Question 1

Ice is _____ than water because _____.

Accepted Answer

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 
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 B

Question 2

Which statement about buffers is TRUE?

Accepted Answer

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. 
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. B

Question 3

Briefly define "isotonic," "hypotonic," and "hypertonic" solutions. (b) Describe what happens when a cell is placed in each of these types of solutions.

Accepted Answer

(a) Definitions:

- Isotonic Solution: An isotonic solution is one where the concentration of solutes is equal both inside and outside the cell. This results in no net movement of water across the cell membrane, maintaining the cell's shape and volume.

- Hypotonic Solution: A hypotonic solution has a lower concentration of solutes compared to the inside of the cell. This causes water to move into the cell by osmosis, potentially leading to cell swelling and possibly bursting if the influx is excessive.

- Hypertonic Solution: A hypertonic solution has a higher concentration of solutes than the inside of the cell. This causes water to move out of the cell, leading to cell shrinkage or crenation as the cell loses water.

(b) Cellular Response in Different Solutions:

- In an Isotonic Solution: When a cell is placed in an isotonic solution, there is no net movement of water into or out of the cell. The cell remains in equilibrium with its environment, and its shape and volume are maintained. This is the ideal situation for most cells, as it does not disrupt their normal function.

- In a Hypotonic Solution: When a cell is placed in a hypotonic solution, water enters the cell due to the higher solute concentration inside the cell compared to the surrounding solution. As water flows into the cell, it swells and may eventually burst in a process called lysis if the cell wall is not strong enough to withstand the pressure. This is particularly a concern for animal cells, which lack a rigid cell wall. Plant cells, on the other hand, have a cell wall that provides structural support and prevents them from bursting, though they may become turgid, which is a healthy state for plant cells.

- In a Hypertonic Solution: When a cell is placed in a hypertonic solution, water moves out of the cell to the surrounding solution where the solute concentration is higher. This results in the cell shrinking or crenating. In plant cells, this can lead to plasmolysis, where the cell membrane pulls away from the cell wall as the cell loses water. This can be detrimental to the cell, as it can impair cellular processes and may lead to cell death if the dehydration is severe.

Question 4

According to the titration curve to the right, acid A is _____ because the pH _____.

Accepted Answer

A)  weak; resists change when 50% titrated. 
B)  strong; resists change when 50% titrated. 
C)  weak; changes dramatically when 100% titrated. 
D)  strong; changes dramatically when 100% titrated. 
E)  It cannot be determined from the information given. 
A)  weak; resists change when 50% titrated. 
B)  strong; resists change when 50% titrated. 
C)  weak; changes dramatically when 100% titrated. 
D)  strong; changes dramatically when 100% titrated. 
E)  It cannot be determined from the information given.

Question 5

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:

Accepted Answer

A)  5.60. 
B)  8.90. 
C)  9.13. 
D)  9.32. 
E)  The pH cannot be determined from this information. 
A)  5.60. 
B)  8.90. 
C)  9.13. 
D)  9.32. 
E)  The pH cannot be determined from this information.

Question 6

Which of the following would have the GREATEST effect on osmotic pressure?

Accepted Answer

A)  M NaCl (MW = 58 g/mol) 
B)  M CaCl2 (MW = 111 g/mol) 
C)  M glucose (MW = 180 g/mol) 
D)  M sucrose (MW = 342 g/mol) 
E)  All of the answer choices would have the same effect. 
A)  M NaCl (MW = 58 g/mol) 
B)  M CaCl2 (MW = 111 g/mol) 
C)  M glucose (MW = 180 g/mol) 
D)  M sucrose (MW = 342 g/mol) 
E)  All of the answer choices would have the same effect.

Question 7

Which property of water has had the MOST profound consequence for aquatic organisms?

Accepted Answer

A)  Water has a high specific heat. 
B)  Water has a high heat of vaporization. 
C)  Due to hydrogen bonding, solid water is less dense than liquid water. 
D)  Water has a high melting point. 
E)  Nonpolar molecules are poorly soluble in water. 
A)  Water has a high specific heat. 
B)  Water has a high heat of vaporization. 
C)  Due to hydrogen bonding, solid water is less dense than liquid water. 
D)  Water has a high melting point. 
E)  Nonpolar molecules are poorly soluble in water.

Question 8

The high degree of cohesion of water molecules influences which processe?

Accepted Answer

A)  Plants can transport dissolved nutrients from roots to leaves. 
B)  Water can combine with carbon dioxide to form glucose. 
C)  Loss of water causes lettuce leaves to wilt. 
D)  Water is split by the energy of sunlight through photosynthesis. 
E)  Water can be used as a product in respiration. 
A)  Plants can transport dissolved nutrients from roots to leaves. 
B)  Water can combine with carbon dioxide to form glucose. 
C)  Loss of water causes lettuce leaves to wilt. 
D)  Water is split by the energy of sunlight through photosynthesis. 
E)  Water can be used as a product in respiration.

Question 9

Which statement does NOT describe a reason that water can act as a heat buffer for cells and organisms?

Accepted Answer

A)  Water has a high specific heat. 
B)  Water has an extended hydrogen-bonding network. 
C)  Water can auto-ionize. 
D)  A large amount of heat is required to raise the temperature of water by 1 °C. 
E)  All of the statements describe reasons that water can act as a heat buffer. 
A)  Water has a high specific heat. 
B)  Water has an extended hydrogen-bonding network. 
C)  Water can auto-ionize. 
D)  A large amount of heat is required to raise the temperature of water by 1 °C. 
E)  All of the statements describe reasons that water can act as a heat buffer.

Question 10

Which statement does NOT describe a strategy used by multicellular animals to maintain osmotic balance with their surroundings?

Accepted Answer

A)  Cells have a contractile vacuole, an organelle that pumps water out of the cell. 
B)  Animals have a high concentration of albumin and other proteins in blood plasma. 
C)  Cells actively pump out Na+ and other ions. 
D)  Cells store fuel as a polysaccharide instead of as simple sugars. 
E)  All of the statements describe a strategy to maintain osmotic balance. 
A)  Cells have a contractile vacuole, an organelle that pumps water out of the cell. 
B)  Animals have a high concentration of albumin and other proteins in blood plasma. 
C)  Cells actively pump out Na+ and other ions. 
D)  Cells store fuel as a polysaccharide instead of as simple sugars. 
E)  All of the statements describe a strategy to maintain osmotic balance.

Question 11

Explain the fact that triethylammonium chloride ((CH3CH2)3N-HCl) is more soluble in water than is triethylamine ((CH3CH2)3N).

Accepted Answer

The solubility of a compound in water is

Question 12

The conjugate base of H2PO4 -1 is:

Accepted Answer

A)  H3PO4. 
B)  H2PO42-. 
C)  HPO42-. 
D)  HPO43-. 
E)  PO43-. 
A)  H3PO4. 
B)  H2PO42-. 
C)  HPO42-. 
D)  HPO43-. 
E)  PO43-.

Question 13

For each of the pairs below, circle the conjugate base.
RCOOH
RCOO-
RNH2
RNH3+
H2PO4-
H3PO4
H2CO3
HCO3-

Accepted Answer

It appears that the question is asking t

Question 14

Which diagram CORRECTLY represent a hydrogen bond?

Accepted Answer

A)  A and D 
B)  A and C 
C)  B and C 
D)  C and D 
E)  B and D 
A)  A and D 
B)  A and C 
C)  B and C 
D)  C and D 
E)  B and D

Question 15

Ibuprofen is a weak acid with a pKa of 4.9 (shown with the ionizable hydrogen with a star). It is absorbed through the stomach and the small intestine as a function of polarity-charged and very polar molecules are absorbed slowly; neutral hydrophobic molecules absorb quickly. If the stomach pH is about 1.5 and the small intestine pH is about 6, where (and why) will more ibuprofen be absorbed into the bloodstream?

Accepted Answer

A)  More ibuprofen will be absorbed in the small intestine because it will be uncharged due to the pH being greater than the pKa. 
B)  More ibuprofen will be absorbed in the stomach because it will be uncharged due to the pH being lower than the pKa. 
C)  More ibuprofen will be absorbed in the small intestine because it will be charged due to the pH being greater than the pKa. 
D)  More ibuprofen will be absorbed in the stomach because it will be charged due to the pH being lower than the pKa. 
E)  Ibuprofen will be absorbed equally well in both the stomach and small intestine. 
A)  More ibuprofen will be absorbed in the small intestine because it will be uncharged due to the pH being greater than the pKa. 
B)  More ibuprofen will be absorbed in the stomach because it will be uncharged due to the pH being lower than the pKa. 
C)  More ibuprofen will be absorbed in the small intestine because it will be charged due to the pH being greater than the pKa. 
D)  More ibuprofen will be absorbed in the stomach because it will be charged due to the pH being lower than the pKa. 
E)  Ibuprofen will be absorbed equally well in both the stomach and small intestine.

Question 16

Which statement about biologically important gases is TRUE?

Accepted Answer

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. 
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.

Question 17

Which result influences the lower limit for an atom's van der Waals radius?

Accepted Answer

A)  The electron clouds begin to repel each other. 
B)  The nuclei begin to repel each other. 
C)  The transient dipole is cancelled out by the neighboring atom. 
D)  The electron clouds begin to attract each other. 
E)  The nuclei begin to attract each other. 
A)  The electron clouds begin to repel each other. 
B)  The nuclei begin to repel each other. 
C)  The transient dipole is cancelled out by the neighboring atom. 
D)  The electron clouds begin to attract each other. 
E)  The nuclei begin to attract each other.

Question 18

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:

Accepted Answer

A)  6.5. 
B)  6.8. 
C)  7.2. 
D)  7.4. 
E)  7.5. 
A)  6.5. 
B)  6.8. 
C)  7.2. 
D)  7.4. 
E)  7.5.

Question 19

Which attribute contributes to water's unusual properties?

Accepted Answer

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. 
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.

Question 20

The OH- concentration of a solution is 4.3 × 10-10 M. What is the pH?

Accepted Answer

A)  -9.37 
B)  9.37 
C)  -4.63 
D)  4.63 
E)  13.4 
A)  -9.37 
B)  9.37 
C)  -4.63 
D)  4.63 
E)  13.4

Exam 2: Water

Ice is _____ than water because _____.

Which statement about buffers is TRUE?

Briefly define "isotonic," "hypotonic," and "hypertonic" solutions. (b) Describe what happens when a cell is placed in each of these types of solutions.

According to the titration curve to the right, acid A is _____ because the pH _____.

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:

Which of the following would have the GREATEST effect on osmotic pressure?

Which property of water has had the MOST profound consequence for aquatic organisms?

The high degree of cohesion of water molecules influences which processe?

Which statement does NOT describe a reason that water can act as a heat buffer for cells and organisms?

Which statement does NOT describe a strategy used by multicellular animals to maintain osmotic balance with their surroundings?

Explain the fact that triethylammonium chloride ((CH3CH2)3N-HCl) is more soluble in water than is triethylamine ((CH3CH2)3N).

The conjugate base of H2PO4 -1 is:

For each of the pairs below, circle the conjugate base. RCOOH RCOO- RNH2 RNH3+ H2PO4- H3PO4 H2CO3 HCO3-

Which diagram CORRECTLY represent a hydrogen bond?

Which statement about biologically important gases is TRUE?

Which result influences the lower limit for an atom's van der Waals radius?

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:

Which attribute contributes to water's unusual properties?

The OH- concentration of a solution is 4.3 × 10-10 M. What is the pH?

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

Filters

Ice is _ than water because _.

According to the titration curve to the right, acid A is _ because the pH _.

Explain the fact that triethylammonium chloride ((CH₃CH₂)₃N-HCl) is more soluble in water than is triethylamine ((CH₃CH₂)₃N).

The conjugate base of H₂PO₄^-¹ is:

For each of the pairs below, circle the conjugate base. RCOOH RCOO^- RNH₂ RNH₃⁺ H₂PO₄^- H₃PO₄ H₂CO₃ HCO₃^-

A compound has a pK_a 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:

The OH^- concentration of a solution is 4.3 × 10^-¹⁰ M. What is the pH?