Question 1

Biological buffering systems include:

Accepted Answer

A)  histidine. 
B)  bicarbonate. 
C)  phosphate. 
D)  bicarbonate and phosphate. 
E)  histidine, bicarbonate, and phosphate. 
A)  histidine. 
B)  bicarbonate. 
C)  phosphate. 
D)  bicarbonate and phosphate. 
E)  histidine, bicarbonate, and phosphate.

Question 2

Explain with an appropriate diagram why amphipathic molecules tend to form micelles in water. What force drives micelle formation?

Accepted Answer

Amphipathic molecules have both hydrophi

Question 3

Which factor contributes to the bent shape of a water molecule?

Accepted Answer

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. 
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.

Question 4

In which reaction does water NOT participate as a reactant (rather than as a product)?

Accepted Answer

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 
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

Question 5

Which compound would result in the formation of a clathrate structure?

Accepted Answer

A)  CH2O 
B)  CH4 
C)  NH3 
D)  CH3CH2OH 
E)  None of the answers is correct. 
A)  CH2O 
B)  CH4 
C)  NH3 
D)  CH3CH2OH 
E)  None of the answers is correct.

Question 6

Which statement is TRUE about the properties of aqueous solutions?

Accepted Answer

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. 
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.

Question 7

If a person is suffering from acidosis, which treatment/action would NOT be a wise choice?

Accepted Answer

A)  intravenous administration of bicarbonate 
B)  hyperventilating 
C)  breathing into a paper bag 
D)  vigorous exercise 
E)  All of these treatments/actions could be used to counteract acidosis. 
A)  intravenous administration of bicarbonate 
B)  hyperventilating 
C)  breathing into a paper bag 
D)  vigorous exercise 
E)  All of these treatments/actions could be used to counteract acidosis.

Question 8

Consider an acetate buffer, initially at the same pH as its pKa (4.76). When sodium hydroxide (NaOH) is mixed with this buffer, the:

Accepted Answer

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. 
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.

Question 9

According to the titration curve to the right, acid A has a pKa of:

Accepted Answer

A)  0.2. 
B)  0.5. 
C)  3.2. 
D)  3.8. 
E)  4.8. 
A)  0.2. 
B)  0.5. 
C)  3.2. 
D)  3.8. 
E)  4.8.

Question 10

Hydrophobic interactions make important energetic contributions to:

Accepted Answer

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. 
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.

Question 11

The dipole moment in a water molecule Which statement about hydrogen bonds is NOT true?

Accepted Answer

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. 
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.

Question 12

A 0.6 M solution of a weak acid had a pH of 5.8. What is the pKa of the solution?

Accepted Answer

A)  11.3 
B)  10.5 
C)  8.2 
D)  5.7 
E)  2.9 
A)  11.3 
B)  10.5 
C)  8.2 
D)  5.7 
E)  2.9

Question 13

For a weak acid with a pKa of 6.0, show how you would calculate the ratio of acid to salt at pH 5.

Accepted Answer

To calculate the ratio of acid to salt f

Question 14

Which statement CORRECTLY describes the situation of the cell in the diagram? The black dots represent solute molecules.

Accepted Answer

A)  The cell is in a hypotonic solution; water will move in and cause the cell to swell. 
B)  The cell is in a hypotonic solution; solutes will move in and cause the cell to swell. 
C)  The cell is in a hypotonic solution; water will move out and cause the cell to shrink. 
D)  The cell is in a hypertonic solution; solutes will move in and cause the cell to swell. 
E)  The cell is in a hypertonic solution; water will move out and cause the cell to shrink. 
A)  The cell is in a hypotonic solution; water will move in and cause the cell to swell. 
B)  The cell is in a hypotonic solution; solutes will move in and cause the cell to swell. 
C)  The cell is in a hypotonic solution; water will move out and cause the cell to shrink. 
D)  The cell is in a hypertonic solution; solutes will move in and cause the cell to swell. 
E)  The cell is in a hypertonic solution; water will move out and cause the cell to shrink.

Question 15

Which property of water does NOT contribute to the fitness of the aqueous environment for living organisms?

Accepted Answer

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 
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

Question 16

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?

Accepted Answer

A)  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. 
A)  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.

Question 17

Suppose you have just added 100 mL of a solution containing 0.5 mol of acetic acid per liter to 400 mL of 0.5 M NaOH. What is the final pH? (The pKa of acetic acid is 4.7.)

Accepted Answer

To calculate the final pH of the solutio

Question 18

Define pKa for a weak acid in the following two ways: (1) in relation to its acid dissociation constant, Ka, and (2) by reference to a titration curve for the weak acid.

Accepted Answer

The term "pK" seems to be a typographica

Question 19

Which process would NOT disrupt the weak interactions between two biomolecules in solution?

Accepted Answer

A)  heating the solution 
B)  cooling the solution 
C)  lowering the pH of the solution 
D)  increasing the ionic strength of the solution 
E)  All of the answer choices would disrupt interactions between biomolecules 
A)  heating the solution 
B)  cooling the solution 
C)  lowering the pH of the solution 
D)  increasing the ionic strength of the solution 
E)  All of the answer choices would disrupt interactions between biomolecules

Question 20

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?

Accepted Answer

A)  acid A 
B)  Water is as good as either of the acids available. 
C)  acid B 
D)  Both are equally effective. 
A)  acid A 
B)  Water is as good as either of the acids available. 
C)  acid B 
D)  Both are equally effective.

Exam 2: Water

Biological buffering systems include:

Explain with an appropriate diagram why amphipathic molecules tend to form micelles in water. What force drives micelle formation?

Which factor contributes to the bent shape of a water molecule?

In which reaction does water NOT participate as a reactant (rather than as a product)?

Which compound would result in the formation of a clathrate structure?

Which statement is TRUE about the properties of aqueous solutions?

If a person is suffering from acidosis, which treatment/action would NOT be a wise choice?

Consider an acetate buffer, initially at the same pH as its pKa (4.76). When sodium hydroxide (NaOH) is mixed with this buffer, the:

According to the titration curve to the right, acid A has a pKa of:

Hydrophobic interactions make important energetic contributions to:

The dipole moment in a water molecule Which statement about hydrogen bonds is NOT true?

A 0.6 M solution of a weak acid had a pH of 5.8. What is the pKa of the solution?

For a weak acid with a pKa of 6.0, show how you would calculate the ratio of acid to salt at pH 5.

Which statement CORRECTLY describes the situation of the cell in the diagram? The black dots represent solute molecules.

Which property of water does NOT contribute to the fitness of the aqueous environment for living organisms?

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?

Suppose you have just added 100 mL of a solution containing 0.5 mol of acetic acid per liter to 400 mL of 0.5 M NaOH. What is the final pH? (The pKa of acetic acid is 4.7.)

Define pKa for a weak acid in the following two ways: (1) in relation to its acid dissociation constant, Ka, and (2) by reference to a titration curve for the weak acid.

Which process would NOT disrupt the weak interactions between two biomolecules in solution?

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?

The Foundations of Biochemistry

Amino Acids, Peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

DNA-Based Information Technologies

Lipids

Biological Membranes and Transport

Biosignaling

Bioenergetics and Biochemical Reaction Types

Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, Nucleotides, and Related Molecules

Hormonal Regulation and Integration of Mammalian Metabolism

Genes and Chromosomes

DNA Metabolism

RNA Metabolism

Protein Metabolism

Regulation of Gene Expression

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Consider an acetate buffer, initially at the same pH as its pK_a (4.76). When sodium hydroxide (NaOH) is mixed with this buffer, the:

According to the titration curve to the right, acid A has a pK_a of:

A 0.6 M solution of a weak acid had a pH of 5.8. What is the pK_a of the solution?

For a weak acid with a pK_a of 6.0, show how you would calculate the ratio of acid to salt at pH 5.

Suppose you have just added 100 mL of a solution containing 0.5 mol of acetic acid per liter to 400 mL of 0.5 M NaOH. What is the final pH? (The pK_a of acetic acid is 4.7.)

Define pK_a for a weak acid in the following two ways: (1) in relation to its acid dissociation constant, K_a, and (2) by reference to a titration curve for the weak acid.

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 pK_a = 6.5, or acid B, with pK_a = 7.5?