Test bank for
biochemistry,
campbell –
Complete - exam
questions with
answers key
Page 1
,1. The dipole moment in a water molecule which statement about hydrogen bonds is not
true?
A) Hydrogen bonds account for the anomalously high boiling point of water.
B) In liquid water, the average water molecule forms hydrogen bonds with three to
four other water molecules.
C) Individual hydrogen bonds are much weaker than covalent bonds.
D) Individual hydrogen bonds in liquid water exist for many seconds and sometimes
for minutes.
E) The strength of a hydrogen bond depends on the linearity of the three atoms
involved in the bond.
2. A true statement about hydrophobic interactions is that they:
A) Are the driving force in the formation of micelles of amphipathic compounds in
water.
B) Do not contribute to the structure of water-soluble proteins.
C) Have bonding energies of approximately 20–40 kjoule per mole.
D) Involve the ability of water to denature proteins.
E) Primarily involve the effect of polar solutes on the entropy of aqueous systems.
3. Hydrophobic interactions make important energetic contributions to:
A) Binding of a hormone to its receptor protein.
B) Enzyme-substrate interactions.
C) Membrane structure.
D) Three-dimensional folding of a polypeptide chain.
E) All of the answers are correct.
4. Dissolved solutes alter some physical (colligative) properties of the solvent water
because they change the:
A) Concentration of the water.
B) Hydrogen bonding of the water.
C) Ionic bonding of the water.
D) Ph of the water.
Page 2
, E) Temperature of the water.
5. Osmosis is movement of a:
A) Charged solute molecule (ion) across a membrane.
B) Gas molecule across a membrane.
C) Nonpolar solute molecule across a membrane.
D) Polar solute molecule across a membrane.
E) Water molecule across a membrane.
6. A hydronium ion:
A) Has the structure h3o+.
B) Is a hydrated hydrogen ion.
C) Is a hydrated proton.
D) Is the usual form of one of the dissociation products of water in solution.
E) All of the answers are correct.
7. The ph of a solution of 1 m hcl is:
A) 0.
B) 0.1.
C) 1.
D) 10.
E) –1.
8. The ph of a solution of 0.1 m naoh is:
A) 0.1.
B) 1.0.
C) 12.8.
D) 13.
E) 14.
Page 3
, 9. Which statement is true about the properties of aqueous solutions?
A) A ph change from 5.0 to 6.0 reflects an increase in the hydroxide ion concentration
([oh–]) of 20%.
B) A ph change from 8.0 to 6.0 reflects a decrease in the proton concentration ([h+])
by a factor of 100.
C) Charged molecules are generally insoluble in water.
D) Hydrogen bonds form readily in aqueous solutions.
E) The ph can be calculated by adding 7 to the value of the poh.
10. The ph of a sample of blood is 7.4, while gastric juice is ph 1.4. The blood sample has:
A) 0.189 times the [h+] as the gastric juice.
B) 5.29 times lower [h+] than the gastric juice.
C) 6 times lower [h+] than the gastric juice.
D) 6000 times lower [h+] than the gastric juice.
E) One million times lower [h+] than the gastric juice.
11. The aqueous solution with the lowest ph is:
A) 0.01 m hcl.
B) 0.1 m acetic acid (pka = 4.86).
C) 0.1 m formic acid (pka = 3.75).
D) 0.1 m hcl.
E) 10–12 m naoh.
12. The aqueous solution with the highest ph is:
A) 1 m hcl.
B) 1 m nh3 (pka = 9.25).
C) 0.5 m nahco3 (pka = 3.77).
D) 0.1 m naoh.
E) 0.001 m naoh.
Page 4
,13. Phosphoric acid is tribasic, with pka's of 2.14, 6.86, and 12.4. The ionic form that
predominates at ph 3.2 is:
A) H3po4.
B) h2po –4.
C) hpo 2–4 .
D) po 3–
4 .
E) None of the answers is correct.
14. Which statement about buffers is true?
A) A buffer composed of a weak acid of pka = 5 is stronger at ph 4 than at ph 6.
B) At ph values lower than the pka, the salt concentration is higher than that of the
acid.
C) The ph of a buffered solution remains constant no matter how much acid or base is
added to the solution.
D) The strongest buffers are those composed of strong acids and strong bases.
E) When ph = pka, the weak acid and salt concentrations in a buffer are equal.
15. A compound has a pka of 7.4. To 100 ml of a 1.0 m solution of this compound at ph
8.0 is added 30 ml of 1.0 m hydrochloric acid. The resulting solution is ph:
A) 6.5.
B) 6.8.
C) 7.2.
D) 7.4.
E) 7.5.
16. The henderson-hasselbalch equation:
A) Allows the graphic determination of the molecular weight of a weak acid from
its ph alone.
B) Does not explain the behavior of di- or tri-basic weak acids.
C) Employs the same value for pka for all weak acids.
D) Is equally useful with solutions of acetic acid and of hydrochloric acid.
E) Relates the ph of a solution to the pka and the concentrations of acid and conjugate
base.
Page 5
,17. Consider an acetate buffer, initially at the same ph as its pka (4.76). When sodium
hydroxide (naoh) is mixed with this buffer, the:
A) Ph remains constant.
B) Ph rises more than if an equal amount of naoh is added to an acetate buffer
initially at ph 6.76.
C) Ph rises more than if an equal amount of naoh is added to unbuffered water at ph
4.76.
D) Ratio of acetic acid to sodium acetate in the buffer falls.
E) Sodium acetate formed precipitates because it is less soluble than acetic acid.
18. A compound is known to have a free amino group with a pka of 8.8, and one other
ionizable group with a pka between 5 and 7. To 100 ml of a 0.2 m solution of this
compound at ph 8.2 was added 40 ml of a solution of 0.2 m hydrochloric acid. The ph
changed to 6.2. The pka of the second ionizable group is:
A) The ph cannot be determined from this information.
B) 5.4.
C) 5.6.
D) 6.0.
E) 6.2.
19. Three buffers are made by combining a 1 m solution of acetic acid with a 1 m solution
of sodium acetate in the ratios shown below.
1 m acetic acid 1 m sodium acetate
Buffer 1: 10 ml 90 ml
Buffer 2: 50 ml 50 ml
Buffer 3: 90 ml 10 ml
Which statement is true of the resulting buffers?
A) Ph of buffer 1 < ph of buffer 2 < ph of buffer 3
B) Ph of buffer 1 = ph of buffer 2 = ph of buffer 3
C) Ph of buffer 1 > ph of buffer 2 > ph of buffer 3
D) The problem cannot be solved without knowing the value of pka.
E) None of the statements is true.
Page 6
,20. A 1.0 m solution of a compound with 2 ionizable groups (pka's = 6.2 and 9.5; 100 ml
total) has a ph of 6.8. If a biochemist adds 60 ml of 1.0 m hcl to this solution, the
solution will change to ph:
A) 5.60.
B) 8.90.
C) 9.13.
D) 9.32.
E) The ph cannot be determined from this information.
21. You want to maintain ph = 7.0 for an enzyme-catalyzed reaction that will produce
hydrogen ions along with the desired product. At equal concentrations, which weak
acid, if any, will serve as the better buffer for the reaction: acid a, with pka = 6.5, or
acid b, with pka = 7.5?
A) Acid a
B) Water is as good as either of the acids available.
C) Acid b
D) Both are equally effective.
22. In which reaction does water not participate as a reactant (rather than as a product)?
A) Conversion of an acid anhydride to two acids
B) Conversion of an ester to an acid and an alcohol
C) Conversion of atp to adp
D) Photosynthesis
E) Production of gaseous carbon dioxide from bicarbonate
23. Which property of water does not contribute to the fitness of the aqueous environment
for living organisms?
A) Cohesion of liquid water due to hydrogen bonding
B) High heat of vaporization
C) High specific heat
D) The density of water being greater than the density of ice
E) The very low molecular weight of water
Page 7
,24. The ionization of water is due to the strongly electronegative element:
A) Hydrogen donating an electron to oxygen.
B) Oxygen donating an electron to hydrogen.
C) Hydrogen receiving an electron from oxygen.
D) Oxygen receiving an electron from hydrogen.
E) None of the answers is correct.
25. Which attribute contributes to water's unusual properties?
A) The geometry of the molecule
B) The polarity of the molecule
C) The ability of water molecules to hydrogen bond
D) The dipole moment in a water molecule
E) All of the answers are correct.
26. Which factor contributes to the bent shape of a water molecule?
A) The dipole moment in a water molecule
B) The unshared electron pairs on the oxygen atom
C) The electronegativity difference between hydrogen and oxygen
D) The unequal electron sharing between hydrogen and oxygen
E) All of the answers are correct.
27. Ice is than water because .
A) Less dense; frozen water maintains more hydrogen bonds than liquid water
B) Less dense; liquid water maintains more hydrogen bonds than frozen water
C) Denser; frozen water maintains more hydrogen bonds than liquid water
D) Denser; liquid water maintains more hydrogen bonds than frozen water
E) Denser; frozen water cannot hydrogen bond
Page 8
,28. Which diagram correctly represent a hydrogen bond?
A) A and d
B) A and c
C) B and c
D) C and d
E) B and d
29. Which statement about biologically important gases is true?
A) O2 and co2 are the most important gases for living things and are therefore very
soluble in water.
B) O2 and co2 are both polar and are therefore very soluble in water.
C) O2 and co2 are both nonpolar molecules and are therefore both poorly soluble in
water.
D) Co2 contains polar bonds but o2 is nonpolar; therefore, co2 is very soluble in
water, but o2 is poorly soluble in water.
E) All biologically important gases are very soluble in water.
30. Which statement about hydrogen bonds is not true?
A) Hydrogen bonds are highly directional.
B) Hydrogen bonds are capable of holding molecules in a specific geometric
arrangement.
C) Hydrogen bonds are strongest when the three atoms in the bond are in a straight
line.
D) Hydrogen bonds are strongest when the oxygen atom is perpendicular to the
hydrogen donor.
E) Hydrogen bonds place a hydrogen ion directly between two partial negative
charges.
Page 9
, 31. Which compound would result in the formation of a clathrate structure?
A) Ch2o
B) Ch4
C) Nh3
D) Ch3ch2oh
E) None of the answers is correct.
32. Which diagram correctly illustrates the clustering of lipids in the formation of a
micelle?
A) A
B) B
C) Both a and b
D) Neither a nor b
33. Dissolving a nonpolar solute in water the order of the solvent and the
dynamic interplay among water molecules that occurs in pure water.
A) Increases; decreases
B) Increases; increases
C) Decreases; decreases
D) Decreases; increases
E) Decreases; stabilizes
34. Which statement regarding long-chain fatty acids in aqueous solution is not true?
A) Fatty acids in small concentrations are surrounded by highly ordered water
molecules in a “cage-like” structure.
B) Fatty acids will cluster together to minimize the lipid surface area.
Page 10
biochemistry,
campbell –
Complete - exam
questions with
answers key
Page 1
,1. The dipole moment in a water molecule which statement about hydrogen bonds is not
true?
A) Hydrogen bonds account for the anomalously high boiling point of water.
B) In liquid water, the average water molecule forms hydrogen bonds with three to
four other water molecules.
C) Individual hydrogen bonds are much weaker than covalent bonds.
D) Individual hydrogen bonds in liquid water exist for many seconds and sometimes
for minutes.
E) The strength of a hydrogen bond depends on the linearity of the three atoms
involved in the bond.
2. A true statement about hydrophobic interactions is that they:
A) Are the driving force in the formation of micelles of amphipathic compounds in
water.
B) Do not contribute to the structure of water-soluble proteins.
C) Have bonding energies of approximately 20–40 kjoule per mole.
D) Involve the ability of water to denature proteins.
E) Primarily involve the effect of polar solutes on the entropy of aqueous systems.
3. Hydrophobic interactions make important energetic contributions to:
A) Binding of a hormone to its receptor protein.
B) Enzyme-substrate interactions.
C) Membrane structure.
D) Three-dimensional folding of a polypeptide chain.
E) All of the answers are correct.
4. Dissolved solutes alter some physical (colligative) properties of the solvent water
because they change the:
A) Concentration of the water.
B) Hydrogen bonding of the water.
C) Ionic bonding of the water.
D) Ph of the water.
Page 2
, E) Temperature of the water.
5. Osmosis is movement of a:
A) Charged solute molecule (ion) across a membrane.
B) Gas molecule across a membrane.
C) Nonpolar solute molecule across a membrane.
D) Polar solute molecule across a membrane.
E) Water molecule across a membrane.
6. A hydronium ion:
A) Has the structure h3o+.
B) Is a hydrated hydrogen ion.
C) Is a hydrated proton.
D) Is the usual form of one of the dissociation products of water in solution.
E) All of the answers are correct.
7. The ph of a solution of 1 m hcl is:
A) 0.
B) 0.1.
C) 1.
D) 10.
E) –1.
8. The ph of a solution of 0.1 m naoh is:
A) 0.1.
B) 1.0.
C) 12.8.
D) 13.
E) 14.
Page 3
, 9. Which statement is true about the properties of aqueous solutions?
A) A ph change from 5.0 to 6.0 reflects an increase in the hydroxide ion concentration
([oh–]) of 20%.
B) A ph change from 8.0 to 6.0 reflects a decrease in the proton concentration ([h+])
by a factor of 100.
C) Charged molecules are generally insoluble in water.
D) Hydrogen bonds form readily in aqueous solutions.
E) The ph can be calculated by adding 7 to the value of the poh.
10. The ph of a sample of blood is 7.4, while gastric juice is ph 1.4. The blood sample has:
A) 0.189 times the [h+] as the gastric juice.
B) 5.29 times lower [h+] than the gastric juice.
C) 6 times lower [h+] than the gastric juice.
D) 6000 times lower [h+] than the gastric juice.
E) One million times lower [h+] than the gastric juice.
11. The aqueous solution with the lowest ph is:
A) 0.01 m hcl.
B) 0.1 m acetic acid (pka = 4.86).
C) 0.1 m formic acid (pka = 3.75).
D) 0.1 m hcl.
E) 10–12 m naoh.
12. The aqueous solution with the highest ph is:
A) 1 m hcl.
B) 1 m nh3 (pka = 9.25).
C) 0.5 m nahco3 (pka = 3.77).
D) 0.1 m naoh.
E) 0.001 m naoh.
Page 4
,13. Phosphoric acid is tribasic, with pka's of 2.14, 6.86, and 12.4. The ionic form that
predominates at ph 3.2 is:
A) H3po4.
B) h2po –4.
C) hpo 2–4 .
D) po 3–
4 .
E) None of the answers is correct.
14. Which statement about buffers is true?
A) A buffer composed of a weak acid of pka = 5 is stronger at ph 4 than at ph 6.
B) At ph values lower than the pka, the salt concentration is higher than that of the
acid.
C) The ph of a buffered solution remains constant no matter how much acid or base is
added to the solution.
D) The strongest buffers are those composed of strong acids and strong bases.
E) When ph = pka, the weak acid and salt concentrations in a buffer are equal.
15. A compound has a pka of 7.4. To 100 ml of a 1.0 m solution of this compound at ph
8.0 is added 30 ml of 1.0 m hydrochloric acid. The resulting solution is ph:
A) 6.5.
B) 6.8.
C) 7.2.
D) 7.4.
E) 7.5.
16. The henderson-hasselbalch equation:
A) Allows the graphic determination of the molecular weight of a weak acid from
its ph alone.
B) Does not explain the behavior of di- or tri-basic weak acids.
C) Employs the same value for pka for all weak acids.
D) Is equally useful with solutions of acetic acid and of hydrochloric acid.
E) Relates the ph of a solution to the pka and the concentrations of acid and conjugate
base.
Page 5
,17. Consider an acetate buffer, initially at the same ph as its pka (4.76). When sodium
hydroxide (naoh) is mixed with this buffer, the:
A) Ph remains constant.
B) Ph rises more than if an equal amount of naoh is added to an acetate buffer
initially at ph 6.76.
C) Ph rises more than if an equal amount of naoh is added to unbuffered water at ph
4.76.
D) Ratio of acetic acid to sodium acetate in the buffer falls.
E) Sodium acetate formed precipitates because it is less soluble than acetic acid.
18. A compound is known to have a free amino group with a pka of 8.8, and one other
ionizable group with a pka between 5 and 7. To 100 ml of a 0.2 m solution of this
compound at ph 8.2 was added 40 ml of a solution of 0.2 m hydrochloric acid. The ph
changed to 6.2. The pka of the second ionizable group is:
A) The ph cannot be determined from this information.
B) 5.4.
C) 5.6.
D) 6.0.
E) 6.2.
19. Three buffers are made by combining a 1 m solution of acetic acid with a 1 m solution
of sodium acetate in the ratios shown below.
1 m acetic acid 1 m sodium acetate
Buffer 1: 10 ml 90 ml
Buffer 2: 50 ml 50 ml
Buffer 3: 90 ml 10 ml
Which statement is true of the resulting buffers?
A) Ph of buffer 1 < ph of buffer 2 < ph of buffer 3
B) Ph of buffer 1 = ph of buffer 2 = ph of buffer 3
C) Ph of buffer 1 > ph of buffer 2 > ph of buffer 3
D) The problem cannot be solved without knowing the value of pka.
E) None of the statements is true.
Page 6
,20. A 1.0 m solution of a compound with 2 ionizable groups (pka's = 6.2 and 9.5; 100 ml
total) has a ph of 6.8. If a biochemist adds 60 ml of 1.0 m hcl to this solution, the
solution will change to ph:
A) 5.60.
B) 8.90.
C) 9.13.
D) 9.32.
E) The ph cannot be determined from this information.
21. You want to maintain ph = 7.0 for an enzyme-catalyzed reaction that will produce
hydrogen ions along with the desired product. At equal concentrations, which weak
acid, if any, will serve as the better buffer for the reaction: acid a, with pka = 6.5, or
acid b, with pka = 7.5?
A) Acid a
B) Water is as good as either of the acids available.
C) Acid b
D) Both are equally effective.
22. In which reaction does water not participate as a reactant (rather than as a product)?
A) Conversion of an acid anhydride to two acids
B) Conversion of an ester to an acid and an alcohol
C) Conversion of atp to adp
D) Photosynthesis
E) Production of gaseous carbon dioxide from bicarbonate
23. Which property of water does not contribute to the fitness of the aqueous environment
for living organisms?
A) Cohesion of liquid water due to hydrogen bonding
B) High heat of vaporization
C) High specific heat
D) The density of water being greater than the density of ice
E) The very low molecular weight of water
Page 7
,24. The ionization of water is due to the strongly electronegative element:
A) Hydrogen donating an electron to oxygen.
B) Oxygen donating an electron to hydrogen.
C) Hydrogen receiving an electron from oxygen.
D) Oxygen receiving an electron from hydrogen.
E) None of the answers is correct.
25. Which attribute contributes to water's unusual properties?
A) The geometry of the molecule
B) The polarity of the molecule
C) The ability of water molecules to hydrogen bond
D) The dipole moment in a water molecule
E) All of the answers are correct.
26. Which factor contributes to the bent shape of a water molecule?
A) The dipole moment in a water molecule
B) The unshared electron pairs on the oxygen atom
C) The electronegativity difference between hydrogen and oxygen
D) The unequal electron sharing between hydrogen and oxygen
E) All of the answers are correct.
27. Ice is than water because .
A) Less dense; frozen water maintains more hydrogen bonds than liquid water
B) Less dense; liquid water maintains more hydrogen bonds than frozen water
C) Denser; frozen water maintains more hydrogen bonds than liquid water
D) Denser; liquid water maintains more hydrogen bonds than frozen water
E) Denser; frozen water cannot hydrogen bond
Page 8
,28. Which diagram correctly represent a hydrogen bond?
A) A and d
B) A and c
C) B and c
D) C and d
E) B and d
29. Which statement about biologically important gases is true?
A) O2 and co2 are the most important gases for living things and are therefore very
soluble in water.
B) O2 and co2 are both polar and are therefore very soluble in water.
C) O2 and co2 are both nonpolar molecules and are therefore both poorly soluble in
water.
D) Co2 contains polar bonds but o2 is nonpolar; therefore, co2 is very soluble in
water, but o2 is poorly soluble in water.
E) All biologically important gases are very soluble in water.
30. Which statement about hydrogen bonds is not true?
A) Hydrogen bonds are highly directional.
B) Hydrogen bonds are capable of holding molecules in a specific geometric
arrangement.
C) Hydrogen bonds are strongest when the three atoms in the bond are in a straight
line.
D) Hydrogen bonds are strongest when the oxygen atom is perpendicular to the
hydrogen donor.
E) Hydrogen bonds place a hydrogen ion directly between two partial negative
charges.
Page 9
, 31. Which compound would result in the formation of a clathrate structure?
A) Ch2o
B) Ch4
C) Nh3
D) Ch3ch2oh
E) None of the answers is correct.
32. Which diagram correctly illustrates the clustering of lipids in the formation of a
micelle?
A) A
B) B
C) Both a and b
D) Neither a nor b
33. Dissolving a nonpolar solute in water the order of the solvent and the
dynamic interplay among water molecules that occurs in pure water.
A) Increases; decreases
B) Increases; increases
C) Decreases; decreases
D) Decreases; increases
E) Decreases; stabilizes
34. Which statement regarding long-chain fatty acids in aqueous solution is not true?
A) Fatty acids in small concentrations are surrounded by highly ordered water
molecules in a “cage-like” structure.
B) Fatty acids will cluster together to minimize the lipid surface area.
Page 10
