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What is the reason for the existence of the hydrophobic effect?
the inability of charged molecules to dissolve in water
the tendency of polar molecules to self-associate in the presence of an aqueous solution
the tendency of water molecules to make a bond with hydrophobic proteins
the property of nucleic acids to dissolve in water
the tendency of nonpolar molecules to self-associate in the presence of an aqueous solution
the tendency of nonpolar molecules to self-associate in the presence of an aqueous solution
Which statement about interactions in the formation of the DNA double helix is INCORRECT?
Phosphate groups repel one another resulting in the helical shape of the DNA molecule.
Ionic bonds between oppositely charged functional groups are responsible for the formation of the double helix.
Van der Waals interactions are nearly optimal in a double-helical structure.
Nonpolar surfaces of the bases are moved into contact with each other due to a more complete base stacking.
Surface complementarity maximizes the formation of hydrogen bonds and van der Waals interactions while minimizing the nonpolar surface area exposed to the aqueous environment.
Ionic bonds between oppositely charged functional groups are responsible for the formation of the double helix.
What is FALSE regarding the laws of thermodynamics?
Energy can be neither created nor destroyed.
Total entropy of the universe is always decreasing as continuous formation of ordered structures results in less disorder in the universe.
The local decrease in enthalpy will increase the entropy of the surroundings.
Heat is a manifestation of the kinetic energy associated with the random motion of molecules.
Ordered structures can be formed within a system only if the entropy of the surroundings will proportionally increase.
Total entropy of the universe is always decreasing as continuous formation of ordered structures results in less disorder in the universe.
How was the fact that formation of the double helix does not violate the second law of thermodynamics experimentally confirmed?
in a water bath monitoring the change in heat to sustain constant Gibbs energy in the bath
in a water bath monitoring the change in heat to sustain a constant temperature in the bath
in a water bath monitoring the change in entropy to sustain a constant temperature in the bath
in a water bath monitoring the change in entropy to check whether it remains constant
in a water bath monitoring the free energy to sustain constant heat content in the bath
in a water bath monitoring the change in heat to sustain a constant temperature in the bath
The structure of DNA described by Watson and Crick includes:
a sugar-phosphate backbone that lies on the inside of the helix.
base pairs that are stacked on the outside of the triple helix.
base pairs that are stacked on the inside of the double helix.
a triple helix.
a triple helix composed of three intertwined strands.
base pairs that are stacked on the inside of the double helix.
What did Watson and Crick suggest to be significant about the base-pairing found in the DNA helix?
The DNA sequence was determined by the sequence of RNA.
It allowed the DNA to twist in a helix.
Only one of the strands could act as a template.
The mechanism of copying genetic information was apparent from the structure of the double helix.
The DNA could be circular.
The mechanism of copying genetic information was apparent from the structure of the double helix.
What gives proteins such a dominant role in biochemistry?
ability to self-replicate
ability to act as a blueprint
ability to spontaneously fold into complex three-dimensional structures
usage of 40 different building blocks
rigidity of the peptide backbone
ability to spontaneously fold into complex three-dimensional structures
Order the type of interactions by the bond strength in descending value.
van der Waals interactions, covalent bonds, hydrogen bonds
hydrophobic interactions, hydrogen bonds, electrostatic interactions
covalent bonds, hydrogen bonds, van der Waals interactions
hydrogen bonds, covalent bonds, van der Waals interactions
covalent bonds, van der Waals interactions, hydrogen bonds
covalent bonds, hydrogen bonds, van der Waals interactions
In DNA replication, the new strand always grows in the _____ direction.
5’- 3’
Under physiological conditions, most DNA is in the form of a _______ form helix.
Z
A
D
B
B
What is the technique on which the Watson–Crick model was based?
radioactive labeling
X-ray diffraction
electron microscopy
absorbance spectrophotometry
spectrofluorometry
X-ray diffraction
Although the right-handed double helix is the most well-known DNA structure, DNA can also form:
branched chains.
straight chains.
left-handed helices.
tight globules.
triple strands.
left-handed helices.
What is NOT a key property that enables proteins to participate in a wide range of functions?
Proteins are linear polymers built of different amino acids.
Some proteins are quite rigid, whereas others display considerable flexibility.
Proteins can interact with one another and with other biological macromolecules to form complex assemblies.
Proteins have a high molecular weight.
Proteins contain different functional groups.
Proteins have a high molecular weight.
What does an α-amino acid consist of?
carboxylic acid group, δ carbon, imine radical, hydrogen atom, distinctive R group
carboxylic acid group, ε carbon, nitro group, hydrogen atom
alcohol group, α carbon, amino group, nitrogen atom, distinctive R group, hydrogen atom
carboxylic acid group, α carbon, amino group, hydrogen atom, distinctive R group
carbonyl group, α carbon, amino group, oxygen atom, distinctive R group
carboxylic acid group, α carbon, amino group, hydrogen atom, distinctive R group
In an acidic solution (pH = 1), what is the ionization state of glycine?
The amino group is positively charged ; the carboxyl group is neutral.
The amino group is negatively charged; the carboxyl group is negatively charged.
The amino group is neutral; the carboxyl group is neutral.
The amino group is positively charged; the carboxyl group is positively charged.
The amino group is positively charged; the carboxyl group is negatively charged.
The amino group is positively charged ; the carboxyl group is neutral.
Which amino acid has the one-letter abbreviation K?
lysine
histidine
valine
asparagine
alanine
lysine
What is the amino-terminal residue and what is the carboxyl-terminal residue in the sequence of amino acids Gly-Tyr-Gly-Phe-Leu?
Glycine is N-terminal and leucine is C-terminal.
There are no N-terminal and C-terminal residues in the sequences of amino acids.
Tyrosine is N-terminal and leucine is C-terminal.
Phenylalanine is N-terminal and leucine is C-terminal.
Leucine is N-terminal and glycine is C-terminal.
Glycine is N-terminal and leucine is C-terminal.
Knowledge of the amino acid sequences is important for several reasons. What is NOT one of those reasons?
Knowledge of the sequence of a protein can help to prevent mutations.
Changes in the amino acid sequence can lead to abnormal protein functioning and disease.
Amino acid sequences determine the three-dimensional structures of proteins.
The sequence of a protein reveals much about its evolutionary history.
The sequence of a protein is necessary to determine its function.
Knowledge of the sequence of a protein can help to prevent mutations.
What is the configuration of peptide bonds in proteins?
Almost all peptide bonds are in the cis configuration.
Half of all peptide bonds are in the trans configuration and the other half are in the cis configuration.
Almost all peptide bonds are in the trans configuration.
Approximately one third are in the cis configuration and rest are in the trans configuration.
Approximately one third are in the trans configuration and rest are in the cis configuration.
Almost all peptide bonds are in the trans configuration.
Which amino acid forms disulfide bonds?
serine
cysteine
proline
histidine
methionine
cysteine
What amino acid residue would MOST likely be buried in the interior of a water soluble protein, rather than on the surface?
Ser
Trp
Arg
Asp
Lys
Trp
In lab you explored the structure of lysozyme using computational software. What insight could be gained about the function of lysozyme simply by observing its structure? (Choose all correct responses.)
Delta G of the reaction
location of the active site
rate of the enzyme-catalyzed reaction
catalytic efficiency of the enzyme
amino acids that might be involved in binding the substrate or catalysis
-location of the active site
-amino acids that might be involved in binding the substrate or catalysis
The RNA world hypothesis states that life was based on RNA before DNA-based life evolved. Compare and contrast the structure/function of DNA and RNA. Based on your understanding of the structure/function of RNA compared to DNA, make an argument supporting the RNA world hypothesis. What evolutionary advantage does DNA give to modern living organisms?
It is commonly assumed by beginning science students that formation of hydrogen bonds between complementary bases drives the formation of the double helix. Explain why this is not the case.
A proton exists in a solution as:
H+.
a deprotonated water molecule.
a hydronium ion.
H2O+.
a water molecule.
a hydronium ion.
Which statement is INCORRECT if the buffer capacity is not consumed upon addition of a strong acid to the solution?
Such a buffer is not actually a buffer and cannot mitigate the pH changes.
The pH differs from the pKa value of the buffer's base component.
There are more deprotonated forms of the buffer compound than protonated ones.
There are more protonated forms of the buffer compound than deprotonated ones.
When hydrogen ions are added to this buffer solution they remain free.
There are more deprotonated forms of the buffer compound than protonated ones.
What are the primary chemical components present in a phosphate buffer at pH = 7.4?
H3PO4 and HPO42–
HPO42– and PO43–
H3PO4 and PO43–
H2PO4– and PO43–
H2PO4– and HPO42–
H2PO4– and HPO42–
Choose the correct groups for Thr, Lys, Trp, respectively, on the basis of general chemical characteristics.
positively charged; hydrophobic; polar but not charged
negatively charged; hydrophobic; positively charged
polar but uncharged; negatively charged; hydrophobic
polar but uncharged; positively charged; hydrophobic
positively charged; positively charged; polar but not charged
polar but uncharged; positively charged; hydrophobic
What is the term for the combination helix-turn-helix?
tertiary structure
motif
globular protein
domain
supertetriary structure
motif
What is the simplest sort of quaternary structure?
a tetramer consisting of two identical subunits and diverse subunits
a dimer consisting of two different subunits
a monomer
a dimer consisting of two identical subunits
a trimer consisting of two identical subunits and one diverse subunit
a dimer consisting of two identical subunits
In the ribonuclease experiments performed by Anfinsen, β-mercaptoethanol reduced:
all incorrectly paired bonds and stabilized the protein structure.
incorrectly paired disulfide bonds, allowing them to reform with the correct pairing until the most stable conformation of the protein had been obtained.
all bonds and destroyed the protein structure.
all charged residues, and the protein was unable to take part in signaling.
all bonds, and the unfolded protein molecules became tangled up with one another to form aggregates.
incorrectly paired disulfide bonds, allowing them to reform with the correct pairing until the most stable conformation of the protein had been obtained.
The overall three-dimensional structure of a single polypeptide is referred to as _____ structure.
supersecondary
primary
secondary
quaternary
tertiary
tertiary
The amino acids Tyrosine, Asparagine, and Serine:
are negatively charged at pH = 7.0.
are positively charged at pH = 7.0.
have aromatic rings.
are polar.
have double bonds in side chains.
are polar
The term quaternary with respect to protein structure stands for:
the ability to form all four kinds of noncovalent bonds.
a repeating structure stabilized by intrachain hydrogen bonds.
a linear sequence of four amino acids.
the only four amino acids that can form hydrogen bonds.
a multisubunit structure.
a multisubunit structure.
What pair of amino acids is positively charged at a neutral pH?
Cys, Met
Asp, Glu
Tyr, Arg
Leu, Pro
Lys, Arg
Lys, Arg
What amino acid residue would MOST likely be buried in the interior of a water-soluble globular protein?
Phe
Asp
Lys
Ser
Gln
Phe
Protein concentration can be determined using a spectrophotometer due to protein's absorbance of light at 280 nm.
True
False
True
What is another name for molecular exclusion chromatography?
gel-filtration chromatography
gel electrophoresis
affinity chromatography
ion-exchange chromatography
high-performance liquid chromatography
gel-filtration chromatography
What method can be used to separate proteins only by their charge?
ion-exchange chromatography
gel-filtration chromatography
dialysis
affinity chromatography
gel electrophoresis
ion-exchange chromatography
Which technique is used to determine the amino acid sequence of proteins?
tandem mass spectrometry.
electrophoresis.
affinity chromatography.
gel-filtration chromatography.
ion-exchange chromatography.
tandem mass spectrometry.
Knowledge of the amino acid sequences is important for several reasons. What is NOT one of those reasons?
Changes in the amino acid sequence can lead to abnormal protein functioning and disease.
The sequence of a protein is necessary to determine its function.
Knowledge of the sequence of a protein can help to prevent mutations.
Amino acid sequences determine the three-dimensional structures of proteins.
The sequence of a protein reveals much about its evolutionary history.
Knowledge of the sequence of a protein can help to prevent mutations.
An α helix is a coil stabilized by:
intrachain nitrogen bonds between the carbonyl nitrogen of a residue and the amide nitrogen of the sixth residue away.
intrachain nitrogen bonds between the carbonyl nitrogen of a residue and the amide nitrogen of the second residue away.
intrachain hydrogen bonds between the carbonyl oxygen of a residue and the amide hydrogen of the fourth residue away.
extrachain oxygen bonds between the carbonyl oxygen of a residue and the amide nitrogen of the fifth residue away.
extrachain hydrogen bonds between the carbonyl hydrogen of a residue and the amide oxygen of the third residue away.
intrachain hydrogen bonds between the carbonyl oxygen of a residue and the amide hydrogen of the fourth residue away.
A β sheet is formed by linking two or more β strands lying next to one another through:
nitrogen bonds.
disulfide bridges.
oxygen bonds.
ionic bonds.
hydrogen bonds.
hydrogen bonds.
What level of protein structure is composed of α helices, β sheets, and turns?
supersecondary
quaternary
primary
secondary
tertiary
secondary
Which of the following have an influence on the tertiary structure of a protein? (Choose all correct responses.)
interaction with other molecules
rotation of the peptide bonds
solvent
primary structure
What amino acid residue would MOST likely be buried in the interior of a water-soluble globular protein?
Asp
Arg
Trp
Ser
Lys
Trp
Suppose you have grown a culture of bacteria that have been engineered to express a protein that binds glucose. You would like to purify this protein. List in order a sequence of three techniques that you might employ to purify this protein. Briefly, explain what is accomplished with each technique.
Explain how comparing the amino acid sequence of a protein like lysozyme from several different species can provide insight into the nature of the functional regions of the protein, such as the active site, for example.
What molecule stores oxygen in muscle cells?
individual α subunits of hemoglobin
hemoglobin
myoglobin
individual β subunits of hemoglobin
metmyoglobin
myoglobin
As the partial pressure of carbon dioxide increases, the affinity of oxygen binding to hemoglobin:
decreases then increases.
increases then decreases.
increases.
decreases.
stays the same.
decreases.
Select all that apply. The binding of 2-3-bisphosphogycerate to the T state of hemoglobin:
pushes the equilibrium between T and R states toward the T state.
decreases its affinity for oxygen binding.
increases its affinity for oxygen binding.
stabilizes the equilibrium between T and R states.
displaces oxygen from hemoglobin.
-pushes the equilibrium between T and R states toward the T state.
-decreases its affinity for oxygen binding.
What is the Bohr effect?
the alteration of hemoglobin conformation in the presence of carbon monoxide
the ability of hemoglobin to retain oxygen when competing for a substrate with myoglobin
the regulation of oxygen binding by hydrogen ions and carbon dioxide
the ability of myoglobin to retain oxygen when competing for a substrate with hemoglobin
the regulation of oxygen binding by 2,3-BPG
the regulation of oxygen binding by hydrogen ions and carbon dioxide
The Bohr effect influences the oxygen-binding curve by:
shifting the oxygen-binding curve to the left.
shifting the oxygen-binding curve up and to the right.
shifting the oxygen-binding curve to the right.
making the oxygen-binding curve smoother.
making the oxygen-binding curve sharper.
shifting the oxygen-binding curve to the right.
What type of binding is indicated by a sigmoidal-shaped binding curve?
uncooperative
reversible
noncompetitive
competitive
cooperative
cooperative
What statement is CORRECT concerning the oxygenation plot of proteins X and Y shown below?
Protein X corresponds to myoglobin, and protein Y corresponds to hemoglobin.
Protein X exhibits tighter oxygen binding than protein Y.
Proteins X and Y contain a single binding site.
Protein Y exhibits tighter oxygen binding than protein X.
Protein X corresponds to hemoglobin, and protein Y corresponds to myoglobin.
Protein X exhibits tighter oxygen binding than protein Y.
Consider the oxygen-binding profile at three different pH values of 7.6, 7.4, and 7.2. Which statement is MOST accurate?
Curve Z most likely corresponds to pH 7.6.
pH has no effect on oxygenation of hemoglobin.
Curve Y most likely corresponds to pH 7.4.
Curve X most likely corresponds to pH 7.2.
Hb has a higher affinity for oxygen at the pH of curve Z.
Curve Y most likely corresponds to pH 7.4.
A reason hemoglobin is sensitive to changes in pH is that the T state of hemoglobin is stabilized by a salt bridge between β1 Asp 94 and the C-terminal _____ of the β1 chain.
tyrosine
serine
histidine
lysine
proline
histidine
What is the structure of the hemoglobin molecule?
α2β1 trimer
α2 dimer
β2 dimer
α2β2 tetramer
α1β2 trimer
α2β2 tetramer
How does oxygen binding change the quaternary structure of hemoglobin?
After oxygen binding, one αβ dimer of hemoglobin shifts with respect to the other by a rotation of 180 degrees. It decreases the binding affinity of other sites.
After oxygen binding, one αβ dimer of hemoglobin shifts with respect to the other by a rotation of 15 degrees. It decreases the binding affinity of other sites.
After oxygen binding, one αβ dimer of hemoglobin shifts with respect to the other by a rotation of 15 degrees. It increases the binding affinity of other sites.
After oxygen binding, the hemoglobin protein denatures, which increases the binding affinity of other sites.
After oxygen binding, the iron atom pulls on the proximal lysine residue.
After oxygen binding, one αβ dimer of hemoglobin shifts with respect to the other by a rotation of 15 degrees. It increases the binding affinity of other sites.
Oxygen binding at the coordination site causes:
formation of the hemoglobin tetramer
the iron atom to move from the plane of the porphyrin towards the outside.
the iron atom to rearrange the electrons to become effectively larger.
release of the iron atom from the heme prosthetic group
the iron atom to move from outside the plane of the porphyrin into the plane.
the iron atom to move from outside the plane of the porphyrin into the plane.
Oxygen binding to hemoglobin is dependent on the partial pressure of oxygen. From a physiological perspective, why is this important?
Aside from partial pressure of oxygen, there are other mechanisms that influence hemoglobin's affinity for oxygen. From a physiological perspective what is the value of having all of these different ways of fine-tuning the affinity of hemoglobin for oxygen?
A system is at equilibrium when
ΔG for the system is negative.
ΔG for the system is positive.
ΔG for the system is zero.
ΔH for the system is zero.
ΔH for the system is negative.
ΔG for the system is zero.
The ΔG of a reaction depends on the:
nature of the reactants alone.
nature of the products alone.
difference in free energy between the reactants and the products.
molecular mechanism of the transformation.
free energy of activation.
difference in free energy between the reactants and the products.
When ΔG° for a reaction is positive:
the reaction is endergonic and can take place spontaneously.
the reaction is endergonic and cannot take place spontaneously regardless of concentrations of reactants and products.
the reaction's spontaneity depends on the concentrations of the reactants and products.
the reaction is exergonic and can take place spontaneously regardless of concentrations of reactants and products.
the reaction is exergonic and cannot take place spontaneously.
the reaction's spontaneity depends on the concentrations of the reactants and products.
A reaction can occur spontaneously only if ΔG is:
zero.
lower than ΔG°.
higher than ΔG°.
positive.
negative.
negative
What statement about enzymes is CORRECT?
They accelerate reactions by factors of as much as a million or more.
All known enzymes are proteins.
Enzymes force reactions to proceed in only one direction.
These molecules alter the equilibrium of the reaction.
Enzymes alter the standard free energy of the reaction.
They accelerate reactions by factors of as much as a million or more.
Select all that apply. Examples of cofactors include:
vitamins
polypeptides
Zn2+, Mg2+, and Ni2+.
subunits
proteins
-vitamins
-Zn2+, Mg2+, and Ni2+.
What does an α-amino acid consist of?
carboxylic acid group, δ carbon, imine radical, hydrogen atom, distinctive R group
alcohol group, α carbon, amino group, nitrogen atom, distinctive R group, hydrogen atom
carboxylic acid group, α carbon, amino group, hydrogen atom, distinctive R group
carboxylic acid group, ε carbon, nitro group, hydrogen atom
carbonyl group, α carbon, amino group, oxygen atom, distinctive R group
carboxylic acid group, α carbon, amino group, hydrogen atom, distinctive R group
What is the reason for the existence of the hydrophobic effect?
the tendency of water molecules to make a bond with hydrophobic proteins
the tendency of nonpolar molecules to self-associate in the presence of an aqueous solution
the tendency of polar molecules to self-associate in the presence of an aqueous solution
the property of nucleic acids to dissolve in water
the inability of charged molecules to dissolve in water
the tendency of nonpolar molecules to self-associate in the presence of an aqueous solution
Knowledge of the amino acid sequences is important for several reasons. What is NOT one of those reasons?
The sequence of a protein reveals much about its evolutionary history.
Changes in the amino acid sequence can lead to abnormal protein functioning and disease.
The sequence of a protein is necessary to determine its function.
Amino acid sequences determine the three-dimensional structures of proteins.
Knowledge of the sequence of a protein can help to prevent mutations.
Knowledge of the sequence of a protein can help to prevent mutations.
What is FALSE regarding the laws of thermodynamics?
Energy can be neither created nor destroyed.
The local decrease in enthalpy will increase the entropy of the surroundings.
Ordered structures can be formed within a system only if the entropy of the surroundings will proportionally increase.
Heat is a manifestation of the kinetic energy associated with the random motion of molecules.
Total entropy of the universe is always decreasing as continuous formation of ordered structures results in less disorder in the universe.
Total entropy of the universe is always decreasing as continuous formation of ordered structures results in less disorder in the universe.
What is the configuration of peptide bonds in proteins?
Half of all peptide bonds are in the trans configuration and the other half are in the cis configuration.
Almost all peptide bonds are in the cis configuration.
Approximately one third are in the cis configuration and rest are in the trans configuration.
Approximately one third are in the trans configuration and rest are in the cis configuration.
Almost all peptide bonds are in the trans configuration.
Almost all peptide bonds are in the trans configuration.
A β sheet is formed by linking two or more β strands lying next to one another through:
nitrogen bonds.
disulfide bridges.
hydrogen bonds.
ionic bonds.
oxygen bonds.
hydrogen bonds.
Two complementary single stranded DNA molecules in solution will spontaneously come together to form a double helix. How can this be experimentally confirmed?
The DNA double helix can be observed to have higher entropy than single stranded DNA.
The heat released upon formation of the double helix can be measured.
Formation of the double helix can be observed under a light microscope.
Measurement of heat exchange can demonstrate that there is no heat absorbed or released upon formation of the double helix.
The heat absorbed upon formation of the double helix can be measured.
The heat released upon formation of the double helix can be measure
What is the structure elucidation technique that was used to generate the data on which the models of lysozyme that you observed in lab 1 were based?
absorbance spectrophotometry
X-ray diffraction
radioactive labeling
spectrofluorometry
electron microscopy
X-ray diffraction
Which amino acid forms disulfide bonds?
cysteine
histidine
methionine
serine
proline
cysteine
What level of protein structure is composed of α helices, β sheets, and turns?
supersecondary
tertiary
secondary
primary
quaternary
secondary
What gives proteins such a dominant role in biochemistry?
ability to spontaneously fold into complex three-dimensional structures
usage of 40 different building blocks
ability to act as a blueprint
ability to self-replicate
rigidity of the peptide backbone
ability to spontaneously fold into complex three-dimensional structures
Order the type of interactions by the bond strength in descending value.
van der Waals interactions, covalent bonds, hydrogen bonds
hydrophobic interactions, hydrogen bonds, electrostatic interactions
covalent bonds, van der Waals interactions, hydrogen bonds
hydrogen bonds, covalent bonds, van der Waals interactions
covalent bonds, hydrogen bonds, van der Waals interactions
covalent bonds, hydrogen bonds, van der Waals interactions
Two complementary single stranded DNA molecules will spontaneously form a double helix. Which response best explains the role of hydrogen bonding in this process?
hydrogen bonds are the weakest interactions that are involved in formation of the double helix.
hydrogen bonds keep the double helix from separating into two single stranded DNA molecules
hydrogen bonds between complementary base pairs causes formation of the double helix
hydrogen bonds play no role because the bases are hydrophobic
hydrogen bonds are responsible for the specificity of the interaction between the two strands of the double helix
hydrogen bonds are responsible for the specificity of the interaction between the two strands of the double helix
In lab you explored the structure of lysozyme using computational software. What insight could be gained about the function of lysozyme simply by observing its structure? (Choose all correct responses.)
location of the active site
amino acids that might be involved in binding the substrate or catalysis
catalytic efficiency of the enzyme
rate of the enzyme-catalyzed reaction
Delta G of the reaction
location of the active site
amino acids that might be involved in binding the substrate or catalysis
What is another name for molecular exclusion chromatography?
gel electrophoresis
high-performance liquid chromatography
affinity chromatography
gel-filtration chromatography
ion-exchange chromatography
gel-filtration chromatography
What method can be used to separate proteins only by their charge?
gel-filtration chromatography
dialysis
gel electrophoresis
ion-exchange chromatography
affinity chromatography
ion-exchange chromatography
The functional magnetic resonance imaging (fMRI) measures:
the electrical activity of neurons.
the magnetic properties of hemoglobin.
changes in the ratio of oxygenated and deoxygenated hemoglobin.
changes in the ratio of hemoglobin and myoglobin.
the velocity of the blood flow.
changes in the ratio of oxygenated and deoxygenated hemoglobin.
Oxygen binding to the heme iron atom causes:
the iron atom to move from the plane of the porphyrin towards the outside.
release of the iron atom from the heme prosthetic group
the iron atom to move from outside the plane of the porphyrin into the plane.
formation of the hemoglobin tetramer
the iron atom to rearrange the electrons to become effectively larger.
the iron atom to move from outside the plane of the porphyrin into the plane.
A proton exists in a solution as:
a deprotonated water molecule.
H+.
a hydronium ion.
a water molecule.
H2O+.
a hydronium ion.
What would be the pH of a buffer solution made from 0.20 M CH3COOH and 0.05 M CH3COO– that has pKa = 4.7.
4.7
4.9
4.1
5.3
5.0
4.1
A buffer consists of...
A weak acid and its conjugate base in solution at pH much higher than the pKa of the acid
A weak acid in solution at pH much lower than the pKa of the acid
A weak acid and its conjugate base in solution at pH within 1 pH unit of the pKa of the acid
A weak acid and its conjugate base in solution at pH much lower than the pKa of the acid
A strong acid in solution at pH much lower than the pKa of the acid
A weak acid and its conjugate base in solution at pH within 1 pH unit of the pKa of the acid
What is the term for the combination helix-turn-helix?
domain
globular protein
motif
supertetriary structure
tertiary structure
motif
What is the structure of the hemoglobin molecule?
α1β2 trimer
β2 dimer
α2β1 trimer
α2β2 tetramer
α2 dimer
α2β2 tetramer
How does oxygen binding change the quaternary structure of hemoglobin?
After oxygen binding, one αβ dimer of hemoglobin shifts with respect to the other by a rotation of 15 degrees. It decreases the binding affinity of other sites.
After oxygen binding, one αβ dimer of hemoglobin shifts with respect to the other by a rotation of 15 degrees. It increases the binding affinity of other sites.
After oxygen binding, one αβ dimer of hemoglobin shifts with respect to the other by a rotation of 180 degrees. It decreases the binding affinity of other sites.
After oxygen binding, the hemoglobin protein denatures, which increases the binding affinity of other sites.
After oxygen binding, the iron atom pulls on the proximal lysine residue.
After oxygen binding, one αβ dimer of hemoglobin shifts with respect to the other by a rotation of 15 degrees. It increases the binding affinity of other sites.
What type of binding is indicated by a sigmoidal-shaped binding curve?
reversible
uncooperative
noncompetitive
competitive
cooperative
cooperative
The overall three-dimensional structure of a single polypeptide is referred to as _____ structure.
super secondary
tertiary
quaternary
primary
secondary
tertiary
What statement is CORRECT concerning the oxygenation plot of proteins X and Y shown below?
Proteins X and Y contain a single binding site.
Protein X corresponds to hemoglobin, and protein Y corresponds to myoglobin.
Protein X corresponds to myoglobin, and protein Y corresponds to hemoglobin.
Protein X exhibits tighter oxygen binding than protein Y.
Protein Y exhibits tighter oxygen binding than protein X.
Protein X exhibits tighter oxygen binding than protein Y.
The amino acids Tryptophan, Tyrosine, and Phenylalanine:
have aromatic rings.
are polar.
are positively charged at pH = 7.0.
are negatively charged at pH = 7.0.
have hydroxyl groups in their side chains
have aromatic rings.
The term quaternary with respect to protein structure stands for:
a multisubunit structure.
the only four amino acids that can form hydrogen bonds.
a repeating structure stabilized by intrachain hydrogen bonds.
the ability to form all four kinds of noncovalent bonds.
a linear sequence of four amino acids.
a multisubunit structure.
What pair of amino acids is positively charged at a neutral pH?
Tyr, Arg
Leu, Pro
Asp, Glu
Lys, Arg
Cys, Met
Lys, Arg
What amino acid residue would MOST likely be buried in the interior of a water-soluble globular protein?
Valine
Glutamate
Lysine
Threonine
Aspartate
Valine
Protein concentration can be determined using a spectrophotometer due to protein's absorbance of light at 360 nm.
True
False
False
A system is at equilibrium when
ΔG for the system is negative.
ΔG for the system is positive.
ΔG for the system is zero.
ΔH for the system is negative.
ΔH for the system is zero.
ΔG for the system is zero.
Note
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