BioChem Questions 1
What is the net charge of alanine at pH 12 (round up or down to the closest integer)? A) -1 B) 0 C) 1 D) 2 E) 3
A) -1
Which of the following amino acids would you expect to have the greatest solubility in water at physiological pH (pH=7.4) A) Aspartic acid B) Glutamic acid C) Tyrosine D) Methionine E) Isoleucine
A) Aspartic acid
Which of the following statements is true? A) Cystine is an oxidized form of cystein. B) Histidine contains an phenyl group in its side chain. C) Asparagine is a positively charge amino acid. D) Lysine contains a hydroxyl group in its side chain. E) Serine contains a sulfhydryl group in its side chain
A) Cystine is an oxidized form of cystein
Different protein separation techniques use different characteristics of proteins for their separation. Please associate one of the characteristics of proteins labeled (A) to (D) with the separation method listed in questions (18) - (22). List of characteristics: (A) charge, (B) size, (C) binding to an antibody or some other ligand, (D) solubility in salt solutions (solubility depends on ionic strength). 07118. Gel filtration chromatography 07119. Separation by precipitation in ammonium sulfate 07120. Anion exchange chromatography 07121. Cation exchange chromatography 07122. Affinity chromatography
18. Gel Filtration --> Size 19. Separation by precipitation in ammonium sulfate --> Solubility in slat solution (solubility depends on ionic strength) 20. Anion exchange chromatography --> charge 21. Cation exchange chromatography --> charge 22. Affinity chromatography --> binding to an antibody or some other ligand
Which of the following statements is true? A) In a sandwich ELISA, the antigen to be detected is sandwiched between two antibodies. One is immobilized and the other is added in solution. B) In an indirect ELISA, the antigen-binding (detection) antibody is coupled with an enzyme that converts a substrate into a colored product. C) ELISA is a technique that allows all reagents to be added simultaneously. D) ELISA is a technique that derives its name from the first name of its inventor. E) For indirect ELISAs only monoclonal antibodies can be used.
A) In a sandwich ELISA, the antigen to be detected is sandwiched between two antibodies. One is immobilized and the other is added in solution.
Which of the following statements about helical structures of proteins is true? 4 A) In proteins, most α-helices are right handed. B) The collagen helix is an α-helix. C) Collagen is a coiled coil, with two helices winding around each other. D) Protein α-helices have a water-filled empty space inside that is shaped like a long column. E) The α-helix completes a turn after about 5-6 amino acids.
A) In proteins, most α-helices are right handed.
The side chains of which of the following amino acids carry a positive charge at physiological pH? A) Lysine B) Aspartate C) Glutamine D) Serine E) Cysteine
A) Lysine
Which of the following statements is true? A) Naturally occurring amino acids are L amino acids. B) Naturally occurring amino acids are D amino acids. C) Naturally occurring amino acids are mixtures of L and D amino acids. D) Amino acids in right handed helices are D amino acids, those in left handed helices are L amino acids. E) All L amino acids are levorotatory, all D amino acids are dextrorotatory.
A) Naturally occurring amino acids are L amino acids
Choose the correct ranking of electronegativity of the following elements: A) O > N > C > H B) N > O > C > H C) C > H > N > O D) N > O > H > C E) H > O > N > C
A) O > N > C > H
Which properties of which amino acids allow protein concentration to be determined by light absorption? A) The absorbance of tyrosine and tryptophan at 280 nm B) The absorbance of arginine and lysine at 220 nm C) The absorbance of all amino acids at 280 nm D) The delocalized electron clouds of the peptide bond resonance structure E) The absorbance of proline and methionine at 280 nm.
A) The absorbance of tyrosine and tryptophan at 280 nm
A peptide has the following sequence: KNTS. Which of the following statements about this peptide is true? A) The amino terminus is attached to a lysine. B) The peptide has one free amino group. C) The peptide contains one side chain with a hydroxyl group. D) The peptide is very hydrophobic. E) The peptide contains an arginine residue.
A) The amino terminus is attached to a lysine
Which of the following interactions falls off least steeply with distance (best maintains its strength with increasing distance)? A) The electrostatic (Coulomb) attraction between oppositely charged atoms. B) The attractive component of the van der Waals interaction. C) The hydrogen bond. D) The repulsive component of the van der Waals interaction. E) The interaction between two induced dipoles.
A) The electrostatic (Coulomb) attraction between oppositely charged atoms.
Which of the following statements characterize coordination bonds with metals? A) The metal typically acts as a Lewis acid, accepting an electron pair, and its binding partner acts as a Lewis base, donating an electron pair. B) In metal coordination bonds, one electron is provided by the metal, the other by its binding partner. Both electrons are shared approximately equally between both bonding partners. C) Transition metals such as Fe2+ can maximally form four metal coordination bonds. D) Metal coordination bonds typically involve hydrogens which need to carry a partial positive charge and the metal needs to carry a partial negative charge. E) Metal coordination bonds are typically stronger than regular covalent bonds.
A) The metal typically acts as a Lewis acid, accepting an electron pair, and its binding partner acts as a Lewis base, donating an electron pair.
Which of the following statements about phi (Φ) and psi (Ψ) angles is true? A) The phi angle describes rotation around a bond between the alpha carbon and the amide nitrogen. 15 B) The psi angle is 0 (zero) when the polypeptide chain is fully extended. C) Phi and psi angles describe the conformation of amino acid side chains. D) Phi and psi angles are characteristic of the amino acid sequence and are preserved (unchanged) during protein folding. E) Phi and psi angles describe two different types of rotation around the peptide bond.
A) The phi angle describes rotation around a bond between the alpha carbon and the amide nitrogen.
Which of the following statements is true? A) The serum of animals that have been immunized with a protein antigen contains a mixture of antibodies with slightly different specificity. B) Once a monoclonal antibody has bound to a protein, other antibodies can no longer bind. C) Antibodies can be used to detect proteins, but not to purify them. D) Monoclonal antibodies are obtained by purifying antibodies contained in the serum of immunized animals. E) Antibodies to a mouse protein can only be obtained by immunizing mice.
A) The serum of animals that have been immunized with a protein antigen contains a mixture of antibodies with slightly different specificity.
In a single polypeptide chain, proteins often have regions with a defined function that fold independently from other parts of the protein. These regions are called: A) domains. B) oligomers. C) peptides. D) motifs. E) subunits.
A) domains.
The tetrapeptide AKST A) has two amino groups B) has one amino group belonging to threonine and a carboxyl group belonging to alanine C) has a thiol group on one of the side chains D) has a net negative charge E) would typically be fond in the interior of proteins.
A) has two amino groups
Which net charge would you expect for aspartic acid between pH 6 and 7? A) -2 B) -1 C) 0 D) 1 E) 2
B) -1
The table on the right shows the protein content of different fractions obtained during purification of an enzyme (a protein) and the total enzyme activity in each fraction. Which fraction contains enzyme of the highest purity? A) 1 B) 2 C) 3 D) 4 E) 5 Fraction Total protein (mg) Enzyme activity (units) 1 400 80,000 2 3 45,000 3 100 60,000 4 10,000 100,000 5 3,000 90,000
B) 2
The weak acid HA has a dissociation constant of 10-3 . After dissolving HA in water, the concentration of A- is 0.1 mM, and the concentration of HA is 1 mM. What is the approximate pH of that solution? A) 1 B) 2 C) 3 D) 4 E) 5
B) 2
The pKa of a water soluble compound is 6. At approximately which pH do you expect 90% of the compound molecules to be protonated? A) 4 B) 5 C) 6 D) 7 E) 8
B) 5
The following table shows measurements made on fractions generated during the purification of an enzyme protein. Enzyme activity is given in units. Fraction volume (ml) Total protein (mg) Total activity (units) A) 1,400 10,000 100,000 B) 6 3 45,000 C) 80 100 60,000 D) 90 400 80,000 E) 280 3,000 100,000
B) 6 3 45,000
Which of the following amino acid side chains can form a covalent link within a polypeptide chain or between polypeptide chains? A) Ser B) Cys C) Lys D) Glu E) Asn
B) Cys
The side chain of which of the following amino acids has a pKa close to physiological pH? 3 A) Lysine B) Histidine C) Leucine D) Aspartate E) Glutamine
B) Histidine
Which of the following statements is true? A) L- and D-amino acids are different conformations of the same chemical entity. B) L- and D-amino acids are enantiomers. C) L- and D-amino acids occur in nature at approximately equal abundance. D) D-amino acids can be converted into L-amino acids by rotation around the Cα-sidechain bond axis. E) The alpha carbon (Cα) of the amino acid glycine is, like the Ca of other amino acids, a chiral center.
B) L- and D-amino acids are enantiomers.
Which of the following amino acids will be found at increased frequency in the interior of globular proteins: A) Aspartate B) Leucine C) Arginine D) Lysine E) Serine
B) Leucine
Which of the following amino acids would you expect to be predominantly inside a globular protein or on its surface? A) Aspartate inside B) Lysine outside C) Isoleucine outside D) Phenylalanine outside E) Arginine inside
B) Lysine outside
Which of the following statements is true? A) Polyclonal antibodies are pools of antibodies from different lines of cloned animals. B) Monoclonal antibodies detect a single epitope on a protein. C) Monoclonal antibodies can be purified from the serum of genetically identical (inbred) strains of mice. D) The generation of polyclonal antibodies requires the fusion of many antibody-producing Bcells with immortal tumor cells. E) For ELISAs only monoclonal antibodies can be used.
B) Monoclonal antibodies detect a single epitope on a protein.
Which of the following statements about protein structure is true? A) Protein primary structure describes the structure of the polypeptide backbone. B) Protein secondary structure is determined and maintained largely by hydrogen bonds between backbone atoms. C) Turns connect secondary structure elements, but turns are themselves part of tertiary structure. D) Because proline is a more rigid structure, it does not favor sharp turns of direction and is therefore seldom found in turns. E) The beta-conformation requires that two polypeptide chains run in opposite direction from one another.
B) Protein secondary structure is determined and maintained largely by hydrogen bonds between backbone atoms.
Which of the following levels of structure is generated by repetitive hydrogen bonding between main chain carbonyl oxygens (CO) and main chain amide groups (NH)? A) Primary structure B) Secondary structure C) Tertiary structure D) Quaternary structure E) None of the above
B) Secondary structure
Affinity chromatography separates proteins primarily according to A) size of the proteins relative to the size of the column beads B) binding to a ligand linked to column beads C) charge of the protein compared with the charge of the column beads D) solubility of the protein in salt solutions 17 E) binding of a ligand that is applied to the mobile phase of the column
B) binding to a ligand linked to column beads
Chaperones typically assist in A) oxygen transport B) protein folding C) enzymatic catalysis D) stabilization of fibrous proteins E) muscle contraction
B) protein folding
Which of the following statements about protein structure is true? A) β-sheets are stabilized by intrachain hydrogen bonds between amide nitrogens and carbonyl oxygens of amino acids that are about four residues apart in the sequence of the protein. B) β-turns are stabilized by hydrogen bonds between the first and the fourth amino acid in the turn. C) Turns usually contain five or more amino acids. D) Collagen contains three intertwined α-helices. E) Leucine and phenylalanine are the most frequent amino acids in β-turns
B) β-turns are stabilized by hydrogen bonds between the first and the fourth amino acid in the turn.
What is the approximate charge of the amino acid alanine at pH 6? A) -2. B) -1. C) 0. D) +1. E) +2.
C) 0.
One milliliter of a 1M solution of sodium hydroxide is diluted into 1 liter of water. What is the pH of that solution? A) 3 B) 10-3 C) 11 D) 10-11 E) 6
C) 11
What is the pH if 10 ml of a 2M solution of NaOH is mixed with 10 ml of 1 M HCl and the mixture is diluted to 1 liter with water? A) 10-12 B) 10-2 C) 12 D) 2 7 E) 1
C) 12
Which of the following statements is true? A) HbA1c is a Schiff base intermediate of the reaction of glucose with hemoglobin. B) HbA1c is a useful indicator of the current glucose concentration, for example to detect hypoglycemia. C) A content of 10% HbA1c would indicate of poor glucose control of a diabetic individual. D) HbA1c is an advanced glycation end product. E) HbA1c is not formed in healthy individuals.
C) A content of 10% HbA1c would indicate of poor glucose control of a diabetic individual.
Which of the following statement about amyloid is true? A) Amyloid forms in the brain, but not other organs. B) Amyloid is the product of covalent linkage of proteins to form large clusters. C) Amyloid is the product of self-association of partially denatured proteins. D) Amyloid is another name for multimeric proteins. E) Amyloid diseases can be cured by amyloid-dissolving laser radiation
C) Amyloid is the product of self-association of partially denatured proteins.
Which of the following amino acids has a guanidinium group in its side chain? A) Isoleucine B) Glutamate C) Arginine D) Threonine E) Glycine
C) Arginine
Which of the following types of bonds is usually the strongest A) Hydrogen bonds B) Van der Waals interactions C) Covalent bonds D) Charge-charge interactions E) Charge-dipole interactions
C) Covalent bonds
The information contained in a Ramachandran plot can be used to A) Determine the conformation of amino acid side chains. 5 B) Determine the distribution of charges of the side chains. C) Determine the abundance of secondary structure elements of the polypeptide main chain (backbone). D) Determine the angle of rotation about the peptide bond. E) Determine the distances between Cα and carbonyl carbon (Φ), and Cα and the amide nitrogen (Ψ).
C) Determine the abundance of secondary structure elements of the polypeptide main chain (backbone).
Which of the following is the correct order of electronegativity? A) O < H < N < C B) H < N < C < O C) H < C < N < O D) N < C < O < H E) C < H < N < O
C) H < C < N < O
Which of the following statements about HbA1c is true? A) HbA1c is a Schiff base intermediate when glucose reacts with hemoglobin. B) HbA1c is an advanced glycation end product. C) HbA1c is a stable post-Amadori product. D) HbA1c is used to measure acute glucose concentrations in plasma. E) HbA1c only forms in patients with diabetes.
C) HbA1c is a stable post-Amadori product.
Which of the following statements comparing regular covalent bonds and coordination bonds is true? A) The bond between oxygen and hydrogen in water is a coordination bond. B) In regular covalent bonds, the bond electrons are always shared equally between the bonding partners. C) In coordination bonds, one partner donates both bonding electrons, the other accepts both. D) Coordination bonds, for example between oxygen and Fe2+ are much stronger than the regular covalent bond between oxygen and carbon. E) Coordination bonds are important for metallo-organic and general chemistry, but not for biochemistry.
C) In coordination bonds, one partner donates both bonding electrons, the other accepts both
Which of the following describes the long-range interactions in proteins that involve the side chains of amino acids? A) Primary structure B) Secondary structure C) Tertiary structure D) Quaternary structure E) None of the above
C) Tertiary structure
Which of the following statements about the hydrophobic interaction is true? A) The hydrophobic interaction is based on the formation of ordered water molecules at the contact site of two hydrophobic surfaces. B) The hydrophobic interaction is a repulsive force between oily substances in water. C) The hydrophobic interaction is driven by the displacement of ordered water molecules on the hydrophobic surface of molecules when they contact each other. D) The hydrophobic interaction is expected to be temperature-independent. E) The hydrophobic interaction plays a role in protein-protein contact but not in the folding of a single polypeptide chain.
C) The hydrophobic interaction is driven by the displacement of ordered water molecules on the hydrophobic surface of molecules when they contact each other.
HbA1c is A) a reversible Schiff base B) an indicator of blood glucose levels currently present in blood plasma C) a post-Amadori product 6 D) an advanced glycation end product. E) None of the above
C) a post-Amadori product
Which of the following types of protein modification are usually unwanted (usually associated with pathogenic events such as inflammation)? A) glycosylation B) phosphorylation C) nitration D) acetylation E) addition of a fatty acid chain
C) nitration
Which of the following bonds in a peptide does not allow free rotation? A) The bond between the backbone amide (NH) nitrogen and Cα. B) The bond between Cα and the backbone carbonyl (CO) carbon. C) The bond between backbone Cα and side chain Cβ D) The bond between the backbone amide (NH) nitrogen and the backbone carbonyl (CO) carbon. E) The side chain Cβ and side chain Cγ of lysine
D) The bond between the backbone amide (NH) nitrogen and the backbone carbonyl (CO) carbon.
The ionic product of water [H+][OH-] is A) 7 B) 10-7 M2 C) 14 D) 10-14 M2 E) -log[H+ ]
D) 10-14 M2
If the concentration of hydroxyl ions in an aqueous solution is 10-3 M, the pH of the solution is A) 7 B) 4 C) 10-7 D) 11 E) 3
D) 11
Eleven (11) mmoles of an acid HA are dissolved in 1 liter of water. At pH 7, the concentration of Ais 1 mM and the concentration of HA is 10 mM. What is the pKa of HA? A) 5 B) 6 C) 7 D) 8 E) 9
D) 8
Which of the following statements is true? A) In a sandwich ELISA, the antibody carrying the tag is sandwiched between the antigen and the detection antibody. B) In a direct ELISA, the tag is directly attached to the antigen. C) In an indirect ELISA, the antigen is indirectly attached to the plate, through an antibody. D) Antibodies are so useful for the detection of protein antigens because antibodies are highly specific. E) Antibodies can only be raised against proteins, not other types if molecules, such as carbohydrates.
D) Antibodies are so useful for the detection of protein antigens because antibodies are highly specific.
Which of the following amino acids has a guanidinium group in its side chain? A) Alanine B) Lysine C) Aspartic acid D) Arginine E) Tyrosine
D) Arginine
Which of the following statements is true? 14 A) Cystin is the protonated form of cystein. B) Cystin is the reduced form of cystein. C) The equilibrium between cystin and cystein is an acid-base equilibrium. D) Cystein plays a role in the formation of disulfide bonds in proteins. E) Cystein contains a hydroxyl group in its side chain.
D) Cystein plays a role in the formation of disulfide bonds in proteins.
Carbon is a group __________ element A) I B) II C) III D) IV E) V
D) IV
Which of the following statements about mass spectrometry is true? A) Electrospray mass spectrometry relies on a laser beam to both ionize the protein and to introduce it into the gas phase. B) The name electrospray mass spectrometry derives its name from the fact that the sample containing the protein is sprayed onto a matrix which facilitates ionization. C) In electrospray mass spectrometry proteins are ionized by a short electrical pulse of high voltage. D) In electrospray mass spectrometry the mass to charge ratio of proteins is measured. E) Mass spectrometry had its peak earlier during this decade, but its use is now declining.
D) In electrospray mass spectrometry the mass to charge ratio of proteins is measured.
Which of the following statements about gel electrophoresis is true? A) Gel electrophoresis resembles gel filtration in the sense that larger proteins move faster in the gel than smaller proteins. B) The use of sodium dodecyl sulfate (SDS) helps preserve the native conformation of the proteins to be separated. C) SDS gel electrophoresis allows the separation and detection of hydrophilic, but not hydrophobic proteins. D) In gel electrophoresis, proteins are pulled thought the gel by an electric field. E) In non-denaturing electrophoresis, proteins are separated by a size alone.
D) In gel electrophoresis, proteins are pulled thought the gel by an electric field
A solution contains two proteins that have about the same size, but one is positively charged the other negatively. What would be the best method to separate them? A) Ammonium sulfate precipitation B) Gel filtration C) SDS-PAGE D) Ion exchange chromatography E) High speed centrifugation
D) Ion exchange chromatography
Which of the following statements about mass spectrometry techniques is true? A) In electrospray mass spectrometry, analytes (molecules to be detected) are introduced into the gas phase by a short intense laser pulse. B) In "time of flight" mass spectrometry, analytes are introduced into the vacuum chamber by a glass capillary held at a high voltage. C) A disadvantage of mass spectrometry is its low sensitivity compared with, for example, gel electrophoresis. D) Mass spectrometry techniques separate analyte molecules according to their mass to charge ratio. E) Time of flight mass spectrometry is better suited than antibody-based techniques to discriminate between proteins of the same mass.
D) Mass spectrometry techniques separate analyte molecules according to their mass to charge ratio.
In keratin two α-helices are wound around each other to form a superhelix. This association of two helices is an example of A) Primary structure B) Secondary structure C) Tertiary structure D) Quaternary structure E) Intramolecular structure
D) Quaternary structure
Which of the following structural features are part of the secondary structure of a protein? A) The pattern of disulfide bonds in a protein B) The way a multimeric protein is assembled from subunits C) The structure of the protein's amino acid side chains D) Repetitive local structural features stabilized by hydrogen bonds between backbone functional groups E) The complete covalent structure of a protein
D) Repetitive local structural features stabilized by hydrogen bonds between backbone functional groups
Which of the following centrifugation steps are required for the preparation of microsomes (intracellular membrane vesicles)? A) Spin at low speed, take pellet. B) Spin at low speed, take supernatant, spin at intermediate speed (10,000g), take pellet. C) Spin at low speed, take supernatant, spin at intermediate speed (10,000g), take supernatant, spin at high speed, take supernatant. D) Spin at low speed, take supernatant, spin at intermediate speed (10,000g), take supernatant, spin at high speed, take pellet. E) Spin at low speed, take supernatant.
D) Spin at low speed, take supernatant, spin at intermediate speed (10,000g), take supernatant, spin at high speed, take pellet.
Which of the bonds in protein main chains mentioned in A to D does not allow rotation around it's axis? A) The bond connecting Cα with the main chain amide nitrogen B) The bond connecting Cα with the first atom of the side chain C) The bond connecting Cα with the main chain carbonyl carbon D) The bond connecting the main chain carbonyl carbon with the main chain amide nitrogen E) All of the above mentioned bonds allow free rotation about their axes.
D) The bond connecting the main chain carbonyl carbon with the main chain amide nitrogen
Which of the following statements about the peptide bond is true? A) The peptide bond is a bond between the alpha carbon and an adjacent nitrogen. B) The peptide bond is an ester bond. C) The peptide bond is thermodynamically stable, meaning that the equilibrium is in favor of formation of the peptide bond rather than its dissociation. D) The peptide bond is an amide bond between an amide nitrogen of one amino acid with the carbonyl carbon of the next. E) The nitrogen participating in the peptide bond exhibits nearly complete tetrahedral geometry.
D) The peptide bond is an amide bond between an amide nitrogen of one amino acid with the carbonyl carbon of the next.
If fatty acid molecules are mixed with water which of the following events will occur? A) The fatty acid molecule will trigger the formation of an increased number of flickering clusters of water molecules. B) The entropy will increase upon mixing. C) The carboxylate head groups will associate with each other at the inside of a micelle. D) The water molecules will form "clathrate-like structures" around the hydrocarbon tail of the fatty acid molecules. E) None of the above.
D) The water molecules will form "clathrate-like structures" around the hydrocarbon tail of the fatty acid molecules.
How far apart in sequence are the amino acid residues (X,Y) that interact in an α-helix? 16 A) one residue (X Y) (they are next to each other) B) two residues (X - Y) C) three residues (X - - Y D) four residues (X - - - Y) E) five residues (X - - - - Y)
D) four residues (X - - - Y)
Which of the following statements is true? A) The collagen helix is a prototypical α-helix. B) The collagen helix is a helix formed by three α-helices. C) Most α-helices are left handed. D) Beta sheets are stabilized by hydrogen bonds between amino acids that are next to each other in sequence. E) 3 to 4 amino acids form a complete turn of an α-helix.
E) 3 to 4 amino acids form a complete turn of an α-helix.
When Zn2+ binds a water molecule in a protein, how is this bond best characterized? A) A symmetric covalent bond B) A hydrogen bond C) A covalent double bond D) A van der Waals bond E) A coordination bond
E) A coordination bond
Which of the following statements make proper use of the terms "protein subunit" and "protein domain" A) Subunits are segments of a polypeptide chain with distinct functions. B) A tetrameric protein contains four domains. C) A heterotrimeric protein contains three different domains. D) A homodimeric protein contains two identical domains. E) A domain is an independently folding region of a polypeptide chain.
E) A domain is an independently folding region of a polypeptide chain.
Which of the following statements is true? A) β-amyloid is a fiber with high α-helical content. B) Amyloid can form only in the brain of patients with Alzheimer's disease. C) Amyloid is formed by the aggregation of fully folded proteins. D) Amyloid formation requires full denaturation of proteins. E) Amyloid forms by self-association of partially unfolded proteins.
E) Amyloid forms by self-association of partially unfolded proteins.
Please rank the solubility of the following amino acids at pH 7.0: A) Valine > isoleucine > aspartate B) Isoleucine > aspartate > valine C) Aspartate > isoleucine > valine D) Valine > aspartate > isoleucine E) Aspartate > alanine > isoleucine
E) Aspartate > alanine > isoleucine
Which of the following statements about protein structure is true? A) Most naturally occurring α-helices are left handed. B) In an α-helix, the amino acid side chains alternately point in- and outwards relative to the helix axis. C) An α-helix has a hollow interior of about 2 Å in diameter. D) An α-helix is stabilized by repetitive hydrogen bonding between side chains. E) Each turn of an α-helix contains about 3.6 amino acids.
E) Each turn of an α-helix contains about 3.6 amino acids.
Which of the following statements about glycine is true? 2 A) When glycine is part of a polypeptide chain, its α-carbon becomes asymmetric. B) Glycine is the only amino acid that allows free rotation around the peptide bond. C) There are two enantiomers, L-glycine and D-glycine. D) Glycine has a negatively charged side chain. E) Glycine, when part of a polypeptide chain, allows a greater range of Φ and Ψ angles than other amino acids.
E) Glycine, when part of a polypeptide chain, allows a greater range of Φ and Ψ angles than other amino acids.
Which statement about covalent bonds that occur in biological molecules is correct? A) In coordination bonds, for example between nitrogen and Fe2+, both bonding atoms donate a single electron. B) In regular covalent bonds between carbon and oxygen the bonding electrons are equally shared between both atoms. C) A double bond between carbons (-C=C-) allows free rotation around the bond axis. D) Coordination bonds, although important in inorganic chemistry, are not important in biochemistry. E) In regular single covalent bonds, a bonding electron pair is shared between both bonding atoms.
E) In regular single covalent bonds, a bonding electron pair is shared between both bonding atoms.
Which of the following statements about electrophoretic separation techniques is true? A) Isoelectric focusing separates proteins according to size. B) SDS-PAGE (polyacrylamide electrophoresis using SDS) separates proteins according to size and charge. C) Non-denaturing electrophoresis is better suited to determine a protein's molecular weight than denaturing electrophoresis. D) All electrophoretic techniques rely on the movement of buffer molecules in an electric field which carry proteins with them. E) In two dimensional electrophoresis isoelectric focusing is combined with denaturing gel electrophoresis (SDS-PAGE).
E) In two dimensional electrophoresis isoelectric focusing is combined with denaturing gel electrophoresis (SDS-PAGE).
Which of the following proteins have high α-helical content? A) Silk B) Porin C) α-hemolysin from Staphylococcus aureus D) Fatty acid binding protein E) Keratin
E) Keratin
Which of the following statements about the melting of water ice is true? A) The change in ΔH during melting is favors the liquid state of water. B) The contribution of entropy to the free energy of melting decreases with temperature. C) During melting more hydrogen bonds are formed, driving the melting process forward. D) The higher disorder of water molecules in liquid water is unfavorable for the melting process. E) Melting is an entropy driven process.
E) Melting is an entropy driven process.
Which of the following is usually an unwanted covalent modifications of a protein? A) Proteolytic cleavage at specific sites by specific enzymes B) Formation of disulfide bridges C) Addition of a fatty acid chain D) Enzymatic glycosylation E) Non-enzymatic glycation
E) Non-enzymatic glycation
Amino acid residues commonly found in the middle of β turns are: A) Ala and Gly B) hydrophobic C) two Cys D) those with ionized R-groups E) Pro and Gly
E) Pro and Gly
In a mixture of the five proteins listed below with their molecular weights (MW), which should elute first in size-exclusion (gel-filtration) chromatography? A) cytochrome c MW = 13,000 B) immunoglobulin G MW = 145,000 C) ribonuclease A MW = 13,700 D) serum albumin MW = 68,500 E) RNA polymerase MW = 450,000
E) RNA polymerase MW = 450,000
Which of the following statements make proper use if the terms "domain" and "subunit"? A) The terms "domain" and "subunit" can be used interchangeably. B) Protein subunits are independently folding units of a single polypeptide chain. C) The extracellular, transmembrane and intracellular portions of a transmembrane protein are different subunits of the transmembrane protein. D) The viral capsid of poliovirus contains more than twenty domains. E) Subunits are components of oligomeric or multimeric proteins.
E) Subunits are components of oligomeric or multimeric proteins.
A small amount (1 mmole) of imidazole (pKa ≅ 6.9) is dissolved in 1 l of a buffer solution with pH 7.4 (100 mM concentration of buffer). Which of the following statements describe what will happen? A) The pH of the solution will decrease because the pKa of imidazole is smaller than the original pH of the buffer. B) Imidazole will dissociate completely. C) The predominant form of imidazole will be positively charged. D) The protonated form of imidazole will predominate in solution. E) The conjugate base of the dissolved solute will predominate in solution.
E) The conjugate base of the dissolved solute will predominate in solution.
Which of the following modifications are typical for normal collagen: A) nitration. B) glycation. C) addition of a fatty acid chain. D) acetylation. E) hydroxylation.
E) hydroxylation.
The Ramachandran plot... A) is a plot of all angles in a protein that allow free rotation. B) plots the hydrophobicity of each amino acid in a protein. C) allows cis and trans peptide bonds to be distinguished. D) contains all the information required for a complete description of a protein's tertiary structure. E) is a plot of the Phi (Φ) and Psi (Ψ) angles of each amino acid residue.
E) is a plot of the Phi (Φ) and Psi (Ψ) angles of each amino acid residue.
Which of the following proteins or protein segment has a high β-sheet content? A) Keratin B) Ferritin C) The transmembrane portion of membrane proteins with a single transmembrane domain D) Myoglobin E) α-hemolysin
E) α-hemolysin
