Reduced coenzymes, caffeine b. High-energy phosphate compounds, caffeine c. Chlorophyll, caffeine d. Hemoglobin, chlorophyll e. Reduced coenzymes, high-energy phosphate compounds

Q: "High-energy" compounds exhibit large negative free energy of hydrolysis and include all EXCEPT: a. phosphate esters. b. enol phosphates. c. acyl phosphates. d. guanidino phosphates. e. thioesters.

Q: Virtually all life on earth depends on energy ULTIMATELYfrom: a. the power company. b. batteries. c. the green-house effect. d. the sun. e. activation energy.

Q: Based upon the following reactions, what would be the G°'for the formation of ATP from phosphoenolpyruvate and ADP?ATP -> ADP + PiG°' = -31.5 kJ/molphosphoenolpyruvate -> pyruvate + PiG°' = -62.2 kJ/mola. -93.7 kJ/molb. -30.7 kJ/molc. +30.7 kJ/mold. +93.7 kJ/mole. cannot determine from given information

Q: To predict whether pairs of coupled reactions will proceed spontaneously:a. Subtract the smaller from the larger G.b. Sum the G°' values for each reaction.c. Add the S values for each reaction at constant temperature.d. The absolute value of the positive G°' must be larger than the value of the negative G°'.e. None are true.

Q: All describe modified standard state for a thermodynamic parameter EXCEPT:a. designated with a prime ( ' ) symbol.b. H+ ion of 10-7 M.c. 10-6 M for solutions.d. 1 atm. for gases.e. When the solvent is water at pH = 7.

Q: For an endothermic reaction to be spontaneous, which of the following must be true? a. heat must be given off by the reaction b. energy must be added to the reaction c. the temperature must be very low d. the entropy must increase substantially e. none of the above are true

Q: Thermodynamic parameters (entropy, enthalpy, free energy, and internal energy) are given for an unknown enzyme. Explain which results would be expected for the breaking of hydrogen bonds and the exposure of hydrophobic groups from the interior during the unfolding process of a protein.a. Entropy change, S, is zerob. Enthalpy change, H, is positivec. The reaction is spontaneousd. Enthalpy change, H, is negativee. Entropy change, S, is positive

Q: The standard state free energy change, G, is:a. positive when the reaction is unfavorable.b. an expression of Keq.c. negative when the reaction is favorable.d. equal to H - TS.e. none of the above.

Q: An interaction between two subunits of a protein was determined to have a G°'= -57.05 kJ/mol. What is the Keqfor the reaction at 25°C?a. 1.02b. 1.32c. 10-10d. 1010e. cannot determine from given information

Q: All are true about G EXCEPT?a. A positive or negative G tells us which direction the reaction will proceed.b. G depends upon the concentration of the reactants and products.c. G is affected by temperature.d. G is affected by pressure and pH.e. G is negative for endergonic reactions.

Q: Given the following reaction, what can be said about the equilibrium concentrations of the components of the reaction? (do not assume that concentrations began at standard conditions)pyruvate + NADH + H+ lactate + NAD+G°' = -25.2 kJ/mola. [pyruvate] > [NADH]b. [pyruvate] < [NAD+]c. [NAD+] > [NADH]d. [pyruvate] > [lactate]e. cannot determine

Q: Which equation definesa system at equilibrium?a. G > 0b.G° = Gc. G = 0d. G° = 0e. G = RT ln ([products]/[reactants])

Q: Entropy, S, is exactly zero at: a. 25ï‚°C b. 0ï‚°C c. 25ï‚°K d. 0ï‚°K e. 38ï‚°C

Q: Which example has the greatest increase in entropy, S?a. freezing waterb. sublimation of CO2c. melting iced. shattering glasse. boiling gasoline

Q: Entropy change, S, isa. the sum of heat absorbed and work.b. not a thermodynamic state function.c. a measure of disorder in a system.d. determined by pressure change at a constant temperature.e. equal to the heat transferred at constant pressure and volume.

Q: Which of the following statements is true for the Second Law of Thermodynamics? a. Systems tend to proceed from disordered states to ordered states. b. The entropy of the system plus its surroundings is unchanged by reversible processes c. The entropy of the system plus its surroundings decreases for irreversible processes. d. Naturally occurring processes never proceed toward equilibrium. e. All of the above are true

Q: An example of an open system would be: a. a chemical reaction taking place in a closed beaker. b. a steam radiator. c. an insulated bomb reactor. d. a pot of boiling water. e. contents of a calorimeter.

Q: Calorimetry measures ____ by a biochemical process.a. heat absorbed or given off, H,b. pressure change inside calorimeter createdc. water pressure createdd. entropy change, S,e. volume change, V, created

Q: Enthalpy change, H, is:a. the sum of heat absorbed and work.b. not a thermodynamic state function.c. a measure of disorder in a system.d. determined by pressure change at a constant temperature.e. equal to the heat transferred at constant pressure and volume.

Q: Internal energy is all EXCEPT: a. includes all the energy that might be exchanged in physical or chemical processes. b. path dependent. c. referred to as a state function d. commonly designated E or U. e. none, all are true.

Q: Which statement pertaining to the three basic systems is true? a. The internal energy of an isolated system is mostly conserved. b. Open systems can exchange matter with other open systems. c. Open systems can exchange matter with a closed system. d. The internal energy of an open system is always constant. e. A closed system can accept heat from an isolated system.

Q: Living systems are: a. closed systems exchanging only energy with the surroundings. b. isolated systems that are totally contained. c. open systems exchanging only energy with the surroundings. d. open systems exchanging both energy and matter with their surroundings. e. none of the above.

Q: Thermodynamics does NOT: a. describe the flow and interchange of heat, energy, and matter. b. allow the determination of whether a reaction is spontaneous. c. provide information on the rate of a reaction. d. consider heat flow and entropy production. e. consider the effect of concentration on net free energy change of a reaction.

Q: A weak acid is 33% dissociated at pH 5.0. What is the pKafor this acid?a. 4.5 b. 4.7 c. 5.3d. 5.5e. cannot be determined from the information provided

Q: Which of the following statements is INCORRECT about the nature of the hydrogen bonda. The donor is a hydrogen atom bonded to an atom that is less electronegative than hydrogen. b. The more linear the bond, the stronger the interaction. c. The acceptor is a fairly electronegative atom containing a nonbonding pair of electrons.d. It is a type of noncovalent bond.e. All of the above statements are true about the nature of the hydrogen bond

Q: Formic acid is the active agent in an ant bite. What is the ratio of base/acid for formic acid (pKa = 3.9) in the blood stream at pH 7.4?a. 3.16 x 10-4 b. 3.16 x 103 c. 0.54d. 1.90e. cannot be determined based upon the provided information

Q: Which of the following would be the conjugate acid of hydrogen phosphate, HPO4-2?a. H2PO4- b. H3PO4 c. H2PO4-2d. H2PO4-e. none of the above

Q: If a weak acid is 25% deprotonated at pH 4, what would the pKabe? a. 3.40 b. 3.52 c. 4.48 d. 4.60 e. cannot determine from given information

Q: Aspirin contains a carboxylic acid with a pKaof 3.5. Which of the following is true? a. Aspirin will be mostly protonated in the stomach b. Aspirin will be mostly protonated in the bloodstream c. Aspirin will be easily absorbed in the stomach due to its negative charge d. Aspirin will be easily transported in the bloodstream due to its negative charge e. both a and d are correct

Q: If an abundance of an organic acid with a pKaof 3.9 is found in the bloodstream, which of the following is true? a. it will be mostly protonated b. it will be mostly deprotonated c. it will form an effective buffer d. it will cause metabolic acidosis e. both b and d are correct

Q: Hypoventilation is characterized by inability to excrete CO2rapidly enough and can be caused by all EXCEPT: a. anesthetics. b. depressant drugs. c. narcotics. d. lung diseases. e. encephalitis.

Q: When preparing an acetate buffer at pH 4.5 with 0.01 M solutions of acetic acid (pKa= 4.8) and sodium acetate, the volume of acetic acid needed would be ____ the volume of sodium acetate solution. a. equal to b. less than half of c. more than half of d. about six times e. about twice

Q: The enzyme fumarase has a pH optimum of about 7.6. What would be the buffer of choice to study this enzyme?a. lactic acid (Ka = 1.38 x 10-4, pKa = 3.86)b. bicarbonate (Ka = 6.3 x 10-11, pKa = 10.24)c. acetic acid (Ka = 1.74 x 10-5, pKa = 4.76)d. succinate (Ka = 2.34 x 10-6, pKa = 5.63)e. tris-hydroxymethyl aminomethane (Ka = 8.32 x 10-9, pKa = 8.07)

Q: Which of the following weak acids would make the best buffer at pH = 5.0?a. acetic acid (Ka = 1.74 x 10-5, pKa = 4.76)b. H2PO4- (Ka = 1.38 x 10-7, pKa = 7.20)c. bicarbonate (Ka = 6.3 x 10-11, pKa = 10.24)d. tris-hydroxymethyl aminomethane (Ka = 8.32 x 10-9, pKa = 8.07)e. lactic acid (Ka = 1.38 x 10-4, pKa = 3.86)

Q: Water is particularly suited as a solvent for biosystems because it has all of the following characteristics EXCEPT: a. Water is a medium for ionization enhancing the variety of chemical species. b. Water is innocuous, yet a powerful solvent. c. Water is an excellent solvent for nonpolar substances. d. Water is relatively chemically inert, yet dissolves a variety of solutes. e. Through hydrophobic interactions, lipids coalesce into membranes in water.

Q: Hyperventilation is a physiological mechanism to:a. lower [CO2 (g)] in the blood and increase blood pH.b. raise [CO2 (g)] in the blood and increase blood pH.c. lower [CO2 (g)] in the blood and decrease blood pH.d. raise [CO2 (g)] in the blood and decrease blood pH.e. lower [CO2 (g)] in the blood and increase [HCO3-].

Q: Intracellular pH is maintained primarily by the ____ and ____ buffer systems, and the extracellular pH by the ____ buffer system.a. HPO42-/H2PO4-; HCO3-/H2CO3; histidineb. H3PO4/H2PO4-; histidine; HCO3-/H2CO3c. HCO3-/H2CO3; H3PO4/H2PO4-; histidined. HPO42-/H2PO4-; histidine; HCO3-/H2CO3e. HCO3-/H2CO3; histidine; H3PO4/H2PO4-

Q: Buffer systems are effective when the pH values are within ____ pH unit(s) of the pKavalue. a. 1 b. 2 c. 3 d. 4 e. 5

Q: Buffers have all of the following characteristics EXCEPT: a. they have relatively flat titration curves at the pH(s) where they buffer. b. they resist changes in their pH as acid or base is added. c. they are typically composed of a weak acid and its conjugate base. d. they buffer best for polyprotic acids half-way between the two pKa values. e. buffer where the amounts of conjugate base are nearly equivalent to the amounts of weak acid.

Q: pH = pKawhen:a. [A-]/[HA] = 0b. log ([A-]/[HA]) = 1c. [A-] >> [HA]d. [A-] = [HA]e. log ([HA]/[A-]) = 1

Q: A plasma pH of 6.8 doesn't seem too far away from a normal pH of 7.4, but at pH 6.8 the H+concentration is ____ times greater than at pH 7.4 and results in severe acidosis. a. 0.1 b. 0.6 c. 4 d. 10 e. 20

Q: What ionic form(s) is/are most prevalent at pH 7.0? The pKavalues of phosphoric acid are 2.1, 7.2, 12.4.a. HPO4-2b. H2PO4-c. HPO4-2 and PO4-3d. H2PO4- and HPO4-2e. All are correct

Q: Which of the following pairs would be the best buffer at pH 10.0? a. Acetic acid and sodium acetate (pKa = 4.76) b. H2CO3 and NaHCO3 (pKa values are 3.77 and 10.4) c. Lactic acid and sodium lactate (pKa = 3.86) d. NaH2PO4 and Na2HPO4 (pKa values are 2.1, 7.2, 12.4) e. Sodium succinate and succinic acid (pKa = 4.21)

Q: Estimate the pH of the resulting solution prepared by mixing 1.0 mole of solid disodium phosphate (Na2HPO4) and 1.25 mole of hydrochloric acid. The pKavalues for phosphoric acid are 2.1, 7.2, 12.4. a. pH < 2.1 b. pH = 2.1 c. 2.1 < pH < 7.2 d. pH = 7.2 e. 7.2 < pH < 12.4

Q: If 0.1 moles of Na2HPO4and 0.1 moles of NaH2PO4are mixed in water, what is the resulting pH? The pKavalues for phosphoric acid are 2.1, 7.2, 12.4. a. 2.1 b. 4.65 c. 7.2 d. 9.8 e. 12.4

Q: All are examples of weak electrolytes EXCEPT: a. hydrochloric acid. b. acetic acid. c. lactic acid. d. phosphoric acid. e. carbonic acid.

Q: Grapefruit juice at pH 3.2 contains about ____ times as much H+as orange juice at pH 4.3.a. 0.9b. 10-7.5c. 10-2d. 12e. 101

Q: Water ionizes because: a. the smaller electronegative oxygen atom strips the electron from one of its hydrogen atoms, leaving the proton to dissociate. b. the larger electronegative oxygen atom strips the electron from one of its hydrogen atoms, leaving the proton to dissociate. c. the smaller electropositive oxygen atom strips the electron from one of its hydrogen atoms, leaving the proton to dissociate. d. the larger electropositive oxygen atom strips the electron from one of its hydrogen atoms, leaving the proton to dissociate. e. None of the above

Q: To ____ the osmotic pressure created by the contents of their cytosol, cells tend to store substances such as amino acids and sugars in ____ form. a. increase, monomeric b. minimize, polymeric c. minimize, monomeric d. maximize, polymeric e. increase, polymeric

Q: By limiting the orientation that neighboring water molecules can assume, solutes give ____ to the solvent and ____ the dynamic interplay among H2O molecules that occurs in pure water. a. pressure, disrupt b. disorder, increase c. disorder, decrease d. order, diminish e. order, increase

Q: In micelles: a. polar ends form hydrophobic interactions with water. b. nonpolar ends form hydrophilic interactions with water. c. hydrocarbon tails form hydrophobic interactions with water. d. polar ends are hydrophobic and nonpolar ends are hydrophilic. e. hydrocarbon tails are excluded from the water into hydrophobic domains.

Q: Amphiphilic (amphipathic) molecules include: a. sugars. b. acidic amino acids. c. inorganic salts. d. water. e. salts of fatty acids.

Q: The H-bonded water around an ionic substance tends to ____; and the H-bonded water around nonpolar solutes tends to ____. a. inhibit ionization, promote hydrophobic interactions b. inhibit ionization, inhibit hydrophobic interactions c. not impact ionization, inhibit hydrophobic interactions d. promote ionization, not impact hydrophobic interactions e. promote ionization, promote hydrophobic interactions

Q: The ____ bonding of water with the polar functional groups on nonionic polar solutes such as sugars are ____ than the intermolecular attractions between solute molecules allowing solute molecules to readily dissolve in water. a. ionic, stronger b. hydrogen, weaker c. hydrophobic, stronger d. hydrogen, stronger e. ionic, weaker

Q: The average lifetime of a hydrogen bond connection in water is on the order of 10: a. picoseconds. b. microseconds. c. milliseconds. d. seconds. e. nanoseconds.

Q: Pure liquid water consists of H2O molecules: a. held in a rigid three-dimentional network. b. with local preference for linear geometry. c. with large numbers of strained or broken hydrogen bonds. d. which do not switch H-bonds readily. e. all are true.

Q: Hydrogen bonds in ice are all EXCEPT: a. directional. b. straight. c. weak. d. responsible for the lower density of ice over liquid water. e. holding water molecules in ice apart.

Q: The solvent with the highest dielectric constant in this group is: a. water. b. acetic acid. c. ethanol. d. hexane. e. benzene.

Q: Because of its highly polar nature, water is an excellent solvent for polar substances, but NOT for: a. salts. b. sugars. c. aldehydes and ketones. d. hydrocarbons. e. alcohols and amines.

Q: The unrivaled ability to form ____ hydrogen bonds per liquid water molecule is the source of the strong intermolecular attractions unique to water. a. 1 b. 2 c. 3 d. 4 e. 5

Q: All are true for water for a substance of its molecular weight that is neither metallic nor ionic EXCEPT: a. a high surface tension. b. a chemically inert solvent, which has a great capacity to dissolve a diverse spectrum of molecules and ions. c. a positive volume of melting. d. a high dielectric constant. e. a high capacity to form hydrogen bonds

Q: Properties of water that render it so suited to its role as a medium of life include all EXCEPT:a. Unrivaled ability to form hydrogen bonds.b. Unusually high dielectric constant of water explains water's ability to surround ions and increase the ions' attraction for one another.c. Unparalleled ability to orient around nonpolar solutes to promote hydrophobic interactions.d. The small, but significant, tendency to form H+ and OH- ions.e. None, all are true.

Q: Which of the following molecules is not generally incorporated into macromolecules?a. amino acids b. monosaccharides c. nucleotidesd. fatty acidse. all of the above are incorporated into macromolecules

Q: A carboxylic acid at pH 7.4 would most likely form a(n) ___________ with a(n) ____________.a. ionic interaction / amineb. ionic interaction / ketonec. hydrogen bond / alcohold. hydrogen bond / aldehydee. both a and c are correct