Question 1

Which of the following weak acids would make the best buffer at pH = 5.0?

Accepted Answer

A)  acetic acid (Ka = 1.74 × 10−5, pKa = 4.76) 
B)  H2PO4− (Ka = 1.38 × 10−7, pKa = 7.20) 
C)  bicarbonate (Ka = 6.3 × 10−11, pKa = 10.24) 
D)  tris-hydroxymethyl aminomethane (Ka = 8.32 × 10−9, pKa = 8.07) 
E)  lactic acid (Ka = 1.38 × 10−4, pKa = 3.86) 
A)  acetic acid (Ka = 1.74 × 10−5, pKa = 4.76) 
B)  H2PO4− (Ka = 1.38 × 10−7, pKa = 7.20) 
C)  bicarbonate (Ka = 6.3 × 10−11, pKa = 10.24) 
D)  tris-hydroxymethyl aminomethane (Ka = 8.32 × 10−9, pKa = 8.07) 
E)  lactic acid (Ka = 1.38 × 10−4, pKa = 3.86) A

Question 2

Explain the role that water plays in living systems.​

Accepted Answer

Water is a "poor" solvent for nonpolar substances. Thus, through hydrophobic interactions, lipids coalesce, membranes form, boundaries are created delimiting compartments, and the cellular nature of life is established. Because of its very high dielectric constant, water is a medium for ionization. Ions enrich the living environment in that they enhance the variety of chemical species and introduce an important class of chemical reactions. They provide electrical properties to solutions and therefore to organisms. The thermal properties of water allow effective temperature regulation in living organisms. The heat generated within an organism as a result of metabolism can be efficiently eliminated through evaporation or conduction of water.
​

Question 3

All are examples of weak electrolytes EXCEPT:

Accepted Answer

A)  hydrochloric acid. 
B)  acetic acid. 
C)  lactic acid. 
D)  phosphoric acid. 
E)  carbonic acid. 
A)  hydrochloric acid. 
B)  acetic acid. 
C)  lactic acid. 
D)  phosphoric acid. 
E)  carbonic acid. A

Question 4

Calculate the equilibrium constant, Keq, for 1 L of pure water.​

Accepted Answer

The dissociation of water into hydrogen

Question 5

The unrivaled ability to form ____ hydrogen bonds per liquid water molecule is the source of the strong intermolecular attractions unique to water.

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5 
A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 6

​Discuss the dielectric constant of water. Write the equation used to calculate the dielectric constant.

Accepted Answer

The attractions between the water molecu

Question 7

What ionic form(s) is/are most prevalent at pH 7.0? The pKa values of phosphoric acid are 2.1, 7.2, and 12.4.

Accepted Answer

A)  HPO4−2 
B)  H2PO4− 
C)  HPO4−2 and PO4−3 
D)  H2PO4− and HPO4−2 
E)  All are correct 
A)  HPO4−2 
B)  H2PO4− 
C)  HPO4−2 and PO4−3 
D)  H2PO4− and HPO4−2 
E)  All are correct

Question 8

Water ionizes because:

Accepted Answer

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 
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

Question 9

Pure liquid water consists of H2O molecules:

Accepted Answer

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. 
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.

Question 10

The enzyme fumarase has a pH optimum of about 7.6. What would be the buffer of choice to study this enzyme?

Accepted Answer

A)  lactic acid (Ka = 1.38 × 10−4, pKa = 3.86) 
B)  bicarbonate (Ka = 6.3 × 10−11, pKa = 10.24) 
C)  acetic acid (Ka = 1.74 × 10−5, pKa = 4.76) 
D)  succinate (Ka = 2.34 × 10−6, pKa = 5.63) 
E)  tris-hydroxymethyl aminomethane (Ka = 8.32 × 10−9, pKa = 8.07) 
A)  lactic acid (Ka = 1.38 × 10−4, pKa = 3.86) 
B)  bicarbonate (Ka = 6.3 × 10−11, pKa = 10.24) 
C)  acetic acid (Ka = 1.74 × 10−5, pKa = 4.76) 
D)  succinate (Ka = 2.34 × 10−6, pKa = 5.63) 
E)  tris-hydroxymethyl aminomethane (Ka = 8.32 × 10−9, pKa = 8.07)

Question 11

Which of the following statements is INCORRECT about the nature of the hydrogen bond

Accepted Answer

A)  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. 
A)  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.

Question 12

pH = pKa when:

Accepted Answer

A)  [A−]/[HA] = 0 
B)  log ([A−]/[HA]) = 1 
C)  [A−] >> [HA] 
D)  [A−] = [HA] 
E)  log ([HA]/[A−]) = 1 
A)  [A−]/[HA] = 0 
B)  log ([A−]/[HA]) = 1 
C)  [A−] >> [HA] 
D)  [A−] = [HA] 
E)  log ([HA]/[A−]) = 1

Question 13

Water is particularly suited as a solvent for biosystems because it has all of the following characteristics EXCEPT:

Accepted Answer

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. 
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.

Question 14

The solvent with the highest dielectric constant in this group is:

Accepted Answer

A)  water. 
B)  acetic acid. 
C)  ethanol. 
D)  hexane. 
E)  benzene. 
A)  water. 
B)  acetic acid. 
C)  ethanol. 
D)  hexane. 
E)  benzene.

Question 15

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?

Accepted Answer

A)  3.16 × 10-4 
B)  3.16 × 103 
C)  0.54 
D)  1.90 
E)  cannot be determined based upon the provided information 
A)  3.16 × 10-4 
B)  3.16 × 103 
C)  0.54 
D)  1.90 
E)  cannot be determined based upon the provided information

Question 16

Explain weak electrolytes with an example.​

Accepted Answer

Substances with only a slight tendency t

Question 17

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.

Accepted Answer

A)  equal to 
B)  less than half of 
C)  more than half of 
D)  about six times 
E)  about twice 
A)  equal to 
B)  less than half of 
C)  more than half of 
D)  about six times 
E)  about twice

Question 18

Intracellular pH is maintained primarily by the ____ and ____ buffer systems, and the extracellular pH by the ____ buffer system.

Accepted Answer

A)  HPO42−/H2PO4−; HCO3−/H2CO3; histidine 
B)  H3PO4/H2PO4−; histidine; HCO3−/H2CO3 
C)  HCO3−/H2CO3; H3PO4/H2PO4−; histidine 
D)  HPO42−/H2PO4−; histidine; HCO3−/H2CO3 
E)  HCO3−/H2CO3; histidine; H3PO4/H2PO4− 
A)  HPO42−/H2PO4−; HCO3−/H2CO3; histidine 
B)  H3PO4/H2PO4−; histidine; HCO3−/H2CO3 
C)  HCO3−/H2CO3; H3PO4/H2PO4−; histidine 
D)  HPO42−/H2PO4−; histidine; HCO3−/H2CO3 
E)  HCO3−/H2CO3; histidine; H3PO4/H2PO4−

Question 19

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.

Accepted Answer

A)  pressure, disrupt 
B)  disorder, increase 
C)  disorder, decrease 
D)  order, diminish 
E)  order, increase 
A)  pressure, disrupt 
B)  disorder, increase 
C)  disorder, decrease 
D)  order, diminish 
E)  order, increase

Question 20

Grapefruit juice at pH 3.2 contains about ____ times as much H+ as orange juice at pH 4.3.

Accepted Answer

A)  0.9 
B)  10−7.5 
C)  10−2 
D)  12 
E)  101 
A)  0.9 
B)  10−7.5 
C)  10−2 
D)  12 
E)  101

Exam 2: Water: the Medium of Life

Which of the following weak acids would make the best buffer at pH = 5.0?

Explain the role that water plays in living systems.​

All are examples of weak electrolytes EXCEPT:

Calculate the equilibrium constant, Keq, for 1 L of pure water.​

The unrivaled ability to form ____ hydrogen bonds per liquid water molecule is the source of the strong intermolecular attractions unique to water.

​Discuss the dielectric constant of water. Write the equation used to calculate the dielectric constant.

What ionic form(s) is/are most prevalent at pH 7.0? The pKa values of phosphoric acid are 2.1, 7.2, and 12.4.

Water ionizes because:

Pure liquid water consists of H2O molecules:

The enzyme fumarase has a pH optimum of about 7.6. What would be the buffer of choice to study this enzyme?

Which of the following statements is INCORRECT about the nature of the hydrogen bond

pH = pKa when:

Water is particularly suited as a solvent for biosystems because it has all of the following characteristics EXCEPT:

The solvent with the highest dielectric constant in this group is:

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?

Explain weak electrolytes with an example.​

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.

Intracellular pH is maintained primarily by the ____ and ____ buffer systems, and the extracellular pH by the ____ buffer system.

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.

Grapefruit juice at pH 3.2 contains about ____ times as much H+ as orange juice at pH 4.3.

The Facts of Life: Chemistry Is the Logic of Biological Phenomena

Thermodynamics of Biological Systems

Amino Acids and the Peptide Bond

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, Tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Membranes and Membrane Transport

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Recombinant Dna, Cloning, Chimeric Genes, and Synthetic Biology

Enzymeskinetics and Specificity

Mechanisms of Enzyme Action

Enzyme Regulation

Molecular Motors

Metabolism: an Overview

Glycolysis

The Tricarboxylic Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Lipid Biosynthesis

Nitrogen Acquisition and Amino Acid Metabolism

Synthesis and Degradation of Nucleotides

Metabolic Integration and Organ Specialization

Dna Metabolism: Replication, Recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Completing the Protein Life Cycle: Folding, Processing, and Degradation

The Reception and Transmission of Extracellular Information

Filters

Explain the role that water plays in living systems.

Calculate the equilibrium constant, K_eq, for 1 L of pure water.

Discuss the dielectric constant of water. Write the equation used to calculate the dielectric constant.

What ionic form(s) is/are most prevalent at pH 7.0? The pK_a values of phosphoric acid are 2.1, 7.2, and 12.4.

Pure liquid water consists of H₂O molecules:

pH = pK_a when:

Explain weak electrolytes with an example.

When preparing an acetate buffer at pH 4.5 with 0.01 M solutions of acetic acid (pK_a = 4.8) and sodium acetate, the volume of acetic acid needed would be ____ the volume of sodium acetate solution.

Intracellular pH is maintained primarily by the and buffer systems, and the extracellular pH by the buffer system.

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.

Grapefruit juice at pH 3.2 contains about ____ times as much H⁺ as orange juice at pH 4.3.