Description
Biochemistry 5th Edition International Edition by Reginald H. Garrett – Test Bank
Sample Questions
Instant Download With Answers
Chapter 2—Water: The Medium of Life
MULTIPLE CHOICE
- Properties of water that render it so suited to its role as a medium of life include all EXCEPT:
| a. | Unrivaled ability to form hydrogen bonds. |
| b. | Unusually high dielectric constant of water explains water’s ability to surround ions and increase the ions’ attraction for one another. |
| c. | Unparalleled ability to orient around nonpolar solutes to promote hydrophobic interactions. |
| d. | The small, but significant, tendency to form H+ and OH– ions. |
| e. | None, all are true. |
ANS: B PTS: 1
- All are true for water for a substance of its molecular weight that is neither metallic nor ionic EXCEPT:
| a. | a high surface tension. |
| b. | a chemically inert solvent, which has a great capacity to dissolve a diverse spectrum of molecules and ions. |
| c. | a positive volume of melting. |
| d. | a high dielectric constant. |
| e. | a high capacity to form hydrogen bonds |
ANS: C PTS: 1
- The unrivaled ability to form ____ hydrogen bonds per liquid water molecule is the source of the strong intermolecular attractions unique to water.
| a. | 1 |
| b. | 2 |
| c. | 3 |
| d. | 4 |
| e. | 5 |
ANS: D PTS: 1
- Because of its highly polar nature, water is an excellent solvent for polar substances, but NOT for:
| a. | salts. |
| b. | sugars. |
| c. | aldehydes and ketones. |
| d. | hydrocarbons. |
| e. | alcohols and amines. |
ANS: D PTS: 1
- The solvent with the highest dielectric constant in this group is:
| a. | water. |
| b. | acetic acid. |
| c. | ethanol. |
| d. | hexane. |
| e. | benzene. |
ANS: A PTS: 1
- Hydrogen bonds in ice are all EXCEPT:
| a. | directional. |
| b. | straight. |
| c. | weak. |
| d. | responsible for the lower density of ice over liquid water. |
| e. | holding water molecules in ice apart. |
ANS: C PTS: 1
- Pure liquid water consists of H2O molecules:
| 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. |
ANS: C PTS: 1
- The average lifetime of a hydrogen bond connection in water is on the order of 10:
| a. | picoseconds. |
| b. | microseconds. |
| c. | milliseconds. |
| d. | seconds. |
| e. | nanoseconds. |
ANS: A PTS: 1
- The ____ bonding of water with the polar functional groups on nonionic polar solutes such as sugars are ____ than the intermolecular attractions between solute molecules allowing solute molecules to readily dissolve in water.
| a. | ionic, stronger |
| b. | hydrogen, weaker |
| c. | hydrophobic, stronger |
| d. | hydrogen, stronger |
| e. | ionic, weaker |
ANS: D PTS: 1
- The H-bonded water around an ionic substance tends to ____; and the H-bonded water around nonpolar solutes tends to ____.
| a. | inhibit ionization, promote hydrophobic interactions |
| b. | inhibit ionization, inhibit hydrophobic interactions |
| c. | not impact ionization, inhibit hydrophobic interactions |
| d. | promote ionization, not impact hydrophobic interactions |
| e. | promote ionization, promote hydrophobic interactions |
ANS: E PTS: 1
- Amphiphilic (amphipathic) molecules include:
| a. | sugars. |
| b. | acidic amino acids. |
| c. | inorganic salts. |
| d. | water. |
| e. | salts of fatty acids. |
ANS: E PTS: 1
- In micelles:
| a. | polar ends form hydrophobic interactions with water. |
| b. | nonpolar ends form hydrophilic interactions with water. |
| c. | hydrocarbon tails form hydrophobic interactions with water. |
| d. | polar ends are hydrophobic and nonpolar ends are hydrophilic. |
| e. | hydrocarbon tails are excluded from the water into hydrophobic domains. |
ANS: E PTS: 1
- 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.
| a. | pressure, disrupt |
| b. | disorder, increase |
| c. | disorder, decrease |
| d. | order, diminish |
| e. | order, increase |
ANS: D PTS: 1
- To ____ the osmotic pressure created by the contents of their cytosol, cells tend to store substances such as amino acids and sugars in ____ form.
| a. | increase, monomeric |
| b. | minimize, polymeric |
| c. | minimize, monomeric |
| d. | maximize, polymeric |
| e. | increase, polymeric |
ANS: B PTS: 1
- Water ionizes because:
| 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 |
ANS: B PTS: 1
- Grapefruit juice at pH 3.2 contains about ____ times as much H+ as orange juice at pH 4.3.
| a. | 0.9 |
| b. | 10–7.5 |
| c. | 10–2 |
| d. | 12 |
| e. | 101 |
ANS: D PTS: 1
- All are examples of weak electrolytes EXCEPT:
| a. | hydrochloric acid. |
| b. | acetic acid. |
| c. | lactic acid. |
| d. | phosphoric acid. |
| e. | carbonic acid. |
ANS: A PTS: 1
- If 0.1 moles of Na2HPO4 and 0.1 moles of NaH2PO4 are mixed in water, what is the resulting pH? The pKa values for phosphoric acid are 2.1, 7.2, 12.4.
| a. | 2.1 |
| b. | 4.65 |
| c. | 7.2 |
| d. | 9.8 |
| e. | 12.4 |
ANS: C PTS: 1
- Estimate the pH of the resulting solution prepared by mixing 1.0 mole of solid disodium phosphate (Na2HPO4) and 1.25 mole of hydrochloric acid. The pKa values for phosphoric acid are 2.1, 7.2, 12.4.
| a. | pH < 2.1 |
| b. | pH = 2.1 |
| c. | 2.1 < pH < 7.2 |
| d. | pH = 7.2 |
| e. | 7.2 < pH < 12.4 |
ANS: C PTS: 1
- Which of the following pairs would be the best buffer at pH 10.0?
| a. | Acetic acid and sodium acetate (pKa = 4.76) |
| b. | H2CO3 and NaHCO3 (pKa values are 3.77 and 10.4) |
| c. | Lactic acid and sodium lactate (pKa = 3.86) |
| d. | NaH2PO4 and Na2HPO4 (pKa values are 2.1, 7.2, 12.4) |
| e. | Sodium succinate and succinic acid (pKa = 4.21) |
ANS: B PTS: 1
- What ionic form(s) is/are most prevalent at pH 7.0? The pKa values of phosphoric acid are 2.1, 7.2, 12.4.
| a. | HPO4–2 |
| b. | H2PO4– |
| c. | HPO4–2 and PO4–3 |
| d. | H2PO4– and HPO4–2 |
| e. | All are correct |
ANS: B PTS: 1
- A plasma pH of 6.8 doesn’t seem too far away from a normal pH of 7.4, but at pH 6.8 the H+ concentration is ____ times greater than at pH 7.4 and results in severe acidosis.
| a. | 0.1 |
| b. | 0.6 |
| c. | 4 |
| d. | 10 |
| e. | 20 |
ANS: C PTS: 1
- pH = pKa when:
| a. | [A–]/[HA] = 0 |
| b. | log ([A–]/[HA]) = 1 |
| c. | [A–] >> [HA] |
| d. | [A–] = [HA] |
| e. | log ([HA]/[A–]) = 1 |
ANS: D PTS: 1
- Buffers have all of the following characteristics EXCEPT:
| a. | they have relatively flat titration curves at the pH(s) where they buffer. |
| b. | they resist changes in their pH as acid or base is added. |
| c. | they are typically composed of a weak acid and its conjugate base. |
| d. | they buffer best for polyprotic acids half-way between the two pKa values. |
| e. | buffer where the amounts of conjugate base are nearly equivalent to the amounts of weak acid. |
ANS: D PTS: 1
- Buffer systems are effective when the pH values are within ____ pH unit(s) of the pKa value.
| a. | 1 |
| b. | 2 |
| c. | 3 |
| d. | 4 |
| e. | 5 |
ANS: A PTS: 1
- Intracellular pH is maintained primarily by the ____ and ____ buffer systems, and the extracellular pH by the ____ buffer system.
| 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– |
ANS: D PTS: 1
- Hyperventilation is a physiological mechanism to:
| a. | lower [CO2 (g)] in the blood and increase blood pH. |
| b. | raise [CO2 (g)] in the blood and increase blood pH. |
| c. | lower [CO2 (g)] in the blood and decrease blood pH. |
| d. | raise [CO2 (g)] in the blood and decrease blood pH. |
| e. | lower [CO2 (g)] in the blood and increase [HCO3–]. |
ANS: A PTS: 1
- Water is particularly suited as a solvent for biosystems because it has all of the following characteristics EXCEPT:
| 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. |
ANS: C PTS: 1
- Which of the following weak acids would make the best buffer at pH = 5.0?
| 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) |
ANS: A PTS: 1
- The enzyme fumarase has a pH optimum of about 7.6. What would be the buffer of choice to study this enzyme?
| 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) |
ANS: E PTS: 1
- 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.
| a. | equal to |
| b. | less than half of |
| c. | more than half of |
| d. | about six times |
| e. | about twice |
ANS: E PTS: 1
- Hypoventilation is characterized by inability to excrete CO2 rapidly enough and can be caused by all EXCEPT:
| a. | anesthetics. |
| b. | depressant drugs. |
| c. | narcotics. |
| d. | lung diseases. |
| e. | encephalitis. |
ANS: E PTS: 1
- If an abundance of an organic acid with a pKa of 3.9 is found in the bloodstream, which of the following is true?
| a. | it will be mostly protonated |
| b. | it will be mostly deprotonated |
| c. | it will form an effective buffer |
| d. | it will cause metabolic acidosis |
| e. | both b and d are correct |
ANS: E PTS: 1
- Aspirin contains a carboxylic acid with a pKa of 3.5. Which of the following is true?
| a. | Aspirin will be mostly protonated in the stomach |
| b. | Aspirin will be mostly protonated in the bloodstream |
| c. | Aspirin will be easily absorbed in the stomach due to its negative charge |
| d. | Aspirin will be easily transported in the bloodstream due to its negative charge |
| e. | both a and d are correct |
ANS: E PTS: 1
- If a weak acid is 25% deprotonated at pH 4, what would the pKa be?
| a. | 3.40 |
| b. | 3.52 |
| c. | 4.48 |
| d. | 4.60 |
| e. | cannot determine from given information |
ANS: C PTS: 1
- Which of the following would be the conjugate acid of hydrogen phosphate, HPO4-2?
| a. | H2PO4– | d. | H2PO4– |
| b. | H3PO4 | e. | none of the above |
| c. | H2PO4-2 | ||
ANS: A PTS: 1
- 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?
| a. | 3.16 ´ 10-4 | d. | 1.90 |
| b. | 3.16 ´ 103 | e. | cannot be determined based upon the provided information |
| c. | 0.54 | ||
ANS: B PTS: 1
- Which of the following statements is INCORRECT about the nature of the hydrogen bond
| a. | The donor is a hydrogen atom bonded to an atom that is less electronegative than hydrogen. | d. | It is a type of noncovalent bond. |
| b. | The more linear the bond, the stronger the interaction. | e. | All of the above statements are true about the nature of the hydrogen bond |
| c. | The acceptor is a fairly electronegative atom containing a nonbonding pair of electrons. | ||
ANS: A PTS: 1
- A weak acid is 33% dissociated at pH 5.0. What is the pKa for this acid?
| a. | 4.5 | d. | 5.5 |
| b. | 4.7 | e. | cannot be determined from the information provided |
| c. | 5.3 | ||
ANS: C PTS: 1
Chapter 4—Amino Acids and the Peptide Bond
MULTIPLE CHOICE
- The intrinsic properties of the 20 amino acids include all EXCEPT:
| a. | a-Carbon is symmetric. |
| b. | The capacity to polymerize. |
| c. | Novel acid-base properties. |
| d. | Varied structure and chemical functionality in side chains. |
| e. | Chirality |
ANS: A PTS: 1
- The amino and carboxyl groups of amino acids react in a head-to-tail fashion, eliminating water, and forming a covalent ____ linkage typically referred to as a(n) ____ bond.
| a. | ester, aromatic |
| b. | anhydride, phosphoanhydride |
| c. | amide, peptide |
| d. | dehydration, hydrogen |
| e. | none of the above |
ANS: C PTS: 1
- Because peptide bond formation is thermodynamically ____, biological systems must couple peptide bond formation to a thermodynamically ____ reaction.
| a. | favorable, favorable |
| b. | unfavorable, unfavorable |
| c. | favorable, unfavorable |
| d. | unfavorable, favorable |
| e. | none of the above |
ANS: D PTS: 1
- All of the statements about the classification of these amino acids are correct EXCEPT:
| a. | Aspartic acid and asparagine are acidic amino acids. |
| b. | Alanine and valine are neutral, nonpolar amino acids. |
| c. | Serine and glutamine are polar, uncharged amino acids. |
| d. | Lysine and arginine are basic amino acids. |
| e. | Tyrosine and phenylalanine are aromatic amino acids. |
ANS: A PTS: 1
- The difference between serine and homoserine is the same as between cysteine and homocysteine. This change from the common amino acid is:
| a. | one additional methylene (-CH2-) group. |
| b. | one additional carboxyl group. |
| c. | two additional amine groups. |
| d. | presence of a ring system. |
| e. | one additional amine group. |
ANS: A PTS: 1
- Which of the following amino acids has more than one chiral carbon?
| a. | serine |
| b. | lysine |
| c. | threonine |
| d. | cysteine |
| e. | aspartic acid |
ANS: C PTS: 1
- Which of the listed amino acids is classified as a basic amino acid?
| a. | leucine |
| b. | phenylalanine |
| c. | aspartate |
| d. | asparagine |
| e. | lysine |
ANS: E PTS: 1
- All of the amino acids EXCEPT ____ have both free a-amino and free a-carboxyl groups.
| a. | aspartic acid |
| b. | proline |
| c. | asparagine |
| d. | lysine |
| e. | valine |
ANS: B PTS: 1
- The amino acid with a side-chain pKa near neutrality and which therefore plays an important role as proton donor and acceptor in many enzyme catalyzed reactions is:
| a. | histidine. |
| b. | cysteine. |
| c. | proline. |
| d. | serine. |
| e. | methionine. |
ANS: A PTS: 1
- The pKa of the a-carboxyl group of an amino acid is ____ by the presence on the amine group.
| a. | greatly increased (>2 pH units) |
| b. | greatly decreased (> 2 pH units) |
| c. | unchanged |
| d. | slightly increased (1-2 pH units) |
| e. | slightly decreased (1-2 pH units) |
ANS: B PTS: 1
- Which statement about these amino acids and amino acid derivatives is correct?
| a. | GABA (g-aminobutyric acid) is a potent inhibitory neurotransmitter derived from aspartic acid. |
| b. | Ornithine is an important metabolic intermediate found in the urea cycle. |
| c. | Epinephrine is a hormone derived from tryptophan. |
| d. | Serotonin is a neurotransmitter derived from tyrosine. |
| e. | Histamine is a neurotransmitter derived from glutamine. |
ANS: B PTS: 1
- At which of the following pH values would histidine (pKa values of 1.8, 6.0 and 9.2) be found with a net negative charge?
| a. | 1.0 |
| b. | 4.0 |
| c. | 8.0 |
| d. | 11.0 |
| e. | none of the above |
ANS: D PTS: 1
- What is the pH of a serine solution in which the a-amine group (pKa 9.2) is 33% deprotonated?
| a. | 8.7 |
| b. | 8.9 |
| c. | 9.0 |
| d. | 9.5 |
| e. | 9.8 |
ANS: B PTS: 1
- Glutamic acid has pKa values of 2.2, 4.3 and 9.7. Calculate the isoelectric point for glutamic acid.
| a. | 3.25 |
| b. | 4.3 |
| c. | 5.4 |
| d. | 7.0 |
| e. | 8.6 |
ANS: A PTS: 1
- If the pI of a peptide is 4.6, ____ might be present while ____ would probably be absent.
| a. | Glu / Lys |
| b. | His / Ser |
| c. | Arg / His |
| d. | Asp / Gly |
| e. | Cys / Tyr |
ANS: A PTS: 1
- An amino acid + an aldehyde ® water + ?
| a. | amide. |
| b. | ester. |
| c. | substituted amide. |
| d. | hemiacetal. |
| e. | Schiff base. |
ANS: E PTS: 1
- The pKa of the cysteine side chain ____ group is 8.32, so it is about 11% deprotonated at pH ____.
| a. | acid, 3.2 |
| b. | amino, 8.5 |
| c. | hydroxyl, 10.2 |
| d. | sulfhydryl, 7.4 |
| e. | none of the above |
ANS: D PTS: 1
- Ninhydrin has all these properties EXCEPT:
| a. | It reacts with an amino acid by oxidatively deaminating its amino group. |
| b. | It can be used to detect the location of amino acids following chromatography. |
| c. | It produces a purple colored product upon reaction with alanine. |
| d. | It produces a yellow product upon reaction with histidine. |
| e. | It can be used to quantify most amino acids. |
ANS: D PTS: 1
- All of the following react with the thiol group on cysteine EXCEPT:
| a. | N-ethylmaleimide. |
| b. | iodoacetate. |
| c. | acrylonitrile. |
| d. | “Ellman’s Reagent”. |
| e. | benzaldehyde. |
ANS: E PTS: 1
- Which of the peptides would absorb light at 280 nm?
| a. | Ala-Lys-His |
| b. | Ser-Gly-Asn |
| c. | Ala-Ala-Trp |
| d. | Val-Pro-Leu |
| e. | Ser-Val-Ile |
ANS: C PTS: 1
- Which of the following amino acids absorbs light most strongly between 250 and 300 nm?
| a. | His |
| b. | Phe |
| c. | Trp |
| d. | Tyr |
| e. | None of the above absorb light in this range |
ANS: C PTS: 1
- All are true for stereoisomers EXCEPT:
| a. | A diastereomer is a nonsuperimposable non-mirror image. |
| b. | An enantiomer is a nonsuperimposable mirror image. |
| c. | Diastereomers have different melting points. |
| d. | Diastereomers rotate plane polarized light in equal but opposite directions. |
| e. | None, all are true. |
ANS: D PTS: 1
- All are true statements about L-isoleucine EXCEPT:
| a. | Its enantiomer is named D-isoleucine. |
| b. | L-alloleucine would be its diastereomer. |
| c. | It contains a total of two asymmetric or chiral carbons. |
| d. | It can also be named as (2S,3S)-isoleucine using the (R,S) system. |
| e. | Its diastereomer would be named D-leucine. |
ANS: E PTS: 1
- Using a cation exchange resin, a mixture of four amino acids is separated using an elution gradient of increasing NaCl solution. What would be the correct elution sequence?
| a. | Asp, Arg, Ser, Lys |
| b. | Arg, Asp, Lys, Ser |
| c. | Lys, Arg, Asp, Ser |
| d. | Asp, Ser, Lys, Arg |
| e. | Ser, Asp, Lys, Arg |
ANS: D PTS: 1
- When using a strongly acidic polystyrene resin (Dowex-50) chromatography column, the separation is PRIMARILY by:
| a. | ion exchange chromatography. |
| b. | gas-liquid chromatography. |
| c. | partition chromatography. |
| d. | liquid-liquid partition chromatography. |
| e. | none of the above. |
ANS: A PTS: 1
- Which of the following is classified as a neutral polar amino acid?
| a. | Asp | d. | Ser |
| b. | Leu | e. | Trp |
| c. | His | ||
ANS: D PTS: 1
- For the peptide Ala-His-Glu-Val-Asp-Cys-Lys-Leu, what is the net charge at pH 3?
| a. | -1 | d. | +2 |
| b. | 0 | e. | +3 |
| c. | +1 | ||
ANS: D PTS: 1
- Where Ca is the a-carbon, N represents the amide nitrogen and Co is the carbonyl carbon of amino acids in a peptide, the peptide backbone of a protein consists of the repeated sequence:
| a. | -Ca-N-Co– |
| b. | -N-Co-Ca– |
| c. | -N-Ca-Co– |
| d. | -Co-Ca-N- |
| e. | none of the above |
ANS: C PTS: 1
- The peptide bond has partial ____ character.
| a. | hydrogen bond |
| b. | double bond |
| c. | triple bond |
| d. | van der Waals bond |
| e. | all of the above |
ANS: B PTS: 1
- Which of the following IS NOT a result of resonance in peptide bonds?
| a. | approximately 40% double bond (coplanar) character. |
| b. | restricted rotation in the peptide backbone at the N-Ca bond and Ca-Co bond. |
| c. | the coplanar six atoms of the peptide bond group of atoms. |
| d. | a Ca-carbon that is out of the coplanar group of atoms. |
| e. | Co-N bond distance that is shorter than normal, but longer than C=N bonds. |
ANS: D PTS: 1
- Which of the following atoms IS NOT contained within the amide plane of the peptide backbone?
| a. | Ca-carbon. |
| b. | amide nitrogen. |
| c. | side chain carbons. |
| d. | carbonyl carbon. |
| e. | none, all are included. |
ANS: C PTS: 1
Reviews
There are no reviews yet.