Third 50

Question 1

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.

Answer 1

activation of the Fmoc blocked residue.

Question 2

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.

Answer 2

determining the phases of diffracted X-rays.

Question 3

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

secondary structure elements.

large proteins.

protein unfolding.

static protein structures.

Answer 3

protein unfolding.

Question 4

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.

Answer 4

epitopes.

Question 5

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

dialysis

gel electrophoresis

size exclusion chromatography

affinity chromatography

Answer 5

affinity chromatography

Question 6

Which animal is most often used to generate monoclonal antibodies?

rabbit

chicken

goat

mouse

Answer 6

mouse

Question 7

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

heart

liver

spleen

red blood

Answer 7

spleen

Question 8

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.

Answer 8

primary antibody.

Question 9

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

monoclonal primary

polyclonal tertiary

monoclonal secondary

polyclonal secondary

Answer 9

monoclonal primary

Question 10

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

immunofluorescence

Western blot

immunoprecipitation

ELISA

Answer 10

immunoprecipitation

Question 11

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

Answer 11

decreases; increase

Question 12

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.

Answer 12

The protein resembles a porin.

Question 13

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.

Answer 13

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

Question 14

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

glucose

2,3-bisphosphoglycerate

O2

CO2

Answer 14

2,3-bisphosphoglycerate

Question 15

Nuclear receptors are a type of

metabolic enzyme.

structural protein.

transport protein.

cell signaling protein.

Answer 15

cell signaling protein.

Question 16

Which of the following is NOT a transport protein?

maltoporin

hemoglobin

Na+ channel

DNA polymerase

Answer 16

DNA polymerase

Question 17

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.

Answer 17

The protein dissociated into individual subunits.

Question 18

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

Answer 18

fetal e subunit; myoglobin

Question 19

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

2%

20%

38%

81%

Answer 19

20%

Question 20

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.

Answer 20

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

Question 21

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

Answer 21

passive transport of molecules down a concentration gradient

Question 22

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

Answer 22

12

Question 23

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.

Answer 23

Asp351 in SERCA.

Question 24

Which of the following is NOT an ABC transporter?

cystic fibrosis transmembrane conductance regulator protein

SERCA

multidrug resistance protein

maltose transporter from E. coli

Answer 24

SERCA

Question 25

Titin functions to connect __________ to __________. myosin proteins; Z-disk proteins myosin proteins; thin filament proteins actin proteins; Z-disk proteins myosin proteins; tropomyosin

Answer 25

myosin proteins; Z-disk proteins

Question 26

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.

Answer 26

hemoglobin in the presence of 2,3-BPG.

Question 27

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

Answer 27

Lys82 --> Asp82

Question 28

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.

Answer 28

chemical gradients.

Question 29

Which of the following is NOT a passive transporter protein? porin Cl− channel Ca2+-ATPase transporter protein Ca2+ channel

Answer 29

Ca2+-ATPase transporter protein

Question 30

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.

Answer 30

It involves a conformational change of the enzyme.

Question 31

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

Answer 31

200

Question 32

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

Answer 32

cofactor; holoenzyme

Question 33

An enzyme that requires the coenzyme nicotinamide adenine dinucleotide belongs to which enzyme class? transferases isomerases ligases oxidoreductases

Answer 33

oxidoreductases

Question 34

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

Answer 34

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

Question 35

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

Answer 35

species A

Question 36

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.

Answer 36

stable.

Question 37

All of the following are common catalytic reaction mechanisms in enzyme active sites EXCEPT __________ catalysis. acid–base covalent metal ion van der Waals

Answer 37

van der Waals

Question 38

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

Answer 38

covalent

Question 39

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

Answer 39

reversible covalent modification

Question 40

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

Answer 40

Phe

Question 41

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

Answer 41

isomerization

Question 42

Which amino acid acts as a general acid and a general base in the mechanism of chymotrypsin? Ser195 His57 Gly193 Asp102

Answer 42

His57

Question 43

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

Answer 43

electrophilic attack on the scissile bond

Question 44

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.

Answer 44

act as a general acid on the intermediate.

Question 45

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].

Answer 45

is a second-order rate constant.

Question 46

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.

Answer 46

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

Question 47

KM is equal to k1 / (k−1 + k2). (k−1 + k2) / k1. 1/2 vmax. vmax[S] / v0.

Answer 47

(k−1 + k2) / k1.

Question 48

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.

Answer 48

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

Question 49

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

Answer 49

covalent bond

Question 50

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.

Answer 50

The inhibitor is a reversible inhibitor.