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BIOCHEM > Third 50 > Flashcards

Third 50 Flashcards

1
Q

The step in solid-phase peptide synthesis that occurs at number 2 is

deblocking of the residue attached to the resin.

coupling of the amino acid.

cleavage from the resin.

activation of the Fmoc blocked residue.

A

activation of the Fmoc blocked residue.

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2
Q

One of the most difficult steps in X-ray crystallography is

using the correct radio frequency pulses to perturb the nuclear spin.

determining the phases of diffracted X-rays.

dissolving the protein in the appropriate solvent.

obtaining a large enough sample for analysis.

A

determining the phases of diffracted X-rays.

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3
Q

Protein NMR is more useful than X-ray crystallography for studying

secondary structure elements.

large proteins.

protein unfolding.

static protein structures.

A

protein unfolding.

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4
Q

The specific sites on the antigen that interacts with the antibody are called

epitopes.

immunoglobin light chains.

immunoglobin heavy chains.

variable-domain amino acid residues.

A

epitopes.

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5
Q

During the production of polyclonal antibodies, how are the antigen-specific antibodies purified?

dialysis

gel electrophoresis

size exclusion chromatography

affinity chromatography

A

affinity chromatography

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6
Q

Which animal is most often used to generate monoclonal antibodies?

rabbit

chicken

goat

mouse

A

mouse

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7
Q

In monoclonal antibody generation, the cells that produce the antibody in the animal are located in __________ cells.

heart

liver

spleen

red blood

A

spleen

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8
Q

The part of the Western blot that contains the protein-specific recognition and facilitates the antigen-antibody interactions is the

SDS-PAGE gel.

primary antibody.

tertiary antibody.

filter membrane.

A

primary antibody.

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9
Q

In an ELISA, the detection antibody is a __________ antibody.

monoclonal primary

polyclonal tertiary

monoclonal secondary

polyclonal secondary

A

monoclonal primary

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10
Q

Which technique can be combined with mass spectrometry to identify protein antigens in large cellular complexes?

immunofluorescence

Western blot

immunoprecipitation

ELISA

A

immunoprecipitation

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11
Q

If a metabolic enzyme __________ the energy of activation of a reaction, the rate of product formation will __________.

increases; decrease

decreases; increase

increases; increase

decreases; decrease

A

decreases; increase

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12
Q

A proposed structure of a bacterial membrane protein shows that the distance between successive amino acids in a region crossing the membrane is 3.4 Å. Recall that a typical lipid bilayer is approximately 40 Å across. Which of the following is the most likely description of the protein?

The transmembrane region of the protein resembles the transmembrane region of the Ca2+-ATPase transporter protein.

The primary sequence of the transmembrane region of the protein is composed of approximately nine amino acids.

The protein contains a selectivity channel.

The protein resembles a porin.

A

The protein resembles a porin.

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13
Q

Which of the following statements is true for hemoglobin but NOT myoglobin?

The tertiary structure is made up of a globin fold.

The surface of its tertiary structure contains many hydrophobic amino acids.

It contains a proximal histidine that coordinates the heme group.

It contains a single carboxyl-terminal amino acid.

A

The surface of its tertiary structure contains many hydrophobic amino acids.

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14
Q

Below is a figure of adult hemoglobin. The arrow points to where __________ binds.

glucose

2,3-bisphosphoglycerate

O2

CO2

A

2,3-bisphosphoglycerate

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15
Q

Nuclear receptors are a type of

metabolic enzyme.

structural protein.

transport protein.

cell signaling protein.

A

cell signaling protein.

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16
Q

Which of the following is NOT a transport protein?

maltoporin

hemoglobin

Na+ channel

DNA polymerase

A

DNA polymerase

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17
Q

Oxygen binding is monitored for a solution of hemoglobin. During the experiment, the curve changes from sigmoidal to hyperbolic. Which of the following may be the reason for the change?

A positive allosteric effector was added.

A negative allosteric effector was added.

The protein dissociated into individual subunits.

The protein denatured.

A

The protein dissociated into individual subunits.

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18
Q

The B subunit of adult hemoglobin has higher sequence similarity to __________ than to __________.

fetal e subunit; myoglobin

myoglobin; fetal e subunit

adult a1 subunit; fetal e subunit

myoglobin; adult a1 subunit

A

fetal e subunit; myoglobin

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19
Q

Approximately how many amino acids are identical in both myoglobin and the adult mc119-1.jpg-subunit of hemoglobin?

2%

20%

38%

81%

A

20%

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20
Q

Which of the following is true of sickle cell anemia?

It is a dominant genetic disease.

It is caused by a mutation in the mc120-1.jpg-globin gene.

It is caused by an amino acid substitution in the F helix.

It results in a hemoglobin that contains a hydrophobic amino acid on the surface.

A

It results in a hemoglobin that contains a hydrophobic amino acid on the surface.

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21
Q

What type of transport is depicted in the figure below?

membrane diffusion

passive transport of molecules down a concentration gradient

active transport of molecules down a concentration gradient

active transport of molecules up a concentration gradient

A

passive transport of molecules down a concentration gradient

22
Q

As 18 Na+ ions are exported out of the cell by the Na+-K+ ATPase membrane transport protein, __________ K+ ions are imported into the cell.

2

12

18

24

A

12

23
Q

The mutation that would lead to the most dramatic effect on Ca2+ transport is a mutation of

Ser16 in phospholamban.

Thr17 in phospholamban.

Asp351 in SERCA.

Ser17 in E2P.

A

Asp351 in SERCA.

24
Q

Which of the following is NOT an ABC transporter?

cystic fibrosis transmembrane conductance regulator protein

SERCA

multidrug resistance protein

maltose transporter from E. coli

A

SERCA

25
Q

Titin functions to connect __________ to __________.

myosin proteins; Z-disk proteins

myosin proteins; thin filament proteins

actin proteins; Z-disk proteins

myosin proteins; tropomyosin

A

myosin proteins; Z-disk proteins

26
Q

An oxygen binding curve of fractional saturation versus pO2 displays a sigmoidal shape. This is the oxygen binding curve for

myoglobin.

hemoglobin that has been dissociated into individual subunits.

hemoglobin in the presence of 2,3-BPG.

myoglobin in the presence of 2,3-BPG.

A

hemoglobin in the presence of 2,3-BPG.

27
Q

A mutation in the B subunit of hemoglobin is discovered that reduces the affinity of 2,3-BPG binding. Which of the following mutations is most likely to have this consequence?

Val1 –> Ile1

Asp99 –> Glu99

Lys82 –> Asp82

Glu6 –> Val6

A

Lys82 –> Asp82

28
Q

Passive transporter proteins allow molecules to move across a membrane in response to

chemical gradients.

ADP/ATP ratio.

ATP/ADP ratio.

activated signal transduction pathways.

A

chemical gradients.

29
Q

Which of the following is NOT a passive transporter protein?

porin

Cl− channel

Ca2+-ATPase transporter protein

Ca2+ channel

A

Ca2+-ATPase transporter protein

30
Q

Which of the following is true of the induced-fit model of enzyme catalysis but NOT of the lock and key model of enzyme catalysis?

It was proposed by Emil Fischer.

It involves weak interactions of a substrate with an enzyme.

It involves a conformational change of the enzyme.

It involves noncovalent interactions of the substrate with the enzyme.

A

It involves a conformational change of the enzyme.

31
Q

What is the rate enhancement as a result of the presence of an enzyme if the uncatalyzed rate of the reaction is 1.2 mc131-1.jpg 102 mmol/sec and the catalyzed rate is 2.4 mc131-2.jpg 104 mmol/sec?

0.005

200

2.88 mc131-3.jpg 106

2

A

200

32
Q

Nitrite reductase contains two histidine amino acids that coordinate a Cu2+ ion. When the ion is present in the enzyme, the ion is a __________ and the enzyme is a __________.

cofactor; apoenzyme

cofactor; holoenzyme

coenzyme; apoenzyme

coenzyme; holoenzyme

A

cofactor; holoenzyme

33
Q

An enzyme that requires the coenzyme nicotinamide adenine dinucleotide belongs to which enzyme class?

transferases

isomerases

ligases

oxidoreductases

A

oxidoreductases

34
Q

A reaction coordinate diagram comparing an uncatalyzed reaction with an enzyme-catalyzed reaction can directly illustrate that the enzyme __________, but will not directly illustrate that the enzyme __________.

orients the substrates appropriately for the reaction to occur; provides an alternative path for product formation

provides an alternative path for product formation; stabilizes the transition state

stabilizes the transition state; orients the substrates appropriately for the reaction to occur

stabilizes the transition state; provides an alternative path for product formation

A

stabilizes the transition state; orients the substrates appropriately for the reaction to occur

35
Q

Enzymes from four different species catalyze the same reaction. Based on the reaction coordinate diagrams below, which species contains an enzyme that experiences more bonding interactions with the transition state of the reaction?

species A

species B

species C

species D

A

species A

36
Q

Many medicinal drugs are transition state analogs. They are good drugs because they can interact with the target enzyme active site and are

higher in energy than the transition state.

identical in structure to the transition state.

stable.

polar.

A

stable.

37
Q

All of the following are common catalytic reaction mechanisms in enzyme active sites EXCEPT __________ catalysis.

acid–base

covalent

metal ion

van der Waals

A

van der Waals

38
Q

When a nucleophile present in the enzyme attacks an electrophilic substrate to form an enzyme-substrate intermediate, this is an example of __________ catalysis.

covalent

acid–base

metal ion

hydrophobic

A

covalent

39
Q

The regulation of a biomolecule through the addition or removal of a molecular tag involves __________ reactions.

coenzyme-dependent redox

reversible covalent modification

metabolite transformation

isomerization

A

reversible covalent modification

40
Q

In a reversible covalent modification reaction involving the phosphorylation of a target protein, which of the following amino acids is LEAST likely to be modified with a phosphate group?

Ser

Phe

Tyr

Thr

A

Phe

41
Q

Which type of reaction does not change the molecular formula of the product compared with that of the substrate?

condensation

reduction

hydrolysis

isomerization

A

isomerization

42
Q

Which amino acid acts as a general acid and a general base in the mechanism of chymotrypsin?

Ser195

His57

Gly193

Asp102

A

His57

43
Q

Which of the following is NOT a function of the Mg2+ ions in the mechanism of enolase?

orientation of substrate in the active site

stabilizing the intermediate

making the proton at the C-2 position more acidic

electrophilic attack on the scissile bond

A

electrophilic attack on the scissile bond

44
Q

The role of Glu211 in the mechanism of enolase is to

facilitate the orientation of the phosphate group of the substrate.

act as a general base on the substrate.

act as a general acid on the intermediate.

make the proton at the C-2 position more acidic.

A

act as a general acid on the intermediate.

45
Q

For a reaction of Q + R –> P, the rate constant

is equal to [Q][R] / [P].

has units of s−1.

is a second-order rate constant.

is equal to [P] / [Q][R].

A

is a second-order rate constant.

46
Q

Which of the following is an assumption made when using Michaelis–Menten kinetics?

The conversion of E + P –> ES does not occur.

k1 > k2

v0 = vmax at low [S]

The conversion of EP –> E + P is rapid.

A

The conversion of EP –> E + P is rapid.

47
Q

KM is equal to

k1 / (k−1 + k2).

(k−1 + k2) / k1.

1/2 vmax.

vmax[S] / v0.

A

(k−1 + k2) / k1.

48
Q

An experiment is performed in which the kinetics of an enzyme-catalyzed reaction at different pHs is monitored. It is found that the Km does not change but that the kcat increases as the pH goes above 7. Which of the following is true?

A chemical group within the enzyme that has a pKa of around 7 is likely involved in the catalytic mechanism.

A chemical group with a pKa of around 7 must be deprotonated in order for substrate to bind.

A chemical group with a pKa of around 7 must be positively charged in order for the substrate to bind.

Protons are acting as positive heterotropic allosteric effectors of this enzyme.

A

A chemical group within the enzyme that has a pKa of around 7 is likely involved in the catalytic mechanism.

49
Q

Which type of interaction is more likely to be found between an enzyme and an irreversible inhibitor?

covalent bond

hydrogen bond

ionic interaction

van der Waals interaction

A

covalent bond

50
Q

A mixture of enzyme and inhibitor is run through a size-exclusion chromatography column. The activity of the enzyme is assessed before and after the chromatography. The enzyme has more activity after the chromatography step. Which of the following is true?

The enzyme was not eluted fully from the column.

The enzyme was denatured during chromatography.

The inhibitor is a reversible inhibitor.

The inhibitor is an irreversible inhibitor.

A

The inhibitor is a reversible inhibitor.

BIOCHEM (7 decks)

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