ALL FINAL ISH-BIOCHEM

In order to perform PCR, which of the following describes the reagents that must be included in the reaction mixture?

DNA fragment, primers flanking the region of interest, dNTPs, DNA polymerase

An enzyme-linked immunosorbent assay requires

an antibody that binds the protein of interest.

You are purifying a nuclease by affinity chromatography. To determine which fractions contain the protein of interest, you test samples of all fractions for their ability to break down DNA. This is an example of

an enzyme assay

______ is a homopolymer composed of (1-4)-linked N-acetyl-D-glucosamine residues that is the principle structural component of the exoskeleton of various groups of invertebrates.

chitin

In most peptide groups the ______ conformation is not sterically favored.

cis

Plasmids are small, circular DNA molecules that are used in ___

cloning

The production of multiple identical organisms from a single ancestor is called ___

cloning

Since proteins are limited in their abilities to catalyze oxidation-reduction reactions, enzymes often employ ______ to assist with catalysis.

coenzymes

In ______, the inhibitor binds to a site involved in both substrate binding and catalysis.

competitive inhibition

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

competitive inhibition

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

competitive inhibition

The term best used to express the ability of two molecules to form a noncovlent complex is:

complimentarity

Simultaneous stimulation of a reaction by general acid and general base catalysis is defined as

concerted acid-base catalysis

A chaperonin

helps fold some proteins in their lowest energy state

The formation of a dipeptide from two amino acids involves

hydrolysis

The _____________ of an amino acid can be used to predict whether an amino acid side chain folds towards the inside or outside of a globular protein.

hydropathy

The driving force for formation of lipid bilayers from glycerophospholipids and sphingolipids is:

hydrophobic effect

______ chromatography is a method of fractionating a protein mixture according to differences in polarity.

hydrophobic interaction

A first step in purifying a protein that was initially associated with fatty substances would be

hydrophobic interaction chromatography

A technique that can be used to separate proteins based primarily on the presence of non-polar residues on their surface is called

hydrophobic interaction chromatography.

What are the main bonds or forces that stabilize the dimer formed by two myosin heavy chains?

hydrophobic interactions

A graph of the rate of glucose transport via the GLUT1 transporter vs. glucose concentration would have a ________ shape indicating that higher glucose concentrations increase the rate of transport until all the sites are saturated.

hyperbolic

While the binding of O2 to myoglobin as a function of pO2 is described by a simple __________ curve, the binding to hemoglobin is described by a more complex ______ curve.

hyperbolic; sigmoidal

Edman degradation can be used to

identify the N-terminal amino acid of a polypeptide.

ELISA is an example of a(n):

immunological assay.

The chromatography technique that separates native proteins based on charge is ______________ chromatography.

ion-exchange

The strongest non covalent interactions are

ionic interactions

Zwitterions are

ions that bear both negatively and positively charged groups

The disulfide bond between two cysteine molecules

is a covalent bond formed by oxidation

The regular secondary structure that has the most extended (closer to 180/-180) phi and psi torsional angles is the

parallel beta sheet

A rigid, planar structure between at least two amino acids consisting of about 40% double bond character is characteristic of a ______.

peptide bond

The main component of a bacterial cell wall is a ______.

peptidoglycan

nucleoside triphosphates carry energy in the form of

phosphoanhydride bonds

nucleic acids are composed of nucleotides that are linked by ___ bonds

phosphodiester

Nucleotides in a DNA molecule are linked together through

phosphodiester bonds

A common type of covalent modification of regulatory enzymes involves ______ of serine residues.

phosphorylation

A common type of covalent modification of regulatory enzymes involves _______________ serine residues.

phosphorylation of

The laboratory technique that can determine the relative molecular mass of all the subunits of a protein is:

SDS PAGE

What observation about protein refolding or renaturation helped to solidify the connection between primary amino acid sequence and 3-D structure?

Spontaneous refolding of proteins into their native state under physiologic conditions.

Examine the three sequences below for collagen-like proteins. If hydrogen bonding were the most important feature in determining strength in fibrous proteins, which of the following sequences likely has the highest melting temperature and why? (Note: Flp = fluoroproline; Hyp = hydroxyproline) I. Pro-Hyp-Gly-Pro-Hyp-Gly-Pro-Hyp-Gly II. Pro-Flp-Gly-Pro-Flp-Gly-Pro-Flp-Gly III. Gly-Pro-Thr-Gly-Pro-Thr-Gly-Pro-Thr

"1" because Hyp has OH groups

The ______ model of allosterism requires subunits to change conformation simultaneously

Symmetry

In the ___ state of hemoglobin, the iron ion is out of the plane of the porphyrin ring

T

In the _______ state of hemoglobin, the iron ion is out of the plane of the porphyrin ring.

T, weak affinity

Carbohydrate metabolic enzymes bind D-glucose specifically. D-glucose has an estimated caloric value of 1 kcal per 4 grams of carbohydrate. Based on the methods used to convert the energy of D-glucose into a useable form, what would you estimate the caloric value of L-glucose to be using the same method?

0 kcal per 4 grams

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.)

0.014 M

To make an acetate buffer at pH 4.76 starting with 500 ml of 0.1 M sodium acetate (pK acetic acid = 4.76), you could add

0.025 mol of HCl

How many antigen-binding sites are present on an IgM molecule?

10

How many different classes of antibodies are produced by the human immune system?

5

the major carrier of energy in the cell is

Adenosine triphosphate

When a peptide bond is formed, an ___ reacts with a carboxylate group

Amino Group

Certain plasmids containing genes that confer resistance to ____

Amplicillin

A pore that simultaneously transports two different molecules in different directions is called

An Antiport

Humoral immunity refers to that part of the immune response that is mediated by

Antibodies

Which of the following Amino Acids is the least abundant in proteins? A) V B) W C) G D) F E) A

B

Which of the following proteins has a structural motif called an "EF hand"? A) insulin B) calmodulin (CaM) C) receptor tyrosine kinases (RTK) D) cAMP-dependent protein kinase E) scaffold proteins

B

The triacylglycerides are formed from:

C

Myoglobin's secondary structure is primarily composed of ______________. A) parallel β-sheets B) antiparallel β-sheets C) α-helices D) Ω-loops E) polyproline helices

C) α-helices

In the peptide Trp-Ser-Val, valine is at the

C-terminus

Mutations that favor the oxidation of the heme iron(II) to iron(III) can cause ______

Cyanosis

While proteins are usually composed of linear chains of amino acids, branched chains of amino acids and internally cross-linked chains can be found in certain proteins. Polypeptide chains are most commonly linked to each other through

Disulfide Bonds

Uronic acids A) are aldoses where the aldehyde is oxidized to a carboxylic acid. B) are aldoses where the 1° alcohol is oxidized to a carboxylic acid. C) can be found in the pyranose or furanose forms. D) A and C are both correct. E) B and C are both correct.

E

Which amino acid does NOT have a primary amino group? A. Glutamine B. Arginine C. Histidine D. Glutamate E. All of the above have a primary amine

E

Which of the following amino acids does NOT have an ionizable side chain? A) Asp B) Cys C) Lys D) His E) Asn

E

Which of the following amino acids from an integral membrane protein would likely contact the lipid layer of the membrane? A) Asn B) Gln C) Glu D) Gly E) Leu

E

Which of the following is the most abundant disaccharide? A) lactose B) cellulose C) α-amylose D) maltose E) sucrose

E

Which of the following nucleotides contain energy rich bonds? (A) ATP (B) TTP (C) GTP (D) CTP (E) All of the above

E

Which of the following statements about PCR is (are) true? A) Small amounts of DNA can be easily amplified to millions of copies. B) PCR is often used in forensics laboratories. C) PCR reaction products can be used in molecular cloning. D) PCR is used in clinical laboratories. E) All of the above.

E

Which of the following statements are true regarding fatty acids? I. Fatty acids with fewer than 14 carbons are the most common. II. Synthesis of fatty acids occurs in 2 carbon units. III. Fatty acids with conjugated double bonds are the most common type of fatty acid. IV. In higher plants and animals, C16 and C18 species predominate. A) I, II, III, IV B) I, II, III C) I, III D) II, III, IV E) II, IV

E

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

ES complex

Connexin proteins make up the structure of ___

Gap junctions

All the standard amino acids except ___ are optically active

Gly

an example of homopolysaccharide in liver and muscle is ___

Glycogen

When unstable hemoglobin is degraded; degradation products often cause cell lysis, leading to a condition called ______.

Hemolytic Anemia

When oxygen binds to heme, the oxygen forms a hydrogen bond with ___

His E7

___ is a heteropolymer composed of D-glucoronate and N-acetly-D-glucosamine that acts as shock absorber and lubricant

Hyaluronic Acid

What are the main bonds or forces that stabilize the dimer formed by two myosin heavy chains?

Hydrophobic INteractions

Which class of antibodies has been implicated in allergic reactions?

IgE

Chargaff's rules state that

In DNA the number of adenine residues is identical to the number of thymine residues and the number of guanine residues is identical to the number of cytosine residues

eukaryotic genes often contain regions that are transcribed and later excised from the RNA called ___

Introns

KcsA is an example of a(n) ____

Ion Channel

In the tripeptide Lys-Pro-Ile, the C-terminal residue is

Isoleucine

If you add enzyme to a solution containing only the product(s) of a reaction, would you expect any substrate to form?

It depends on the energy difference between E + P and the transition state.

Proteins that bind to specific carbohydrates are called ______.

Lectins

Hemoglobin S, the variant responsible for the misshapen red blood cells characteristic of the disease sickle-cell anemia, is potentially advantageous to heterozygotes because it confers some level of resistance to the disease _________.

Malaria

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

Much less than

Myoglobin is an oxygen binding protein in muscle. Describe in one sentence the overall structure of myoglobin.

Myoglobin is a globular protein composed of 8 helices that forms a hydrophobic pocket that contains the heme group.

The energy needed to drive muscle contraction comes from ATP hydrolysis that is carried out by

Myosin Heads

It is impossiuble for RNA to store genetic information, because

None! RNA CAN store genetic information

About half of the 20 amino acids are called essential because

Our bodies cannot synthesize them and therefor they need to be present in our diets

Mammals and other animals have a circulatory system because diffusion is to slow to supply the tissues with oxygen in animals that are larger than 2 millimeter. Explain in one sentence why these circulatory systems contain hemoglobin or other oxygen binding proteins?

Oxygen-binding proteins increase the solubility of oxygen in the fluid of the circulatory system. This is important because oxygen is not very soluble in aqueous solutions.

The peptide Leu─Cys─Arg─Ser─Gln─Met is subjected to Edman degradation. In the first cycle the peptide first reacts with phenylisothiocyanate under basic conditions. The product of this reaction is incubated with anhydrous trifluoroacetic acid and subsequently with an aqueous acid. What are the products generated in the first cycle.

PTH─Leu and Cys─Arg─Ser─Gln─Met

the GLUT1 transporter functions via ___ transport

Passive-mediated

Hemoglobin's subunits bind oxygen in a ___ manner

Positively cooperative

In a protein, the most conformationally restricted amino acid is ______; the least conformationally restricted is ______.

Pro, Gly

In a protein, the most conformationally restricted amino acid is ___________________; the least conformationally restricted is ____________________.

Pro, Gly

Which amino acid does not have a primary α-amino group?

Proline

The greater the magnitude of the concentration gradient:

The more rapid the rate of diffusion

It appears that the heme group in myoglobin binds the O2. What is the function of the polypeptide?

The polypeptide performs various functions: 1. The polypeptide provides solubility for the heme group, which is very non-polar. 2. The polypeptide prevents permanent oxidation of the Fe(II). 3. The polypeptide helps coordinate the Fe(II) (His F8) 4. The polypeptide forms a H-bond with the O2 (His E7).

See 40 on test bank, it's amazing

This is the best way to study this problem, believe me

In the early 1930's William Rose fed laboratory rats a mixture of all 19 amino acids known to be present in proteins. He observed that his rats lost weight. This observation led to the discovery of ____ as the 20th amino acid found in proteins

Thr

In the tripeptide Lys-Pro-Ile, there are ___ charged groups at pH 7

Three

The value of n, the Hill constant (coefficient), for hemoglobin is about ______ as great as the value for myoglobin.

Three Times

Carbon monoxide binds to heme:

With a higher affinity than Oxygen

The watson and crick model of the double-helical structure for DNA was based in part on evidence from

X-Ray diffraction

The net charge of the zwitterion form of Gly is ___

Zero

Assume a first order reaction, the rate of the reaction 2A→B is dependent on ______.

[A]

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

[S] would need to be 3 Km

What group is attached to the pyrimidine ring in thymine and is not present in uracil?

a Methyl group

A holoprotein contains:

a folded protein chain with associated prosthetic group

a genetic knockout is

a gene that has been inactivated or removed from an organism

. The Ig fold can be described as a

a globular fold composed of a β sandwich.

The oxygen binding by hemocyanins is mediated by

a pair of copper atoms

A radioimmunoassay requires

a radiolabeled standard protein that is used to compete for binding to the antibody.

Treadmilling refers to

actin monomers moving through a microfilament from the + end to the - end.

The ____ signaling pathway relies on GDP/GTP exchange for subsequent synthesis of cAMP.

adenylate cyclase (AC)

The ____ signaling pathway relies on GTP dependent hydrolysis for subsequent synthesis of cAMP.

adenylate cyclase (AC)

Isoproterenol functions as an agonist for receptors that bind hormones synthesized in the ___.

adrenal cortex

The monosaccharides alpha-D-galactose and beta-D-galactose are ____________.

anomers

The quantitation of proteins due to their absorbance at about 280 nm (UV region) is due to the large absorptivity of the _____________ amino acids.

aromatic

The quantitation of proteins due to their absorbance at ~280 nm (UV region) is due to the large absorbtivity of the ________ amino acids.

aromatic

Glutamic acid is an amino acid (pKas are 2.1, 4.1, and 9.5). Calculate the isoelectric point of glutamic acid

at pH 1.0, glutamic acid has an electric charge of +1, at pH 3.0, the electric charge is 0, and at pH 5.0, the electric charge equals -1. Therefor the pKas of the carboxylic acid groups surround the neutral forms. pI = (2.1+4.1)/2 = 3.1

The most rapid way that erythrocytes adapt to high altitudes is

by increasing the intracellular concentration of BPG.

Cellulose is A) a linear copolymer of glucose and galactose. B) a branched polymer of glucose. C) a linear polymer of glucose with β(1-4) linkages. D) a linear polymer of glucose with α(1-4) linkages. E) sometimes called starch.

c

Spontaneous processes characterized by a large negative Gibb's free energy:

can be coupled to drive endothermic reactions to completion

The interaction (cross-talk) of various signaling pathways

can be minimized by scaffold proteins.

In ______ chromatography, a protein mixture must be applied to the column at a low pH so that the proteins will have a net positive charge and bind to the column.

cation exchange

The methods that sanger developed for DNA sequencing using dideoxy nucleotides is called the ___ method

chain-terminator

What can be done to increase the rate at which a protein of interest moves down an ion-exchange chromatography column?

change the pH of the eluant

What is a good procedure for eluting a protein of interest from an ion-exchange column?

change the pH of the eluant

KcsA is an example of a ___ ionophore

channel-forming

Acid-base catalysis may be accomplished by

charge delocalization

Molecules that contain a(n) ______ are capable of absorbing light.

chromophore

The endoprotease ______ cleaves polypeptides on the C-terminal side of certain bulky hydrophobic amino acid residues.

chymotrypsin

The strength of _______ comes from close packing of glycine residues and the characteristics of hydroxyproline allowing formation of a left- handed helical conformation which combines with two other left handed structures to form a right-handed triplet helix.

collagen

Clustering several amino acid residues with appropriate pK values at an active site can promote a(n) _________ catalytic mechanism.

concerted acid-base

The hormone _____ is responsible for a variety of actions including the ability to cope with stress.

cortisol

Large rate enhancement in enzyme catalysis may occur when binding the substrate via _________ attachment.

covalent

A molecule that often functions as a second messenger is ______.

cyclic AMP

If an enzyme-catalyzed reaction has a low rate at low pH and high rate at higher pH, this implies that a group on either the enzyme or the substrate must be ______ for an efficient reaction.

deprotonated

The pH at the midpoint in the titration of an acid with a base is

equal to the pK of the corresponding acid

Bulky ring substituents preferentially occupy ______ positions in the chair conformation.

equatorial

The preferred chair conformation in aqueous solution for glucopyranose has:

equatorial C6

A protein that has had few changes in its amino acid sequence over evolutionary history is labeled

evolutionarily conserved

A phylogenetic tree depicts ___________ of proteins.

evolutionary relationships

Gated ion channels

exist because active transporters cannot maintain the gradient at a rate equal to non-gated ion flow.

To help prevent denaturation of proteins in solution, steps are taken to avoid _________ and adsorption to surfaces.

foaming

Alcohol dehydrogenase catalyzes the conversion of methanol to _________ and is, therefore, classified as a(an)________.

formaldehyde; oxidoreductase

A pentapepide contains ________________ peptide bonds.

four

Proton transfer from an acid, lowering the free energy of a reaction's transition state, is characteristic of

general acid catalysis

Proton abstraction by a conjugate base, lowering the free energy of a reaction's transition state, is characteristic of

general base catalysis

The α cells of the islets of Langerhans secrete _____ in response to ____ glucose levels in the liver.

glucagon; low

GABA is a neurotransmitter derived from ___

glutamate

The smallest smallest aldose is

glyceraldehyde

They ______ are a class of amphipathic molecules that comprise the major lipid components of the cell membrane.

glycerophospholipids

Alcohols react with aldehydes to form

hemiacetals

Alcohols react with ketones to form

hemiketals

A property of water that is required for its polarity is:

high electronegativity of O over H

Nucleoside triphosphates are useful for energy transfer because the phosphoanhydride bonds are relatively

high energy

If the cDNA for a protein has been cloned, it may be possible to obtain large quantities of the protein by _________________ in bacteria.

high level expression

The acronym HPLC stands for

high performance liquid chromatography

The catalytic mechanism of bovine pancreatic RNase A relies upon acid-base catalysis involving the amino acid __________.

histidine

Irreversible enzyme inhibitors

inactivate the enzyme

Zymogens are:

inactive enzymes that are activated after proteolysis

The absence of 2,3-BPG causes hemoglobin's affinity for oxygen to______

increase

The oxidation of collagen by prolyl oxidase:

increases intermolecular H-bonding

The gland that is predominately responsible for producing the hormone that is released in response to consumption of a meal particularly high in carbohydrates.

islets of Langerhans

A technique that can be used to separate proteins based primarily on their pI is called

isoelectric focusing

An amide bond between a side-chain carboxylate and an α-amino group is called a(n)

isopeptide bond

The sterol hormone cholesterol in human cells is synthesized from:

isoprene

Different enzymes that catalyze the same reaction, although may be found in different tissues, are known as ______.

isozymes

DNA polymerase from Thermus aquaticus is used in PCR because

it is stable at high temperatures

On a transition state diagram for a one-step very spontaneous reaction a large peak (high Δ G‡)would imply a ______ rate for the reaction.

low

SDS-PAGE separates proteins primarily due to differences in

mass

A fast and common method for determining the protein concentration in column effluent is

measuring light absorption at 280 nm.

Zwitterions are

neutral ions that bear both negatively and positively charged groups

A derivative of______ is the major lipid in lung surfactant.

phosphatidylcholine

Nucleoside triphosphates carry energy in the form of

phosphoanhydride bonds

Hydrophobic interaction chromatography can be used to separate proteins based on differences in

polarity

In order for DEAE to act as an anion exchanger, it must have a ______.

positive charge

In general molecular chaperone proteins function by

preventing premature folding by binding hydrophobic regions of the protein.

The linear sequence of amino acids held by peptide bonds is the protein's _______________ structure.

primary

The Ca2+—ATPase requires ATP directly and is therefore an example of ______ transport.

primary active

The classic experiment demonstrating that reduced and denatured RNase A could refold into the native form demonstrates that ____________________.

primary structure can determine tertiary structure

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

proton transfer with a pK close to 4

On a transition state diagram for a multistep reaction the step with the greatest ΔG is the ______________________.

rate determining step

On a transition state diagram for a multistep reaction, the step with the greatest ΔG is the ______.

rate-determining step

The final step in the folding of disordered polypeptides into ordered functional protein is the formation of ______________.

rearrangement in the molten globule state

Proteins that bind molecules and elicit a cellular response are called _____.

receptors

Chaperonins such as the GroEL/ES system

require ATP hydrolysis.

The first G protein-coupled receptor (GPCR) to be structurally analyzed at the atomic level was _____.

rhodopsin

A historical experiment exploring denaturation upon β- mercaptoethanol reduction of disulfide bonds and spontaneous renaturation upon dialysis to remove the β- mercaptoethanol was carried out using the protein ______. This experiment demonstrated the importance of disulfide bonds and amino acid sequence in folding of proteins.

ribonuclease A (RNase A)

The salting in of proteins can be explained by:

salt counter-ions reducing electrostatic attractions between protein molecules.

A fast way for nature to generate new proteins is:

shuffling protein domains or motifs

Natural proteins most commonly contain linear polypeptides between 100 and 1000 residues in length. One of the reasons polypeptides outside this range may be disfavored is that

smaller polypeptides do not form stable folded structures.

A transporter that moves two substances simultaneously in the same direction is an example of a(n) __________.

symport

Which of the following nucleic acids provides the key to decoding genetic information?

tRNA

DNA sequencing using the dideoxy method requires

template, primer, DNA polymerase, dNTP's, ddNTP's

The repeating functional unit in a myofibril is called

the Sarcomere

Km is

the [S] that half saturates the enzyme

Km is

the [S] that half-saturates the enzyme

The isoelectronic point of an amino acid is the point where

the amino acid carries no net electrical charge

Which of the following has the most dramatic influence on the characteristics of an individual protein?

the amino-acid sequence

The bulk of aerobic metabolism in eukaryotic cells takes place in

the mitochondria

Experiments by Avery and Colleagues proved that DNA was the substance that ___ a non-pathogenic pneumococcus strain into a virulent strain

transformed

________________ metals are the most common metallic enzyme cofactors.

transition

Transfer RNA molecules are involved in

translation

at a pH below the pKa, the β-carboxylate group of Asp is ___

uncharged; Protonated

A steroid-derived hormone that must be activated by hydroxylation, ______ regulates Ca2+ metabolism.

vitamin D

The boiling point of water is 264 degrees C higher than the boiling point of methane because

water molecules are connected to each other with H bonds

Hydrogen bonds and maximum separation of amino acid side chains make the _____very stable and energetically ______________.

α helix and β sheet, favorable

Based on what you know about fibrous protein structure and sequence, what type of fibrous protein is this sequence most likely to from (You can assume that the protein is longer than what is shown and is repeating as shown, also note the polarity of each amino acid.)? Val - Cys - Lys - Val - Cys - Ala - Cys - Val - Cys - Lys - Val - Cys - Ala - Cys

α keratin

Which polysaccharide is found in a helically coiled conformation?

α-amylose

Starch is a mixture of:

α-amylose and amylopectin

The pK1, pK2, and pKR for the amino acid aspartic acid are 2.0, 9.9, and 3.9, respectively. At pH 7.0, aspartic acid would be charged predominantly as follows:

α-carboxylate -1, α-amino +1, β-Carboxylate -1, Net charge -1

The pK1, pK2, and pKR for the amino acid arginine are 1.8, 9.0, and 12.5, respectively. At pH 7.0 arginine would be charged predominantly as follows:

α-carboxylate-1, α-amino+1, guanidino+1, net charge +1

In a Ramachandran diagram, a larger area represents sterically allowed torsion angles of φ and ψ that are allowed in _____ rather than in ______ because there is greater opportunity for separation of amino acid side chains.

β sheet...α helix

Amphiphilic molecules

have both hydrophilic and hydrophobic groups

The Hill plot shows that the fourth oxygen binds to hemoglobin with a ______-fold greater affinity than the first.

100

The vast majority of polypeptides contain between ______ amino acid residues.

100 and 1000

The rapid transport of K+ ions by the KcsA ion channel moves up to ____ ions per ______.

10^8 ions per Second

IgG is the most common immunoglobulin in the circulatory system and in the extravascular fluid. It is composed of two light chains and two heavy chains. What is the approximate molecular mass of an IgG molecule?

150 kD

The primary structure of mammalian hemoglobin, an α2β2 tetramer, is approximately _____ identical to myoglobin. A) 2% B) 18% C) 50% D) 78% E) 98%

18%

The tripeptide glycylarginylglutamate contains four ionizable groups with pKas of 2.1, 4.1, 9.8, and 12.5. Calculate the pI for this molecule

7.0

Find the initial velocity for an enzymatic reaction when Vmax = 6.5 × 10-5 mol•sec-1, [S] = 3.0 × 10-3 M, KM = 4.5 × 10-3 M and the enzyme concentration at time zero is 1.5 × 10-2 μM

2.6 × 10^-5 mol•sec^-1

Find the initial velocity for an enzymatic reaction when Vmax = 6.5 × 10-5 mol•sec-1, [S] = 3.0 × 10-3 M, KM = 4.5 × 10-3 M and the enzyme concentration at time zero is 1.5 × 10-2 μM.

2.6 × 10^-5 mol•sec^-1

Since there are 20 standard amino acids, the number of possible linear polypeptides of length N can be expressed as:

20^n

The first step in the folding of disordered polypeptides into ordered functional protein is the formation of ______.

2° structure

In Sanger dideoxy DNA sequencing, DNA polymerase I is used to add nucleotides to the ___ end of the growing polynucleotide chain

3'

How many stereoisomers are possible for an aldopentose such as ribose?

8

[S] = KM for a simple enzymatic reaction. When [S] is doubled the initial velocity is

(1/3) Vmax

Which of these polysaccharides is a branched polymer? A) chitin B) amylose C) cellulose D) glycogen E) hyaluronic acid

D

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).

8 x 10^7 min^-1

Which of these polysaccharides is a branched polymer? A) chitin B) amylose C) cellulose D) amylopectin E) hyaluronic acid

D

Organisms composed of cells with two sets of chromosomes are called ___ organisms

diploid

When [S] = KM, ν0 = (_____)× (Vmax).

0.5

The pK1, pK2, and pKR of the amino acid lysine are 2.2, 9.1, and 10.5, respectively. The pK1, pK2, and pKR of the amino acid arginine are 1.8, 9.0, and 12.5, respectively. A student at SDSU wants to use ion exchange chromatography to separate lysine from arginine. What pH is likely to work best for this separation?

10.5

a Double stranded DNA fragment contains 12% adenine residues. Calculate the percentage of Cytosine residues

38%

The classic experiment demonstrating that reduced and denatured RNase A could refold into the native form demonstrates that _______.

1° structure can determine 3° structure

Hemoglobin is a heterotetramer. How many protomers are present in hemoglobin?

2

How many antigen binding sites are present on an IgG molecule?

2

How many antigen-binding sites are present on an IgG molecule?

2

In SDS-PAGE, disulfide-linked polypeptides can be separated after reacting the protein first with ______.

2-mercaptoethanol

Disulfide bonds can be cleaved using

2-mercaptoethanol (β-ME).

How many stereoisomers are possible for a ketopentose such as ribulose?

4

Urea is a water-soluble product of nitrogen metabolism. How many hydrogen bonds can one urea molecule donate to surrounding water molecules?

4

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?

4.8 × 10^2 M•sec^-1

______of the world's human population carries an inherited variant hemoglobin gene.

5%

Humans typically recycle approximately ___ of ATP each day

50 kg

What percentage of the 20 Amino acids is considered to be nutritionally essential to lab animals?

50%

Which of the following proteins are synthesized on free ribosomes? A) mitochondrial proteins B) secretory proteins C) signal peptides D) lysosomal proteins E) transmembrane proteins

A

During muscle contraction A) myosin pulls actin filaments toward the M disk. B) myosin pushes actin filaments toward the Z disk. C) actin pulls myosin toward the Z disk. D) actin pushes myosin toward the M disk. E) All of the answers above are correct.

A

Adipocytes A) are specialized cells for the synthesis of triglycerides. B) are specialized cells for short term energy storage. C) provide compartments for efficient membrane bilayer synthesis. D) exist primarily in a thin layer surrounding major muscle groups as a rapid high energy source. E) All of the above characterize adipocytes.

A

Cholesterol A) incorporation into the membrane results in increased rigidity. B) functions as a precursor to cerebrosides. C) is synthesized in two-carbon units. D) is synthesized from steroid hormones. E) all of the above

A

ClC Cl- channels I. assist in transport by forming a strong electrical dipole with the N-terminal end positively charged. II. effectively funnel ions into the pore via electrostatic interactions with basic amino acids. III. have a selectivity filter constructed from the N-terminal ends of α-helices, whose dipoles attract Cl- ions. IV. rely on the side chain hydroxyl groups from Ser and Tyr. A) I, II, II, IV B) I, II, IV C) II, II, IV D) III, IV E) I, IV

A

Consider the reaction A + B ↔ C + D. After reaching equilibrium at 25°C, the following concentrations of reactants and products were measured: [A] = 10 μM, [B] = 15 μM, [C] = 10 μM, [D] = 10 μM. Calculate ΔG°′ for this reaction. A) 1000 J/mol B) 10 kJ/mol C) 1 J/mol D) insufficient data to determine answer E) none of the above

A

Drug resistance is frequently traced to I. the MDR transporter. II. overexpression of P-glycoprotein. III. increased number of specific ABC transporters. IV. the evolution of selectivity filters. A) I, II, III B) II, III C) I, III D) III, IV E) II, IV

A

Enzymes that bind reaction transition states with greater affinity than substrates or products A) have a lower free energy ES complex than E + S. B) increase reaction rates by decreasing the concentration of the transition state . C) progress slowly due to the stability of the transition state complex. D) compensate for small differences in the energy of the free substrate and free product. E) All of the above are correct.

A

I propose to design a new drug which will act as an inhibitor for an enzyme. If I have used all current information about the mechanism of this enzyme to design this inhibitor and I carefully engineer it with similar chemical properties of the transition state, what type of inhibitor am I attempting to engineer and how will I know if I have succeeded? A) A competitive inhibitor, collect kinetic data both in the presence and absence of inhibitor and watch for a change in Vmax. B) A competitive inhibitor, collect kinetic data both in the presence and absence of inhibitor and watch for a change in KM. C) A uncompetitive inhibitor, collect kinetic data both in the presence and absence of inhibitor and watch for a change in KM. D) A uncompetitive inhibitor, collect kinetic data both in the presence and absence of inhibitor and watch for a change in Vmax. E) None of the above.

A

I-cell disease results in psychomotor retardation, skeletal deformities and death. Which of the following is true regarding this disease? A) The disease results in inclusion of glycosaminoglycans and glycolipids due the absence of an essential carbohydrate marker that directs the lysosomal hydrolases to the lysosome. B) The disease results in inclusion of glycolipids due mutations in the lysosomal hydrolases that render them inactive. C) The disease results in increased expression of SNARE proteins that result in vesicle fusion and exchange of glycosaminoglycans. D) The disease results from the lack of KDEL sequences which would normally signal their return to the ER following Golgi processing. E) All of the above are true.

A

IgG is one of five classes of antibodies that can be produced by our immune system. IgGs have a molecular mass of approximately 150 kDa, what is their subunit composition? A) 2 light chains and 2 heavy chains B) 2 light chains, 2 heavy chains, and a J chain C) 4 light chains, 4 heavy chains, and a J chain D) 6 light chains, 6 heavy chains, and a J chain E) 10 light chains, 10 heavy chains , and a J chain.

A

In a Ramachandran diagram the region representing the angles of φ and ψ that correspond to those commonly made by an amino acid that favors a left-handed α helix are different from those angles commonly made by an amino acid that favors right-handed α helix formation. Which of the following statements provides a plausible explanation for this difference? A) Groups which would normally undergo high steric hindrance in the right-handed arrangement are separated maximally in the left-handed arrangement. B) Left-handed helices have smaller pitch than right-handed helices. C) The peptide backbone can coil tighter in the left-handed helices than in the right-handed helices. D) Left-handed helices exhibit cyclic symmetry, while righthanded helices are asymmetric. E) All of the above are plausible explanations.

A

In bacteria, phospholipids are synthesized: A) on the cytoplasmic face of cell membranes B) at the rough endoplasmic reticulum C) on the extracellular face of the cell membrane D) on site at the endoplasmic reticulum. E) nonenzymatically at the site of the membrane.

A

In two homologous proteins, which residue is most likely to replace a Glu residue as a conservative substitution? A. Asp B. Trp C. Met D. Ile E. Lys

A

Km A) is the concentration of substrate where the enzyme achieves ½ Vmax. B) is equal to Ks. C) measures the stability of the product D) is high if the enzyme has high affinity for the substrate. E) All of the above are correct.

A

Molecular chaperones bind to unfolded or partially folded polypeptide chains in order to accomplish which of the following? A) ensure that improper aggregation of hydrophobic segments does not occur B) engulf the protein in order to ensure that the protein is not damaged by heat denaturation C) facilitate native folding by exposing hydrophobic segments of the protein as it is synthesized D) facilitate aggregation of multiple subunits of a protein during synthesis E) All of the above are accomplished by molecular chaperones.

A

Muscle contraction is triggered A) in response to an increase in the cytoplasmic Ca2+ concentration. B) in response to a decrease in the cytoplasmic Ca2+ concentration. C) in response to an increase in the cytoplasmic cAMP concentration. D) in response to a decrease in the cytoplasmic cAMP concentration. E) in response to an increase in the cytoplasmic titin concentration.

A

Of the transport proteins discussed in the chapter, in general, which of the following do they have in common? A) utilize conformational changes to control flux B) require hydrophobic amino acid side chains to line the pores C) utilize stereospecifcity to selectively transport D) transport ionized substances E) move in the direction of the gradient

A

The Kv channel is transiently closed by ___________. A) a spherical globular segment on the N-terminus B) a C-terminal segment activated by proteolysis C) proteoglycan residues D) an ion larger than the selectivity filter blocking entry E) tightly-bound Ca2+

A

The Michaelis constant KM is defined as I. (k-1 + k2)/k1 II. ½ Vmax III. [S] = [ES] IV. [ES]/2 A) I B) I, II C) II D) I, IV E) II, IV

A

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 A. I & II B. I C. II & IV D. II & III E. IV

A

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. A) I, II B) I C) II, IV D) II, III E) IV

A

The sialic acids A) are important constituents of glycoproteins and glycolipids. B) are N-acetyl glucosamine derivatives. C) incorporate a succinic acid derivative. D) all of the above E) none of the above

A

Vanilomycin A) is a cyclic polypeptide that functions as a K+ carrier. B) is a transmembrane polypeptide that transports K+. C) is a cyclic polypeptide that functions as a Na+ carrier. D) is a transmembrane polypeptide that transports Na+. E) is a β-barrel pore transporter that transfers K+.

A

What is the three-letter abbreviation for the peptide valylarginylisoleucine? A) Val─Arg─Ile B) Val─Agn─Leu C) Vln─Arg─Ile D) Val─Agn─Isl E) Vln─Arg─Leu

A

When considering fibrous proteins, which of the following statements is TRUE? A) Noncovalent interactions contribute to the strength of all of these proteins. B) All of them consist of α helix structure. C) All of them require vitamin C. D) Decrease in amounts of any of them cause scurvy. E) All of these are true of fibrous proteins.

A

Which does not occur when neurons are stimulated? A) Local depolarization results from the opening of Na+ ion channels allowing Na+ to exit the cell. B) Neighboring Na+ ion channels open in response to the change in membrane potential, resulting in a wave of depolarization. C) Depolarization stimulates the opening of ion-gated K+ channels, resulting in repolarization . D) Recovery involves the movement of Na+ out of the cell and K+ into the cell, resulting in the membrane regaining its resting potential. E) All of the above do occur when neuron are stimulated.

A

Which of the following DNA sequences is considered palindromic? A) AAGCTT B) GAACTT C) GAACAA D) AAGCAA E) AAGTTC

A

Which of the following amino acid residues would not provide a side chain for acid-base catalysis at physiological pH? (Assume pK values of each amino acid are equal to the pK value for the free amino acid in solution.) I. leucine II. lysine III. aspartic acid IV. histidine A) I, II, III B) I, II C) I D) II E) I, III

A

Which of the following amino acids is beta branched? A. Thr B. Leu C. Pro D. Ser E. Lys

A

Which of the following amino acids would be first to elute at pH 8.0 from an anion-exchange column? A) lysine B) alanine C) glutamic acid D) asparagine E) glycine

A

Which of the following contribute to the minimization of energy that occurs with protein folding? A) orientating amino acid groups to maximize hydrogen bonding B) folding hydrophobic groups towards the exterior of the protein C) burying polar groups towards the interior of the protein D) extensive cavity formation E) all of the above

A

Which of the following hormones functions by binding to receptors that function directly as transcription factors? A) steroids B) insulin C) epinephrine D) glucagon E) somatostatin

A

Which of the following is (are) an advantage(s) of protein phosphorylation in regards to biochemical signaling? I. Phosphorylation is rapid and specific. II. Phosphorylation is enzymatically reversible. III. Phosphorylation can be amplified by cascade systems. IV. Phosphorylation results in covalent modification of enzymes. A) I, II, III, IV B) II, III, IV C) II, III D) I, II E) III only

A

Which of the following lipid types is the least polar? A) triacylglycerols B) glycerophospholipids C) sphingolipids D) gangliosides E) glycolipids

A

Which of the following polysaccharides cannot be digested by mammalian salivary, gastric, or pancreatic enzymes? A) cellulose B) amylopectin C) amylose D) glycogen E) starch

A

Which of the following statements about hydrophobic interactions is not true? A. They are caused by hydrophobic molecules interacting strongly with each other B. They are the driving force for micelle formation C. When non polar molecules come in contact with water, a highly ordered shell of water molecules forms at the interface between the non polar molecules and water. A hydrophobic interaction is caused by the desire of water molecules to regain the entropy lost during this organization around the non polar substance by excluding the substance from interaction with water molecules. D. They are entropy driven E. They are the main driving force for protein folding into three dimensional structures

A

Which of the following statements describes one reason that plant oils are generally healthier for human consumption than animal fats? A) Plant oils usually contain more unsaturated fatty acids than animal fats. B) Plant oils usually contain more trans fatty acids than animal fats. C) Plant oils usually have a higher degree of saturation than animal fats. D) Plant oils are glycerol based rather than phospholipid based. E) Plant oils have shorter chain fatty acids than animal fats.

A

Which of these characteristics describes the beta sheet? A. Amino acid side chains are located both above and below the plane of the backbone B. Parallel sheets have an amphipathic distribution of side chain. C. The antiparallel sheets are found only in alpha/beta tertiary structures. D. The parallel sheets are the more stable to water denaturation. E. Beta sheets have compact phi/psi angles

A

Which of these techniques uses antibodies to detect very small amounts of specific proteins following separation by SDS-PAGE? A) immunoblotting B) silverstaining C) Coomassie Brilliant Blue staining D) ELISA E) RIA

A

Which statement about actin is not true? A. There are two actin genes, one for F-actin and one for G-actin. B. Monomeric G-actin polymerizes to form F-actin. C. Actin filaments are polar (the ends can be distinguished). D. Actin can bind ATP. E. Actin is a common protein in nonmuscle cells.

A

Which statement about aquaporins is false? A) They transport water and hydronium ions efficiently. B) They exclusively transport water molecules at a high rate. C) They use hydrogen bonding to side chain NH2 groups of two Asn residues to exclude proton transport within the pore. D) They have a narrow constriction approximately equal to the van der Waals diameter of a water molecule. E) They use Arg and His side chains to remove associated water molecules from the 'transported' H2O.

A

Which statement below does not describe fibrous proteins? A) Domains have a globular fold. B) These proteins usually contain only one type of secondary structure. C) These proteins usually exhibit structural or protective characteristics. D) These proteins have usually elongated hydrophilic surfaces. E) These proteins are usually insoluble in water.

A

Which of the following is not a ligand to the porphyrin ring Fe(II) ion in oxymyoglobin? A) His E7 B) His F8 C) Nitrogen atoms in the porphyrin ring D) Oxygen E) all are ligands

A) His E7

AMP stands for

Adenylic acid

The peptide AYDG has an N-terminal ____ residue

Alanine

N-linked oligosaccharides can be covalently linked to proteins at which amino acid?

Asn

In two homologous proteins, which residue is most likely to replace a Glu residue as a conservative substitution?

Asp

A researcher has designed a new drug that will block the release of certain neurotransmitters from the synaptic cleft. Which of the following reactions must be blocked by this new drug? A) The drug binds the receptors in the postsynaptic membrane and blocks neurotransmitter binding. B) The drug binds the presynaptic membrane greatly facilitating the rate of transverse diffusion, thus changing the composition of the membrane. C) The drug enhances activity of SNARE proteins, thus facilitating fusion. D) All of the above are plausible actions of this new drug. E) None of the above is a plausible action of this new drug.

B

Coated vesicles are used to ensure that the enclosed protein maintains its proper orientation. Clathrin is one type of protein used to coat vesicles. Which of the following is true regarding clathrin vesicles? A) They transport proteins between successive components of the Golgi compartments. B) They transport transmembrane proteins and GPI-linked proteins from the Golgi to the plasma membrane. C) They transport proteins from the ER to the Golgi. D) They form a rigid complex capable of protecting protein structure and orientation as it is passed from hydrophobic to hydrophilic environments. E) None of the above.

B

Five graduate students prepare extracts from 5 different tissues. Each student measures the total amount of alcohol dehydrogenase and the total amount of protein in his or her extract. Which extract has the highest specific activity? 1st number: Total protein (mg) 2nd number: Total alcohol dehydrogenase activity (units) A 300 60,000 B 200 80,000 C 3000 96,000 D 5000 100,000 E 1000 200,000

B

Heterotrimeric G proteins I. consist of three subunits, Gα, Gβ, and Gγ. II. function as an autoinhibtory segment. III. can function as a mediator to adenylate cyclase activity. IV. are anchored to the cytoplasmic side of the membrane. A) I, II, IV B) I, III, IV C) I, IV D) I, III E) I only

B

Imagine that a researcher treated a protein with a high concentration of a chaotropic agent. Which of the following is the most likely result of the treatment? I. Nonpolar portions of the protein become more soluble. II. The protein begins to denature , III. The protein stability increases due to hydrophobic collapse, A) I, II, III B) I, II C) II, III D) I, III E) II

B

Lipid bilayers with high concentrations of gangliosides are rare. Which of the following explanations is correct? A) The hydrophobic tails on gangliosides form a conical shape rather than a cylindrical shape making close packing difficult. B) Gangliosides contain large headgroups making close packing difficult. C) Gangliosides contain trans fatty acids resulting in a bent hydrophobic tail making close packing difficult. D) All of the above are correct. E) None of the above is correct.

B

Lung surfactants function to decrease the likelihood of collapse of the alveoli when air is expired. Based on your knowledge of lipids and amphipathic molecules, which of the following explains the mechanism by which the dipalmitoyl phosphatidylcholine (DPPC) can accomplish this task? A) The hydrophilic head groups are bulky and expand the surface area of the alveoli. B) The inclusion of saturated fatty acids on the glycerophospholipid allows close packing of tail groups which are fully extended and prevent collapse upon expiration. C) The hydrophobic portion of the DPPC repel air, forcing the alveoli space open. D) The choline portion of the molecule is bulky, thus increasing surface area of alveoli. E) None of the above explain the mechanism.

B

Noncovalent interactions account for the strength of which of the following structural proteins? A) α keratin B) collagen C) pleated collagen D) A and B E) B and C

B

Of the following, which amino acid is most likely to be found in position 1 or 4 on α keratin? A) Phe B) Ala C) Lys D) Trp E) Pro

B

Rank the melting points of the following fatty acids from highest to lowest: (1) cis-oleic(18:1) (2) linoleic (18:2) (3) steraic (18:0) (4) palmitic (16:0) A) 1 > 2 > 4 > 3 B) 3 > 4 > 1 > 2 C) 3 > 4 > 2 > 1 D) 4 > 3 > 1 > 2 E) 2 > 1 > 4 > 3

B

Rank the melting points of the following fatty acids from highest to lowest: (1) cis-oleic(18:1) (2) trans-oleic (18:1) (3) linoleic (18:2) (4) steraic (18:0) (5) palmitic (16:0) A) 1 > 2 > 3 > 5 > 4 B) 4 > 5 > 2 > 1 > 3 C) 4 > 5 > 3 > 2 > 1 D) 5 > 4 > 2 > 1 > 3 E) none of the above

B

Research scientists are trying to clone a gene. In order to accomplish this task they join two pieces of DNA. Which class of the enzymes below might accomplish this task? A) oxidoreductase B) ligase C) hydrolase D) isomerase E) lyase

B

The Greek-key motif supersecondary structure is the basis of which of the following folded domains? A. All alpha B. All beta C. alpha/beta sandwich D. alpha/beta barrel E. none of the above

B

The folded domain below that has antiparallel beta sheets is the: A. All alpha B. All beta C. alpha/beta sandwich D. alpha/beta barrel E. None of the above

B

The transformation of a monosaccharide into its ______ occurs easily and does not require the assistance of a catalyst. A) epimer B) anomer C) sugar alcohol D) diastereomer E) none of the above

B

Triglycerides contain more metabolic energy per unit weight than glycogen because: I. Glycogen has greater polarity than fatty acids. II. Fatty acids predominate in an anhydrous form III. Fatty acids are less oxidized than carbohydrates. IV. Triglycerides have a higher average molecular mass. A) I, II, III, IV B) I, II, III C) I, II D) II, III E) III

B

When comparing similarities among multiple protein structures, which of the following is false? A) Proteins with the same function from a different species are likely to have similar motifs. B) Proteins with the same function from different species are likely to be more similar in sequence than in structure. C) An effective protein motif isl likely be observed in multiple proteins. D) Proteins with the same motifs are likely to perform similar functions. E) None of the above statements are false.

B

When the cardiac glycoside, digitoxin, is used for heart failure, the effects include: I. inhibition of phosphate hydrolysis from E2 of the (Na+-K+)-ATPase pump II. activation of the (Na+-K+)-ATPase pump III. increase in intracellular Na+ concentration IV. increase in Ca2+ concentration in the sarcoplasmic reticulum A) I, II, III, IV B) I, III, IV C) II, III, IV D) II, III E) I, III

B

Which experiment listed below did NOT verify the fluid mosaic model of membranes? A) observation of lateral movement of membrane across the cell while anchored to a microscope slide. B) monitoring the transverse diffusion of human proteins within a mouse cell membrane. C) membrane fusion between mouse and human cells. D) monitoring the lateral diffusion of fluorphores both bleached and unbleached. E) All of the above describe experiments that verified the fluid mosaic model of membranes.

B

Which features allow the KcsA channel to selectively transport K+? I. The entrance of the channel contains hydrophobic residues which forces the removal of waters of hydration. II. It is attracted to the entrance of the channel via electrostatic interactions. III. The "selectivity filter" involves a narrowing of the channel, allowing only dehydrated K+ access. IV. As K+ is transported through the channel it interacts with −C=O groups from the protein. A) I, II, III, IV B) II, III, IV C) II, III D) III, IV E) I, III

B

Which of the following amino acids has a sulfur atom in its side chain? A. Asn B. Cys C. Phe D. Ser E. Tyr

B

Which of the following amino acids has an uncharged polar side chain at pH 7.0? A) Arg B) Thr C) Glu D) Pro E) Ile

B

Which of the following channels open in response to an extracellular stimulus such as a neurotransmitter? A) mechanoselective channels B) ligand-gated channels C) signal-gated channels D) voltage-gated channels E) All of these are sensitive to an extracellular stimulus..

B

Which of the following correctly describes the reason for the specificity of valinomycin? A) The K+ ion is the only ion small enough to fit through the ion channel. B) The K+ radius is the ideal size for a large binding affinity because it minimizes steric strain and potential for degrees of rotation. C) It selectively binds to the entrance of the transporter which is lined with negatively charged amino acids. D) All of the above describe the specificity. E) None of the above describe the specificity.

B

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 A) II, I, III, IV B) II, I, IV, III C) IV, III, II, I D) I, II, IV, III E) IV, II, III, I

B

Which of the following correctly ranks the steps in the secretory pathway? 1. Synthesis occurs with a leading signal peptide 2. The SRP-ribosome complex binds the SRP receptor-translocon complex 3. The signal peptide binds the SRP and GDP is replaced with GTP 4. GTP hydrolysis results in dissociation of SRP and SR 5. SRP changes in conformation arresting peptide growth 6. The nascent protein begins to fold and post-translational modification is initiated 7. Signal peptidase cleaves the protein from the signal peptide A) 1, 2, 5, 4, 6, 7, 3 B) 1, 3, 5, 2, 4, 7, 6 C) 2, 4, 1, 3, 5, 6, 7 D) 2, 4, 3, 5, 4, 6, 7 E) 1, 3, 4, 2, 5, 7, 6

B

Which of the following correctly states an essential step in the function of heterotrimeric G protein function? A) A cascade of events must occur that ultimately activate protein kinase C. B) Binding of a hormone to a receptor must signal the exchange of GDP for GTP. C) Binding of GTP to the receptor protein must induce a change in conformation of the receptor. D) Binding of cAMP to the α subunit of the G protein must initiate translocation of the subunit. E) All of the above are correct.

B

Which of the following generalizations explains how anabolic steroids can affect muscle growth? A) Anabolic steroids increase the level of testosterone, a hormone predominately found in males. B) Anabolic steroids easily pass through the membrane and bind steroid receptors which migrate to the nucleus and function as a transcription factor. C) Anabolic steroids are water soluble and can transport to the muscle tissue readily. D) Anabolic steroids alter the phosphoinositide pathway, thereby increasing levels of calcium in the cytosol and subsequently increase the strength of muscle contraction. E) None of the above is correct.

B

Which of the following is (are) associated with cAMP binding to cAMP-dependent protein kinase A? I. cAMP binds to the regulatory subunits. II. Tetrameric regulatory subunits and catalytic subunits dissociate. III. Catalytic subunits phosphorylate multiple targets with specific serine and threonine residues. IV. cAMP is membrane bound via phosphoinositol attachment. A) I, II, III, IV B) I, II, III C) I, II D) II, III, IV E) III, IV

B

Which of the following is (are) the result of insulin binding to its receptor? I. MAPK activation, which regulates gene expression via Fos, Jun and Myc. II. PI3K activation leading to an increase in glucose transport. III. High affinity binding of SH2 domains to phosphorylated tyrosines. IV. Autophosphorylation resulting in activation of tyrosine kinase. A) II, III, IV B) I, II, III, IV C) II, III D) I, II E) III only

B

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. A) I, II, III B) I, II, III, IV C) II, II D) III, IV E) II, III, IV

B

Which of the following is TRUE regarding transition state? A) The free energy between the transition state and the reactants must be negative. B) The transition state can be stabilized by covalent catalysis. C) The transition state represents the ES complex. D) Transition state analogs bind the substrate not the enzyme E) All of the above are true.

B

Which of the following is a mixture of two types of polymers? A) cellulose B) starch C) chitin D) glycogen E) amylose

B

Which of the following is always true of hormones? A) Hormones always bind membrane bound receptors. B) Hormones elicit specific cellular responses. C) Hormones are secreted from a gland via a robust network of ducts. D) The release of hormones is influenced by adrenal receptors. E) All of the above are true.

B

Which of the following is evidence for aquaporins? A) Kidney cells are otherwise incapable of maintaining a gradient. B) Kidney cell transport of water molecules can be inhibited by mercuric ions. C) Water, a polar substance, cannot cross the hydrophobic membrane without mediation. D) Rapid rates of water transport require mediation. E) Studies measuring flux of water molecules in the kidney yielded only linear plots of flux vs. [H2O] despite the large excess in water.

B

Which of the following is true about enzymes? I. Enzymes typically catalyze reactions at much higher rates than chemical catalysts 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 A. I, II, III B. I, II, III, IV C. II and II D. III and IV E. II, III, IV

B

Which of the following methods will allow you to determine if a substance used mediated transport? A) Measure the rate of transport to determine if it is high or low relative to other transport systems. B) Evaluate the flux at several different concentrations of the substance and look for hyperbolic dependence. C) Monitor transport rates at a variety of concentrations and confirm a linear dependence. D) Compare rate of transport in an in vitro system to those in vivo. E) None of the above.

B

Which of the following sets of terms has a member that does not belong? A) rhodopsin - heterotrimeric G protein - desensitization B) autoinhibitor segment - receptor tyrosine kinase - SH2 C) propranolol - β-adrenoreceptor - antagonist D) transcortin - aldosterone - adrenal cortex E) adenylate cyclase - cholera toxin - heterotrimeric G protein

B

Which of the following statements is true? A) Amino acids can be derived from purines B) Purines and Pyrimidines can be derived from amino acids C) Corn contains all 20 standard amino acids D) Amino acids can be derived from pyrimidines E) None of the Above

B

Which of the following would be most stable based on the information you have learned about protein structure? A) a loop region with 8 amino acids B) a β sheet region made up of amino acids Val, Ile, Phe C) an α helix made up of Cys, Pro, and Phe D) a β hairpin with 12 amino acids E) All have equal stability.

B

Which of these reagents is commonly used to determine the number of polypeptides in a protein? A) iodoacetate B) dansyl chloride C) 2-mercaptoethanol (β-ME) D) cyanogen bromide E) DEAE

B

Which of these techniques is used to separate proteins mainly based on mass? A) polyacrylamide gel electrophoresis (in the absence of SDS) B) SDS-PAGE C) isoelectric focusing D) immunoblotting E) Western blotting

B

Which one of these characteristics is not true for the α helix? A) There are 3.6 amino acids per turn. B) There is a requirement for glycine every third amino acid residue. C) A hydrogen bond forms between the carbonyl oxygen of the nth amino acid residue and the - NH group of the (n + 4)th amino acid residue. D) Proline is typically not found in the α helix. E) It is right-handed.

B

Which physical characteristic is not commonly used in protein separation? A) solubility B) stereochemistry C) size D) charge E) polarity

B

Which statement about N-linked glycosylation is correct? A) N-linked oligosaccharides are attached to proteins one sugar at the time in the endoplasmic reticulum. B) N-linked sugars are attached to proteins as a 14 residue oligosaccharide during translation in the endoplasmic reticulum. C) N-linked sugars are attached to proteins as a 14 residue oligosaccharide during translation in the cytoplasm. D) N-linked sugars are attached to proteins as a 14 residue oligosaccharide after translation in the Golgi apparatus. E) N-linked oligosaccharides are attached to proteins one sugar at the time in the Golgi apparatus.

B

Which statement does not describe the transport of ions by valinomycin? A) Provides a hydrophilic cage covered by hydrophobic residues. B) Transport may be active or passive. C) The active site binds K+ with greater affinity than Na+ D) Transport results in equilibration of a concentration gradient across membranes. E) All of the above do describe transport by valinomycin.

B

You are trying to separate five proteins, which are listed below, by gel filtration chromatography. Which of the proteins will elute second from the column? A. cytochrome c (12 kDa) B. RNA polymerase (99 kDa) C. glutamine synthetase (621 kDa) D. interferon (34 kDa) E. hemoglobin (62 kDa)

B

Humoral immunity is mediated by soluble molecules. Which cell type produces the soluble molecules that carry out the humoral immunity?

B Cells

When the partial pressure of O2 in venous blood is 30 torr, the saturation of myoglobin with O2 is ______ while the saturation of hemoglobin with O2 is ______.

B) 0.91, 0.55

The conversion of hemoglobin from the T to the R state requires breaking of ___ involving C-terminal residues

ion pairs

A suspension of which of the following is most likely to form a liposome? I. fatty acids II. triacylglycerols III. glycerophospholipids IV. sphingomyelins A) I, II B) II, III C) III, IV D) II, IV E) I, IV

C

Botox is used cosmetically to reduce wrinkles for a limited time interval. The function of Botox is described by which of the following? A) Botox inhibits function of the hemagglutinin tag. B) Botox relaxes small muscles by cleaving the leader peptide prior protein folding. C) Botox functions by inhibiting function of the SNARE protein. D) Botox functions by inhibiting the lysosomal protease cathepsin D. E) None of the above describes the function of Botox.

C

Catecholamines epinephrine and norepinephrine mediate their effects through I. α-adrenoreceptors. II. β-adrenoreceptors. III. receptor tyrosine kinases. IV. monomeric G protein receptors. A) I only B) II only C) I and II D) III and IV E) IV only

C

Cold blooded animals modulate the fatty acid composition of their membranes as a function of temperature in order to A) adjust the membrane thickness and increase thermal insulation. B) maximize available fatty acids for metabolic use. C) ensure consistent membrane fluidity. D) compensate for decreasing cholesterol solubility. E) all of the above

C

Conventional one dimensional NMR spectroscopy is not generally an effective tool for determination of protein structure because... I. Proteins (including small proteins) have a high number of hydrogen atoms. II. NMR requires a high quality protein crystal. III. The NMR spectra exhibit high peak overlap. A) I and II B) II and III C) I and III D) I, II, and III E) III only

C

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? A) D-glucose undergoes simple diffusion more rapidly than mannitol because glucose is less polar. B) D-glucose and D-mannitol enter the erythrocyte via an ion-gated channel. C) D-glucose and D-mannitol are transported via a system that distinguishes the two sugars. D) D-glucose flux through the membrane is linear whereas D-mannitol flux is described by a hyperbolic curve. E) None of the above provides the explanation.

C

Fab fragments can be generated by A) reduction of IgG molecules. B) oxidation of IgG molecules. C) limited digestion of IgG molecules with papain. D) combining two light chains. E) combining two heavy chains.

C

Gap junctions A) connect the cytoplasm to the extracellular solution thus allowing transfer of small molecules out of the cell into the extracellular solution. B) are essential communication channels between the cell and the extracellular solution. C) allow exchange of small molecules between cells within an organ. D) allow intercellular exchange of macromolecules. E) All of the above.

C

In the body hydrogen ions produced from the reaction of carbonic anhydrase are transported into the lumen of the stomach via an ATP utilizing proton pump. The removal of hydrogen ions drives formation of bicarbonate ions and a concentration gradient is formed. Bicarbonate is transported out at the same time that chloride ions are transferred in. Based on this information, which of the following is FALSE? A) The pump driving the driving the hydrogen ions into the lumen must undergo a conformational change. B) The pump driving bicarbonate out and chloride in must be an antiport system. C) The pump driving bicarbonate out and chloride in must require ATP directly. D) The bicarbonate-chloride pump requires ATP indirectly. E) The bicarbonate-chloride pump must require activity of the proton pump.

C

Muscle contraction is directly caused by A) structural changes in actin. B) structural changes in myosin. C) thick and thin filaments sliding past each other. D) structural changes in the Z disk. E) None of the above is correct.

C

Parallel lines on a Lineweaver-Burk plot indicate I. an increase in KM. II. decrease in KM. III. decrease in Vmax. IV. uncompetitive inhibition. A) I, IV B) II, III, IV C) I or II, III D) I or III, II E) I, III, IV

C

Protein kinases are involved in A) the digestion of drugs to potentially toxic byproducts. B) the degradation of enzymes to the component amino acids. C) the phosphorylation of a wide variety of proteins. D) the metabolism of drugs to water soluble, excretable compounds. E) all of the above

C

Radioactively labeled, single-stranded oligonucleotides are often used in in situ hybridization. Which of the probes listed below would work best, when probing for a RNA molecule containing the sequence 5'-AGCTAACGGG- 3'? A) 5'-AGCTAACGGG- 3' B) 5'-GGGCAATCGA- 3' C) 5'-CCCGTTAGCT- 3' D) 5'-TCGATTGCCC- 3' E) all of the above

C

Receptor-mediated endocytosis: A) is comparable to the activities of vesicle fusion. B) superficially resembles binding of a clathrin coated vesicle to the plasma membrane. C) superficially resembles the reverse of vesicle fusion to the plasma membrane. D) mimics the function of the Golgi apparatus. E) functions much like the SNARE mediated fusion process.

C

Somatostatin I. inhibits the release of insulin. II. inhibits the release of glucagon. III. stimulates the release of insulin. IV. stimulates the release of glucagon. A) I only B) II only C) I and II D) III and IV E) IV only

C

The E. coli maltoporin utilizes what has been termed the greasy slide. Which of the following statements best describe the function of the greasy slide? A) There is a pathway of phospholipids that line the inside of the channel and facilitate transport. B) A series of aromatic side chains arrange in a helical pattern matching the relative curvature of the protein backbone, thus provided little restriction to transport. C) Hydroxyl groups on glucose hydrogen bond with polar and charged side chains lining the channel, thus resulting in a series of interactions mimicking a screw-like pathway. D) Constriction in the channel removes waters of hydration, thus making the substrate more hydrophobic and "greasy." E) Amino acids side chains lining the channel are small and non-bulky, making steric constriction essentially non-existent.

C

The _________, which is found embedded in the endoplasmic reticulum, is a _______ protein. A) SRP receptor...signal B) ribosome...transmembrane pore C) translocon...transmembrane pore D) translocon...peripheral E) ribosome...signal

C

The biconcave shape of erythrocytes which maximizes rapid diffusion of oxygen is primarily maintained by A) the covalent attachment of organelles within the cell to the membrane. B) high levels of rigid cholesterol and saturated lipids that strengthen the membrane. C) a network of embedded spectrin that crosslink to other membrane proteins, D) a network of tightly-packed anion channel proteins. E) a relatively low concentration of integral membrane proteins allowing tighter packing of lipid molecules within the membrane.

C

The bonding of alcohols to the anomeric center of a carbohydrate results in the formation of a(n) __________ bond. A) anomeric B) amide C) glycosidic D) ester E) hydrogen

C

The structure and sequence of a protein of unknown function was examined. Which of the following provides the best prediction of the protein's function? A) the observation of several disordered α helical domains. B) the observation of multiple protein subunits. C) the observation of motif known as the Rossmann fold. D) the observation of a large number of random coil regions. E) All of the above offer excellent prediction of the protein's function.

C

The tripeptide glycylarginylglutamate contains four ionizable groups with pKa's of 2.1, 4.1, 9.8, and 12.5. Calculate the pI for this molecule. A. 3.1 B. 6.4 C. 7.0 D. 7.3 E. 8.3

C

Transmembrane proteins I. are predominantly constructed of a single hydrophobic α-helix. II. are often constructed from bundles of hydrophobic α-helices. III. are sometimes constructed from β-barrels with hydrophobic interiors and exteriors. IV. may have transmembrane helices identified by the free energy of transfer to water. A) I, III, IV B) II, III C) II, III, IV D) I, IV E) II, IV

C

Transmembrane proteins I. are predominantly constructed of a single hydrophobic α-helix. II. are often constructed from bundles of hydrophobic α-helices. III. are sometimes constructed from β-barrels with hydrophobic exteriors. IV. may have multiple transmembrane helices. A) I, III, IV B) II, III C) II, III, IV D) I, IV E) II, IV

C

Unsaturated fatty acids: A) are commonly found in plants but not animal membranes B) usually contain a double bond with trans stereochemistry C) produce channels in the membrane for passive diffusion. D) have higher melting points than the analogous saturated fatty acids E) all of the above

C

Which of the amino acids represented below has two chiral centers? A) Ala B) Leu C) Ile D) Pro E) Asn

C

Which of the following DNA sequences (in which N is any nucleic acid residue) is palindromic? A) ANAGCTT B) AANGCTT C) AAGNCTT D) AAGCNTT E) AAGCTNT

C

Which of the following DNA sequences (in which N is any nucleic acid residue) is palindromic? A. ANAGCTT B. AANGCTT C. AAGNCTT D. AAGCNTT E. AAGCTNT

C

Which of the following amino acid residues would provide a side chain capable of increasing the hydrophobicity of a binding site? A) histidine B) lysine C) isoleucine D) arginine E) serine

C

Which of the following amino acids combinations have side chains with groups that have the greatest ability to stabilize the tertiary structure of a protein? A) Lys and Arg B) Cys and Glu C) Glu and Lys D) Gln and Glu E) Pro and Asp

C

Which of the following amino acids would be last to elute at pH 8.0 from an anion-exchange column? A) lysine B) alanine C) glutamic acid D) asparagine E) glycine

C

Which of the following are activated either directly or indirectly by a heterotrimeric G protein subunit? I. phospholipase C II. Herceptin ® III. calmodulin (CaM) sensitive kinase IV. MAPK A) I, II, III, IV B) I, II C) I, III D) II, III, IV E) I, II, IV

C

Which of the following classes of proteins associates with the membrane bilayer with the lowest energy and would therefore be most difficult to separate from the membrane? A) extrinsic proteins B) lipid-linked proteins C) transmembrane proteins D) peripheral proteins E) hydrophilic proteins

C

Which of the following compounds would cross a biological membrane most readily by nonmediated diffusion? A) water B) acetone C) hexane D) acetic acid E) methanol

C

Which of the following gives the best example of a nonrepetitive structure in a protein? A) a random sequence of 12 amino acids with high Pα values forming an α helix B) an amino acid sequence with the following pattern "...a-b-c-d-e-a-b-c-d-a-b-c-d..." C) a 13 residue α helix with a Gln at position n+12 which hydrogen bonds to a residue at position n+10 D) All of the above statements describe nonrepetitive protein structures. E) None of the above describe nonrepetitive protein structures.

C

Which of the following increases the affinity of hemoglobin for O2? A) an increase in BPG concentration B) the formation of N-terminal carbamates C) an increase in pH D) a decrease in pH E) an increase in CO2 concentration

C

Which of the following is (are) NOT found as covalently attached anchors in lipid-linked proteins? A) isoprenoid groups B) fatty acids C) cholesterol and other sterols D) glycosylphosphatidyl inositol groups E) All of the above are found as covalently attached anchors in lipid-linked proteins.

C

Which of the following is (are) characteristic of the (Na+-K+)-ATPase? I. It binds Na+ and K+ simultaneously prior to binding ATP II. It is covalently modified by phosphorylation at an Asp residue when Na+ is present. III. Transport of Na+ and K+ occur in a 1:1 ratio, thus maintaining a balanced gradient until opening of the gated portion of the channel. IV It is essential for excitation of nerve cells. A) I, II, IV B) II, III, IV C) II, IV D) II, III E) II

C

Which of the following is TRUE regarding cofactors? A) Coenzymes are often separate from the enzyme and do not need recharged. B) Metal ions must be covalently attached to function as a cofactor. C) Cofactor is a broad term used for all enzyme "helpers". D) Prosthetic groups can dissociate readily and be regenerated for use in another enzyme. E) An apoenzyme implies that a cofactor is present.

C

Which of the following is true regarding cofactors? A. Coenzymes are often separate from the enzyme and do not need to recharge B. Metal ions must be covalently attached to function as a cofactor C. Cofactor is a broad term used for all enzyme "helpers" including prosthetic groups and coenzymes D. Prosthetic groups can dissociate readily and be regenerated for use in another enzyme E. An apoenzyme implies that a cofactor is present

C

Which of the following lipids would NOT likely be found in a lipid raft? I. glycosphingolipids II. glycerophospholipids III. cholesterol IV. palmitoleic acid A) I, IV B) I, II, IV C) II, IV D) III, IV E) IV

C

Which of the following molecules does NOT contain an energy rich phosphoanhydride bond? (A) ADP (B) GDP (C) AMP (D) CDP (E) all of the above

C

Which of the following occurs first when folding a disordered polypeptide chain into a stable protein formation? A) formation of a low energy state B) association of ordered subunits C) aggregation of hydrophobic regions in the protein D) tertiary structure refinement E) formation of a low entropy state

C

Which of the following polysaccharides cannot be digested by mammalian salivary, gastric, or pancreatic enzymes? A) amylopectin B) amylose C) chitin D) glycogen E) starch

C

Which of the following processes presented in this chapter is (are) readily reversible with the help of enzymes known as thioesterases? A) myristoylation B) glycosylphosphotidylinositalation C) palmitoylation D) all of the above E) none of the above

C

Which of the following statements about nucleotides is FALSE? (A) nucleotides mediate transport of energy within the cell (B) Nucleotides are involved in redox reactions (C) Nucleotides store genetic information (D) Nucleotides are involved in biosynthetic reactions (E) None above

C

Which of the following statements about nucleotides is false? A. Nucleotides mediate transport of energy within the cell. B. Nucleotides are involved in oxidation-reduction reactions. C. Nucleotides store genetic information D. Nucleotides are involved in biosynthetic reactions E. None of the above

C

Which of the following statements about water is incorrect? A. Water is an excellent solvent for polar molecules. B. Pure liquid water has fewer hydrogen bonds on average than water in ice C. Cations are solvated by shells of water molecules oriented with their hydrogen atoms pointed toward the ions D. Nonpolar molecules do not dissolve in water, but form a separate phase. E. Amphiphilic detergents often form micelles with the polar groups on the outside exposed to water (solvent) in the non polar groups sequestered in the interior

C

Which of the following statements are true regarding fatty acids? I. Fatty acids with fewer than 14 carbons are not common. II. Synthesis of fatty acids occurs in 3 carbon units. III. Fatty acids with conjugated double bonds are the most common type of fatty acid. IV. In higher plants and animals, C16 and C18 species predominate. A) I, II, III, IV B) I, II, III C) I, IV D) II, III, IV E) II, IV

C

Which of the following statements concerning the action of G proteins on adenylate cyclase is true? A) G proteins always serve to activate adenylate cyclase. B) G proteins always serve to inhibit adenylate cyclase. C) Some G proteins activate adenylate cyclase, while others inhibit it. D) G proteins do not act on adenylate cyclase at all.

C

Which of the following tripeptides would be expected to be the most hydrophobic? A) KYG B) KYA C) GYA D) DYA E) DYG

C

Which of these are commonly used to label cysteine residues in polypeptides? A. 2-mercaptoethanol (-ME) B. dansyl chloride C. iodacetate D. sodium dodecyl sulfate E. trypsin

C

Which of these following characteristics is true for the alpha helix? A. There are 3.0 amino acids per turn and 10 atoms in a H-bonded loop B. Beta branched amino acids are favorable for alpha helices C. All residues in a helix except those at the N and C termini are H bonded forming a non polar core. D. Proline and Glycine are typically found in the alpha helix. E. The helix is left handed

C

Which of these is not an artificial sweetener? A) saccharine B) aspartame C) maltose D) acesulfame E) alitame

C

You are trying to separate five proteins, which are listed below, by gel filtration chromatography. Which of the proteins will elute first from the column? A) cytochrome c (12 kDa) B) RNA polymerase (99 kDa) C) glutamine synthetase (621 kDa) D) interferon-γ (34 kDa) E) hemoglobin (62 kDa)

C

Which gas does not bind to the porphyrin ring Fe(II) ion in myoglobin? A) NO B) CO C) CO2 D) O2 E) H2S

C) CO2

Consider a hypothetical hemoglobin-like molecule with a Hill coefficient (constant) of 1 and the same p50 value as normal hemoglobin. Choose the statement below that best describes the two proteins. A) There is a cooperative interaction between oxygen-binding sites in both the hypothetical and normal hemoglobins. B) The hypothetical hemoglobin has a greater oxygen affinity than normal hemoglobin. C) The oxygen binding curve for the hypothetical hemoglobin is hyperbolic, and the curve for normal hemoglobin is sigmoidal. D) The two hemoglobins would be able to deliver about the same amount of oxygen to the tissues. E) At pO2 less than p50, normal hemoglobin has a greater YO2 value.

C) The oxygen binding curve for the hypothetical hemoglobin is hyperbolic, and the curve for normal hemoglobin is sigmoidal.

D-Allose is an aldohexose. Methylation of which hydroxyl group on β-D-allopyranose prevents the molecule from mutarotating to α-D-allopyranose?

C1

What is the type of symmetry that relates the protomers in hemoglobin with respect to each other?

C2

Nucleotides contain one or more phosphate groups that are usually attached to the

C3' or C5' atoms

______ are transporters that bind the substance to be transported on one side of the membrane then diffuse through the membrane and release the substance on the other side.

Carrier ionophores

The ___ Character of most standard amino acids causes solutions of amino acids to rotate the plane of polarized light

Chiral

Change in total energy content (symbolized U or E) is best defined as

the sum of heat transfer and work done

Glutathione is a tripeptide containing a central ___ residue

Cysteine

Glycosphingolipids with several attached carbohydrates (including at least one sialic acid) are called: A) plasmalogens B) ceramides C) sphingiosides D) gangliosides E) cerebrosides

D

A Lineweaver-Burk plot is also referred to as I. a sigmoidal plot. II. a linear plot. III. a Michaelis-Menten plot. IV. a double reciprocal plot. A) II B) II, III C) IV D) II, IV E) III, IV

D

A compound that distorts the active site, rendering the enzyme catalytically inactive is called A) a uncompetitive inhibitor B) an allosteric effector C) an inactivator D) a competitive inhibitor E) none of the above

D

A helix has hydrogen bonds between the carbonyl group from residue "n" and the amino group of residue "n+6," which of the following is TRUE? A) It has 3.6 residues per turn. B) It is a random coil, not a helix. C) It is an α helix. D) It has more residues per turn than an α helix. E) It has fewer residues per turn than an α helix.

D

A researcher is developing a new drug for the treatment of influenza. Based on the information presented in the text about the influenza virus, which of the following drug reactions describes the action of this new drug? A) A drug which specifically interrupts the conformational change that results from the pH change in the endosome. B) A drug which enhances the function of a normally quiescent enzyme responsible for cleavage of the carbohydrate component on glycophorin A proteins. C) A drug which readily binds the hemagglutinin tag and results in conformational change. D) All of the above are potential actions of this new drug. E) None of the above is a plausible reaction for this new drug.

D

Adding additional salt to a protein solution can cause which of the following? A) an increase in solubility called 'salting in'. B) a decrease in solubility called 'salting out'. C) protein precipitation from solution. D) all of the above E) none of the above

D

Alterations in genetic information cannot be caused by A) mistakes made during replication B) faulty recombination. C) transposition of genes. D) mistakes made during translation. E) all of the above

D

An uncatalyzed reaction has a rate of 4.2 x 10^(-7) sec^(-1). When an enzyme is added the rate is 3.2 x 10^4 sec ^(-1). Calculate the rate enhancement caused by the enzyme. A. 3.2 x 10^4 B. 7.4 x 10^(-3) C. 1.3 x 10^(-2) D. 7.6 x 10^10

D

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. A) 3.2 × 104 B) 7.4 × 10-3 C) 1.3 × 10-2 D) 7.6 × 1010 E) The data are not appropriate for the calculation requested.

D

Anthrax toxin functions by altering levels of cAMP. The toxin also contains an edema factor, which requires the activity of calmodulin (CaM) for proper function. Based on this information, which of the following can you conclude? A) The toxin alters cAMP dependent cell signaling. B) Calcium levels affect the function of the edema factor. C) Unlike other toxins, the anthrax toxin does not function by altering biochemical signaling. D) A and B E) A and C

D

At equilibrium in solution, D-glucose consists of a mixture of its anomers. Which statement most accurately describes this solution? A) The solution consists of approximately equal amounts of the α- and β-anomers. B) The straight-chain form is present in high concentration. C) The α-anomer is more stable and is slightly preferred over the β-anomer. D) The β-anomer predominates over the α-anomer by a ratio of approximately 2:1. E) None of the answers above is correct.

D

Chitin differs from cellulose due to A) inversion of configuration at the anomeric carbon. B) sulfonation of the C2 OH group. C) a much greater prevalence of branching. D) replacement of the C2 OH group by an acetamido group. E) replacement of the C6 OH group by an amino group.

D

DNA fragments are usually inserted into a plasmid vector and cloned before they are analyzed by chain termination sequencing because A) DNA fragments need to be pure in order to obtain an unambiguous sequence. B) a large number of identical fragments is needed in a sequencing reaction in order to generate detectable amounts of products. C) plasmid vectors have known sequences that can be used for design and annealing of the primer oligonucleotides, which are used to initiate the sequencing reaction. D) all of the above E) none of the above

D

Insertion of cholesterol in a lipid bilayer causes all of the following EXCEPT: A) decrease in transverse diffusion of phospholipids. B) increase in bilayer rigidity to gel-like state. C) decreases the thermal movement of fatty acid alkyl chains D) increases the overall fluidity of the membrane E) all of the above are function s of membrane cholesterol

D

Membrane glycerophospholipids contain head groups with the following chemical characteristics EXCEPT: A) weakly basic B) strongly basic C) zwitterionic D) acidic E) neutral polar

D

N-terminal signal peptides function to direct proteins A) destined for secretion. B) to the endoplasmic reticulum. C) destined to be part of the lysosomes. D) all of the above E) none of the above

D

Ouabain inhibits the (Na+-K+)-ATPase pump, resulting in A) K+ ions moving into the cell along a concentration gradient B) K+ ions bringing water molecules into the cell in order to maintain an osmotic balance C) extra K+ ions and water in cells causing them to swell and lyse D) an increase in the strength of heart muscle contractions when small amounts of Ouabain are used E) all of the above

D

Phospholipase C cleaves PIP2, resulting in an increased cytosolic concentration of I. IP3 (inositolpolyphosphate-3) II. protein kinase C III. cAMP IV. Ca2+ A) I only B) II only C) I, III D) I, IV E) IV only

D

Proteins can denature due to a change in which of the following? A) pH. B) temperature. C) ionic strength. D) all of the above E) none of the above

D

Proteins which are passed from one Golgi compartment to the next in a successive fashion do so via a mechanism called____. A) maturation B) cisternal progression C) retrograde transport D) anterograde transport E) medialgrade transport

D

Proximity effects A) result from active site specificity. B) result from substrate channeling. C) result in increased effective concentration of substrate. D) lower the energy of activation. E) All of the above of the above are correct.

D

Sphingolipids I. contain a glycerol core with a phosphocholine headgroup. II. contain a modified sphingosine. III. often function as receptor components of membranes. IV. function as a precursor to sterols. A) I, II, IV B) II, IV C) I, II, III D) II, III E) II, III, IV

D

The bonding listed below that is considered the driving force for formation of tertiary structure is: A. Electrostatic interactions B. Debbie forces C. Hydrogen bonds D. Hydrophobic effect E. Disulfide bond

D

The protein that forms a transmembrane pore that allows growing polypeptides to pass through the RER membrane is called the ______. A) signal recognition particle B) signal peptide C) docking protein D) translocon E) none of the above

D

The reaction of carbonic anhydrase catalyzes A) the formation of carbamates with the concomitant release of protons. B) the hydration of bicarbonate, resulting in the formation of carbonic acid. C) the reduction of carbon dioxide with the concomitant consumption of protons. D) the hydration of carbon dioxide, forming bicarbonate and protons. E) the hydrolysis of carbamates with the concomitant consumption of protons.

D

The rearrangement of T state hemoglobin to the R state A) occurs in each protein subunit independently when its heme binds oxygen. B) requires the binding of at least three oxygen molecules. C) increases the ion pairing interactions of the C-terminal amino acids. D) involves the movement of the Fe(II) into the heme plane. E) opens a central cavity for BPG binding.

D

The signal peptide sequence I. is often used to direct proteins to the lysosome for incorporation into the lysosome. II. is usually not used for small eukaryotic proteins. III. of some transmembrane proteins is embedded into the membrane as an anchor. IV. is usually cleaved off the completed protein. A) I, IV B) I, II, IV C) II, III, IV D) I, III, IV E) I, II, III, IV

D

Which of the following amino acids from an integral membrane protein would likely contact the membrane? A) Asn B) Gln C) Glu D) Ala E) Asp

D

Which of the following amino acids has a sulfur atom in its side chain? A) Asn B) Ser C) Phe D) Met E) Tyr

D

Which of the following has (have) both a favorable hydrogen bonding pattern and φ and ψ values that fall within the allowed Ramachandran conformational regions?A) α helix B) collagen helix C) β sheet D) all of the above E) none of the above

D

Which of the following is NOT associated with cAMP binding to cAMP-dependent protein kinase A? A) cAMP binds to the regulatory subunits. B) Tetrameric regulatory subunits and catalytic subunits dissociate. C) Catalytic subunits phosphorylate multiple targets with specific serine and threonine residues. D) cAMP is membrane bound via phosphoinositol attachment.

D

Which of the following is comprised primarily of fatty acids and other single tailed amphiphiles? A) lipid bilayers B) two-dimensional membranes C) liposomes D) micelles E) solvent-filled vesicles

D

Which of the following is not an example of a passive-mediated transporter? A) aquaporins B) the Kv ion channel C) GLUT1 D) lactose permease E) none of the above

D

Which of the following is true about membrane proteins embedded within the lipid bilayer? A) An increased temperature of the bilayer decreases the rate of transverse diffusion of the membrane protein. B) They undergo transverse diffusion approximately every 5 seconds at body temperature. C) They undergo transverse diffusion readily at body temperature unless their movement is restricted by other cellular components. D) As the temperature decreases, lateral diffusion of the membrane protein is restricted in bilayers with lipids which have longer chain fatty acids and fewer double bonds. E) Lateral diffusion of the membrane protein occurs independent of bilayer composition and temperature.

D

Which of the following is true about the (Na+-K+)-ATPase transporter? A) Three potassium ions bind to the cytostolic face of the transporter in the E1 state. B) GTP binds to it and is hydrolyzed to form GDP and a high energy phosphorylated glutamyl residue. C) Formation of the high-energy phosphorylated glutamyl residue triggers a conformational shift from the E1 form to the E2 form. D) Phosphate hydrolysis of the E2 state releases potassium ions to the cytosol and results in rearrangement to the E1 state. E) All of the above correctly describe this transporter.

D

Which of the following is true regarding crystalline proteins? A) Many crystallized enzyme proteins remain catalytically active. B) The diffractive pattern observed during X-ray exposure to the crystal can be used to calculate the electron density map of the crystalline protein. C) The larger region indicating electron density with in the electron density map, the more accurate the structure determination. D) A and B are true. E) A, B, and C are true.

D

Which of the following processes would yield and increase in rate? A) the proximity of the reacting groups B) the rotational motions of the substrates and catalytic groups C) the orientations of the substrates and catalytic groups D) all of the above E) none of the above

D

Which of the following segments of the integral membrane protein glycophorin most likely contains the membrane-spanning sequence? A) LSTTEVAMHTTTSSSVSKSY B) SQTNDTHKRDTYAATPRA C) VSEISVRTVYPPEEETGE D) ITLIIFGVMAGVIGTILLI E) YGIRRLIKKSPSDVKPLP

D

Which of the following sequences represents a recognition site for N-linked glycosylation where X is any amino acid except Pro? A) Gln—X—Ser B) His—X—Ser C) Arg—X—Ser D) Asn—X—Ser E) Asp—X—Ser

D

Which of the following statements about actin is not true? A) Actin is the most abundant cytoplasmic protein in many cell types. B) Actin forms microfilaments in many cell types. C) Actin plays an important role in endocytosis. D) Actin is present only as monomers in nonmuscle cells. E) Actin filaments are dynamic, they grow at one end and they lose subunits at the other end.

D

Which of the following statements about the symmetry model of allosterism is NOT true? A. The protein is an oligomer of symmetrically (or pseudo-symmetrically) related subunits B. The oligomer can exist in two conformational states, which are in equilibrium C. The ligand can bind to a subunit in either conformation D. Ligand binding shifts the equilibrium to the weak affinity state of all subunits E. The molecular symmetry of the protein is conserved during the conformational change

D

Which of the following statements applies to all artificial sweeteners? A) Artificial sweeteners cannot be readily metabolized. B) Artificial sweeteners are peptides and provide important amino acids. C) Artificial sweeteners have fewer calories than sucrose. D) Artificial sweeteners are much sweeter than sucrose. E) all of the above

D

Which of the following statements is true regarding collagen? A) The inability to hydroxylate proline results in the inability to synthesize collagen. B) The α helical structure is ideal for intertwining 3 filaments. C) Hydrogen bonds between the ─OH groups of Hyp residues stabilize the helix. D) The requirement for glycine every 3rd amino acid is essential for the triplet helix formation. E) On average, there is one proline for every hydroxyproline.

D

Which of the following statements is true regarding ion channels? A) Protein structure studies indicate a flexible pore size capable of transporting ions of varying size. B) Ions require waters of hydration for sufficient passage through the entire channel. C) Ion channels maintain sodium and potassium ion concentrations that are greater in the extracellular fluid than in the cytosol. D) Channel rigidity minimizes energy states for appropriately sized ions. E) None of the above is true regarding ion channels.

D

Which of the following structural proteins has the greatest elasticity? A) αkeratin B) β ketatin C) collagen D) pleated collagen E) A and B are equal

D

Which of the following substances cannot be used to cleave peptide bonds in polypeptides? A) trypsin B) cyanogen bromide C) endopeptidases D) 2-mercaptoethanol E) pepsin

D

Which of the statements about muscle contraction is not true? A) During muscle contraction the sarcomere becomes shorter. B) During muscle contraction the I band becomes shorter. C) During muscle contraction the H zone becomes shorter. D) During muscle contraction the A band becomes shorter E) During muscle contraction the distance between the Z disk and the M disk becomes shorter.

D

Which of the transporters listed below differs from the others? A) (Na+-K+)-ATPase B) Na+-glucose transporter C) lactose permease D) KcsA E) Ca2+-ATPase

D

Which of these amino acid groups would not make a good nucleophilic catalyst? A) amino B) sulfhydryl C) imidazole D) methyl E) hydroxyl

D

Which of these amino acid groups would not make a good nucleophilic catalyst? A. amino B. sulfhydryl C. imidazole D. methyl E. hydroxyl

D

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. A) I, II, III, IV B) I, III C) I D) III E) IV

D

Which type of catalysis may be carried out using redistribution of electron density to facilitate the transfer of a proton? I. proximity II. acid-base III. covalent IV. strain A) I B) II C) III D) II, III E) II, IV

D

Which would be most likely to be found in the membranes of mouse brain cells? A) cholesterol B) glycerolphospholipids C) GM1, GM2, or GM3 D) all of the above E) none of the above

D

While fatty acids are most often formed by the condensation of __-carbon units, isoprenoids are assembled from __-carbon units. A) 5, 3 B) 4, 2 C) 2, 3 D) 2, 5 E) 3, 4

D

Why can histidine NOT act as a base in the lysosome (an organelle where the pH is close to 4.5)? A) Histidine has a positive charge at pH 4.5. B) Histidine has a side chain pK close to 6. C) Histidine would be protonated at pH 4.5. D) All of the above are correct. E) None of the above is correct.

D

Zymogens are not enzymatically active because A) the active site amino acids have been mutated. B) they have not yet bound the proper cofactor. C) their environment has the wrong pH. D) they are not yet shaped such that essential proximity and orientation catalysis can occur. E) None of the above is correct.

D

Which of the following statements does not apply to the K value in the equation for the oxygen binding curve of myoglobin? A) It is numerically equal to p50. B) It is defined as that oxygen partial pressure at which half of the oxygen binding sites are occupied. C) It is a measure of the affinity of myoglobin for oxygen. E) It is the value of pO2 at which Y = 0.5.

D) If Y > K, then myoglobin is less than 50% saturated with oxygen.

The disulfide bond betwee two cysteine molecules A) is a peptide bond. B) is an ionic interaction that is stable at physiological pH. C) is a covalent bond formed by oxidation. D) is a hydrogen bond between the two sulfhydryl groups. E) is a dipole-dipole interaction.

D) Is covalent bond formed by oxidation

Mutations leading to changes that can be inherited by the next generation have to be introduced into at the ___ level

DNA

in 1944 Avery, MacLeod, and McCarty did experiments with Dipolococcus pneumonia that proved that

DNA can permanently transform a non-pathogenic strain into a pathogenic strain

Why is the decreased affinity of fetal hemoglobin for BPG advantageous?

Decreased BPG binding biases the fetal hemoglobin toward the R state.

At a pH above the pKa, the phenol group of tyrosine is

Deprotonated

The side-chains of amino acids have

Different pKas in peptides as compared to the free amino acids

A patient has low levels of potassium. Which of the following could be affected? I. levels of calcium available for cardiac muscle II. amount of glucose transported through the intestinal lumen III. amount of lactose metabolized IV. chloride ion transport may slow A) I, IV B) II, IV C) II, III D) II, IV E) I, II, IV

E

Alterations in genetic information can be caused by A) mistakes made during replication. B) faulty recombination. C) transposition of genes. D) damage caused by chemicals or radiation. E) all of the above

E

An extremely efficient enzyme called "efficase" catalyzes the conversion of "A" to "B." A researcher decides to mutate the enzyme in order to try to improve its performance. Following active site mutations, a significant reduction in the value of KM and Vmax was observed. Which of the following may have occurred? A) The affinity of the enzyme for the substrate was increased to a point which did not favor propagation (continuation) of the reaction. B) The decrease in Vmax was not related to the decrease in KM. C) If the reaction was first-order, the change in KM cannot have affected Vmax. D) The stability of E+S (E+A as written above) was increased, thereby increasing the KM. E) The reverse reaction (breakdown of EA to E+A) was favored, slowing the Vmax.

E

Compounds that function as "mixed inhibitors" I. interfere with substrate binding to the enzyme II. bind to the enzyme reversibly III. can bind to the enzyme/substrate complex A. I B. II C. III D. II & III E. I, II, & III

E

Compounds that function as "mixed inhibitors" I. interfere with substrate binding to the enzyme. II. bind to the enzyme reversibly. III. can bind to the enzyme/substrate complex. A) I B) II C) III D) II, III E) I, II, III

E

Consider the Schiff base formation reaction discussed in the catalytic mechanisms section of the chapter. What would probably happen if the carboxylate group was stabilized by a nearby positive charge? A) The Schiff base would donate a lone pair of electrons to the substrate. B) The Schiff base would form prior to decarboxylation. C) The reaction would proceed with nucleophilic attack on the enzyme by the electrophilic substrate. D) All of the above would be possible given the discussed mechanism with a stabilized carboxyl group. E) None of the above is plausible considering the discussed mechanism with a stabilized carboxylate group.

E

Cooperativity is an allosteric effect that involves: A. Structural interactions between two or more subunits B. Binding of a molecule to an allosteric effector C. Binding of a substrate to an allosteric site D. Binding of a physiological ligand to its complimentary site E. Both A and D are correct

E

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? A) The D-galactose derivative occupies some of the available binding sites. B) Given the same concentration of glucose available, the number of binding sites with D-glucose present would decrease. C) Given the same concentration of glucose, the rate of D-glucose flux would remain the same with the D-galactose derivative added. D) 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. E) All of the above are true.

E

Double stranded DNA molecules can be cleaved at specific recognition sites by A) RNA polymerase. B) DNA ligase. C) DNA polymerase. D) reverse transcriptase. E) Type II restriction endonucleases.

E

During muscle contraction myosin heads A) walk along thick filaments toward the M disk. B) walk along thick filaments toward the Z disk. C) walk along thin filaments toward the M disk. D) walk along the thin filaments toward the H zone. E) walk along the thin filaments toward the Z disk.

E

Enzyme activity in cells is controlled by which of the following? I. covalent modifications II. modulation of expression levels III. feedback inhibition IV. allosteric effectors A) I B) II C) III D) III, IV E) I, II, III, IV

E

Fourth-order reactions. A) have three or more sequential rate determining steps. B) require a 'Ping Pong' mechanism. C) are best analyzed using Lineweaver-Burk plots. D) exist only when enzymatically catalyzed. E) none of the above.

E

Glycoproteins A) are only found in bacteria. B) are extremely homogeneous. C) are typically less than 1% carbohydrate by weight. D) are assembled under strict genetic control. E) exhibit microheterogeneity.

E

Muscle contraction is directly caused by A) structural changes in actin. B) structural changes in myosin. C) structural changes in the A band. D) structural changes in the Z disk. E) None of the above is correct.

E

Native protein purifications often require multiple reaction steps in order to purify the protein of interest from other proteins. One method used for protein separation in purification procedures is a change from water to an organic solvent. Which of the following would be accomplished by this solvent change? A) Proteins with hydrophobic groups on the interior would maintain their native state. B) Proteins with hydrophilic groups on the exterior would denature and likely precipitate. C) Proteins with exposed hydrophobic groups would maintain their structure and remain in solution. D) Both A and B would occur. E) Both B and C would occur.

E

Noncovalent forces that stabilize protein structure include all of the following except __________. A) the hydrophobic effect B) salt bridges C) electrostatic interactions with metal ions D) hydrogen bonding E) disulfide bridges

E

Noncovalent forces that stabilize protein structure include all of the following except _______________. A. the hydrophobic effect B. salt bridges C. electrostatic interactions with metal ions D. hydrogen bonding E. disulfide bridges

E

Nucleotides play a central role in living organisms because: (A) they mediate transport of energy within the cell (B) They are involved in oxidation-reduction reactions (C) They are involved in intracellular signaling (D) they functions as building blocks for nucleic acids (E) all of the above

E

One of the reasons the primary structure is important for a protein is that it determines the ________________ the molecule adopts in aqueous solutions. A. Secondary structure B. Tertiary structure C. Solution shape D. Complimentary binding sites E. All of the above are true

E

Pseudo-first-order reaction kinetics would be observed for the reaction A + B C A) if [A] or [B] > [C]. B) if [C]>[A] and [C]>[B]. C) if [A] or [B] = 0. D) if [C] = 0. E) none of the above

E

Recombinant DNA technology can be used for A) constructing mutant proteins. B) the industrial production of useful proteins. C) producing transgenic organisms. D) correcting genetic defects. E) all of the above

E

Ribosomes use L amino acids to synthesize proteins. These amino acids are called "L" because A) they are chiral. B) they turn polarized light to the left. C) they are all (S)-amino acids. D) they are all (R)-amino acids. E) none of the above

E

The _________ model describes the cell membrane as an assortment of integral proteins suspended freely in a lipid bilayer. A) FRAP B) cellular fusion C) transverse diffusion D) lateral diffusion E) fluid mosaic

E

The activity of protein kinase A is affected by which of the following? I. caffeine II. levels of cAMP III. phosphodiesterases IV. cholera toxin A) I only B) II only C) I, IV D) I, II, III E) I, II, III, IV

E

The rearrangement of R, high affinity state hemoglobin to the T, low affinity state A. occurs in each protein subunit independently when its heme binds oxygen B. requires the binding of at least 3 oxygen molecules C. increases the ion pairing interactions of the C-terminal amino acids D. involves the movement of the Fe (II) into the heme plane E. None of the above are true

E

The structures/bonds listed below that are considered a high energy substance in cells are: I. phosphoesters II. amides III. phosphoanhydrides IV. thioesters A. II & IV B. I, II, III, & IV C. I & III D. I & II E. III & IV

E

The tripeptide alanyllysylaspartate contains four ionizable groups with pKas of 2.0, 3.9, 9.9, and 10.5. Calculate the pI for this molecule. A) 3.0 B) 6.0 C) 6.2 D) 10.2 E) None of the above

E

Unsaturated fatty acids: A) are commonly found in plants and animals B) usually contain a double bond with cis stereochemistry C) sometimes contain multiple double bonds D) have lower melting points than the analogous saturated fatty acids E) all of the above

E

Which of the following amino acids has a charged polar side chain at pH 7.0? A) Leu B) Ala C) Met D) Trp E) Glu

E

Which of the following amino acids has a charged polar side chain at pH 7.0? A. Leu B. His C. Met D. Trp E. Asp

E

Which of the following are produced in the adrenal cortex? I. Glucorticoids II. mineralcorticoides III. androgens IV. estrogens A) I only B) I, II C) II only D) II, IV E) I, II, III, IV

E

Which of the following changes would not alter the functional characteristics of α keratin? A) Increasing the number of residues per turn to 4.1 while maintaining the same amino acid sequence. B) Substitution of a hydrophilic amino acid for a hydrophobic amino acid at position a and d of the 7-residue pseudorepeat. C) Decreasing the number of cysteine amino acids within each protofilament. D) Changing the environment surrounding the protein to one that is more reductive. E) All of the above would alter the functional characteristics of keratin.

E

Which of the following correctly describes the usefulness of SNAREs? I. They are essential for proper post-translation processing. II. They are a critical element in the function of the secretory pathway. III. They are effective at overcoming electrostatic repulsion between vesicle membranes. IV. They facilitate anchoring between vesicle membranes. A) I, II, III, IV B) II, III C) III D) IV E) III, IV

E

Which of the following correctly describes the usefulness of SNAREs? I. They are essential for proper post-translation processing. II. They are a critical element in the function of the secretory pathway. III. They are effective at overcoming electrostatic repulsion between vesicle membranes. IV. They facilitate anchoring between vesicle membranes. A) I, II, III, IV B) II, III C) III D) IV E) III, IV

E

Which of the following is a disaccharide? A) amylose B) saccharin C) aspartame D) amylopectin E) none of the above

E

Which of the following is an example of a heteropolysaccharide? A) cellulose B) chitin C) starch D) glycogen E) hyaluronic acid

E

Which of the following statements about the symmetry model of allosterism is not true? A) the protein is an oligomer of symmetrically (or pseudosymmetrically) related subunits. B) the oligomer can exist in two conformational states, which are in equilibrium. C) the ligand can bind to a subunit in either conformation. D) the molecular symmetry of the protein is conserved during the conformational change. E) none of the above.

E

Which of the following statements describes integral membrane proteins? I. They protect the contents of the cell from hypertonic extracellular fluid. II. They are easily dissociated from the membrane by changes in pH or high salt concentration. III. They are held tightly in place by hydrophobic effects between the membrane lipid layer and hydrophobic amino acids. A) I, II, III B) I, III C) I D) II E) III

E

Which of the following tripeptides carries a NET positive charge at pH 7.0? A) Ala-Thr-Asn B) Gln-Val-Ser C) Arg-Glu-Met D) Pro-Ile-Leu E) Leu-Lys-Gly

E

Which of the following tripeptides carries a net positive charge at pH 7.0? A. Ala-Thr-Asn B. Gln-Val-Ser C. Arg-Glu-Met D. Pro-Ile-Leu E. Leu-Lys-Gly

E

Which of the following tripeptides would be expected to be the most hydrophobic? A. PFE B. LFE C. PYE D. AFD E. LFQ

E

Which of the statements about muscle contraction is correct? A) During muscle contraction the sarcomere becomes shorter. B) During muscle contraction the I band becomes shorter. C) During muscle contraction the H zone becomes shorter. D) During muscle contraction the distance between the Z disk and the M disk becomes shorter. E) All of the answers above are correct.

E

Which of these are commonly used to cleave peptide bonds in polypeptides? A) 2-mercaptoethanol (β-ME) B) dansyl chloride C) iodoacetate D) sodium dodecyl sulfate E) trypsin

E

Which of these characteristics does not describe the β sheet? A) Amino acid side chains are located both above and below the sheet. B) β sheets have a pleated edge-on appearance. C) They can exist in either parallel or antiparallel configurations. D) The sheets contain as few as two and as many as 22 polypeptide chains. E) Parallel β sheets containing fewer than five chains are the most common

E

Which statement about actin is correct? A) Actin is expressed only in muscle. B) Actin is expressed at low levels in most cells. C) No known function has been described for actin in nonmuscle cells. D) Nonmuscle cells only contain G actin. E) Actin is the most abundant cytoplasmic protein in many cell types.

E

Which statement about antigen-binding sites in antibodies is false? A) An antigen-binding site on an IgG is formed by the amino-terminal ~110 amino acids of a light chain and the amino terminal ~110 amino acids of a heavy chain. B) An antigen-binding site on an IgG is formed by the variable region of a light chain and the variable region of a heavy chain. C) The antigen-binding site is composed of two Ig folds. D) Antigen-binding specificity is determined by the sequences of the hypervariable sequences in both the light chain and the heavy chain. E) Antigen binding specificity is determined exclusively by the sequences in the carboxy-terminal ~110 amino acids in the light chain and the heavy chain.

E

Which statement about insulin is correct? A) Insulin is composed of two polypeptides, the A chain and the B chain. B) Insulin contains an intrachain disulfide bond. C) Insulin contains interchain disulfide bonds. D) The A chain and the B chain of insulin are encoded by a single gene. E) All of the above are correct.

E

Which statement about myosin is not true? A) Myosin is a heterohexamer. B) Myosin contains two globular heads. C) Myosin contains six different polypeptides D) Myosin aggregates to form thick filaments E) All of the answers above are true of myosin

E

Myoglobin's primary physiological role is to facilitate oxygen ________.

E) Diffusion

Phosphoric acid is a polyprotic acid, with pK values of 2.14, 6.86, and 12.38. Which ionic form predominates at pH 7.3?

HPO4^(2-)

During the T to R conformational shift, Fe(II) drags the F-helix via a bond to the side chain of ________.

His F8

___________ is an example of a very slowly evolving protein.

Histone H4

Which of the characteristics of collagen structure listed below contrubute to the tensile strength of collagen? I. Collagen is made up of a triplet helix where 3 left-handed helices twist together in a right handed sense. II. Collagen includes at repeating sequence of amino acids with glycine every 3 amino acids in a helix with about 3 amino acids per turn. III. The three left-handed helices are staggered to allow close packing between glycine residues and rigidity from the bulky and inflexible proline/hydroxyproline.

I, II, and III

An enzyme is near maximum efficiency when

Kcat/Km is diffusion controlled

All amino acids derived from proteins have the same stereochemical conformation a

L-glyceraldehyde

All amino acids derived from proteins have the same stereochemical conformation as

L-glyceraldehyde

Some abnormal hemoglobins have Hill coefficients that are ______ that of normal hemoglobin, indicating that their ability to bind oxygen cooperatively has been compromised.

Less than

The formation of a dipeptide from two amino acids involves...

Loss of water

Inside our cells, free nucleotides are almost always associated with

MG²⁺ counterions

Either dansyl chloride or Edman's reagent can be used to identify the ______ of a protein.

N-terminal amino acid

In the intestinal epithelium, glucose enters the cell in symport with ______, which is subsequently ejected by ________.

Na+; the Na+/K+ pump

Protein dynamics is a field of study that examines the movements with in a protein. Which type of protein structure determination would be most useful to study this type of change?

Nuclear Magnetic Resonance (NMR)

When solving a protein structure using X-ray crystallography, the crystallographer generates a 3-D grid called an electron density map based on the observed diffraction pattern. The higher the resolution, the more detailed the electron density map and therefore the easier it is to identify what atoms (and therefore what amino acids) are in a given position. Based on the three choices below, in which of the following groups could the two of amino acids be the easiest to differentiate regardless of resolution? I. Leucine vs. Isoleucine II. Phenylalanine vs. Alanine III. Glutamate vs. Glutamic acid

Only those in group II could be differentiated

Nucleotides in a DNA molecule are linked together through

Phosphodiester bonds

A two-substrate enzymatic reaction in which one product is produced before the second substrate binds to the enzyme has a ______ mechanism.

Ping Pong

Small circular DNA molecules used to carry foreign DNA fragments are called ___

Plasmids

______ are bacterial proteins forming a β barrel structure with a central aqueous channel.

Porins

What type of gradient is required for efficient lactose transport in E. coli?

Proton

at a pH below the pKa, the ε-amino group of lysine is

Protonated

Cytosine, uracil, and thymine are derivatives of ___

Pyrimidine

Sickle cell hemoglobin does not form fibers in the ______ form

R

The Na+-glucose transport system requires generation of a gradient by another transporter and is therefore an example of ______ transport.

Secondary active

RNA occurs primarily as single stranded molecules that can give rise to ___ structures

Stem-loop

Hemoglobin's p50 value is about ______ as great as myoglobin's p50 value.

Ten Times

Myoglobin and a single chain of hemoglobin have similar ______ structures

Tertiary

What is the primary physiological function of myoglobin in most mammals?

The primary physiological function of myoglobin in most mammals is to increase the solubility for O2 in muscle tissue and thereby increasing the diffusion rate.

Ribosomes use L amino acids to synthesize proteins. These amino acids are called "L" because

They have a configuration of groups around the Cα that an be related to the configuration of groups around the asymmetric carbon in L-glyceraldehyde

______ metals are the most common metallic enzyme cofactors.

Transition

In sickle-cell anemia, the negatively charged glutamic acid residue is replaced by the neutral amino acid ____________.

Valine

Max Perutz's investigation of the structure of hemoglobin primarily utilized_____.

X-ray crystallography

a Genomic library is

a collection of cloned DNA fragments representing all of an organisms DNA

DNA sequencing by chain-termination method utilizes DNA polymerase I to make a complementary copy of the target or template DNA molecule. A reaction with a 20 bp template and a dideoxyadenosine nucleotides as terminators results in the production of a 5 bp fragment. Based on this result, we can conclude that the template contains

a thymine at position 16

The supersecondary structure that forms DNA binding elements are:

alpha/turn/alpha supersecondary structure

A chemical feature of linear proteins is:

amino and carboxy termini.

The characteristic chemical construction of membrane lipids are ______.

amphiphiles

Both α(1→4) and α(1→6) bonds can be found in the plant product______.

amylopectin

In molecular cloning, transformed organisms must be identified. One common method for accomplishing this involves the inclusion of ___ in the plasmid

an antibiotic resistance gene

If the gene for myoglobin is "knocked out" in mice, the mice:

appear normal, with lighter colored muscle tissue

Eicosanoids are 20-carbon compounds derived from ______.

arachidonic acid

Typically, modified amino acids, those with side chain modifications that are present in proteins

are formed by modification of standard side chain residues after the protein is synthesized

The alpha/beta barrel is composed of this supersecondary structure:

beta-alpha-beta

The E+S→ E+P reaction is ______.

bimolecular

BPG stands for

bisphosphoglycerate

The pK1, pK2, and pKR of the amino acid histdine are 1.8, 9.3, and 6.0, respectively. The pK1, pK2, and pKR of the amino acid arginine are 1.8, 9.0, and 12.5, respectively. You have a mixture of histidine and arginine, how would you try to separate these two amino acids?

cation exchange chromatography at pH 9

An increase in pCO2 causes hemoglobin's affinity for oxygen to ___

decrease

An increase in pCO2 causes hemoglobin's affinity for oxygen to ______________.

decrease

The ______ sugars are monosaccharides in which a hydroxyl group is replaced with a hydrogen atom.

deoxy

In living organisms, genetic information is most often formed in the form of

deoxyribonucleic acid

If an enzyme-catalyzed reaction has a low rate at low pH, and high rate at higher pH, this implies that a group on either the enzyme or the substrate must be _________________ for an efficient reaction.

deprotonated

The ability of receptors to adapt to long-term stimulation by responding to changes in stimulation levels rather than absolute values of stimulation is called

desensitization

Proteins are often constructed from multiple segments of 40-200 amino acid residues, commonly called

domains

Axs refers to

either aspartic acid or asparganine

Curved arrows are conventionally used to illustrate the movement of

electron pairs

Enzymes that hydrolyze the internal peptide bonds (not the peptide bonds of the terminal amino acids) of a protein are classified as

endopeptidases

Enzymes that hydrolyze the internal peptide bonds (not the peptide bonds of the terminal amino acids) of a protein are classified as:

endopeptidases.

Which cellular compartment or organelle is involved in the synthesis of lipids?

endoplasmic reticulum

Evolutionary processes have

enhanced efficient folding pathways.

If antibodies to the protein being assayed are available, a(n) ______ can be carried out.

enzyme-linked immunosorbent assay

Glycosphingolipids with complex carbohydrate head groups that often serve as cellular receptors are ______.

gangliosides

Examine the three sequences below for collagen-like proteins and their melting temperatures (Tm). (Note: Flp = fluoroproline; Hyp = hydroxyproline) Based on this data, what is the most important feature in determining the strength of the collagen protein? 1) ...-Pro-Hyp-Gly-Pro-Hyp-Gly-Pro-Hyp-Gly-... Tm=60oC 2) ...-Pro-Flp-Gly-Pro-Flp-Gly-Pro-Flp-Gly-... Tm=78oC 3) ...-Gly-Pro-Thr-Gly-Pro-Thr-Gly-Pro-Thr-... Tm=30oC

inductive effect

A release of _____ would result in the stimulation of the liver to synthesize glycogen.

insulin

The β cells of the pancreas islets of Langerhans secrete ______ in response to ______ glucose levels in the muscle and/or adipose tissue.

insulin, elevated

Reaction that is first order with respect to A and B

is dependent on the concentration of A and B.

The transition state of an enzyme and substrate reaction

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

The catalytic efficiency of an enzyme can never exceed

k1

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

k2 << k-1

An enzyme is near maximum efficiency when

kcat/KM is near 10^8 M^-1 x s^-1

________ is a fibrous protein that contains a hydrophobic amino acid approximately every 4 residues which forms an α helix with one hydrophobic side.

keratin

The disaccharide commonly found in dairy products is ______.

lactose

For efficient nucleophilic catalysis, a group such as the sulfhydryl on a cysteine residue must be able to form a good ______, in addition to being a good nucleophile.

leaving group

By convention, the sequence of nucleotide residues in a nucleic acid is written ___ starting with the ___ end

left to right using the 5' end

Proteins are synthesized in vivo by the translation of _______

mRNA

Which of the following amino acid residues would provide a side chain capable of increasing the hydrophobicity of a binding site? A. tyrosine B. lysine C. methionine D. arginine E. serine

methionine

Globules of up to several thousand amphiphilic molecules arranged with the hydrophilic groups on the surface and the hydrophobic groups buried in the center that form in water are called

micelles

In vivo protein folding is often assisted by ______.

molecular chaperones

The energy needed to drive muscle contraction comes from ATP hydrolysis that is carried out by

myosin heads

An endergonic reaction with a ____________ H and a ___________ S can be changed into an exergonic reaction by decreasing the temperature.

negative, negative

Metal ion cofactors can coordinate to the substrate or stabilize electrostatic effects by enabling proper ______in the active site.

orientation

Metal ion cofactors offer various ______ states that allow enzymes to accomplished oxidation reduction reactions.

oxidation

Enzyme X catalyzes the addition of a hydroxyl group to substrate Y. In the process a metal cofactor is reduced and then reoxidized. What class of enzyme is X?

oxidoreductase

Hemerythrin and hemocyanin are:

oxygen transport proteins found in invertebrates.

The ionization of amino acids depends on the pH and the pKas of the ionizable groups. The pK1 and pK2 for the amino acid (Asn shown in previous question) are 2.1 and 8.8, respectively. At what pH is the amino acid ionized predominantly as shown?

pH 1.0

In general, proteins are least soluble in water when the pH is close to the ______.

pI (that's an uppercase i, not an l)

A glycerophospholipid in which the C1 substituent linkage forms a vinyl ether that is more easily oxidized than its ester counterpart is called a ______.

plasmalogen

The low pH found in the gut can enhance the digestibility of dietary protein by causing ___.

protein denaturation

Lactose permease uses a ___________ gradient generated ______ to cotransport lactose across the cell membrane.

proton; via oxidative metabolism

For a reaction A + B → C, if the concentration of B is much larger than A so that [B] remains constant during the reaction while [A] is varied, the kinetics will be

pseudo-first-order

Myoglobin and hemoglobin do NOT share similar _____________ structures.

quaternary

Biological systems usually produce a single enantiomer, whereas chemical synthesis produces a ___

racemic mixture

Which of the following 'assays' would be most specific for a particular protein?

radioimmunoassay

A saccharide that has free aldehyde group is called a(n) _____________.

reducing sugar

Repeating values of Φ and ψ make up predictable orientations of amino acid with a chain, this predictable orientation forms ____________.

regular secondary structure

Repeating values of φ and ψ make up predictable orientations of amino acid with a chain, this predictable orientation forms___________.

regular secondary structure

The myelin sheath contains high levels of ______.

sphingomyelins

An example of nonmediated transport is ______.

simple diffusion

Glucose, with its four chiral carbon atoms, has ______ possible stereoisomers.

sixteen

Gel electrophoresis generally separates nucleic acids on the basis of

size

A method to separate proteins based on the size in its native state is ______________ chromatography:

size-exclusion

RNA occurs primarily as single stranded molecules that can give rise to _____________ structures.

stem-loop

In a ______, the φ and ψ angles of the peptide backbone would orient atoms closer than their van der Waals distance.

sterically forbidden conformation

Members of the ______ family have four fused, nonplanar rings and a C3-OH group.

sterol

Which of the following sugars is not a reducing sugar?

sucrose

One of the reasons the primary structure is important for a protein is that it determines the ______ the molecule adopts in aqueous solutions.

three-dimensional shape

DNA sequencing using the Sanger method requires

template, primer, DNA polymerase, mRNA, dNTPs, and ddNTPs

The overall arrangement of the regular structural elements such as the α helix and the β sheet in the protein are considered the protein's ______.

tertiary structure

The Second Law of Thermodynamics states:

that spontaneous processes are characterized by the overall conversion of order to disorder

For β-sheets, the terms 'parallel' and 'antiparalllel' refer to ___________.

the 'direction' of the associated peptide strands

The Bohr effect refers to

the decrease in affinity of Hb for O2 when the pH goes down

O-linked oligosaccharides are commonly attached to the -OH group of _____.

threonine

Protein kinases are involved in

the phosphorylation of a wild variety of proteins

If A + B --> P is a zero-order reaction, the rate is dependent on __________________.

the rate constant

If A→B is a zero-order reaction, the rate is dependent on ______.

the rate constant

At substrate concentrations much lower than the enzyme concentration,

the rate of reaction is expected to be directly proportional to substrate concentration.

Paralogous genes are

the results of gene duplication.

Which of the following bases is NOT present in RNA?

thymine - know structure!

Enzymes catalyze reactions by:

tight binding to the transition state

Knowledge about the tautomeric forms of the bases of nucleic acids is needed

to understand H-Bonding between the complementary bases

Genomic DNA is ___, resulting in the production of ___

transcribed, mRNA

Genomic DNA is __________, resulting in the production of ____________.

transcribed, mRNA

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?

transition metal cations

______ are the lipids that are most abundant even though they are not components of membranes.

triacylglycerols

In the tripeptide Trp-Val-Phe, the N-terminal residue is ___

tryptophan

The pK 1 , pK 2 , and pK R for the amino acid lysine are 2.2, 9.1, and 10.5, respectively. At pH 1.0, lysine would be charged predominantly as follows:

α-carboxylate 0, α-amino +1, ε-amino +1, net charge +2

The pK 1 , pK 2 , and pK R for the amino acid histidine are 1.8, 9.3, and 6.0, respectively. At pH 4.0 would be charged predominantly as follows:

α-carboxylate −1, α-amino +1, imidazole +1, net charge +1

The pK 1 , pK 2 , and pK R for the amino acid cysteine are 1.9, 10.7, and 8.4, respectively. At pH 5.0, cysteine would be charged predominantly as follows:

α-carboxylate −1, α-amino +1, sulfhydryl 0, net charge 0

The pK 1 , pK 2 , and pK R for the amino acid glutamate are 2.1, 9.5, and 4.1, respectively. At pH 11.0, glutamate would be charged predominantly as follows:

α-carboxylate −1, α-amino 0, γ-carboxylate −1, net charge −2