Biochemistry Chapter 2 study set

The pH of a solution of 1 M HCl is: a) 1. b) 0.1. c) 0. d) -1. e) 10.

0

The aqueous solution with the LOWEST pH is: a) 0.1 M acetic acid (pKa = 4.86). b) 0.1 M formic acid (pKa = 3.75). c) 0.1 M HCl. d) 10-12 M NaOH. e) 0.01 M HCl.

0.1 M HCl.

The aqueous solution with the HIGHEST pH is: a) 1 M NH3 (pKa = 9.25). b) 0.001 M NaOH. c) 0.1 M NaOH. d) 0.5 M NaHCO3 (pKa = 3.77). e) 1 M HCl.

0.1 M NaOH.

Milk of magnesia has a pH of 10.2. What is the [OH-] of milk of magnesia? a) 1.58 × 10-5 M b) 1.58 × 10-4 M c) 1.02 × 10-3 M d) 6.31 × 10-4 M e) 6.31 × 10-11 M

1.58 × 10-4 M

he H+ concentration of a solution is 5.6 × 10-5 M. What is the pH? a) -9.75 b) 5.65 c) 9.75 d) -4.25 e) 4.25

4.25

If the Ka of an acid is 1.38 × 10-7, what is the pKa? a) 1.38 b) 6.86 c) 7.14 d) 10.7 e) 8.68

6.86

If the pH of a solution is 5.5, what is the pOH? a) -8.5 b) 14 c) 6.5 d) 8.5 e) -5.5

8.5

What is the CORRECT terminology for reactions A and B in the diagram? (diagram not shown) a) A = phosphorylation, B = phosphatase b) A = condensation, B = hydrolysis c) A = dehydrolysis, B = condensation d) A = hydrolysis, B = condensation e) A = metabolism, B = catabolism

A = hydrolysis, B = condensation

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.

All of the answers are correct.

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.

All of the answers are correct.

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.

All of the answers are correct.

Which diagram CORRECTLY illustrates the clustering of lipids in the formation of a micelle? A. B. heads in, tails out heads out, tails in ~~~~**~~~~ *~~~~ ~~~~* a) A b) B c) both A and B d) neither A nor B

B

Which diagram CORRECTLY represent a hydrogen bond? A. B. C. D . | | O \\ / \ / O | N O | H - - H = = = = - H H - H | | H | O N I O | / \ N | / \ a) A and D b) A and C c) B and C d) C and D e) B and D

B and C

Carbon dioxide, produced by glucose oxidation, is not very soluble. How does the body transport this molecule through blood to be exhaled from the lungs? a) CO2 is only produced in the lungs. b) CO2 can be converted to the more soluble CO for transport. c) CO2 can be directly bound to hemoglobin for transport. d) CO2 can be converted to the more soluble HCO3-1 for transport. e) CO2 can be bound by erythrocytes for transport.

CO2 can be converted to the more soluble HCO3-1 for transport.

Which property of water has had the MOST profound consequence for aquatic organisms? a) Water has a high specific heat. b) Water has a high heat of vaporization. c) Nonpolar molecules are poorly soluble in water. d) Water has a high melting point. e) Due to hydrogen bonding, solid water is less dense than liquid water.

Due to hydrogen bonding, solid water is less dense than liquid water.

Polar molecules cannot easily pass through the cell membrane, but hydrophobic molecules can easily pass through the membrane. The two molecules shown in the diagram both have effects that include raising blood pressure. Comparing two molecules to the right, which statement is TRUE? (molecules not shown) a) Ephedrine can more easily pass through the cell membrane than epinephrine. b) Epinephrine can more easily pass through the cell membrane than ephedrine. c) Both epinephrine and ephedrine can pass through the cell membrane equally well. d) Neither epinephrine nor ephedrine can pass through the cell membrane. e) None of the statements is true.

Ephedrine can more easily pass through the cell membrane than epinephrine.

Which compound acts as a diprotic acid? a) CH3CH2OH b) H2CO3 c) CH3COOH d) NH4+ e) H3PO4

H2CO3

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) H2PO4-. c) HPO42-. d) PO43-. e) None of the answers is correct.

H2PO4-

The conjugate base of H2PO4 -1 is: a) PO43-. b) HPO43-. c) H3PO4. d) H2PO42-. e) HPO42-.

HPO42-

Which statement CORRECTLY describes the forces that drive micelle formation from amphipathic molecules, such as fatty acids, dissolved in water? a) Head groups of the molecules are sequestered in the interior of the micelle, maximizing hydrogen bonding of the hydrophobic tail with surrounding solvent molecules. b) Head groups of the molecules are exposed on the outer surface of the micelle, maximizing hydrogen bonding between hydrophobic tails. c) Head groups of the molecules are exposed on the outer surface of the micelle, minimizing the order of the surrounding solvent molecules. d) Hydrophilic tails are exposed on the outer surface of the micelle, maximizing hydrogen bonding between the tails and surrounding solvent molecules. e) Hydrophobic tails are exposed on the outer surface of the micelle, maximizing hydrogen bonding between head groups.

Head groups of the molecules are exposed on the outer surface of the micelle, minimizing the order of the surrounding solvent molecules.

The dipole moment in a water molecule Which statement about hydrogen bonds is NOT true? a) Individual hydrogen bonds in liquid water exist for many seconds and sometimes for minutes. b) The strength of a hydrogen bond depends on the linearity of the three atoms involved in the bond. c) Hydrogen bonds account for the anomalously high boiling point of water. d) In liquid water, the average water molecule forms hydrogen bonds with three to four other water molecules. e) Individual hydrogen bonds are much weaker than covalent bonds.

Individual hydrogen bonds in liquid water exist for many seconds and sometimes for minutes.

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

M CaCl2 (MW = 111 g/mol)

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? a) More ibuprofen will be absorbed in the small intestine because it will be charged due to the pH being greater than the pKa. b) More ibuprofen will be absorbed in the small intestine because it will be uncharged due to the pH being greater than the pKa. c) More ibuprofen will be absorbed in the stomach because it will be charged due to the pH being lower than the pKa. d) More ibuprofen will be absorbed in the stomach because it will be uncharged due to the pH being lower than the pKa. e) Ibuprofen will be absorbed equally well in both the stomach and small intestine.

More ibuprofen will be absorbed in the stomach because it will be uncharged due to the pH being lower than the pKa.

Which statement about biologically important gases is TRUE? a) CO2 contains polar bonds but O2 is nonpolar; therefore, CO2 is very soluble in water, but O2 is poorly soluble in water. b) O2 and CO2 are both nonpolar molecules and are therefore both poorly soluble in water. c) All biologically important gases are very soluble in water. d) O2 and CO2 are both polar and are therefore very soluble in water. e) O2 and CO2 are the most important gases for living things and are therefore very soluble in water.

O2 and CO2 are both nonpolar molecules and are therefore both poorly soluble in water.

"Proton hopping" essentially means that: a) a free proton moves from one hydroxyl group of ionized water to the next. b) hydronium ions are freer to move among and between water molecules in solution. c) individual protons are freer to move among and between water molecules in solution. d) an individual proton "jumps" from one electronegative group to the next. e) several protons move between hydrogen bonded water molecules causing the net movement of a photon over a long distance in a short time.

Several protons move between hydrogen bonded water molecules causing the net movement of a photon over a long distance in a short time.

According to the Henderson-Hasselbalch equation, when is the pH equal to the pKa? a) when the concentration of acid is close to zero b) when the pH approaches 7 c) when the concentration of the conjugate base is equal to the ionization constant for water d) when the concentration of the conjugate base is equal to the concentration of the acid. e) None of the answers is correct.

When the concentration of the conjugate base is equal to the concentration of the acid.

Water can act as _____ in biological reactions. a) a solvent b) a reactant c) a product d) a solvent, reactant, and product e) both a solvent and reactant

a solvent, reactant, and product

List the acids in INCREASING order of strength (weakest to strongest): nitrous acid (Ka = 4.0 × 10-4); carbonic acid (Ka = 4.4 × 10-7); acetic acid (Ka = 1.7 × 10-5); phosphoric acid (Ka = 7.3 × 10-3) a) carbonic acid, phosphoric acid, nitrous acid, acetic acid b) acetic acid, carbonic acid, nitrous acid, phosphoric acid c) phosphoric acid, nitrous acid, acetic acid, carbonic acid d) acetic acid, nitrous acid, carbonic acid, phosphoric acid e) carbonic acid, acetic acid, nitrous acid, phosphoric acid

carbonic acid, acetic acid, nitrous acid, phosphoric acid

Dissolved solutes alter some physical (colligative) properties of the solvent water because they change the: a) temperature of the water. b) concentration of the water. c) ionic bonding of the water. d) pH of the water. e) hydrogen bonding of the water.

concentration of the water.

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

cooling the solution

Which list correctly shows bond/interaction strength in DECREASING order (strongest to weakest)? Question options: a) ionic bond > covalent bond > hydrogen bond > van der Waals interaction b) covalent bond > hydrogen bond > ionic bond > van der Waals interaction c) covalent bond > van der Waals interaction > ionic bond > hydrogen bond d) covalent bond > ionic bond > hydrogen bond > van der Waals interaction e) hydrogen bond > ionic bond > van der Waals interaction > covalent bond

covalent bond > ionic bond > hydrogen bond > van der Waals interaction

Biological buffering systems include: a) histidine, bicarbonate, and phosphate. b) histidine. c) bicarbonate. d) phosphate. e) bicarbonate and phosphate.

histidine, bicarbonate, and phosphate.

Ice is _____ than water because _____. a) less dense; frozen water maintains more hydrogen bonds than liquid water b) denser; liquid water maintains more hydrogen bonds than frozen water c) denser; frozen water cannot hydrogen bond d) less dense; liquid water maintains more hydrogen bonds than frozen water e) denser; frozen water maintains more hydrogen bonds than liquid water

less dense; frozen water maintains more hydrogen bonds than liquid water

The pH of a sample of blood is 7.4, while gastric juice is pH 1.4. The blood sample has: a) 6000 times lower [H+] than the gastric juice. b) 5.29 times lower [H+] than the gastric juice. c) one million times lower [H+] than the gastric juice. d) 6 times lower [H+] than the gastric juice. e) 0.189 times the [H+] as the gastric juice.

one million times lower [H+] than the gastric juice.

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.

oxygen receiving an electron from hydrogen.

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.

pH of buffer 1 > pH of buffer 2 > pH of buffer 3

In which reaction does water NOT participate as a reactant (rather than as a product)? a) conversion of ATP to ADP b) production of gaseous carbon dioxide from bicarbonate c) conversion of an ester to an acid and an alcohol d) photosynthesis e) conversion of an acid anhydride to two acids

production of gaseous carbon dioxide from bicarbonate

Consider an acetate buffer, initially at the same pH as its pKa (4.76). When sodium hydroxide (NaOH) is mixed with this buffer, the: Question options: a) sodium acetate formed precipitates because it is less soluble than acetic acid. b) pH remains constant. c) ratio of acetic acid to sodium acetate in the buffer falls. d) pH rises more than if an equal amount of NaOH is added to an acetate buffer initially at pH 6.76. e) pH rises more than if an equal amount of NaOH is added to unbuffered water at pH 4.76

ratio of acetic acid to sodium acetate in the buffer falls.

The Henderson-Hasselbalch equation: a) is equally useful with solutions of acetic acid and of hydrochloric acid. b) relates the pH of a solution to the pKa and the concentrations of acid and conjugate base. c) employs the same value for pKa for all weak acids. d) does not explain the behavior of di- or tri-basic weak acids. e) allows the graphic determination of the molecular weight of a weak acid from its pH alone.

relates the pH of a solution to the pKa and the concentrations of acid and conjugate base.

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.

the unshared electron pairs on the oxygen atom

Osmosis is movement of a: a) nonpolar solute molecule across a membrane. b) gas molecule across a membrane. c) polar solute molecule across a membrane. d) charged solute molecule (ion) across a membrane. e) water molecule across a membrane.

water molecule across a membrane.