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Biochem > Wiley Qs - Exam 2 > Flashcards

Wiley Qs - Exam 2 Flashcards

1
Q

D- erythrose is a …
D- fructose is a …
D-glyceraldehyde is a …
D-ribulose is a …

A

aldotetrose
ketohexose
aldotriose
ketopentose

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2
Q

an … is an isomer that differs in configuration at one chiral center

A

epimer

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3
Q

a sugar with a six-membered ring is known as a …

A

pyranose

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4
Q

a sugar forms a cyclic hemiacetal by reaction between an alcohol and an …

A

aldehyde

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5
Q

an aldonic acid is the result of … of the aldehyde group of an aldolase

A

oxidation

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6
Q

True or false:

monosaccharides are aldehyde or ketone derivatives of straight chain hydroxy alcohols that have at least 4 carbon atoms

A

false

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7
Q

monosaccharides have … or more carbon atoms

A

3

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8
Q

D-sugars have the same absolute configuration at the asymmetric center farthest from their carbonyl group as does …

A

D-glyceraldehyde

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9
Q

True or False:

aldoses of 5 or 6 carbons can form planar rings called pyranoses

A

False

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10
Q

aldoses are not planar, but take up the familiar … or … conformations

A

chair; boat

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11
Q

glycogen or amylopectin is a branched polymer of

A

d-glucose alpha(1->4, 1->6)

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12
Q

cellulose is a polymer of

A

d-glucose, beta(1–>4)

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13
Q

sucrose is a … disaccharide

A

nonreducing

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14
Q

glycosaminoglycan is a linear polymer of … and …

A

uronic acid; hexosamine

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15
Q

lactose is a … disaccharide

A

reducing

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16
Q

chitin is a polymer of …

A

N-acetyl-D-glucosamine, beta (1–>4)

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17
Q

amylose is a polymer of

A

D_glucose, alpha (1–>4)

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18
Q

polysaccharides consist of monosaccharides linked by … bonds

A

glycosidic

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19
Q

polysaccharides form .., as well as linear, polymers

A

branched

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20
Q

a sugar having an anomeric carbon that is not in a glycosidic bond is known as a … sugar

A

reducing

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21
Q

… is a mixture of glycans that plants synthesize as their food reserve

A

starch

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22
Q

exo- and endo-… are enzymes that hydrolyze chains of saccharides

A

glycosidases

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23
Q

True or False:

glycogen, the storage polysaccharide of animals is present in all cells, but primarily in skeletal muscle and in liver

A

True

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24
Q

True or False

maltose is a disaccharide that appears when starches are broken down during digestion

A

True

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25
Q

Alternating N-acetylglucsamine and N-acetylmuramic acid, in beta(1–>4) linkages make up the polysaccharide component of ..

A

peptidoglycan

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26
Q

N-linked oligosaccharides are covalently attached to proteins through the side chain, N atom of …

A

Asn

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27
Q

the carbohydrate content of glycoproteins varies by weight from …% to > …%

A

1; 90

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28
Q

true or false:

the flexible cell walls of bacteria are made from peptidoglycan, and permit them to live in hypotonic environments

A

false

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29
Q

bacteria can live in hypotonic media because the peptidoglycan-based cell walls are …

A

rigid

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30
Q 
which of the following forms bilayers spontaneously in water? 
fatty acids
triacylglycerols
glycerophospholipids
cholesterol
A

glycerophospholipids

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31
Q 
a protein studied in the lab dissociates from the cell plasma membrane after treatment with high salt concentrations or changes in pH. What type of protein could this be? 
an ion channel protein 
a peripheral membrane protein 
an integral membrane protein 
a receptor protein
A

a peripheral membrane protein

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32
Q

peripheral membrane proteins associate with the membrane by forming .. and … interactions. peripheral proteins may be dissociated from the membrane by changes in … or …

A

electrostatic; hydrogen bond; pH; salt concentration

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33
Q

you measure the transition (melting) temperature of membranes isolated from bacterial cells. this temperature is higher for Sample A than for Sample B. which of the following could explain this difference?

A. Cells in Sample A were grown at 25°C whereas those in Sample B were grown at 37°C.

B. The lipids from Sample A contain a greater proportion of long chain fatty acids.

C. The lipids from Sample B contain a greater proportion of saturated fatty acids.

Both A and C could explain the difference.

A

B. The lipids from Sample A contain a greater proportion of long chain fatty acids.

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34
Q

Which of the following statements describing cholesterol in biological membranes is TRUE?

Cholesterol is located between the polar head groups of the membrane lipids.

Cholesterol’s planar ring structure is highly flexible, which maximizes its interactions with the acyl tails of neighbouring lipids.

Cholesterol is an important component of the plasma membrane in mammalian cells.

Cholesterol has no effect on the stability or transition temperature of a membrane

A

Cholesterol is an important component of the plasma membrane in mammalian cells.

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35
Q

Which of the following statements about membrane lipids is FALSE?

Glycerophospholipids contain fatty acids linked to glycerol through ester bonds.

Although sphingolipids and glycerophospholipids are structurally dissimilar, their 3-D shapes are similar.

Glycerophospholipids may have a sugar molecule as their polar head group (glycolipids).

Cholesterol inserts in between the fatty acyl tails of other membrane lipids, where it modulates the fluidity of membranes.

A

Glycerophospholipids may have a sugar molecule as their polar head group (glycolipids).

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36
Q

glycerophospholipids always have a … haed group. … and … are the two classes of membrane lipids that have head groups containing one or more sugar residues

A

phosphate; cerebrosides; gangliosides

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37
Q

Which of the following statements describing the function of cholesterol in biological membranes is FALSE?

It limits the movement of some fatty acyl tails within the bilayer, thereby increasing van der Waal’s interactions between them.

It reduces the fluidity of lipid bilayers over a broad temperature range.

It prevents close packing of some fatty acyl tails within the bilayer, thereby decreasing van der Waal’s interactions between them.

It maintains the stability of lipid bilayers over a broad temperature range.

A

It reduces the fluidity of lipid bilayers over a broad temperature range.

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38
Q

Cholesterol plays a significant role in maintaining … over a broad range of temperatures. At high temperatures cholesterol tends to … membrane fluidity as its rigid steroid ring system reduces the movement of fatty acyl tails thereby increasing van der Waal’s interaction between them. At low temperatures it …membrane fluidity as it prevents close packing of acyl tails by fitting in between them.

A

membrane fluidity; reduces; increases

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39
Q

What two properties make triacylglycerols a more efficient storage form of metabolic energy than glycogen?

They are anhydrous and more reduced.

They are anhydrous and less reduced.

They are hydrated and less reduced.

They are hydrated and more reduced.

A

They are anhydrous and more reduced.

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40
Q

Which is not a consequence of the cis double bonds of fatty acids?

Reduced van der Waals interactions among chains

A rigid 30° bend in the hydrocarbon chain

A higher melting temperature

Less efficient packing of the hydrocarbon chains

A

A higher melting temperature

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41
Q

Which of the following correctly rank the steps in erythrocyte glucose transport by GLUT1?

I. Glucose binding results in a conformational change, opening the binding site on the opposite side of the membrane
II. Glucose binds to the transporter on one side of the membrane
III. The transporter reverts to initial conformation
IV. The glucose disassociates

IV, III, II, I

I, II, IV, III

II, I, III, IV

II, I, IV, III

IV, II, III, I

A

II, I, IV, III

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42
Q

Which of the following determines the force that “drives” an ion through an ion channel in a membrane?

The size and shape of the channel.

The concentration gradient across the membrane.

The properties of the selectivity filter.

The size of the ion.

A

The concentration gradient across the membrane.

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43
Q

Ion channels enable the … movement of ions down their concentration gradient. Thus, the force (free energy change) that drives an ion through an ion channel depends on the …

A

passive; size of the concentration gradient

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44
Q

Ouabain inhibits the (Na+–K+)–ATPase pump, resulting in

K+ ions moving into the cell along a concentration gradient

K+ ions bringing water molecules into the cell in order to maintain an osmotic balance

extra K+ ions and water in cells causing them to swell and lyse

an increase in the strength of heart muscle contractions when small amounts of Ouabain are used

all of the above

A

an increase in the strength of heart muscle contractions when small amounts of Ouabain are used

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45
Q

D-glucose is added to cells and the rate of glucose transport is plotted against D-glucose concentration. In the presence of the D-galactose derivative 6-O-benzyl-D-galactose, the curve is shifted to the right, indicating that D-glucose and the D-galactose derivative both compete for a place in the binding site. Which of the following is true?

The D-galactose derivative occupies some of the available binding sites.

Given the same concentration of glucose available, the number of binding sites with D-glucose present would decrease.

Given the same concentration of glucose, the rate of D-glucose flux would remain the same with the D-galactose derivative added.

Presumably a higher concentration of D-glucose would be required in order to maintain the same rate of D-glucose flux as before the D-galactose derivative was added.

All of the above are true.

A

All of the above are true.

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46
Q

The protein components of lipoproteins are known as

A

apoproteins

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47
Q

The Kv channel is transiently closed by ___________.

a spherical globular segment on the N-terminus

a C-terminal segment activated by proteolysis

proteoglycan residues

an ion larger than the selectivity filter blocking entry

tightly-bound Ca2+

A

a spherical globular segment on the N-terminus

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48
Q

Given what you know about the function of the (Na+—K+)—ATPase, which of the following is the most accurate prediction of the structure of its binding site? The binding site is likely to contain multiple:

A. Glu and Asp residues.

B. Lys and Arg residues.

C. Ser and Thr residues.

D. Gln and Asn residues.

Both C and D are correct.

A

A. Glu and Asp residues

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49
Q

The (Na+—K+)—ATPase binds and transports … ions out of the cell and then … ions into the cell. Amino acid side chains that might play a role in binding these positively charged ions are likely to be negatively charged, such as Glu and Asp.

A

3 Na+; 2 K+

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50
Q

Which of the following statements correctly distinguishes transporters (carrier proteins) from porins and ion channels?

A. Transporters exhibit a conformational change when substrate binds but porins and ion channels do not.

B. Porins and ion channels have a permanent hole that passes from one side of the membrane to the other through which solutes pass whereas transporters do not.

C. Porins and ion channels mediate passive transport, while transporters are associated with both passive and active transport.

Both A and B are correct.

All of the above are correct.

A

All of the above are correct

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51
Q

What type of transporter is the sodium-glucose transporter?

A primary antiporter.

A secondary antiporter.

A secondary symporter.

A secondary uniporter.

A primary symporter.

A

A secondary symporter.

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52
Q

The sodium-glucose transporter is a secondary active transporter because it uses free energy in an … to “drive” an energetically unfavorable transport process.

A

ion concentration gradient

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53
Q

Which statement about aquaporins is false?

They transport water and hydronium ions efficiently.

They exclusively transport water molecules at a high rate.

They use hydrogen bonding to side chain NH2 groups of two Asn residues to exclude proton transport within the pore.

They have a narrow constriction approximately equal to the van der Waals diameter of a water molecule.

They use Arg and His side chains to remove associated water molecules from the ‘transported’ H2O.

A

They transport water and hydronium ions efficiently.

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54
Q

Why does secondary active transport require the absence of porins in the membrane?

The porins will dissipate any ionic concentration gradients

The porins will interfere with ATP hydrolysis and will dissipate any ionic concentration gradients.

Porins are passive transporter proteins.

Porins are passive transporter proteins that will interfere with ATP hydrolysis and will dissipate any ionic concentration gradients.

The porins will interfere with ATP hydrolysis.

A

The porins will dissipate any ionic concentration gradients

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55
Q

Which of the following statements about ion channels is FALSE?

Ion channels allow ions to move against their concentration gradient.

Ion channels are integral membrane proteins.

Ion channels are multi-subunit proteins.

The selectivity of an ion channel is dependent upon the amino acids that comprise the mouth of the channel.

A

Ion channels allow ions to move against their concentration gradient.

56
Q

Ion channels enable the movement of ions only …their concentration gradient.

A

down

57
Q

Which of the following is NOT a feature of active transport processes?

They occur via proteins that are classified as uniport, symport, or antiport.

They are highly specific with respect to substrate.

They require input of free energy.

They occur via proteins that form a channel through the membrane.

A

They occur via proteins that form a channel through the membrane.

58
Q

Active transport processes do not occur …

A

through channels.

59
Q

D-Glucose and D-mannitol are similarly soluble, but D-glucose is transported through the erythrocyte membrane four times as rapidly as D-mannitol. What is the most likely explanation?

D-glucose undergoes simple diffusion more rapidly than mannitol because glucose is less polar.

D-glucose and D-mannitol enter the erythrocyte via an ion-gated channel.

D-glucose and D-mannitol are transported via a system that distinguishes the two sugars.

D-glucose flux through the membrane is linear whereas D-mannitol flux is described by a hyperbolic curve.

None of the above provides the explanation

A

D-glucose and D-mannitol are transported via a system that distinguishes the two sugars.

60
Q

The (Na+—K+)—ATPase works through changes in conformation. Which of the following mechanisms is responsible for these changes in conformation?

Induced fit

Phosphorylation

Allostery

Cooperativity

A

Phosphorylation

61
Q

The following are steps which incompletely describe the mechanism by which Na+ and K+ ions are transported by the (Na+—K+)—ATPase. What is the correct sequence for the events listed, assuming that K+ ions have just dissociated?

  1. The phosphate group on the protein is hydrolyzed.
  2. ATP binds to the protein.
  3. The protein’s conformation changes, exposing K+ binding sites to the cell interior.
  4. Na+ ions dissociate.

1, 3, 2, 4

2, 4, 1, 3

2, 3, 1, 4

3, 1, 4, 2

2, 4, 3, 1

A

2, 4, 1, 3

62
Q

Phosphorylation is a form of reversible covalent modification that induces changes in the conformation of a protein. The (Na+—K+)—ATPase changes its conformation in response to … events.

A

cyclical phosphorylation-dephosphorylation

63
Q

Which type is not one of the several families of ATP-dependent transporters?

Z-type ATPases

P-type ATPases

V-type ATPases

F-type ATPases

A

Z-type ATPases

64
Q

Gap junctions

connect the cytoplasm to the extracellular solution thus allowing transfer of small molecules out of the cell into the extracellular solution.

are essential communication channels between the cell and the extracellular solution.

allow exchange of small molecules between cells within an organ.

allow intercellular exchange of macromolecules.

All of the above.

A

allow exchange of small molecules between cells within an organ.

65
Q

The concentration of cytosolic Ca2+ is _________ the extracellular concentration of Ca2+.

4 orders of magnitude greater than

much less than

equal to

dependent upon

2 order of magnitude greater than

A

much less than

66
Q

Valinomycin, a substance which transports K+ ions across lipid bilayers and down their concentation gradient, kills cells. Which of the following is the cause of cell death?

Elevated concentrations of K+ ions inside a cell are toxic.

The (Na+—K+)—ATPase cannot work in the absence of a K+ ion concentration gradient.

A K+ ion concentration gradient is essential for secondary active transport.

Dissipating the K+ ion concentration gradient results in uncontrolled ATP hydrolysis.

A

Dissipating the K+ ion concentration gradient results in uncontrolled ATP hydrolysis.

67
Q

The concentration gradient of K+ ions is generated by the action of the (Na+—K+)—ATPase, which is inhibited when the gradient is …. When the K+ ion concentration gradient is dissipated by …, the activity of the ATPase is uncontrolled and ATP hydrolysis is thus uncontrolled. The cell dies because it runs out of ATP.

A

large; valinomycin

68
Q

kidney cells contain a channel that allows intracellular ammonia to exit the cells
researchers originally believed that cells had no need for such a channel because ammonia is … and … and therefore was expected to be able to pass across a membrane by simple diffusion

A

small; uncharged

69
Q

kidney cells contain a channel that allows intracellular ammonia to exit the cells
the free energy source of the passive mediated ammonia transport via the channel is the …

A

ammonia concentration gradient

70
Q

kidney cells contain a channel that allows intracellular ammonia to exit the cells
the same kidney cells also contain a proton pump that expels H+ from the cells. the free energy source for this active transport system is … the combination of H+ and NH3 outside the cell forms NH4+, which, because it is …, is unable to reenter the cell via the ammonia channel

A

ATP; ionic

71
Q

enzyme activity varies with temperature. as the temperature increases, thermal energy boosts the proportion of reactants that can achieve the … per unit time, so the rate … Above an optimal temperature, the enzyme becomes … and rapidly loses catalytic activity

A

transition state; increases; denatured

72
Q

An uncatalyzed reaction has a rate of 4.2 × 10–7 sec–1. When an enzyme is added the rate is 3.2 × 104 sec–1. Calculate the rate enhancement caused by the enzyme.

  1. 2 × 104
  2. 4 × 10–3
  3. 3 × 10–2
  4. 6 × 1010

The data are not appropriate for the calculation requested.

A

7.6 × 1010

73
Q

The imidazole side chain of histidine can function as either a general acid catalyst or a general base catalyst because

I. the imidazole group has a pKa in the physiological pH range.
II. in the physiological pH range, the nitrogen in the ring can be easily protonated/deprotonated.
III. one guanidino group is protonated, and the other is deprotonated at physiological pH.
IV. the imidazole group is a strong reducing agent at physiological pH.

II, IV

I

II, III

IV

I, II

A

I, II

74
Q

A new serine protease was discovered that preferentially cleaves a peptide bond adjoining a negatively charged side chain. Which of the following is true?

It likely reacts much slower than chymotrypsin.

It likely reaction much faster than chymotrypsin.

The specificity pocket would mimic that of chymotrypsin.

The specificity pocket is likely lined with amino acids such as Arg and Lys.

The specificity pocket would mimic that of trypsin.

A

The specificity pocket is likely lined with amino acids such as Arg and Lys.

75
Q

Which one of the following is correct?

I. All enzymes are highly specific for the reactions they catalyze.
II. Prosthetic groups are loosely associated with the polypeptide chain of an enzyme.
III. If an enzyme-catalyzed reaction requires a group with a low pK to be deprotonated and a group with a higher pK to be protonated, the pH vs. rate curve will have a peak in the middle of the two pK values.
IV. When comparing types of catalysis, the proximity effect provides the largest rate enhancement.

IV

I, II, III, IV

III

I, III

I

A

I, III

76
Q

Which of the following is TRUE about enzymes?

I. Enzymes typically catalyze reactions at much higher rates than chemical catalyst.
II. Enzymes are often very specific for their substrates.
III. Enzyme activities can often be regulated.
IV. Enzymes typically act under milder conditions of temperature and pH than chemical catalysts.

I, II, III

I, II, III, IV

III, IV

II, III

II, III, IV

A

I, II, III, IV

77
Q

A pH versus rate curve with an inflection point at pH~4 suggests the involvement of a(n) ________ in the catalytic step.

proton donation that is mediated by a coenzyme

free proton surrounded by a hydrophobic environment

redox cofactor

proton abstraction that requires a metal ion in close proximity

proton transfer with a pK close to 4

A

proton transfer with a pK close to 4

78
Q

During the course of a catalytic reaction the following occurs: 1) Substrate is covalently bound and oriented with proximity to the active site residues. 2) Negative charge builds up on the substrate and is stabilized. 3) Oxidation of the enzyme followed by reduction to complete the catalytic cycle. What type of chemical species can facilitate these reactions?

prosthetic phosphate groups

electrophilic groups

transtion metal anions

transition metal cations

nucleophilic amino acids

A

transition metal cations

79
Q

Enzymes that bind reaction transition states with greater affinity than substrates or products

have a lower free energy ES complex than E + S.

increase reaction rates by decreasing the concentration of the transition state .

progress slowly due to the stability of the transition state complex.

compensate for small differences in the energy of the free substrate and free product.

All of the above are correct.

A

have a lower free energy ES complex than E + S.

80
Q

Lysozyme requires _____ for effective catalysis.

I. an Asp in a nonpolar environment
II. a negatively charged Asp
III. a Glu that functions as an acid catalyst
IV. a Glu that is deprotonated

I, III

I, IV

II, IV

I, II, III, IV

II, III

A

II, III

81
Q

Zymogens are not enzymatically active because

the active site amino acids have been mutated.

they have not yet bound the proper cofactor.

their environment has the wrong pH.

they are not yet shaped such that essential proximity and orientation catalysis can occur.

None of the above is correct.

A

they are not yet shaped such that essential proximity and orientation catalysis can occur.

82
Q

The transition state of an enzyme and substrate reaction

is stabilized by decreasing the effective concentration.

is stabilized due to the specificity of the active site for the substrate.

is stabilized by enhancing the reverse reaction of E + S ES.

is composed of true covalent bonds which decrease its energy.

must always bind the enzyme active site with lower energy than the products.

A

is stabilized due to the specificity of the active site for the substrate.

83
Q

Which of the following is TRUE regarding transition state?

The free energy between the transition state and the reactants must be negative.

The transition state can be stabilized by covalent catalysis.

The transition state represents the ES complex.

Transition state analogs bind the substrate not the enzyme

All of the above are true.

A

The transition state can be stabilized by covalent catalysis.

84
Q

It is usually easier to calculate an enzyme’s reaction velocity from the rate of appearance of …

rather than the rate of disappearance of a ….

. Enzyme activity is measured as an ….

reaction velocity, the velocity before much …

has been depleted and before much ….

has been generated. It is easier to measure the appearance of a small amount of …

from a baseline of zero …

than to measure the disappearance of a small amount of …

against a background of a high concentration of …

A 
product
substrate
initial
substrate
product
product
product
substrate
substrate
85
Q

It is not necessary for velocity measurements to be made in units of concentration per time (M·s-1, for example) in order to calculate Km because the Km is a ….

concentration (the concentration when the …

velocity equals the ….

velocity divided by two.

A

substrate; initial; maximum

86
Q

Enzyme A catalyzes the reaction
S→P
and has a KM of 50 µM and a Vmax of 100 nM · s-1. Enzyme B catalyzes the reaction
S→Q
and has a KM of 5 mM and a Vmax of 120 nM · s-1.
When 100 µM of S is added to a mixture containing equivalent amounts of enzymes A and B, after 1 minute ….

will be more abundant because …

has a much….

for the substrate than ….
Because …. is …
for the two enzymes, the relative efficiency of the enzymes depends almost entirely on their ….

values.

A

product P; enzyme A; lower Km; Enzyme B; Vmax; approximately the same; Km

87
Q

The type of enzyme inhibition in which Vmax is unaffected is ______.

isozymes

[A]

the rate constant

Ping Pong

bimolecular

ES complex

random ordered

unimolecular

[A]2

competitive inhibition

phosphorylation

small KS

large KS

uncompetitive inhibition

[B]

A

competitive inhibition

88
Q

In uncompetitive inhibition, the inhibitor binds only to the ______.

isozymes

[A]

the rate constant

Ping Pong

bimolecular

ES complex

random ordered

unimolecular

[A]2

competitive inhibition

phosphorylation

small KS

large KS

uncompetitive inhibition

[B]

A

ES complex

89
Q

What is the velocity of a first-order reaction at 37oC when the reactant concentration is 6 × 10-2 M and the rate constant is 8 × 103 sec-1?

  1. 33 × 105 M-1·sec-1
  2. 33 × 105 M·sec
  3. 5 × 10-2 M·sec
  4. 8 × 102 M·sec-1

Not enough data are given to make this calculation

A

4.8 × 102 M·sec-1

90
Q

KM is

a measure of the catalytic efficiency of the enzyme.

equal to half of Vmax.

the rate constant for the reaction ES E + P.

the [S] that half-saturates the enzyme.

a ratio of substrate concentration relative to catalytic power.

A

the [S] that half-saturates the enzyme.

91
Q

In order for an enzymatic reaction obeying the Michaelis-Menten equation to reach 3/4 of its maximum velocity,

[S] would need to be equal to KM

[S] would need to be ½ KM

[S] would need to be 3KM

[S] would need to be ¾ KM

not enough information is given to make this calculation

A

[S] would need to be 3KM

92
Q

The KM can be considered to be the same as the dissociation constant KS for E + S binding if

the concentration of [ES] is unchanged.

ES E + P is fast compared to ES E + S.

k1&raquo_space; k2.

k2 &laquo_space;k-1.

this statement cannot be completed because KM can never approximate KS.

A

k2 &laquo_space;k-1.

93
Q

Find kcat for a reaction in which Vmax is 4 × 10-4 mol·min-1 and the reaction mixture contains one microgram of enzyme (the molecular weight of the enzyme is 200,000 D).

2 × 10-11 min-1

8 × 107 min-1

8 × 109 min-1

2 × 10-14 min-1

4 × 108 min-1

A

8 × 107 min-1

94
Q

Parallel lines on a Lineweaver-Burk plot indicate

decrease in Vmax.

an increase in KM.

uncompetitive inhibition.

decrease in KM.

A

decrease in Vmax.
uncompetitive inhibition.

decrease in KM.

95
Q

Which of the following is (are) true?

E + S –> ES –> P + E (k1, and k-1 on equilibrium arrows for first reaction and k2 on arrow for second rxn)

The [ES] will remain constant if k2 > k1 and k−1 < k2.

The reaction is zero order with respect to [S] if [S]&raquo_space; [E].

It describes a double displacement reaction.

All of the above are true.

None of the above is true.

A

The reaction is zero order with respect to [S] if [S]&raquo_space; [E].

96
Q

For the reaction, the steady state assumption

E + S –> ES –> P + E (k1, and k-1 on equilibrium arrows for first reaction and k2 on arrow for second rxn)

implies that k1=k−1

implies that k−1 and k2 are such that the [ES] = k1[ES]

[P]»[E]

[S] = [P]

ES breakdown occurs at the same rate as ES formation

A

ES breakdown occurs at the same rate as ES formation

97
Q

The breakdown of dopamine is catalyzed by the enzyme monoamine oxidase (MAO). What is the final concentration of product if the starting dopamine concentration is 0.050 M and the reaction runs for 5 seconds. (Assume the rate constant for the reaction is 0.249 s−1.)

  1. 050 M
  2. 014 M
  3. 018 M
  4. 2 M
  5. 025 M
A

0.014 M

98
Q

Consider the following metabolic reaction:

Succinyl-CoA + Acetoacetate Acetoacetyl-CoA + Succinate = –1.25 kJ/mol

The delta G standard for the hydrolysis of Succinyl-CoA is –33.9 kJ/mol. What is the delta g standard for the hydrolysis of Acetoacetyl-CoA: Acetoacetyl-CoA Acetoacetate + CoA

–35.2 kJ/mol

–32.7 kJ/mol

+32.7 kJ/mol

+35.2 kJ/mol

none of the above

A

–32.7 kJ/mol

99
Q

Consider the following metabolic reaction:

Succinyl-CoA + Acetoacetate Acetoacetyl-CoA + Succinate = –1.25 kJ/mol

This reaction is

favorable under standard conditions.

not favorable under standard conditions.

nonspontaneous as written regardless of reactant concentrations.

spontaneous as written only when [succinate] and [acetoacetyl-CoA] are high.

favorability of this reaction as written depends on temperature and reactant concentrations.

A

favorable under standard conditions.

100
Q

Consider the following metabolic reaction:

2-Phosphoglycerate 3-Phosphoglycerate = -4.40 kJ/mol

What can be said about this reaction when the concentration of 2-phosphoglycerate is 0.490 mM and the concentration of 3-phosphoglycerate is 2.90 mM at 25°C?

I. This reaction is endergonic under these conditions.
II. This reaction is exergonic under these conditions.
III. This reaction is at equilibrium under these conditions.
IV. This reaction is not favorable under standard conditions.

I, IV

II only

III only

IV only

None of the above

A

III only

101
Q

The conversion of triacylglycerides into fatty acids for the purpose of energy generation is an example of which of the following?

heterotropism

anaerobism

catabolism

anabolism

glycolysis

A

catabolism

102
Q

ATP contains ________ bonds.

one phosphoanhydride and two phosphoester

two phosphoester and one glycosidic

three phosphoanhydride

one amide and three phosphoanhydride

one phosphoester and two phosphoanhydride

A

one phosphoester and two phosphoanhydride

103
Q

The vitamin ______ is one of the components of coenzyme A, which is involved in _____.

pantothenic acid; carboxylation

pantothenic acid; acyl transfer

cobalamin; acyl transfer

riboflavin; carboxylation

niacin; electron transfer

A

pantothenic acid; acyl transfer

104
Q

Cells control or regulate the flux through metabolic pathways by means of
I. allosteric control of enzymes.
II. covalent modification of enzymes.
III. genetic control of the concentrations of enzymes.
IV. genetic expression of allosteric effectors.

I, II, III, IV

II, III

I, II, IV

I, II, III

I, IV

A

I, II, III

105
Q

Which of the following are factors that contribute to the large negative standard free energy change for the reaction shown below?
ATP ADP + Pi

the increase in resonance stabilization in the reactants compare to the products

the precipitation of the insoluble Pi

the addition of a water molecule to the hydrophilic ATP molecule

the decrease in negative charge repulsion in the products compared to reactants

all of the above

A

the decrease in negative charge repulsion in the products compared to reactants

106
Q

Which of the following is (are) true regarding vitamins?
I. They are essential organic molecules an organism is unable to synthesize.
II. Some water soluble vitamins mediate electron-transfer reactions.
III. In humans, the water soluble vitamins converted into organic coenzymes.
IV. In humans, the fat soluble vitamins mediate group transfer reactions.

I, II, III, IV

I, II, III

II, III, IV

I only

II, IV

A

I, II, III

107
Q

In the catabolic pathway major nutrients are _________ broken down resulting in the synthesis of __________ .

exergonically; ADP

endergonically; ADP

exergonically; ATP

endergonically; NADP+

endergonically; ATP

A

exergonically; ATP

108
Q

In eukaryotes, glycolysis typically occurs in the

mitochondrion.

cytosol.

lysosome.

rough endoplasmic reticulum.

smooth endoplasmic reticulum.

A

cytosol

109
Q

Which compound is in the highest oxidation state?

A) carbon monoxide

B) carbon dioxide

C) ethanol

A, B, and C are equal

A and B are equal

A

B) carbon dioxide

110
Q

Acyl phosphates such as 1,3-bisphosphoglycerate have a ______ phosphoryl group transfer potential compared to ATP, which can be recognized by the _______ values for hydrolysis.

greater; more positive

greater; more negative

lower; more positive

lower; more negative

none of the above

A

greater; more negative

111
Q

Acetyl-CoA contains a ____ bond which often provides the energy required for substrate-level phosphorylation.

phosphoester

phosphoanhydride

phosphothioester

ester

thioester

A

thioester

112
Q

I have discovered a new metabolic enzyme which utilizes NAD+ as a coenzyme. Which of the following could be true based on this information?

It is involved in a catabolic pathway.

It is involved in an anabolic pathway.

It performs acyl group transfer.

It catalyzes a hydrolytic cleavage.

It catalyzes the reduction of the enzyme’s substrate.

A

It is involved in a catabolic pathway.

113
Q

Why is the term “high-energy” bond somewhat of a misnomer in reference to ATP and similar compounds?

These bonds require a large amount of energy to break, but do not contain a large amount of energy.

The term “high-energy” refers to the difference in free energy between the compound and it hydrolyzed product. It does not refer to the bonds energy.

These bonds are actually intermediate in energy.

These compounds are highly charged.

A

The term “high-energy” refers to the difference in free energy between the compound and it hydrolyzed product. It does not refer to the bonds energy.

114
Q

Consider the following metabolic reaction:

Succinyl-CoA + Acetoacetate Acetoacetyl-CoA + Succinate delta G = –1.25 kJ/mol

What is the Keq for this reaction at 25°C?

  1. 66
  2. 602
  3. 00
  4. 22 x 102
  5. 21
A

1.66

115
Q

Which one of the following is not involved in the reactions of glycolysis between glyceraldehyde-3-phosphate and 3-phosphoglycerate?

Generation of ATP.

The formation of a high energy intermediate.

Catalysis by a kinase enzyme.

Oxidation of NADH.

Use of inorganic phosphate.

A

Oxidation of NADH.

116
Q

The oxidation of glyceraldehyde-3-phosphate by NAD+ generates …, i.e. NAD+ is reduced in this step.

A

NADH

117
Q

How is lactate transported out of the muscle and how does it help hemoglobin to release oxygen?

By a lactate/H+ antiporter, which raises the blood pH.

By a lactate/H+ symporter, which raises the blood pH. The transport of this H+ into the bloodstream lowers blood pH.

By a lactate/H+ antiporter, which lowers the blood pH.

By a lactate/H+ symporter, which lowers the blood pH.

A

By a lactate/H+ symporter, which lowers the blood pH

118
Q

energy capture steps of glycolysis:
… –> …
… –> …
… –> …

A

glyceraldehyde 3-phosphate –> 1,3-bisphosphoglycerate
1,3-bisphosphoglycerate –> 3-phosphoglycerate
phosphoenolypyruvate –> pyruvate

119
Q

Which one of the following enzymes catalyzes an “energy investment” reaction in glycolysis?

A. Hexokinase

B. Phosphofructokinase-2

C. Pyruvate kinase

D. Phosphoglycerate kinase

Both A and B are correct.

A

A. Hexokinase

120
Q

Which of the following is a reversible reaction under cellular conditions?

Fructose-6-phosphate + ATP ——> Fructose-1,6 bisphosphate + ADP + H+

1,3-bisphosphoglycerate + ADP ——> 3-phosphoglycerate + ATP

Phosphoenolpyruvate + ADP + H+ —–> Pyruvate + ATP

Glucose-6-phosphate + H2O —–> Glucose + Pi

A

1,3-bisphosphoglycerate + ADP ——> 3-phosphoglycerate + ATP

121
Q

Consider the outline of glycolysis. Which steps include a substrate-level phosphorylation?
… –> …
… –> …

A

1,3-bisphosphoglycerate –> 3-phosphoglycerate

phosphoenolpyruvate –> pyruvate

122
Q

What is the biochemical purpose for the production of lactate in muscle cells?

Its production enhances the activity of the citric acid cycle.

It is produced as a fuel molecule for the Cori cycle.

It is produced to reoxidize cytoplasmic NADH under anaerobic conditions

It replaces pyruvate as a substrate for the pyruvate dehydrogenase complex.

It decreases the pH of the muscle cell, thereby increasing release of oxygen from hemolglobin.

A

It is produced to reoxidize cytoplasmic NADH under anaerobic conditions

123
Q

The enzyme _____forms a Schiff base upon formation of the enzyme-substrate complex allowing aspartate mediated cleavage of the substrate.

hexokinase

phosphoglucose isomerase

glucose-6-phosphatase

phosphoglucose mutase

aldolase

A

aldolase

124
Q

Experimental evidence indicates that glyceraldehyde-3-phosphate dehydrogenase contains a critical ______ residue in its active site, as shown by its inactivation by iodoacetamide.

alanine

aspartate

cysteine

methionine

lysine

A

cysteine

125
Q

Which is the net equation for aerobic glycolysis?

Glucose + 2 ATP 2 lactate + 2 ADP + 2 Pi

Glucose + 2 ADP + 2 Pi + 2 NAD+ 2 pyruvate + 2 ATP + 2 NADH + 2 H2O + 4 H+

Glucose + 2 ADP + 2 Pi 2 lactate + 4 ATP + 4 H+

Glucose + 2 ATP + 2 NAD+ 2 pyruvate + 4 ATP + 4 NADH + 4 H+

Glucose + 2 ADP + 2 Pi + 2 NAD+ 2 lactate + 4 ATP + 2 NADH + 4 H+

A

Glucose + 2 ADP + 2 Pi + 2 NAD+ 2 pyruvate + 2 ATP + 2 NADH + 2 H2O + 4 H+

126
Q

Which of the following metabolic conversions is considered to be the major control point of glycolysis?

fructose-1,6-bisphosphate –> dihydroxyacetone phosphate + glyceraldehyde-3-phosphate

glucose –> glucose-6-phosphate

2-phosphoglyerate –> phosphoenolpyruvate

fructose-6-phosphate –> fructose-1,6-bisphosphate

phosphoenolpyruvate –> pyruvate

A

fructose-6-phosphate –> fructose-1,6-bisphosphate

127
Q

Which of the following enzymes catalyzes the conversion of glucose-1-phosphate to glucose-6-phosphate?

glucose-1-isomerase

glucokinase

glucose-1-phosphatase

phosphoglucomutase

glycogen phosphorylase

A

phosphoglucomutase

128
Q

Which of the following best describes the function of the glycogen debranching enzyme in glycogenolysis?

It cleaves alpha (1–>6) branch points releasing glucose-6-phosphate.

It cleaves alpha (1–>6) branch points releasing glucose-1-phosphate.

It cleaves alpha (1–>6) branch points releasing glucose.

It transfers an alpha (1–>4) linked trisaccharide unit to the nonreducing end of an alternate branch, then cleaves the (16) branch point releasing glucose-1-phosphate.

It transfers an alpha (1–>4) linked trisaccharide to the nonreducing end of an alternate branch, then cleaves the (1–>6) branch point releasing glucose.

A

It transfers an (14) linked trisaccharide to the nonreducing end of an alternate branch, then cleaves the (16) branch point releasing glucose.

129
Q

Which of the following reactions does not occur in mammals?

pyruvate + NADH –> lactate + NAD+

ribulose-5-phosphoate –> ribose-5-phosphate

mannose + ATP –> mannose-6-phosphate + ADP + Pi

6-phophogluconate + NADP+ –> ribulose-5-phosphate + NADPH + CO2

pyruvate + NADH + H+ –> CO2 + ethanol + NAD+

A

pyruvate + NADH + H+ –> CO2 + ethanol + NAD+

130
Q

Which reaction below is an oxidation reaction?
I. 1,3-Bisphosphoglycerate (BPG) –> 3-phosphoglycerate (3PG)
II. Glucose –> glucose-6-phosphate (G6P)
III. 2-Phosphoglycerate (2PG)–> 3-phosphoglycerate (3PG)
IV. Glyceraldehyde 3-phosphate (GAP) –>1,3-Bisphosphoglycerate (BPG)
V. Glucose-6-phosphate (G6P) –>fructose-6-phosphate (F6P)

I, III

II, III

III only

IV only

None of the reactions I-V is oxidation reactions.

A

IV only

131
Q

Which of the following enzymes directly converts phosphorylase b into the more active form, phosphorylase a?

cAMP-dependent protein kinase

phosphorylase kinase

protein kinase A

adenylate cyclase

phosphoprotein phosphatase-1

A

phosphorylase kinase

132
Q

What is the net energetic cost of converting two pyruvate to one glucose by gluconeogenesis in ATP equivalents?

2

3

4

6

8

A

6

133
Q

Which of the following metabolic conversions does not occur in gluconeogenesis?

oxaloacetate –> phosphoenolpyruvate

fructose-1,6-bisphosphate –> fructose-6-phosphate

GTP –> CO2 + GDP

NADH + H+ –> NAD+

1,3-bisphosphoglycerate –> 3-phosphoglycerate

A

1,3-bisphosphoglycerate –> 3-phosphoglycerate

134
Q

Which of the following overall sequences is correct with regard to gluconeogenesis?

Oxaloacetate –> PEP –> G6P–> Glucose

Pyruvate–> FBP–> PEP –> Glucose

Lactate –> PEP –> Pyruvate–> G6P

Oxaloacetate–> F6P –> FBP –> Glucose

F6P –> FBP –> Glucose–> G6P

A

Oxaloacetate –> PEP –> G6P–> Glucose

135
Q

Methanol is highly toxic, not because of its own activity, but because it is converted metabolically into formaldehyde, which is the actual poison. What enzyme catalyzes this conversion?

methanol caboxylase

methanol transferase

alcohol transmutase

alcohol carboxylase

alcohol dehydrogenase

A

alcohol dehydrogenase

136
Q

Avidin, a protein intact in raw egg whites, prevents the absorption of biotin in the intestine resulting in biotin deficiency. Which of the following is affected in individuals who consume large amounts of raw egg?

Oxaloacetate –> phosphoenolpyruvate

1,3-Bisphosphoglycerate –> glyceraldehyde-3-phosphate

Fructose-1,6-bisphosphate –> fructose-6-phosphate

Pyruvate –> oxaloacetate

Phosphoenolpyruvate –> 2-phosphoglycerate

A

Pyruvate –> oxaloacetate

137
Q

A deficiency in the enzyme PEPCK (PEP carboxykinase) would

block function of the malate/aspartate shuttle.

block transfer of reducing equivalents across the membrane in the heart and liver.

inhibit formation of ATP via oxidative phosphorylation.

inhibit formation of NADH.

decrease flux through gluconeogenesis.

A

decrease flux through gluconeogenesis.

Biochem (23 decks)

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