Biochemistry Final Exam

Question 1

Humans are which of the following:
A) photoautotrophs
B) chemoautotrophs
C) photoheterotrophs
D) chemoheterotrophs

Answer 1

D) chemoheterotrophs

Question 2

Cyanobacteria are:
A) photoautotrophs
B) chemoautotrophs
C) photoheterotrophs
D) chemoheterotrophs

Answer 2

A) photoautotrophs

Question 3

You discover a new single-celled organism in a salt lake. Subsequent laboratory experiments reveal that the organism can live in the presence or absence of oxygen. This organism would most likely be classified as a:
A) an obligate anaerobe in the Bacterial domain.
B) an obligate anaerobe in the Archaeal domain.
C) a facultative anaerobe in the Archaeal domain.
D) a facultative anaerobe in the Bacterial domain.

Answer 3

C) a facultative anaerobe in the Archaeal domain.

Question 4

Which organelle is found in both plant and animal cells?
A) starch granule
B) chloroplast
C) mitochondria
D) glyoxysome

Answer 4

C) mitochondria

Question 5

Differential centrifugation is based on the differences in sedimentation rate of biological particles of different ______.
A) density
B) size and density
C) size
D) structure

Answer 5

B) size and density

Question 6

Supramolecular complexes, such as chromatin, are held together by:
A) covalent bonds between monomeric units.
B) noncovalent interactions, such as hydrogen bonds.
C) covalent bonds between macromolecules.
D) interactions between the cytoskeleton and organelles.

Answer 6

B) noncovalent interactions, such as hydrogen bonds.

Question 7

Important functional groups in biomolecules include:
A) lipids
B) thioesters
C) nucleic acids
D) carbons

Answer 7

B) thioesters

Question 8

Proteins are classified as macromolecules because they:
A) can associate noncovalently into very large structures.
B) are polymers with molecular weights above ~5,000 Da.
C) can function as enzymes, structural elements, signal receptors, or transporters.
D) are composed of multiple oligomers.

Answer 8

B) are polymers with molecular weights above ~5,000 Da.

Question 9

What nucleobase is not present in DNA?
A) cytosine
B) adenine
C) guanine
D) uracil

Answer 9

D) uracil

Question 10

A living organism is a(n):
A) isolated system
B) closed system
C) open system
D) universe

Answer 10

C) open system

Question 11

Molecules that differ in configuration cannot be:
A) stereoisomers
B) cis-trans isomers
C) chiral centers that are mirror images of each other
D) chiral centers that can be interchanged by rotation of a single bond.

Answer 11

D) chiral centers that can be interchanged by rotation of a single bond.

Question 12

Enantiomers:
A) are only associated with amino acids.
B) can be specific types of diastereomers.
C) are always designated either D or L.
D) can exist for molecules with more than one chiral carbon.

Answer 12

D) can exist for molecules with more than one chiral carbon.

Question 13

An unusual characteristic of H20 is:
A) greater density in solid form (ice) than in liquid form (water).
B) high heat of vaporization.
C) low specific heat.
D) not readily forming intermolecular interactions.

Answer 13

B) high heat of vaporization.

Question 14

Which atom does NOT commonly form hydrogen bonds between or within biological molecules?
A) oxygen
B) hydrogen
C) carbon
D) nitrogen

Answer 14

C) carbon

Question 15

Which statement about hydrogen bonds is false?
A) They only occur between water molecules.
B) They are weak compared with covalent bonds.
C) They cause acid-base reactions in aqueous solutions to be very rapid.
D) They have optimal geometry.

Answer 15

A) They only occur between water molecules.

Question 16

Dissolving table sugar into iced tea is an energetically favorable reaction due to a(n):
A) increase in enthalpy as heat moves into the sugar.
B) decrease in free energy due to broken weak interactions between sugar molecules.
C) increase in entropy as the sugar dissolves.
D) increase in free energy because there is no longer a solvation layer around the sugar crystal.

Answer 16

C) increase in entropy as the sugar dissolves.

Question 17

Nonpolar compounds:
A) force surrounding H2O molecules to become ordered.
B) increase entropy when dissolved in water.
C) decrease enthalpy when dissolved in water.
D) interfere with the hydrogen bonds among H2O molecules.

Answer 17

D) interfere with the hydrogen bonds among H2O molecules.

Question 18

I need to calculate the osmotic pressure of a solvent. I know the concentration of the solute and the temperature of the solution. What else do I need?
A) whether the solute dissociates into 2+ ion species.
B) the vapor pressure of the solvent.
C) the boiling point of the solvent.
D) whether the solute is hydrophobic or hydrophilic.

Answer 18

A) whether the solute dissociates into 2+ ion species.

Question 19

Which condition would cause red blood cells to burst due to excess water passing through the plasma membrane?
A) placing the cells in a solution of higher osmolarity than is present within the cells.
B) placing the cells in a solution of amphipathic molecules.
C) adding a charged solute, such as NaCl, to the cell suspension.
D) placing the cells in a hypotonic solution.

Answer 19

D) placing the cells in a hypotonic solution.

Question 20

The pH of an aqueous solution:
A) must remain at 7.
B) is not affected by added OH-.
C) depends solely on the ionization of water.
D) is a function of the hydrogen ion concentration (to a reasonable approximation).

Answer 20

D) is a function of the hydrogen ion concentration (to a reasonable approximation).

Question 21

When H2O ionizes:
A) the △G° = 0 kJ/mol.
B) it has a measurable Keq.
C) its concentration (7 M) does not appreciably change.
D) free H+ ions are present in solution.

Answer 21

B) it has a measurable Keq.

Question 22

Weak acids:
A) only partially ionize in water.
B) have a pKa < 7.
C) react very slowly with bases.
D) are formed by dilution of strong acids.

Answer 22

A) only partially ionize in water.

Question 23

The pKa of a weak acid:
A) is a function of its concentration.
B) is the pH at which it has no net charge.
C) is <0 at pH >7.
D) can be determined from its titration curve.

Answer 23

D) can be determined from its titration curve.

Question 24

What is the actual function of a buffer system such as acetate/acetic acid?
A) to maintain a constant pH in the event that the concentration of an acid or base increases.
B) to maintain the solution at the pKa.
C) to ensure the solution has no free H+ or OH- within a specific range.
D) to keep the solution within one pH unit of the pKa.

Answer 24

A) to maintain a constant pH in the event that the concentration of an acid or base increases.

Question 25

I need to calculate the pH of a weak acid. I know the concentration of the acid and its conjugate base, and my solution is at 30° C. Using the Henderson-Hasselbach equation, what else do I need?
A) the Kd for H+ of the acid.
B) the total H+ concentration (that is, free and bound to the acid)
C) the free-energy change for the release of the H+.
D) the pKa of the acid.

Answer 25

D) the pKa of the acid.

Question 26

Which statement about buffers is false?
A) they have a maximum buffering capacity at pH 7.
B) they are weak acids and bases.
C) [A-] = [HA] when pH = pKa.
D) they can sometimes be biological macromolecules.

Answer 26

A) they have a maximum buffering capacity at pH 7.

Question 27

Which amino acid(s) has three pKa values?
A) leucine
B) proline
C) lysine
D) threonine
E) cysteine

Answer 27

C) lysine
E) cysteine

Question 28

Which amino acid would most likely be found in the interior of a globular protein?
A) Val
B) D
C) Aspartate
D) Cysteine
E) Y

Answer 28

A) Val

Question 29

Given that all 20 common amino acids have at least two oppositely charges groups, which statement is NOT correct?
A) solutions of amino acids can act as buffers.
B) all amino acids are zwitterions.
C) all amino acids carry at least one charge across the full range of their titration curves.
D) amino acid isoelectric points should be near neutrality.
E) it is not possible to fully deprotonate amino acids.

Answer 29

E) it is not possible to fully deprotonate amino acids.

Question 30

At what pH values will histidine have a net neutral charge?
A) below 1.82
B) between 1.82 and 6.0
C) between 6.0 and 9.17
D) above 9.17
E) there are no pH values where histidine will have a net neutral charge.

Answer 30

C) between 6.0 and 9.17

Question 31

Which statement is correct about peptides?
A) Peptides have no alpha-carboxyl groups.
B) Peptides have their amino acid sequences written from the N-terminus.
C) Peptides do not have isoelectric points.
D) Peptides are not biologically active.
E) Peptide bonds are broken through condensation reactions.

Answer 31

B) Peptides have their amino acid sequences written from the N-terminus.

Question 32

Which statement is correct about proteins?
A) Proteins can consist of more than one polypeptide chain.
B) Proteins consist solely of polymerized amino acids.
C) Proteins all have similar amino acid compositions.
D) Proteins can, by definition, consist of no more than 2,000 amino acid residues.
E) Proteins do not have ionizable groups.

Answer 32

A) Proteins can consist of more than one polypeptide chain.

Question 33

Which protein would elute first from a gel filtration column?
A) Protein A, with Mr=27,000
B) Protein B, with Mr=58,000
C) Protein C, a homodimer with promoter Mr=11,300
D) Protein D, with Mr=15,000

Mr: relative molecular weight

Answer 33

B) Protein B, with Mr=58,000

Question 34

A new protein resembling myosin was reported. Unlike myosin, it binds calcium. Its isoelectric point and molecular weight are very similar to those of myosin. Which method would best separate the new protein from myosin if those two proteins were in the same buffer solution?
A) Ion-Exchange Chromatography
B) Size-Exclusion Chromatography
C) Affinity Chromatography
D) Dialysis
E) Fractionation

Answer 34

C) Affinity Chromatography

Question 35

What measurement increases during purification of an enzyme?
A) Activity
B) Total Protein
C) Specific Activity
D) Fraction Volume

Answer 35

C) Specific Activity

Question 36

Trypsin catalyzes the hydrolysis of peptide bonds in which a Lys or Arg residue contributes a carbonyl group LL-37, an antimicrobacterial peptide with 37 residues has 6 Lys residues and 5 Arg residues. How many smaller peptides will LL-37 yield upon trypsin cleavage?
A) 6
B) 5
C) 12
D) 37
E) 11

Answer 36

C) 12

Question 37

Chemical synthesis of peptides by the Merrifield method:
A) involves synthesizing the peptide and then attaching it to a solid support.
B) is nearly as efficient as peptide bond synthesis in biochemical systems.
C) has a practical upper limit of a polymer of ~500 amino acid residues.
D) proceeds from the carboxyl terminus to the amino terminus.

Answer 37

D) proceeds from the carboxyl terminus to the amino terminus.

Question 38

The heme prosthetic group:
A) consists of protoporphyrin and an iron (II) ion.
B) is found only in myoglobin and hemoglobin.
C) contains a single iron atom in its ferrous (Fe2+) state that has a total of 4 coordination bonds.
D) is only found bound to protein.

Answer 38

A) consists of protoporphyrin and an iron (II) ion.

Question 39

Myoglobin:
A) has a quaternary structure.
B) contains a pocket for binding heme that is made up of largely the C and D helices.
C) contains multiple binding sites for O2.
D) consists mostly of alpha-helices.

Answer 39

D) consists mostly of alpha-helices.

Question 40

Protein A has a binding site for ligand L with a Ka of 10^8 M^-1. Protein B has a binding site for ligand L with a Ka of 10^5 M^-1. Which protein has the higher affinity for ligand L?
A) Protein A
B) Protein B
C) It is not possible to determine based on only Ka values.

Answer 40

A) Protein A

Question 41

Protein A has a Ka = 6.0 µM^-1 for binding ligand L. Protein B has a Kd=4.0 µM for binding ligand L. Based on this information, which statement is true?
A) Protein B binds L with higher affinity.
B) Protein A is half-saturated with L when [L] is 6.0 µM^-1.
C) The Ka of protein B for L is 0.25 µM^-1.
D) When [L] =1 µM, Y=0.17 for protein A.

Answer 41

C) The Ka of protein B for L is 0.25 µM^-1.

Question 42

When the partial pressure of oxygen is equal to the P50 of myoglobin, what is the value of Y?
A) 0.0
B) 0.25
C) 0.50
D) 0.75
E) 1.00

Answer 42

C) 0.50

Question 43

Oxygen carried by whole blood in animals is bound and transported by hemoglobin in what type of cell?
A) Hemoblastcytes
B) Erythrocytes
C) White Blood Cells
D) Stem Cells
E) Neurons

Answer 43

B) Erythrocytes

Question 44

The alpha and beta subunits of hemoglobin:
A) each contain 4 heme prosthetic groups.
B) contain several stretches of identical amino acids.
C) are both tetramers.
D) have high structural similarity to each other.
E) differ in sequence and structure.

Answer 44

D) have high structural similarity to each other.

Question 45

The T→R transition is triggered by:
A) ion pairs forming between residues and O2 at the A1B2 (and A2B1) interface.
B) the structures of the individual subunits changing.
C) O2 causing the heme to assume a more planar conformation, shifting the position of the His F8 and the F helix.
D) AB subunit pairs sliding past each other and rotating, narrowing the pocket between the alpha subunits.

Answer 45

C) O2 causing the heme to assume a more planar conformation, shifting the position of the His F8 and the F helix.

Question 46

Leghemoglobin is an oxygen-binding protein in root nodules that contain bacteria and fix atmospheric nitrogen. Which statement is true is leg hemoglobin is like myoglobin and not hemoglobin?
A) There are four oxygen-binding sites.
B) The oxygen-binding curve is hyperbolic.
C) There is cooperative oxygen binding.
D) The oxygen-binding curve is sigmoidal.
E) Oxygen binding changes the heme configuration from T to R.

Answer 46

B) The oxygen-binding curve is hyperbolic.

Question 47

Which molecule is a homotropic modulator of oxygen binding to hemoglobin?
A) Oxygen
B) H+
C) Carbon Dioxide
D) Hemoglobin
E) Carbon Monoxide

Answer 47

A) Oxygen

Question 48

A newly discovered protein has multiple subunits, each with a single ligand-binding site. Binding of the ligand to one site increases the binding affinity of other sides for the ligand. The Hill coefficient (nH) is:
A) Equal to 1
B) Greater than 1
C) Less than 1
D) Not able to be calculated.

Answer 48

B) Greater than 1

Question 49

There are 2 binding sites for acetylcholine (neurotransmitter) on its receptor. What would be the shape of a Hill plot if there were cooperatively of binding?
A) Hyperbolic
B) Linear
C) Sigmoidal, with a sharp change in slope.
D) Two sigmoidal areas linked together, one for each binding event.
E) Two sigmoidal lines, one higher than the other on the graph.

Answer 49

C) Sigmoidal, with a sharp change in slope.

Question 50

In peripheral tissues:
A) The affinity of hemoglobin for oxygen increases and the protein binds more O2.
B) CO2 is excreted.
C) The structural effects of H+ and CO2 binding to hemoglobin favor the R state.
D) O2 is released.

Answer 50

D) O2 is released.

Question 51

What is the actual, significant effect of 2,3-biphosphoglycerate on oxygen binding by hemoglobin?
A) There is an increase in Kd for oxygen in peripheral tissues.
B) A higher concentration of oxygen can bind at high altitudes compared to low altitudes.
C) The affinity of hemoglobin for oxygen in peripheral tissues increases at high altitudes.
D) Heme further decreases affinity for both CO2 and H+ in lungs, allowing more O2 to bind.
E) It has no effect on O2 affinity, but it forces heme into the R state.

Answer 51

A) There is an increase in Kd for oxygen in peripheral tissues.

Question 52

Which statement is false?
A) Hemoglobin can be considered a dimer of alpha-beta dimers.
B) O2 binding to myoglobin is allosteric but not cooperative.
C) 2,3-biphosphoglycerate decreases the affinity of hemoglobin for O2.
D) Fetal hemoglobin has a lower affinity for BPG than normal adult hemoglobin.
E) The Glu6 to Val6 that causes sickle cell anemia produces a hydrophobic patch on hemoglobins surface.

Answer 52

B) O2 binding to myoglobin is allosteric but not cooperative.

Question 53

The molecular structure for which individual antibody or T-cell receptor is specific is known as:
A) An epitope
B) It’s target
C) An immune response
D) An immunoglobulin fold

Answer 53

A) An epitope

Question 54

Which statement is false?
A) T lymphocytes produce immunoglobulins.
B) Immunoglobulins target foreign bacteria and viruses for destruction.
C) Memory cells allow the body to quickly respond to viruses it has encountered before.
D) Clonal selection increases the number of immune system cells that can respond to a particular pathogen.
E) Vaccines stimulate the production of memory cells.

Answer 54

A) T lymphocytes produce immunoglobulins.

Question 55

Which description is associated with immunoglobulin G?
A) Consists of two Fc fragments and two Fab fragments.
B) Consists of one heavy and one light chain.
C) Most abundant immunoglobulin.
D) Important in the allergic response.

Answer 55

C) Most abundant immunoglobulin.

Question 56

Which biochemical principle is not true of immunoglobulins as examples of protein structure and function?
A) Disulfide linkages strengthen the quaternary structure.
B) Because the antigen-binding domain has high affinity, there is no observed induced fit.
C) Amino acid chain flexibility and bond rotation permit optimal epitope binding.
D) There are two specific and identical binding sites with high affinity on the same molecule.
E) There is 100% sequence homology between the two antigen-binding sites.

Answer 56

B) Because the antigen-binding domain has high affinity, there is no observed induced fit.

Question 57

Polyclonal antibodies:
A) Are synthesized by a population of identical B cells.
B) All recognize the same epitope.
C) Are identical to monoclonal antibodies.
D) Are used as analytic reagents in Western blot assays.

Answer 57

D) Are used as analytic reagents in Western blot assays.

Question 58

Which biochemical structure is NOT present in myosin?
A) A motif
B) A fibrous region
C) A globular region
D) A prosthetic group
E) An enzyme

Answer 58

D) A prosthetic group

Question 59

Thin filaments:
A) Only consist of F actin.
B) Are the only type of filament in the A band.
C) Assemble as successive monomeric actin molecules add to one end.
D) Are rodlike structures.

Answer 59

C) Assemble as successive monomeric actin molecules add to one end.

Question 60

Which of the major proteins involved in muscle contraction hydrolyzes ATP?
A) Actin
B) Troponin
C) Myosin
D) Tropomyosin

Answer 60

C) Myosin

Question 61

Enzymes:
A) Are proteins (with few exceptions).
B) Can be denatured and still retain full activity.
C) Have names always ending in “-ase.”
D) Are also referred to as
“coenzymes.”

Answer 61

A) Are proteins (with few exceptions).

Question 62

In enzymes, which inorganic ion does NOT serve as a cofactor?
A) Zn2+
B) Cu2+
C) Ca2+
D) Mg2+

Answer 62

C) Ca2+

Question 63

An apoenzyme:
A) Is the nonprotein component of a holoenzyme.
B) Always requires an inorganic ion for its activity.
C) Requires a cofactor for its activity.
D) Is an enzyme consisting of RNA rather than protein.

Answer 63

C) Requires a cofactor for its activity.

Question 64

Some enzymes require an inorganic ion for catalytic function. When this inorganic ion is very tightly or covalently bound by the enzyme it is called a(n):
A) Apoenzyme
B) Prosthetic Group
C) Holoenzyme
D) Catalyst

Answer 64

B) Prosthetic Group

Question 65

______ is NOT an E.C. class name for enzymes.
A) Transferases
B) Polymerases
C) Lyases
D) Isomerases

Answer 65

B) Polymerases

Question 66

What is the free-energy starting point for a reverse reaction designated as?
A) Transition State
B) Ground State
C) Biochemical Standard Free Energy
D) Activation Energy

Answer 66

B) Ground State

Question 67

The conversion of sucrose to CO2 and water has a very large and negative △G’°. Why is the conversion NOT spontaneous?
A) Only some reactions have a negative △G’°.
B) Conversion requires heat and O2.
C) Conversion requires the presence of cofactors.
D) There is a very large activation barrier.

Answer 67

D) There is a very large activation barrier.

Question 68

What does an enzyme change relative to an uncatalyzed reaction?
A) The equilibrium constant.
B) The rate of the reaction.
C) The pH.
D) The free energy change of the reaction.

Answer 68

B) The rate of the reaction.

Question 69

Which statement is true regarding the relationship between the biochemical standard free-energy change and the equilibrium constant, Keq?
A) The relationship between free-energy change and equilibrium is exponential.
B) A decrease in Keq translates into a more negative free energy.
C) The higher the temperature, the less the reaction favors product formation.
D) Small changes in free energy can lead to large changes in equilibria.

Answer 69

D) Small changes in free energy can lead to large changes in equilibria.

Question 70

If a first-order reaction for the unimolar reaction S →P has a rate constant k of 0.05s^-1, how is this interpreted qualitatively?
A) 0.05% of the available S will be converted to P in 1 second.
B) 5% of the available S will be converted to P in 1 second.
C) 0.05% of the available P will be converted to S in 1 second.
D) 5% of the available P will be converted to S in 1 second.

Answer 70

B) 5% of the available S will be converted to P in 1 second.

Question 71

How does the concept of “induced fit” support the current theory of substrate-enzyme interaction?
A) Enzyme structure is rigid, allowing for competition for the active site and easy ejection of the final product.
B) Enzyme conformational changes demonstrate feedback regulation of the enzyme and the ability to “turn off” activity.
C) Having a rigid structure allows the enzyme to bind the substrate and stabilize the ES complex.
D) Enzyme conformation changes allow additional stabilizing interactions with the transition state and enhance the activity.

Answer 71

D) Enzyme conformation changes allow additional stabilizing interactions with the transition state and enhance the activity.

Question 72

Binding energy is defined as the:
A) Energy derived from noncovalent enzyme-substrate interaction.
B) Energy derived from release of the product and release from the EP interaction.
C) Energy released from the conversion of ES to EP.
D) Difference in the uncatalyzed activation energy and catalyzed activation energy.

Answer 72

A) Energy derived from noncovalent enzyme-substrate interaction.

Question 73

What is the primary source of the energy enzymes used to reduce activation energies?
A) Desolvation of the substrate
B) Kinetic energy from the transition state
C) Noncovalent enzyme-substrate interaction
D) Covalent enzyme-product interaction

Answer 73

C) Noncovalent enzyme-substrate interaction

Question 74

How does the induced fit mechanism of enzyme catalysis work?
A) The enzyme assumes a conformation identical to the substrate.
B) The enzyme undergoes a conformational change to maximize weak interactions to the substrate.
C) The substrate binds to the active site of the enzyme.
D) The enzyme undergoes entropy reduction to accommodate substrate.

Answer 74

B) The enzyme undergoes a conformational change to maximize weak interactions to the substrate.

Question 75

How does the concept of “induced-fit” support the current theory of substrate-enzyme interaction?
A) Enzyme structure is rigid, allowing for competition for the active site and easy ejection of the final product.
B) Enzyme conformational changes demonstrate feedback regulation of the enzyme and the ability to “turn-off” activity.
C) Having a rigid structure allows the enzyme to bind to the substrate and stabilize the ES complex.
D) Enzyme conformation changes allow additional stabilizing interactions with the transition state and enhance the activity.

Answer 75

D) Enzyme conformation changes allow additional stabilizing interactions with the transition state and enhance the activity.

Question 76

Which statement about enzymes is false?
A) They lower the activation energy of a reaction.
B) They alter the overall thermodynamics of a reaction.
C) A substantial amount of their catalytic power results from binding of the substrate(s) through weak interactions.
D) They increase the rates of reactions by 10^5 fold to 10^17 fold.

Answer 76

B) They alter the overall thermodynamics of a reaction.

Question 77

Which amino acid might be expected to have the least effect on the function of an enzyme if it replaces a Glu residue in the enzyme?
A) Gly
B) Lys
C) His
D) Asp

Answer 77

D) Asp

Question 78

After you mix a substrate and an enzyme together, there is an initial transient period, the pre-steady state. What happens during the pre-steady state?
A) [Et] decreases until it reaches a constant level.
B) [S] decreases until it reaches a constant level.
C) [P] increases until it reaches a constant level.
D) [ES] increases until it reaches a constant level.

Answer 78

D) [ES] increases until it reaches a constant level.

Question 79

Which statement is false about the saturation effect?
A) The maximum initial rate of the catalyzed reaction is observed.
B) Virtually all of the enzyme is present as the ES complex.
C) It is responsible for the linear increase of V0 with an increase in [S].
D) Further increases in [S] have no effect on rate.

Answer 79

C) It is responsible for the linear increase of V0 with an increase in [S].

Question 80

For a specific substrate/enzyme system, which condition will ALWAYS result in an increase in V0 (assuming nothing else changes)?
A) A decrease in Km and an increase in Vmax.
B) An increase in pH.
C) An increase in [S].
D) A decrease in [Et].

Answer 80

A) A decrease in Km and an increase in Vmax.

Question 81

In deriving the Michaelis-Menten equation, what is the steady-state assumption?
A) [P] is negligible and k2 can be ignored.
B) The rate of formation of ES is equal to the rate of its breakdown.
C) The amount of substate bound by the enzyme at any given time is negligible compared with the total [S].
D) The reaction is a one-substrate enzyme-catalyzed reaction.

Answer 81

B) The rate of formation of ES is equal to the rate of its breakdown.

Question 82

What is the definition of Km, the Michaelis constant?
A) The rate at which enzyme is turning substrate into product at 1/2Vmax.
B) The V0 at 1/2 maximal [S].
C) The number of molecules of substrate converted to product per second.
D) The concentration of substrate at which the enzyme is operating at half its maximal velocity.

Answer 82

D) The concentration of substrate at which the enzyme is operating at half its maximal velocity.

Question 83

The Km on a Lineweaver-Burk plot is:
A) Equal to the Y-intercept.
B) Equal to the slope of the line.
C) The reciprocal of the Y-intercept.
D) The negative reciprocal of the X-intercept.

Answer 83

D) The negative reciprocal of the X-intercept.

Question 84

In drug design, a drug’s affinity for a selected target, such as an enzyme, is an important factor in assessing a drug’s potential. The higher the affinity, the better the candidate. Under conditions where Kd measures affinity, which drug would be the BEST candidate?
A) Drug A: 10^-4
B) Drug B: 10^-6
C) Drug C: 10^-8
D) Drug D: 10^-10

Answer 84

D) Drug D: 10^-10

Question 85

The rate-limiting step of an enzyme-catalyzed reaction:
A) Is always the last step.
B) Has a rate constant equal to kcat.
C) Is always the fastest step.
D) Is always slower than the rate of diffusion of the substrate to the active site.

Answer 85

B) Has a rate constant equal to kcat.

Question 86

Pepsin, a peptidase found in the stomach, it has an optimal pH of about 1.6. Normally the gastric juice pH is between 1 and 2. An individual experiencing heartburn dissolves baking soda in water and drinks the mixture to neutralize the stomach acid. What happens to pepsin activity in this case?
A) Activity will decrease due to a decrease in pH.
B) Activity will decrease due to an increase in pH.
C) Activity will increase due to a decrease in pH.
D) Activity will increase due to an increase in pH.

Answer 86

B) Activity will decrease due to an increase in pH.

Question 87

Which statement is false for a competitive inhibitor?
A) It is often structurally similar to substrate.
B) It does not change Vmax.
C) It is irreversible.

Answer 87

C) It is irreversible.

Question 88

Which statement is false for an uncompetitive inhibitor?
A) Uncompetitive inhibitors bind at a site distinct from the substrate active site.
B) Uncompetitive inhibitors bind only to the ES complex.
C) Uncompetitive inhibitors are reversible.
D) Uncompetitive inhibitors affect the apparent Km but not the Vmax.

Answer 88

D) Uncompetitive inhibitors affect the apparent Km but not the Vmax.

Question 89

Which statement is true about both mixed inhibitors and uncompetitive inhibitors?
A) Both inhibitors bind to the active site of an enzyme.
B) Both inhibitors affect the Km but not the Vmax.
C) Both inhibitors can bind to the enzyme-substate complex.
D) Both inhibitors can bind to either the free enzyme or the enzyme-substrate complex.

Answer 89

C) Both inhibitors can bind to the enzyme-substate complex.

Question 90

Which type of inhibitor binds to the active site of an enzyme and undergoes the initial steps of the reaction before combining irreversibly with the enzyme?
A) Mixed inhibitors.
B) Suicide inactivators.
C) Transition-state analogs.
D) Competitive inhibitors.

Answer 90

B) Suicide inactivators.

Question 91

Which three amino acids form the catalytic triad in chymotrypsin?
A) Ser, Asp, Lys
B) Glu, Ser, Asp
C) Ser, Asp, His
D) Phe, Tyr, Ala

Answer 91

C) Ser, Asp, His

Question 92

A(n) ________ is a(n) ________ with two monosaccharide units.
A) Oligosaccharide; Polysaccharide
B) Polysaccharide; Oligosaccharide
C) Disaccharide; Oligosaccharide
D) Disaccharide; Polysaccharide

Answer 92

C) Disaccharide; Oligosaccharide

Question 93

What chemical feature determines if a sugar is an aldose or a ketose?
A) The direction of rotation of polarized light.
B) The position of the carbonyl carbon.
C) If the enantiomers resemble either glyceraldehyde or dihydroxyacetone.
D) If the epimers differ in configuration around one carbon or more than one carbon.

Answer 93

B) The position of the carbonyl carbon.

Question 94

Glucose is a monosaccharide with a(n):
A) Aldehyde functional group and six carbons.
B) Ketone functional group and six carbons.
C) Aldehyde functional group and seven carbons.
D) Ketone functional group and seven carbons.

Answer 94

A) Aldehyde functional group and six carbons.

Question 95

Which statement is false regarding the enantiomers of glyceraldehyde?
A) The enantiomers of glyceraldehyde are mirror images of each other.
B) Because glyceraldehyde contains one chiral center, it has two enantiomers.
C) In the Fischer projection formula for D-glyceraldehyde, the hydroxyl group is on the right.
D) Glyceraldehyde does not occur in optically active isomeric forms.

Answer 95

D) Glyceraldehyde does not occur in optically active isomeric forms.

Question 96

A monosaccharide with a ketone functional group and seven carbons:
A) Can never exist in cyclic form.
B) Is a ketoheptose.
C) Is the monosaccharide found in RNA but not DNA.
D) Has a single chiral center.

Answer 96

B) Is a ketoheptose.

Question 97

What name is given to monosaccharides that differ in configuration about the hemiacetal carbon atom?
A) Enantiomers
B) Isomers
C) Epimers
D) Anomers

Answer 97

D) Anomers

Question 98

Cyclization of monosaccharides:
A) Is the reaction of hemiketal or hemiacetal formation.
B) It is irreversible.
C) Creates alpha and beta epimers.
D) Only occurs in hexoses.

Answer 98

A) Is the reaction of hemiketal or hemiacetal formation.

Question 99

Using the Fischer projection of D-glucose, identify which statement is true of the Haworth perspective formula of alpha-D-glucopyranose.
A) The terminal -CH2OH group projects downward.
B) The anomeric hydroxyl is on the opposite side from C-6
C) The hydroxyl group on C-2 is placed pointing up.
D) The cyclic structure is a five-membered ring.

Answer 99

B) The anomeric hydroxyl is on the opposite side from C-6

Question 100

Which reaction is one that is NOT common of glucose?
A) Mutarotation
B) Oxidation to an aldonic acid.
C) Oxidation to a uronic acid.
D) Oxidation by reducing sugars.

Answer 100

D) Oxidation by reducing sugars.

Question 101

What term is given to carbohydrates linked by their anomeric carbons?
A) Nonreducing sugars.
B) Glycosides
C) Anomers
D) Hemiketals

Answer 101

A) Nonreducing sugars.

Question 102

Following the convention for naming reducing oligosaccharides, what is the name of lactose?
A) α-L-glucopyranose-(1,6)-α-L galactopyranosyl
B) β-D-glucopyranose-(1,4)-β-D-galactopyranosyl
C) β-D-galactopyranosyl-(1,4)-β-D-glucopyranose
D) α-L-galactopyranosyl-(1,6)-α-L-glucopyranose

Answer 102

C) β-D-galactopyranosyl-(1,4)-β-D-glucopyranose

Question 103

Which of these sugars is nonreducing?
A) Trehalose
B) Glucose
C) Maltose
D) Lactose

Answer 103

A) Trehalose

Question 104

Which item is NOT associated with disaccharides?
A) O-glycosidic linkages
B) Formation of a ketal or acetal.
C) Never having free anomeric carbons.
D) Sucrose.

Answer 104

C) Never having free anomeric carbons.

Question 105

Why does (R,S)-aspartame NOT stimulate the sweet receptor?
A) Site AH+ cannot bind the partially negative oxygen of the carboxylic acid.
B) Site B- cannot hydrogen bond with the amine nitrogen.
C) Site X cannot accommodate the hydrophobic benzene ring of (R,S).
D) None of the sites can interact with (R,S)-aspartame.

Answer 105

C) Site X cannot accommodate the hydrophobic benzene ring of (R,S).

Question 106

Which statement is false regarding homopolysaccharides and heteropolysaccharides?
A) Homopolysaccharides contain a single monomeric sugar species.
B) Some homopolysaccharides serve as structural elements in animal exoskeletons.
C) Heteropolysaccharides serve as storage forms of monosaccharides that are used as fuel.
D) In animal tissues, the extracellular space is occupied by several types of heteropolysaccharides.

Answer 106

C) Heteropolysaccharides serve as storage forms of monosaccharides that are used as fuel.

Question 107

What O-glycosidic bond is commonly found in amylose, amylopectin, and glycogen?
A) (β→1,4)
B) (α1→6)
C) (β1→6)
D) (α1→4)

Answer 107

D) (α1→4)

Question 108

A glycogen molecule with 28 branches has how many nonreducing and reducing ends?
A) 28 nonreducing. and 28 reducing ends.
B) 29 nonreducing and 1 reducing end.
C) 1 nonreducing end and 29 reducing ends.
D) 1 nonreducing ends and 1 reducing end.

Answer 108

B) 29 nonreducing and 1 reducing end.

Question 109

Even though amylose and cellulose are made of similar homopolysaccharide chains, they have very different properties. Why?
A) The β-glycosidic linkage of glucose molecules in cellulose form interchain and intrachain hydrogen bonds that produce straight, stable fibers that exclude water.
B) Cellulose is composed of galactose, while amylose is composed of glucose.
C) The α-glycosidic linkage of glucose molecules in amylose causes it to form helices that exclude water.
D) Amylose makes a linear polymer which cannot make hydrogen bonds.

Answer 109

A) The β-glycosidic linkage of glucose molecules in cellulose form interchain and intrachain hydrogen bonds that produce straight, stable fibers that exclude water.

Question 110

Why are chitin and cellulose hydrophobic and essentially insoluble in an aqueous media?
A) Because polymers of these molecules pack so tightly together, there is no geometric space left for water.
B) Because they form many internal hydrogen bonds, they leave no sites for binding to water.
C) Because there are no enzymes that can break the beta linkages.
D) Because the linear polymer cannot make hydrogen bonds.

Answer 110

B) Because they form many internal hydrogen bonds, they leave no sites for binding to water.

Question 111

Which characteristic is NOT one that is true of glycosaminoglycans?
A) Found in extracellular matrix.
B) Always contain sulfates.
C) Are heteropolysaccharides.
D) Are disaccharide repeat units.

Answer 111

B) Always contain sulfates.

Question 112

The glycosylaminoglycan hyaluronan:
A) Is a homopolysaccharide.
B) Consists of alternating resides of D-glucuronnic acid and N-acetylglucosamine.
C) Is covalently linked to specific proteins.
D) Is a much shorter polymer than heparin.

Answer 112

B) Consists of alternating resides of D-glucuronnic acid and N-acetylglucosamine.

Question 113

Which statement about glycoconjugates is false?
A) The glycosaminoglycan chain of the proteoglycan can bind to extracellular proteins through electrostatic interactions.
B) Glycolipids are found in specific organelles, such as Golgi complexes.
C) Glycosphingolipids play a role in signal transduction.
D) The oligosaccharide portions of glycoproteins are very heterogeneous.

Answer 113

B) Glycolipids are found in specific organelles, such as Golgi complexes.

Question 114

Which statement about proteoglycans is false?
A) They contain protein.
B) They can affect ligand-receptor interactions.
C) They are always extracellular.
D) They contain glycosaminoglycans.

Answer 114

C) They are always extracellular.

Question 115

A laboratory is studying the binding properties of a glycoprotein on the plasma membrane. What amino acids should they analyze for the presence of branched heteropolysaccharides?
A) Ser, Thr, and Tyr
B) Ser, Thr, and Asn
C) Trp, Tyr, and Phe
D) Lys, His, and Arg

Answer 115

B) Ser, Thr, and Asn

Question 116

Glycoproteins:
A) Contain unbranched oligosaccharides.
B) Are sometimes intracellular.
C) Have oligosaccharides covalently attached to aspartate residues.
D) Are a small fraction of the total number of proteins in a human cell.

Answer 116

B) Are sometimes intracellular.

Question 117

Which of these is NOT a glycoconjugate?
A) Trehalose
B) Syndecan
C) Glypican
D) Glycosphingolipid

Answer 117

A) Trehalose

Question 118

Oligosaccharides are:
A) Never found in mucins.
B) Classified as a N- or O- linked when found in gangliosides.
C) Found in bacterial lipopolysaccharides.
D) Never attached to hormones.

Answer 118

C) Found in bacterial lipopolysaccharides.

Question 119

Which statement about selectins is false?
A) They mediate cell-cell recognition.
B) They are involved in the movement of immune system cells.
C) They can be involved in the process rejection of transplanted organs.
D) They are intracellular.

Answer 119

D) They are intracellular.

Question 120

Lectins:
A) Often bind their ligand via multiple weak interactions.
B) Bind their ligand with relatively low specificity.
C) Prevent viruses from binding to their target cells.
D) Are carbohydrates that bind to receptor proteins.

Answer 120

A) Often bind their ligand via multiple weak interactions.

Question 121

Fatty acids:
A) Can be branched or unbranched.
B) Are highly oxidized storage forms of hydrocarbons.
C) Are referred to as “saturated” if they have one or more C-C double bonds.
D) Never exceed 20 carbons in length, by definition.

Answer 121

A) Can be branched or unbranched.

Question 122

Which statement regarding linoleum acid [18:2(△9,12) is false?
A) It has one carboxylic functional group.
B) It has 2 double bonds.
C) It has 20 carbons.
D) It has a C-C double bond between carbons 9 and 10.

Answer 122

C) It has 20 carbons.

Question 123

If we did not inject lipids in our diets, we would be deficient in:
A) Vitamin A
B) Vitamin D
C) Vitamin E
D) Vitamin K
E) All of these answers are correct.

Answer 123

E) All of these answers are correct.

Question 124

Triacylglycerols:
A) Always have at least one fatty acid with a trans double bond.
B) Consist of glycerol and three different fatty acids.
C) Consist of glycerol and three identical fatty acids.
D) Are a major energy storage form.

Answer 124

D) Are a major energy storage form.

Question 125

Where do we store triacylglycerol (triglyceride)?
A) In the lumen of the ER.
B) In the mitochondria.
C) In the lipid droplet.
D) In the nucleus.

Answer 125

C) In the lipid droplet.

Question 126

What is the advantage of storing energy in the form of triacylglycerol over glycogen?
A) Triacylglycerol has a lower melting temperature.
B) Glycogen hydrolysis is poorly regulated.
C) Because triacylglycerol is bigger, it takes up more space inside the cell.
D) Because triacylglycerol is hydrophobic and excludes water, it takes up less space.

Answer 126

D) Because triacylglycerol is hydrophobic and excludes water, it takes up less space.

Question 127

Which statement is false?
A) Naturally occurring fatty acids usually have an even number of carbons.
B) Wax esters contain long chain fatty acids and long chain alcohols.
C) Triacylglycerols are polar due to their ester functional groups.
D) The number of C-C double bonds in fatty acid affects its melting point.

Answer 127

C) Triacylglycerols are polar due to their ester functional groups.

Question 128

Glycophospholipids do NOT contain:
A) Fatty acids
B) Ester linkages
C) Glycerol
D) A mono- or disaccharide

Answer 128

D) A mono- or disaccharide

Question 129

Which statement is false?
A) Glycerophospholipids are named as derivatives of the parent compound, phosphatidic acid.
B) Ether lipids may be saturated or contain a double bond.
C) Platelet-activating factor is a glycerophospholipid.
D) The storm of the chloroplast is rich in galactolipids, composed of a diacylglycerol with one or two linked galactose residues.

Answer 129

D) The storm of the chloroplast is rich in galactolipids, composed of a diacylglycerol with one or two linked galactose residues.

Question 130

________ a parent compound or compounds of sphingolipids.
A) Phospholipases are
B) Glycerol-3-phosphate is
C) Sphingomyelins are
D) Ceramides are

Answer 130

D) Ceramides are

Question 131

Which sphingolipids have a single monosaccharide as a component?
A) Cerebrosides
B) Gangliosides
C) Globosides
D) Plasmalogens

Answer 131

A) Cerebrosides

Question 132

What are the products of phospholipase D degradation of phosphatidylethanolamine?
A) Diacylglycerol and phosphocholine
B) Diacylglycerol and phosphoethanolamine
C) Phosphatidate and ethanolamine
D) Phosphatidate and choline

Answer 132

C) Phosphatidate and ethanolamine

Question 133

Which statement regarding cholesterol is false?
A) It is the precursor for steroid hormones.
B) It is the precursor for bile acids.
C) It is not usually a component of eukaryotic membranes.
D) It has a hydrophilic functional group.

Answer 133

C) It is not usually a component of eukaryotic membranes.

Question 134

Membrane lipids do NOT include:
A) Glycerophospholipids
B) Triacylglycerols
C) Sphingolipids
D) Glycolipids

Answer 134

B) Triacylglycerols

Question 135

Which statement is false?
A) Phosphorylated derivatives of phosphatidylinositol regulate cell structure and metabolism.
B) Extracellular signals activate a specific phospholipase C in the membrane, which hydrolyzes PIP2 to release two products that act as intracellular messengers.
C) Formation of PIP3 in response to extracellular signals brings the proteins together in signaling complexes at the surface of the plasma membrane.
D) PIP3 is a potent regulator of protein kinases.

Answer 135

D) PIP3 is a potent regulator of protein kinases.

Question 136

Which statement regarding eicosanoids is false?
A) They are produced from arachidonate.
B) They are classified as neither prostaglandins nor thromboxanes.
C) They act as paracrine hormones.
D) They have many different effects.

Answer 136

B) They are classified as neither prostaglandins nor thromboxanes.

Question 137

A novel subclass of thromboxane was discovered in lipids isolated from a newly discovered poison dart from the Amazon valley. What unique structural feature is likely present in these lipids?
A) Four conjugated double bonds.
B) A six membered ring
C) A long chain alcohol bound to a double ring
D) A five membered ring

Answer 137

B) A six membered ring

Question 138

Steroid hormones:
A) Act locally.
B) Travel through the bloodstream on lipid carriers.
C) Bind to receptor proteins in the nucleus to change metabolism.
D) Have low affinity for their receptors.

Answer 138

C) Bind to receptor proteins in the nucleus to change metabolism.

Question 139

Which statement is false regarding vitamin D3?
A) Serves as a hormone precursor.
B) Forms from a photochemical reaction driven by UV light.
C) Biologically active in the intestine, kidney, and bone.
D) Cure for the disease rickets.

Answer 139

C) Biologically active in the intestine, kidney, and bone.

Question 140

Vitamin A1 and its derivatives:
A) Are involved in regulating cell growth and differentiation.
B) Contain only trans C-C bonds.
C) Are not stored in the body in significant amounts.
D) Act as antioxidants.

Answer 140

A) Are involved in regulating cell growth and differentiation.

Question 141

Which statement is true?
A) Vitamin E is a hormone precursor.
B) Vitamin D regulates milk production in mammary glands.
C) Prostaglandins are found only in the prostate gland.
D) Membrane sphingolipids can be used to produce intracellular messengers.

Answer 141

D) Membrane sphingolipids can be used to produce intracellular messengers.

Question 142

Which of the following hormones regulate calcium uptake in the intestines and calcium levels in the kidney and bone?
A) Tocopherols
B) Carotenoids
C) Calcitriol
D) 7-dehydrocholesterol

Answer 142

C) Calcitriol

Question 143

Which statement is false?
A) Ubiquinone is involved in electron transport.
B) Natural pigments are often lipids with conjugated double bonds.
C) Many lipids have structures based on repeating isoprene units.
D) Vitamin D is essential for the dissolution of blood clots.

Answer 143

D) Vitamin D is essential for the dissolution of blood clots.

Question 144

Which method is NOT typically used in the purification of lipids?
A) Ammonium sulfate precipitation.
B) Extraction with organic solvents.
C) Thin-layer chromatography.
D) Gas chromatography.

Answer 144

A) Ammonium sulfate precipitation.

Question 145

Lipids were extracted from plasma membranes. What method could be used to separate them by exploiting differences in volatility?
A) Gas chromatography
B) Adsorption-column chromatography
C) Thin-layer chromatography
D) Mass spectroscopy

Answer 145

A) Gas chromatography

Question 146

Mass spectrometry:
A) Cannot be used with lipids other than fatty acids.
B) Can determine the mass but not the identity of a lipid.
C) Can be used to identify individual lipids in complex mixtures.
D) Cannot determine the location of double bonds in a fatty acid.

Answer 146

C) Can be used to identify individual lipids in complex mixtures.

Question 147

Micelles were constructed for delivery of a hydrophobic chemotherapeutic drug. What change would INCREASE the diameter of the micelles?
A) Increasing the concentration of the cholesterol.
B) Increasing the length of the acyl chains used to make them.
C) Increasing the concentration of polyunsaturated fatty acids.
D) Using lipids with head groups having greater polarity.

Answer 147

B) Increasing the length of the acyl chains used to make them.

Question 148

Which amphipathic lipids aggregate is favored to form when glycerophospholipids are mixed with water?
A) No aggregate will form.
B) Micelle
C) Bilayer
D) Vesicle (liposome)

Answer 148

C) Bilayer

Question 149

Which statement is false?
A) All biological membranes have the same composition.
B) All biological membranes contain lipids.
C) Amphipathic molecules may form micelles rather than bilayers depending on their structures.
D) Biological membranes typically contain proteins.

Answer 149

A) All biological membranes have the same composition.

Question 150

Which type of transport requires energy?
A) Active
B) Diffusion
C) Osmosis
D) Passive

Answer 150

A) Active

Question 151

The picture represents which type of cellular transport? (Description: Intracellular vesicle merging with plasma membrane to release components).
A) Exocytosis
B) Endocytosis
C) Osmosis
D) Passive Transport

Answer 151

A) Exocytosis

Question 152

If particles are too large to enter the membrane and they need help from channel proteins but require no energy, what type of transport is represented?
A) Facilitated Diffusion
B) Osmosis
C) Active Transport
D) Passive Transport

Answer 152

A) Facilitated Diffusion

Question 153

Which statement is false regarding lipid transfer proteins (LTP’s)?
A) They are solvable in water.
B) They have a hydrophilic pocket for binding lipids.
C) In some cases, ATP is needed to drive the process.
D) The rate of lipid movement from one membrane to another in vivo is significantly greater than the rate of vesicle budding and fusion.

Answer 153

B) They have a hydrophilic pocket for binding lipids.

Question 154

An amphitropic protein:
A) Has both basic and acidic surfaces.
B) Switches from one face of a membrane to the other.
C) Is sometimes associated with a membrane and sometimes not.
D) Is never a peripheral membrane protein.

Answer 154

C) Is sometimes associated with a membrane and sometimes not.

Question 155

Which statement is true?
A) Monotopic integral proteins have small hydrophilic domains that hold the proteins to the membrane.
B) Bitopic proteins span the bilayer twice.
C) A hydrophobic sequence of 20 amino acid residues will span the lipid bilayer when in the alpha-helical conformation.
D) Membrane proteins do not co-crystallize with phospholipids.

Answer 155

C) A hydrophobic sequence of 20 amino acid residues will span the lipid bilayer when in the alpha-helical conformation.

Question 156

Which statement is true regarding hydropathy plots?
A) A negative hydropathy index indicates the residue number is hydrophobic.
B) A region with more than 20 residues of high hydropathy index is presumed to be a transmembrane segment.
C) An integral protein must have at least one sequence of 20 hydrophilic residues.
D) Hydropathy plots plot residue number (y-axis) against average hydropathy index (x-axis).

Answer 156

B) A region with more than 20 residues of high hydropathy index is presumed to be a transmembrane segment.

Question 157

Which statement is true?
A) Hydropathy analysis provides a measure of H-bonding within the transmembrane portion of a membrane-spanning protein.
B) For all glycoproteins of a plasma membrane, the glycosylated domains are always found on the extracellular face of the bilayer.
C) Proteins may be embedded in, but never span, a biological membrane.
D) Once a membrane is synthesized, the lipid composition of each monolayer does not change.

Answer 157

B) For all glycoproteins of a plasma membrane, the glycosylated domains are always found on the extracellular face of the bilayer.

Question 158

Membrane fluidity:
A) Is maximal when the membrane lipids are in the L0 state.
B) Is a function of temperature if composition is held constant.
C) Increases with saturated fatty acid content.
D) Is not affected by sterol content.

Answer 158

B) Is a function of temperature if composition is held constant.

Question 159

Liposomes were constructed for an experiment with liver cells in culture. The experiment will be at 25C and not 37C. Which change could NOT increase liposome fluidity at the lower temperature?
A) Increasing the concentration of sterols.
B) Increasing the concentration of polyunsaturated fatty acids in phospholipids.
C) Decreasing the concentration of saturated fatty acids in sphingolipids.
D) Increasing the concentration of triacylglycerols in liposomes.

Answer 159

D) Increasing the concentration of triacylglycerols in liposomes.

Question 160

A cell was happily growing at 37C, but the temperature was then changed to 40C. What modifications to the plasma membrane could a cell make to counteract the increase in temperature?
A) Add more cholesterol into the plasma membrane.
B) Introduce more saturated fatty acids into the phospholipids.
C) Decrease the number of double bonds in fatty acids in the phospholipids.
D) All of the answers are correct.

Answer 160

D) All of the answers are correct.

Question 161

Which statement regarding caveolae is false?
A) They are a means of expanding the cell surface.
B) Their extracellular leaflets are lipid rafts.
C) They tend to be cholesterol poor.
D) They result from the formation of caveolin dimers.

Answer 161

C) They tend to be cholesterol poor.

Question 162

What can be learned from the hydropathy plot of caveolin?
A) The protein may have several alpha-helices and at least one beta-strand.
B) There is a calcium-binding domain.
C) There are three polypeptides in the functional protein.
D) It provides a prediction of two membrane spanning regions.

Answer 162

D) It provides a prediction of two membrane spanning regions.

Question 163

What other name can be given to a nucleotide?
A) Glycosylated Nucleoside
B) Purinated Pentose
C) Deoxyribonucleotide
D) Nucleoside Phosphate

Answer 163

D) Nucleoside Phosphate

Question 164

Which of the following is NOT a pyrimidine base?
A) Cytosine
B) Uracil
C) Adenosine
D) Thymine

Answer 164

C) Adenosine

Question 165

Which of the following is NOT part of a deoxyribonucleotide?
A) Deoxyribonucleoside
B) Phosphate
C) A nitrogenous base
D) Ribose

Answer 165

D) Ribose

Question 166

What name is given to the nucleotide found in DNA and NOT in RNA?
A) Uridylate
B) Thymidine
C) Uracil
D) Deoxythymidylate

Answer 166

D) Deoxythymidylate

Question 167

What is DNA more stable than RNA?
A) RNA can never be double-stranded; therefore, DNA is more stable.
B) The 2’-hydroxyl groups in RNA (absent in DNA) are directly involved in the hydrolysis of oligonucleotides.
C) Thymine forms more stable hydrogen bonds than uracil.
D) RNA does not have secondary structure.

Answer 167

B) The 2’-hydroxyl groups in RNA (absent in DNA) are directly involved in the hydrolysis of oligonucleotides.

Question 168

A strand of DNA or RNA:
A) Contains 5’-2’ phosphodiester bonds.
B) Might be an oligonucleotide.
C) Has a C-terminus and an N-terminus.
D) Has no charge.

Answer 168

B) Might be an oligonucleotide.

Question 169

The property of nucleotide bases that affects the three-dimensional structure of nucleic acids is:
A) Their weakly acidic nature.
B) Their absorption of UV light at wavelengths above 280 nm.
C) Their hydrophilic nature.
D) Their existence in tautomeric forms depending on pH.

Answer 169

D) Their existence in tautomeric forms depending on pH.

Question 170

A sample of DNA isolated from an unidentified species of bacteria, adenine makes up 28% of the total bases. Which statement is false about the relative proportions of the bases in the DNA sample?
A) The DNA must contain 28% C.
B) A and T bases account for 56% of the bases.
C) G and C base pairs account for 44% of the bases.
D) C, T, and G bases account for 72% of the bases.

Answer 170

A) The DNA must contain 28% C.

Question 171

Which statement is true about the three-dimensional structure of DNA?
A) Native DNA consists of two parallel chains in a right-handed double-helical arrangement.
B) Complementary base pairs, A=C and G=T, are formed by hydrogen bonds between chains in the helix.
C) The base pairs are stacked parallel to the long axis of the double helix.
D) The offset pairing of the two strands creates a major groove and a minor groove on the surface of the duplex.

Answer 171

D) The offset pairing of the two strands creates a major groove and a minor groove on the surface of the duplex.

Question 172

Which statement regarding bases in DNA is false?
A) They absorb UV light.
B) Pyrimidines are aromatic; purines are not.
C) They have vertical stacking interactions.
D) They hydrogen bond between two or more complementary DNA strands.

Answer 172

B) Pyrimidines are aromatic; purines are not.

Question 173

Some effort has been made to extract DNA from fossilized dinosaur bonds that have been buried for many millions of years in arid climates. In what form is this DNA MOST likely to be found?
A) A
B) B
C) Z
D) Completely denatured.

Answer 173

A) A

Question 174

Which of the following is NOT associated with DNA structure?
A) Z-DNA
B) G tetraplexes
C) Three hydrogen bonds between A and T
D) Pyrimidines in the anti-conformation.

Answer 174

C) Three hydrogen bonds between A and T

Question 175

Which statement regarding mRNA is false?
A) It is always monocistronic.
B) It carries genetic information to the ribosomes.
C) It is formed by transcription.
D) It can be of varying lengths.

Answer 175

A) It is always monocistronic.

Question 176

Which structure is found in RNA but would be the result of a mutation of faulty annealing in DNA?
A) Hairpin.
B) Double-stranded helix.
C) Cruciform
D) Bulge

Answer 176

D) Bulge

Question 177

Which statement is false regarding a solution of DNA subjected to extreme of pH?
A) The viscosity of the solution will decrease sharply.
B) Hydrogen bonds between paired bases will be disrupted.
C) Covalent bonds in the DNA will be broken.
D) Base-stacking interactions will be disrupted.

Answer 177

C) Covalent bonds in the DNA will be broken.

Question 178

Which statement is false about nucleotides and nucleic acids undergoing non enzymatic transformation?
A) Several nucleotide bases undergo spontaneous loss of their exocyclic amino groups.
B) Hydrolysis of the N-B-glycosol bond between the base and the pentose creases a DNA lesion called an AP site.
C) Ionizing radiation induces the condensation of two ethylene groups to form a cyclobutene ring.
D) UV irradiation can result in a 6-4 photoproduct, a type of pyrimidine dimer.

Answer 178

C) Ionizing radiation induces the condensation of two ethylene groups to form a cyclobutene ring.

Question 179

Mutations in RNA can result from:
A) Deamination of ribose.
B) UV-induced purine dimers.
C) Alkylation of the phosphodiester bond.
D) Oxidation of deoxyribose.

Answer 179

D) Oxidation of deoxyribose.

Question 180

In the simplest form, polymerase chain reaction:
A) Is remarkably insensitive to contamination.
B) Requires reverse transcription.
C) Requires two oligonucleotide primers.
D) Requires a minimum of 10,000 copies of DNA to be amplified.

Answer 180

C) Requires two oligonucleotide primers.

Question 181

Which statement is true?
A) Hydrolysis of the alpha, beta, and gamma phosphoester bonds of a nucleotide is used as a source of chemical energy.
B) dATP is the most common source of chemical energy in cells.
C) CTP hydrolysis can be a source of chemical energy.
D) Hydrolysis of ATP to ADP and phosphate releases about 14 kJ/mol of free energy.

Answer 181

C) CTP hydrolysis can be a source of chemical energy

Question 182

In which way nucleotides NOT be involved in signaling?
A) Cyclic dGMP as a second messenger.
B) As precursors for synthesizing second messengers.
C) Extracellular ADP binding to its receptor.

Answer 182

A) Cyclic dGMP as a second messenger.

Question 183

Which answer choice shows a correctly named bacterial gene?
A) dnaA
B) dnaA (italics)
C) DnaA
D) DnaA (italics)

Answer 183

C) DnaA

Question 184

What type of bond must be made between Ozazaki fragments in order to make a complete DNA strand?
A) Hydrogen
B) Disulfide
C) Ester
D) Phosphodiester
E) Ionic

Answer 184

D) Phosphodiester

Question 185

Which statement correctly describes the reaction catalyzed by DNA polymerase I?
A) The nucleophile is the alpha phosphate of the incoming deoxynucleoside 5’-triphosphate.
B) The nucleophile is the 3’-OH group of the nucleotide at the 3’ end of the growing strand.
C) The nucleophile is the 3’-OH group of the nucleotide at the 5’ of the growing strand.
D) The nucleophile is the gamma phosphate of the incoming deoxynucleoside 5’-triphosphate.

Answer 185

B) The nucleophile is the 3’-OH group of the nucleotide at the 3’ end of the growing strand.

Question 186

Which statement does NOT describe a fundamental feature of DNA replication?
A) It requires a template.
B) It is semiconservative.
C) It begins at a DNA location known as an origin.
D) It involves polymerizing deoxyribonuclotides only.

Answer 186

D) It involves polymerizing deoxyribonuclotides only.

Question 187

Processivity is defined as:
A) How many errors are incorporated into the DNA per 1,000 bases.
B) The average number of nucleotides added before a polymerase dissociates.
C) The rate at which nucleotides are added to the DNA.
D) The number of DNA polymerases bound to one DNA molecule.
E) Which DNA polymerase is performing the elongation.

Answer 187

B) The average number of nucleotides added before a polymerase dissociates.

Question 188

DNA polymerases:
A) All have a 5’ to 3’ exonuclease activity for proofreading.
B) Only polymerize in a 5’ to 3’ direction.
C) Are all highly processive.
D) Are only found at replication forks.

Answer 188

B) Only polymerize in a 5’ to 3’ direction.

Question 189

Which protein is Not necessary to initiate DNA replication in E. coli?
A) Helicases
B) Primases
C) Topoisomerases
D) DNA-binding proteins
E) All of them are necessary

Answer 189

E) All of them are necessary

Question 190

The lagging strand in DNA replication:
A) Requires its own replisome.
B) Is synthesized after the leading strand.
C) Is an inescapable consequence of replicating both strands of template DNA at a single replication fork.
D) Causes the formation of Okazaki fragements in the leading strand.

Answer 190

C) Is an inescapable consequence of replicating both strands of template DNA at a single replication fork.

Question 191

A research project using E. coli has come to a halt because DNA replication is blocked. It seems that the DNA strands are not separating. What enzyme is likely faulty?
A) Helicase (DnaB protein).
B) Topoisomerase I.
C) DNA ligase.
D) One of the DNA primases.
E) DNA polymerase I.

Answer 191

A) Helicase (DnaB protein).

Question 192

DNA repair is necessary because:
A) Any mutation in DNA will affect the function of the product of the gene in which it occurs.
B) While the mutation is necessary for evolution, most mutations do not confer a biological advantage and therefore represent more danger than they do opportunity.
C) DNA replication results in approximately one mistake made per 10^6 nucleotides polymerized.
D) DNA is chemically unstable.

Answer 192

B) While the mutation is necessary for evolution, most mutations do not confer a biological advantage and therefore represent more danger than they do opportunity.

Question 193

Which statement is true about the Ames test?
A) It can be used to screen for potential human carcinogens.
B) It requires a histidine-rich environment.
C) It requires a strain of antibiotic-resistant bacteria.
D) It involves sacrificing lab animals and evaluating them for tumors.

Answer 193

A) It can be used to screen for potential human carcinogens.

Question 194

Which statement regarding DNA mismatch repair in E. coli is false?
A) If both strands appear to be parental (“correct”), the mismatch repair system can still repair the strand with the mistake (through a process still poorly understood).
B) The parental (“correct”) strand can be distinguished by its methylation.
C) A single mismatch may require replacing hundreds of nucleotides on the unmethylated strand.
D) It involves exonucleases.

Answer 194

B) The parental (“correct”) strand can be distinguished by its methylation.

Question 195

In base-excision repair pathway, a DNA glycosylase creates:
A) An AP site.
B) An alkylated base.
C) A pyrimidine dimer.
D) A gap of 12 to 13 nucleotides.

Answer 195

A) An AP site.

Question 196

Nucleotide-excision repair:
A) Is required when the DNA lesion to be repaired does not cause a detectable distortion in the DNA structure.
B) In both bacteria and eukaryotes requires removal of 60-70 nucleotides.
C) Involves DNA polymerase II in E. coli.
D) Occurs in all free-living organisms.

Answer 196

D) Occurs in all free-living organisms.

Question 197

DNA must be replicated with extremely high fidelity, and maintained free of structural defects in order to propagate a species. Which structural change in DNA, considered damage, CANNOT be repaired?
A) Pyrimidine dimers.
B) Mismatched bases.
C) Methylation of bases, such as 1-methylguanine or 3-methylcytosine.
D) Uracil incorporated into DNA.
E) All of these can be repaired.

Answer 197

E) All of these can be repaired.

Question 198

Which statement about transcription is false?
A) Transcription uses a DNA strand as the template.
B) Transcription is more selective than replication.
C) Most RNA molecules in the transcriptome code for proteins.
D) The majority of the human genome is transcripted into RNA.

Answer 198

C) Most RNA molecules in the transcriptome code for proteins.

Question 199

What metal plays an important role in transcription, a role similar to phosphoryl group transfer?
A) Manganese
B) Iron
C) Copper
D) Magnesium
E) Cobalt

Answer 199

D) Magnesium

Question 200

E. coli RNA polymerase does NOT require:
A) A template DNA strand.
B) ATP, GTP, UTP, and CTP.
C) Two Mg2+.
D) A Mg2+ and Mn2+

Answer 200

D) A Mg2+ and Mn2+

Question 201

Other than having U in the RNA in place of T in the DNA, the base sequence of transcribed RNA:
A) Is identical to the template DNA strand sequence.
B) Is identical to the complementary DNA strand sequence.
C) Is the reverse of the template DNA strand sequence.
D) Is the reverse of the nontemplate DNA strand sequence.

Answer 201

B) Is identical to the complementary DNA strand sequence.

Question 202

Which subunit is NOT part of the E coli. DNA-dependent RNA polymerase holoenzyme?
A) Alpha subunit
B) Beta subunit
C) Gamma subunit

Answer 202

C) Gamma subunit

Question 203

What valuable piece of information is obtained by DNA footprinting?
A) The location of a promotor region of DNA.
B) The specific sequence of bases to which a particular protein binds.
C) The location of the 5’ end of a coding sequence.
D) All the DNA sequences in a genome to which a known DNA sequence binds.
E) The location(s) in geometric DNA to which a known sequence of RNA binds.

Answer 203

B) The specific sequence of bases to which a particular protein binds.

Question 204

When does the sigma subunit dissociate from the RNA polymerase core subunits?
A) Randomly as the polymerase enters the elongation phase of transcription.
B) When NusA displaces it.
C) When the promotor region has passed through.
D) Exactly when the second NTP has been added to the chain.

Answer 204

A) Randomly as the polymerase enters the elongation phase of transcription.

Question 205

Signal transduction systems incorporate molecules that have other cellular functions. What second messenger ion or molecule plays a role in activating bacterial gene transcription?
A) cGMP
B) Inositol 1,4,5-triphosphate
C) 1,2-diacylglycerol
D) Ca2+
E) cAMP

Answer 205

E) cAMP

Question 206

Which factor is NOT associated with the process of terminal transcription?
A) Sequence-dependent binding of termination protein in eukaryotes.
B) Dephosphorylation of the CTD of Pol II in eukaryotes.
C) The action of p helicase in E. coli.
D) The hairpin formation in the RNA product of E. coli RNA polymerase.

Answer 206

A) Sequence-dependent binding of termination protein in eukaryotes.

Question 207

Which eukaryotic RNA polymerase is responsible for transcribing MOST rRNA’s?
A) Pol I
B) Pol II
C) Pol III
D) Pol I and Pol II

Answer 207

A) Pol I

Question 208

Which statement about general transcription factors is false?
A) They are required at every Pol II promotor.
B) They are usually designed TFII with an additional identifier.
C) They are highly conserved in all eukaryotes.
D) They are proteins that block the synthesis of RNA at specific genes.

Answer 208

D) They are proteins that block the synthesis of RNA at specific genes.

Question 209

Which factor is NOT associated with the function of promotors?
A) Different sigma factors in E. coli specific for specific promotors.
B) Requirement of several transcription factors to properly position Pol II at the promotor in eukaryotes.
C) Binding of the E. coli core RNA polymerase, directed by its sigma factor, to a promotor.
D) Pol II in eukaryotes having strict specificity for the TATA box and Inr sequence.

Answer 209

D) Pol II in eukaryotes having strict specificity for the TATA box and Inr sequence.

Question 210

Which is NOT a phase of eukaryotic transcription?
A) Elongation
B) Assembly
C) Preparation
D) Termination
E) Initiation

Answer 210

C) Preparation

Question 211

What is removed from the RNA primary transcript in order to produce mRNA?
A) TATA boxes
B) Recombination signal sequences
C) Introns
D) Promotor sites
E) Polyadenylation

Answer 211

C) Introns

Question 212

Which factor is NOT a typical modification found in a eukaryotic mRNA?
A) Polyadenylation of the 3’ end.
B) Addition of a 5’ cap.
C) Exon addition
D) Intron removal

Answer 212

C) Exon addition

Question 213

What is the 5’ cap, structurally?
A) 7-methylguanosine on the 5’ end of RNA
B) A sequence of adenosine residues added to the 5’ end of the RNA.
C) 3-methyluracil added to the 5’ end of the RNA
D) 5-methylguanosine on the 3’ end of the RNA
E) Methylation of the 5’ base of RNA, preventing further addition of bases.

Answer 213

A) 7-methylguanosine on the 5’ end of RNA

Question 214

The 5’ cap:
A) Is composed of 4-methylguanosine.
B) Is attached via a 5’, 3’-triphosphate linkage.
C) Protects the rRNA from degradation.
D) Participates in binding of the mRNA to the ribosome to initiate translation.
E) All of the answers are correct.

Answer 214

D) Participates in binding of the mRNA to the ribosome to initiate translation.

Question 215

Posttranscriptional modification are NOT made to bases in:
A) Ribosomal RNA
B) Messenger RNA
C) Transfer RNA
D) Silencing RNA
E) All of these can have posttranscriptional modifications.

Answer 215

E) All of these can have posttranscriptional modifications.

Question 216

Crick’s adaptor hypothesis was verified with the discovery of:
A) DNA
B) mRNA
C) rRNA
D) tRNA

Answer 216

D) tRNA

Question 217

In principle, how many reading frames does any given single-stranded DNA or mRNA sequence possess?
A) 1
B) 2
C) 3
D) 4

Answer 217

C) 3

Question 218

How many codon combinations actually encode amino acids?
A) 20
B) 32
C) 61
D) 64

Answer 218

C) 61

Question 219

Why is the genetic code said to be “degenerate”?
A) The first base in a codon is the most important for coding, followed by the second base, and the third base is least important.
B) Each amino acid can be specified by more than one codon.
C) Fewer amino acids are coded by the four bases than was expected.
D) The less complexity in an organism, the fewer codons are specified.
E) The genetic code deteriorates with each replication (generation), unless proofreading functions correct for errors.

Answer 219

B) Each amino acid can be specified by more than one codon.

Question 220

Which statement does NOT describe a feature of the genetic code?
A) It consists of nonoverlapping triplet codons, with three possible reading frames.
B) Bacteria have a slightly different code than do eukaryotes.
C) It is degenerate.
D) Base pairing of the 3’ base of the mRNA codon to the 5’ base of the tRNA anticodon is often not “normal” Watson-Crick base pairing.

Answer 220

B) Bacteria have a slightly different code than do eukaryotes.

Question 221

What mediates the interaction between the nucleotide triplets present on tRNA molecules and triplet codons?
A) Ionic Bonds
B) Hydrogen Bonds
C) Covalent Bonds
D) Peptide Bonds

Answer 221

B) Hydrogen Bonds

Question 222

Mutation of the codon GAU to which codon would MOST likely result in a protein with unaltered or minimally altered function?
A) GAG
B) GUG
C) GCG
D) GGG

Answer 222

A) GAG

Question 223

Which mutation is an example of a translation mutation?
A) G to A
B) G to T
C) A to C
D) A to T

Answer 223

A) G to A

Question 224

Why do a great many eukaryotic proteins start with a Met residue on the amino terminus?
A) At the start of synthesis, only the Met tRNA can bind to the regulatory site on the small ribosomal subunit.
B) Most proteins are soluble and the signal sequence always starts with a Met.
C) The sulfur of Met forms a thirster linkage to the small ribosomal subunit during synthesis.
D) The initiation codon also codes for Met.
E) There is currently no accepted hypothesis for this observation.

Answer 224

D) The initiation codon also codes for Met.

Question 225

Given the initiation and elongation phases of protein synthesis, how many nucleoside triphosphates (or their equivalents) are hydrolyzed to nucleoside diphosphates in order to make one peptide bond?
A) One
B) Two
C) More than four
D) More than eight
E) There is no hydrolysis. All the reactions are phosphoryl transfers.

Answer 225

C) More than four

Question 226

Which statement about post translational modifications of newly synthesized proteins is false?
A) The amino-terminal fMet or Met residue may be enzymatically removed.
B) The amino-terminal Met residue in eukaryotes may be N-acetylated.
C) Carboxyl-terminal residues are never modified or removed.
D) Sequences that help direct the protein to its ultimate destination in the cell may be removed by specific peptidases.

Answer 226

C) Carboxyl-terminal residues are never modified or removed.