Biochemisty Sapling

Which of the following correctly identifies the priority of common substituents in the RS system? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. -OH > -COOH > -CH2OH > -H B. -H > -CH2OH > -COOH > -OH C. -COOH > -OH > -CH2OH > -H D. -COOH > -CH2OH > -OH > -H E. none of the above

A. -OH > -COOH > -CH2OH > -H

An unusual characteristic of H2O is A. greater density in solid form (ice) than in liquid form (water). B. not readily forming intermolecular interactions. C. high heat of vaporization. D. low specific heat.

C. high heat of vaporization.

Which of the following plays a large role in maintaining the secondary structure of proteins? A. ionic bonds B. peptide bonds C. hydrogen bonds D. hydrophobic interactions

C. hydrogen bonds

What feature of a disease classifies it as a prion disease? A. if it affects the central nervous system B. if it results from protein aggregation C. if the infectious agent is a protein D. if the diseases are fatal E. none of these define prion diseases

C. if the infectious agent is a protein

The pH of an aqueous solution A. must remain at 7. B. depends solely on the ionization of water. C. is a function of hydrogen ion concentration (to a reasonable approximation). D. is not affected by added OH−.

C. is a function of hydrogen ion concentration (to a reasonable approximation).

A reaction will always be aerodynamically spontaneous if A. DELTA G DEGREES>0 B. DELTA G=0 C. it is coupled to another reaction D. DELTA H<0 and DELTA S>0

D. DELTA H<0 and DELTA>0

The backbone of a polypeptide chain can be pictured as a series of rigid planes, with consecutive planes sharing a common point of rotation at __________. A. the nitrogen B. the carbonyl carbon C. the side chain D. the alpha carbon

D. the alpha carbon

Which statement regarding the Miller and Urey experiments is false? A. CO and CO2 were produced B. The starting gaseous mixture included NH3, CH4, H20, H2S, and H2 C. Amino acids, hydroxy acids, and aldehydes were formed in the experiments D. the energy used to drive the reaction was provided by boiling the liquid phase

D. the energy used to drive the reaction was provided by boiling the liquid phase

Denaturing followed by renaturing of a protein A. requires heat. B. always results in the protein regaining its function. C. requires breaking and reforming disulfide bonds. D. demonstrates that primary structure dictates tertiary structure.

D. demonstrates that primary structure dictates tertiary structure.

Which molecule has the same hybridization on the central atom as water? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. all of the above B. dihydrogen monosulfide, H2S C. ammonia, NH3 D. carbon tetrachloride, CCl4

A. all of the above

A substance that can act as either an acid or a base is _______. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. amphoteric B. di-ionizable C. ambiprotic D. amphipathic

A. amphoteric

Living cells A. are in a dynamic steady state far from equilibrium B. are closed systems C. exist because they do not obey the second law of thermodynamics D. use anabolic pathways to drive catabolic pathways

A. are in a dynamic steady state far from equilibrium

Which of the following reagents will not react with the N-terminal amino group of a peptide? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. iodoacetamide B. fluorodinitrobenzene C. phenylisothiocyanate D. dabsyl chloride E. dansyl chloride

A. iodoacetamide

The β‑sheet A. is primarily stabilized by hydrogen bonds. B. can be either parallel or perpendicular. C. has strands in which the R groups of the amino acids are all on the same side of the sheet. D. is composed of amino acid residues all very near each other in the primary structure.

A. is primarily stabilized by hydrogen bonds.

Denaturing gel electrophoresis separates proteins based on differences in A. mass. B. shape. C. charge. D. amino acid content.

A. mass.

Proteins that are folded in their thermodynamically stable and functional form(s) are considered to be ___ proteins. A. native B. denatured C. crystallized D. globular

A. native

A generic protein that is 387 amino acid residues long will have a molecular weight A. estimated at 387 daltons. B. estimated at 49536 daltons. C. estimated at 42570 daltons. D. There is not enough information to answer the question.

C. estimated at 42570 daltons. The average weight of a amino acid is 110 Da. MW of the generic protein = 387 x 110 Da = 42570 Da

A protein that consists of mostly one type of secondary structure, has a relatively simple tertiary structure and its function is to provide structural support is likely a __________ protein. A. regulatory B. quaternary C. fibrous D. globular

C. fibrous

What is the standard free-energy change for a reaction at 25 °C if the equilibrium constant is 5.0 x 102? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. -15.4 kJ/mol B. 15.4 kJ/mol C. -1.3 kJ/mol D. 1.3 kJ/mol

ΔG° - RTln Keq A. -15.4 kJ/mol

Which is not made of fibrous protein? A. myoglobin B. collagen C. silk D. hair

A. myoglobin

A protein in a functional conformation is called a ___________ protein. A. native B. primordial C. first order D. homologous

A. native

The _______ is not an example of a type of protein secondary structure. BETA SHEET ALPHA TURN BETA TURN

ALPHA TURN

Which reaction type is the reverse reaction of a condensation reaction? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. phosphorylation B. hydrolysis C. reduction D. synthesis

B. hydrolysis

Which item is the predominant factor in protein stability? A. salt bridges B. the hydrophobic effect C. hydrogen bonds D. disulfide bonds

B. hydrophobic effect

f the absorption of a solution at 300 nm is 0.100, what is the absorption if the concentration is doubled? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 0.050 B. It does not change because the absorption is a unique constant for the solute. C. 0.200 D. 0.400

C. 0.200

Which amino acid is most favored in an α-helical conformation? A. Gly B. Arg C. Ala D. Asp E. Asn

C. Ala

Which statement is false? A. DELTA G DEGREES is a function of Keq B. Most biocatalysts are proteins C. At equilibrium, equal amounts of products and reactants are present D. When reactants become products, they do so through an intermediate transition state

C. At equilibrium, equal amounts of products and reactants are present

Glycine and acetic acid both have a carboxylic group. Which statement is true? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Acetic acid has an acid strength about 100 times stronger than glycine because it is not affected by any other functional groups. B. The acids groups are equally strong (about the same tendency to ionize). C. Glycine's acid group is stronger due to the electron withdrawing property of glycine's amino group. D. Glycine's acid group is weaker due to the electron withdrawing property of glycine's amino group.

C. Glycine's acid group is stronger due to the electron withdrawing property of glycine's amino group.

Unrepaired mistakes during the replication of DNA that lead to changes in the genetic information are called __________. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. transformations B. transfigurations C. mutations D. adaptations

C. mutations

Which is not a class of conjugate proteins? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. metalloproteins B. glycoproteins C. organoproteins D. lipoproteins

C. organoproteins

Which protein would elute first from a gel filtration column? A. protein C, a homodimer with protomer 𝑀r=11300 B. protein A, with 𝑀r=27000 C. protein B, with 𝑀r=58400 D. protein D, with 𝑀r=15600

C. protein B, with 𝑀r=58400

Metabolites are small molecules A. that collectively make up the proteome of a cell B. that are informational molecules C. that generally consist of approximately 1000 different substances D. that are not impeded by the plasma membrane

C. that generally consist of approximately 1000 different substances

Which of the following best defines the term secondary structure with respect to proteins? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. a description of the covalent backbone of a protein, including the sequence of the amino acids B. the three-dimensional structure of a multisubunit protein C. the local spatial arrangement of the main-chain atoms in a segment of a polypeptide chain D. the three-dimensional conformation of a protein in its native folded state

C. the local spatial arrangement of the main-chain atoms in a segment of a polypeptide chain

In an acetic acid solution with a pH of 5.00, what is the ratio of acetate ion to acetic acid (not ionized)? The pKa of acetic acid is 4.76. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 0.02 B. 0.58 C. 1.0 D. 1.7

D. 1.7

How many buffering regions would be seen on a titration curve of a diprotic acid? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 1 B. 0 C. 3 D. 2

D. 2

Which statement likely describes the earliest cells formed on Earth? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Aerobic due to a far greater oxygen concentration in the atmosphere than exists today. B. Anaerobic due to a far greater oxygen concentration in the atmosphere than exists today. C. Aerobic due to a far smaller oxygen concentration in the atmosphere than exists today. D. Anaerobic due to a far smaller oxygen concentration in the atmosphere than exists today.

D. Anaerobic due to a far smaller oxygen concentration in the atmosphere than exists today.

Which statement regarding protein structure is true? A. Entropy is generally not a consideration when determining stability. B. Van der Waals interactions are insignificant. C. Hydrophilic side chains are never found in the interior. D. Hydrophobic side chains are usually in the interior of the native structure.

D. Hydrophobic side chains are usually in the interior of the native structure.

What is the proper three-letter abbreviation for isoleucine? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Isl B. Ilu C. Iso D. Ile

D. Ile

If a change in conditions causes the equilibrium constant, Keq, to increase, what effect does that have on the free energy change (ΔG°)? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. It has no effect on ΔG°. B. It increases ΔG°. C. It could increase or decrease ΔG° depending on the specific reaction. D. It decreases ΔG°.

D. It decreases ΔG°.

Which organelle is not membrane-bound? A. a lysosome B. the Golgi complex C. a peroxisome D. a ribosome

D. a ribosome

Why are buffers important in living systems? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. They help maintain structures, for example, protein structure. B. They allow for best functioning of enzymes by maintaining optimum pH. C. They protect against influx of unusual amounts of acidic or alkaline substances. D. all of the above

D. all of the above

Which of the following types of proteins are exceptions to the two simple rules of protein folding: (1) Hydrophobic residues are found buried in the interior of a protein; and (2) the number of hydrogen bonds and ionic interactions within the protein are maximized? A. globular proteins B. transmembrane proteins C. proteins with intrinsically disordered segments D. both b and c

D. both b and c

Which of the following is not water soluble? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. glucose B. ethanol C. glyceraldehyde D. butane

D. butane

Molecules that assist the folding of proteins are called ________. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. escort proteins B. renaturants C. flexions D. chaperones

D. chaperones

Edman degradation A. is the use of proteases for cleaving larger polypeptide chains into peptides. B. is the most common way to determine the amino acid sequence of a protein. C. can be used only to sequence peptides and not proteins. D. identifies the N‑terminal amino acid of a peptide.

D. identifies the N‑terminal amino acid of a peptide.

Which characteristic of protein is not associated with proteostasis? A. synthesis B. degradation C. refolding D. structure

D. structure

Which belongs to the family of intermediate filament (IF) proteins? A. cellulose B. lysozyme C. myoglobin D. α-keratins

D. α-keratins

Which is a difference between γ and β turns? A. γ turns rarely contain glycine; β turns frequently contain glycine B. γ turns have trans proline; β turns have cis proline C. γ turns contain disulfide bonds; β turns have hydrogen bonds D. γ turns have three amino acids; β turns have four amino acids

D. γ turns have three amino acids; β turns have four amino acids

The ammonium ion has a pKa of 9.25, whereas acetic acid has a pKa of 4.76. What can we say about these weak acids based on these constants? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. At pH 9.25, NH4+ = NH3. B. At pH > 9.25, NH4+ < NH3. C. At pH 4.76, NH4+ > NH3. D. At pH 9.25, CH3COOH < CH3COO-. E. All of these are accurate statements.

E. All of these are accurate statements.

A scientist working with human cells accidentally incubated the cells in water instead of the phosphate-buffered saline solution she should have used. What effect, if any, will this have on the cells? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Since water is hypotonic compared to the cells, water will move out of the cells and the cells will shrink. B. Since water is hypertonic compared to the cells, water will move into the cells and the cells will swell. C. Since water is hypertonic compared to the cells, water will move out of the cells and the cells will shrink. D. Because the cells are in an isotonic solution, there will be no effect. E. Since water is hypotonic compared to the cells, water will move into the cells and the cells will swell.

E. Since water is hypotonic compared to the cells, water will move into the cells and the cells will swell.

In an SDS-PAGE experiment, a protein migrates much faster than expected relative to protein standards, based on its known molecular weight. What could cause this? A. The voltage was too high. B. The buffer ionic strength was too low. C. The current was too high. D. The electrophoresis wasn't run long enough. E. The protein had a very high intrinsic negative charge.

E. The protein had a very high intrinsic negative charge.

Classify the words or phrases as descriptions or examples of fibrous proteins, globular proteins, or both. Exhibit secondary protein structure intermediate filaments myoglobin plymers of amino acids soluble in water insoluble in water function as structural proteins in the cell some function as enzymes structure is somewhat spherical structure is rod-like hemoglobin Polymers of amino acids

Fibrous Proteins -structure is rod-like -insoluble in water -usually function as structural proteins in the cell -intermediate filaments Globular Proteins -some function as enzymes -structure is somewhat spherical -hemoglobin -soluble in water Both -polymers of amino acids -exhibit secondary protein structure

Classify each protein example according to its highest level of protein structure. The amino acid sequence of myoglobin myoglobin with heme hemoglobin The C helix of ALPHA-lactalbumin

The amino acid sequence of myoglobin PRIMARY myoglobin with heme TERTIARY hemoglobin QUARTERNARY The C helix of ALPHA-lactalbumin SECONDARY

A small generic section of the primary structure of an α helix is given by −amino amino acid1− amino acid2− amino acid3− amino acid4− amino acid5− amino acid6− amino acid7 Which amino acid residue's backbone forms a hydrogen bond with the backbone of the seventh (7th) residue?

amino acid 3 n+4

1. William Astbury discovered that the X‑ray diffraction pattern of wool shows a repeating structural unit of approximately 5.2 Å along the length of the wool fiber. Choose the statement that explains the observed 5.2 Å length of the repeating structural unit in the wool polypeptide, α‑keratin. A. The wool polypeptide α‑keratin consists primarily of α‑helices arranged as coiled coils, where the length of each complete turn of the helix is 5.2 Å. B. The wool polypeptide α‑keratin has a fully extended backbone and does not contain any regular secondary structure elements. C. The wool polypeptide α‑keratin exists primarily as a B‑form double helix, where the length of each complete turn of the helix is 5.2 Å. D. The wool polypeptide α‑keratin is composed of small hydrophobic amino acids that form tightly packed β‑sheets. The length of each repeating structural unit in the β‑sheet is 5.2 Å. 2. When Astbury steamed and stretched the wool and held it, the X‑ray pattern showed a new repeating structural unit that was approximately 7.0 Å long. When the stretched wool was allowed to shrink, the X‑ray pattern again showed a repeating unit of approximately 5.2 Å. What can you conclude about the structure of α‑keratin in the steamed and stretched wool? A. When wool is steamed and stretched, the coiled-coil structure of α-keratin disrupts. The two strands of α‑keratin become single α helices with repeating units that are approximately 7.0 Å long. B. When wool is steamed and stretched, the peptide bonds in α‑keratin break, resulting in an increase in the length of the repeated structural units to 7.0 Å. C. When wool is steamed and stretched, the α‑keratin polypeptide extends and changes from the α conformation to the β conformation, where the length of the repeated structural units is 7.0 Å. D. When wool is steamed and stretched, the α‑keratin backbone takes on a fully extended conformation and does not have any regular secondary structure elements.

1) The wool polypeptide \alpha keratin consists primarily of \alpha helices arranged in coiled coils, where length of each complete turn of the helix is 5.2 A 2) as we know that wool pepteide \alpha keratin consists primarily of \alpha helices arranged in coiled coils, where length of each complete turn of the helix is 5.2 A, now when wool is steamed and stretched the alpha helix converted to beta plate of 7 A repeat.

Beta ( 𝛽 ) sheets are a type of secondary structure in proteins. A segment of a single chain in an antiparallel 𝛽 sheet has a length of 193 Å . How many residues are in this segment? number of residue:?

55.14 residue The structural repeat of a beta sheet is 7 angstroms / 2 amino acids. So 193 A / 3.5 A/residue = 55.14 amino acids

Alpha helices are a type of secondary structure in proteins. What is the length of a 31.0 kDa single‑stranded α‑helical protein segment? Assume a mean residue mass of 110 Da Length: _____ A^o

A 31.0 kDa single-stranded ALPHA helix contains about 282 residues 31.0kDa x (1000Da/1kDa) x (1 residue/110 Da)= 281.8181818 amino acid residues. A single turn of the helix (each repeating unit) extens about 5.4 A. There are 3.6 residues per turn. Therefore, the rise per residue is 1.5 A. The length of this segment is 423A 282 residues x (1.5 A/1 residue)=423 A OR no.of amino acid residues = 31000 / 110 = 281.8181818 amino acid residues. Are 3.6 per turn =>no of turns = 281.8181818/3.6 = 78.28282828 turns. length of Each turn =0.54 nm Total length = 78.28282828 x 0.54 = 42.27272727 nm. (If answering in angstroms: 42.27272727nm x 10A/1nm = 422.7272727 A)

What is the net charge of histidine at pH = 1? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. +2 B. +1 C. 0 D. -1 E. -2

A. +2

Using the Henderson-Hasselbalch equation, calculate the percentage of an ammonia solution that would be in the ionic form at pH 9.40, assuming a pKa for the ammonium ion of 9.25. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 41.5% B. 29.1% C. 1.41% D. 58.5% E. 70.9%

A. 41.5%

Forty-two percent of a propionic acid solution is in its acidic form at pH 5.5. What is the pKa of propionic acid? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 5.4 B. 3.2 C. 7.8 D. 2.3 E. 5.6

A. 5.4

How many turns are there in a typical α helix with a length of 4.86 nm? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 9 B. 0.9 C. 26 D. 260

A. 9

Which of the following peptides would have a +1 charge at pH = 7? A. Ala-Gly-Asn-Leu-Lys B. A. Ala-Gly-Asn-Leu-Lys C. Ala-Gly-Asp-Leu-Lys D. Ala-Glu-Arg-Leu-Pro E. Arg-Gln-Lys-Leu-Lys

A. Ala-Gly-Asn-Leu-Lys

Which of the following statements is false regarding bacterial and animal cells? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Bacterial cells do not have a plasma membrane and have a cell wall instead. B. Bacterial cells have their genetic material located in the cytoplasm, while animal cells have their genetic material in the nucleus. C. Animal cells have membrane-bound organelles, but bacterial cells do not. D. Bacterial cells are smaller than animal cells.

A. Bacterial cells do not have a plasma membrane and have a cell wall instead.

Why does butanol (CH3CH2CH2CH2OH) have a higher boiling point than methanol (CH2OH)? The boiling points are 117°C and 65°C, respectively. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Butanol has a greater surface area and consequently more van der Waals forces among molecules. B. Butanol is more polar than methanol. C. All of the above D. Butanol has a greater capacity to hydrogen bond.

A. Butanol has a greater surface area and consequently more van der Waals forces among molecules.

Which type of hydrogen bond stabilizes most secondary structures? (The hydrogen bond is represented by dots, ···.) Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. C=O ··· H-N B. C=O ··· N-Cα C. C=O ··· C=O D. H-N ··· C=O

A. C=O ··· H-N

Which statement regarding the acid-base characteristics of the 20 common amino acids is false? A. Each has three pKa values. B. They have a characteristic isoelectric point. C. They generally exist as zwitterions at physiological pH. D. They can act as buffers.

A. Each has three pKa values.

Which of the following is true regarding troponin C? A. It has 2 calcium-binding domains. B. It has 2 amino and 2 carboxyl termini. C. It has quaternary structure. D. It has many protein fibers cross-linked together.

A. It has 2 calcium-binding domains.

Consider a carboxyl group that is part of a protein. Which statement is false? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. It has the same pKa as a carboxyl group that is not part of a protein. B. It could be paired with a cation group in the interior of a protein for structure stabilization. C. The pKa will likely be different if the carboxyl group is in the middle of the protein and protected from the surrounding aqueous environment. D. The ionization state of the carboxyl group can change based on the pH to which it is exposed.

A. It has the same pKa as a carboxyl group that is not part of a protein.

Which statement is true about insulin? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. It has two chains joined by covalent bonds. B. It is a dimer of αβ protomers. C. It is a small peptide of only nine amino acids. D. It has an unusually high lysine content.

A. It has two chains joined by covalent bonds.

Which describes a solvation layer for a hydrophobic protein solute? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. It is a highly ordered, low-entropy layer of water surrounding a solute. B. It is the exterior surface of a hydrophobic solute that often contains many salt bridges. C. It is a layer of water around the solute that is highly randomized due to the few interactions water has with the solute. D. The solvation layer is the outer layer of the protein that contains the most polar amino acids in the protein.

A. It is a highly ordered, low-entropy layer of water surrounding a solute.

Which of the following statements is false with regard to specific activity? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. It refers to the total units of enzyme in a solution. B. It is a measure of the purity of an enzyme. C. It refers to the number of enzyme units per milligram of total protein. D. It increases during the purification of an enzyme

A. It refers to the total units of enzyme in a solution.

Which statement regarding amino acids is true? A. Not all of them are used in making proteins. B. Five of the ones used in making proteins are either acidic or basic. C. All of the R groups are either polar or charged. D. At physiological pH, they have no charges.

A. Not all of them are used in making proteins.

Which of the following amino acids introduces a kink into an α helix and is thus rarely found in one? A. Proline B. Glycine C. Leucine D. Alanine

A. Proline

In cells, proteins fold into their native conformation in a matter of seconds. What does this show about the folding process? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Proteins do not find their native conformation by trial-and-error. B. Helices form first, then β structures. C. All proteins are assisted in folding by chaperones. D. Proteins frequently are trapped in metastable states, otherwise random folding would be on the scale of picoseconds.

A. Proteins do not find their native conformation by trial-and-error.

Which four statements about amino acids are true? A. The Leu side chain does not form hydrogen bonds with other amino acids B. Methionine has one sterocenter (chiral center) C. Phe can undergo oxidation to form Tyr D. The form of glycine used by the human body is D-glycine E. Leucine has an overall charge at physiological pH (7.4) F. Methionine is a thiol G. Asn and Gln are polar amino acids

A. The Leu side chain does not form hydrogen bonds with other amino acids B. Methionine has one sterocenter (chiral center) C. Phe can undergo oxidation to form Ty G. Asn and Gln are polar amino acids

What is proteostasis? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. The continuous maintenance of an active set of cellular proteins. B. The collective list of all proteins in a given cell. C. The process of cooperative folding of a protein. D. The set of all reactions catalyzed by protein enzymes.

A. The continuous maintenance of an active set of cellular proteins.

If a 1.0 M solution of NaCl is diluted to 0.5 M, how will the strength of the average ionic attractions between Na+ and Cl- change? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. The forces will be about one-fourth as strong. The force depends on the inverse square of the separation distance. B. The attractions will be half as strong in the 0.5 M solution due to greater average distance between ions. C. The attractions will be stronger due to proton hopping. D. The attractions will be weaker due to greater solvation of each ion by wa

A. The forces will be about one-fourth as strong. The force depends on the inverse square of the separation distance.

Why are salt bridges much stronger when they occur at the interior of a protein as compared to its surface? A. The interior of the protein has a much lower dielectric constant than the solvent so there is no shielding of the charges. B. Salt bridges become covalent at the core of a protein because there are no other charges around. C. A salt bridge inside a protein causes induced dipoles to interact with the ions. D. There is no difference in strength between salt bridges at the surface and the core of a protein. E. Because a salt bridge neutralizes the charges on each ionic group and makes it very non-polar, so it also interacts by hydrophobic forces.

A. The interior of the protein has a much lower dielectric constant than the solvent so there is no shielding of the charges.

A buffer solution is made by mixing appropriate amounts of sodium acetate and acetic acid. What effect on pH is there with the addition of sodium chloride? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. The pH is unchanged because neither sodium nor chloride ions shift the equilibrium. B. The pH decreases because the equilibrium will shift toward the acetate ion. C. The pH will increase due to hydrolysis of the chloride ion. D. The pH will increase because the equilibrium will shift toward acetic acid.

A. The pH is unchanged because neither sodium nor chloride ions shift the equilibrium.

Select the true statements about protein secondary structure. A. The secondary level of protein structure refers to the spatial arrangement of short segments of the protein. B. In a β‑pleated sheet, the side chains extend above and below the sheet. C. Disulfide bonds stabilize secondary structure. D. In an α‑helix, the side chains are located inside the helix. E. The α‑helix is held together by hydrogen bonds between the amide N−H and C=O groups.

A. The secondary level of protein structure refers to the spatial arrangement of short segments of the protein. B. In a β‑pleated sheet, the side chains extend above and below the sheet. E. The α‑helix is held together by hydrogen bonds between the amide N−H and C=O groups.

Which statement regarding the tertiary structure of proteins is false? A. The tertiary structure of a protein is destabilized by the hydrophobic effect. B. Amino acid residues far apart in primary structure may interact with each other in the tertiary structure. C. Many proteins can be classified as either globular or fibrous (but not both). D. Quaternary structure is the description of how the tertiary structures in a multi‑subunit protein are arranged with respect to each other.

A. The tertiary structure of a protein is destabilized by the hydrophobic effect.

Which of the following statements is false regarding amino acids? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. They are found in the D-form in proteins. B. They can be grouped according to the properties of their R groups. C. pH can influence the charge of an amino acid. D. All amino acids have amino groups and carboxyl groups.

A. They are found in the D-form in proteins.

Which statement is true about the configuration of amino acids in proteins? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. They are in the L-configuration. B. They are in the D-configuration. C. The amount of each configuration varies widely among proteins. D. There is usually about an equal mix of the L and D configurations.

A. They are in the L-configuration.

Reverse turns are classified as secondary structure because _____. A. They are stabilized by hydrogen bonds between backbone amide groups. B. They link together α-helices. C. They link together β-sheets. D. They only occur at interior protein positions. E. They are not as important as primary structure.

A. They are stabilized by hydrogen bonds between backbone amide groups.

Which of the following amino acids has an uncharged polar side chain at pH 7? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Thr B. Ile C. Arg D. Pro

A. Thr

Which statement about the titration curve for a weak acid is correct? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. When a strong acid is 50% titrated, the pH of the solution is lower than for a weak acid. B. It takes less base to fully titrate a strong acid than a weak acid. C. When a strong acid is 50% titrated, the pH of the solution is higher than for a weak acid. D. A strong acid and a weak acid will have the same pH when the solution is 50% titrated. E. It takes more base to fully titrate a strong acid than a weak acid.

A. When a strong acid is 50% titrated, the pH of the solution is lower than for a weak acid.

Which component is absolutely necessary for purification of a protein? A. a means of detecting the protein B. column chromatography C. the gene sequence of the protein D. a centrifuge

A. a means of detecting the protein

Which acid and its conjugate base would be the best buffer at pH = 4.7? A. acetic acid; Ka = 1.8 x 10^-5 B. 2-amino-2-hydroxymethyl-propane-1,3-diol (Tris); Ka= 6.3 x 10^-9 C. formic acid; Ka = 1.8 x 10^-4 D. 4-morpholineethanesulfonic acid (MES); Ka = 7.9 x 10^-7 E. 4-(2-hydroxyethyl)piperazine-1ethanesulfonic acid (HEPES); Ka = 3.2 x 10^-8

A. acetic acid; Ka = 1.8 x 10^-5

What generally happens during a successful enzyme purification protocol (comparing crude extract to final product)? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. activity decreases and specific activity increases B. activity increases and specific activity decreases C. activity and specific activity increase D. activity and specific activity decrease

A. activity decreases and specific activity increases

The α‑helix is A. affected by the identities of the residues near each end. B. stablized by amino acid R‑group interactions. C. stabilized primarily by the hydrophobic effect. D. a left‑handed helix with 3.6 amino acids per turn.

A. affected by the identities of the residues near each end.

If a scientist wanted to separate two similarly sized and charged proteins, which method of column chromatography would be best? A. affinity B. anion exchange C. cation exchange D. size exclusion

A. affinity

The amino acid sequences of proteins A. can be used to establish evolutionary relationships between organisms. B. are also referred to as consensus sequences. C. are similar within a given organism. D. are an example of tertiary structure.

A. can be used to establish evolutionary relationships between organisms.

Enantiomers A. can exist for molecules with more than one chiral carbon B. are only associated with amino acids C. are always designed either D or L D. can be specific types of diastereomers

A. can exist for molecules with more than one chiral carbon

Which feature is not associated with globular proteins? A. classified as either all α or all β B. intrinsically disordered regions of structure C. domains D. motifs

A. classified as either all α or all β

The double helix that is formed after DNA replication _____. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. contains one parental strand of DNA and one newly synthesized strand of DNA B. contains one parental strand of DNA and one newly synthesized strand of RNA C. contains either two parental DNA strands or two newly synthesized strands of DNA D. contains two strands of DNA, each consisting of material from both the parental and newly synthesized strand E. none of the above

A. contains one parental strand of DNA and one newly synthesized strand of DNA

All of the following are considered to be weak interactions among biomolecules except _____. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. covalent bonds B. ionic interactions C. van der Waals interactions D. hydrogen bonds E. hydrophobic interactions

A. covalent bonds

By convention, amino acid sequences of polypeptides are read: Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. from N-terminus to C-terminus, left to right. B. from N-terminus to C-terminus, right to left. C. from C-terminus to N-terminus, left to right. D. from C-terminus to N-terminus, right to left.

A. from N-terminus to C-terminus, left to right.

Polypeptides that are folded into a roughly spherical shape and may contain several types of secondary structure are classified as ________ proteins. A. globular B. tertiary C. fibrous D. cluster

A. globular

The configurations of ________ are used as the basis for assigning the L and D configurations. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. glyceraldehyde B. glycine C. glutamate D. alanine

A. glyceraldehyde

Strong acids have ___ Ka values and ___ pKa values than weaker acids. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. higher; lower B. lower; lower C. higher; higher D. lower; higher

A. higher; lower

Permanent hair waving is not really permanent because ____. A. new hair that grows has the original pattern of disulfide bonds B. the oxygen in air oxidizes the new disulfide bonds C. sunlight exposure gradually reverses the process D. over time the new disulfide bonds equilibrate back to their original pattern

A. new hair that grows has the original pattern of disulfide bonds

In an oligomeric protein, how are the subunits associated with each other? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. non-covalent interactions B. disulfide bonds C. peptide bonds D. all of the above

A. non-covalent interactions

Weak acids A. only partially ionize in water. B. are formed by dilution of strong acids. C. react very slowly with bases. D. have a p𝐾a< 7

A. only partially ionize in water.

The dimerization of cysteine to cystine is an example of __________. A. oxidation B. reduction C. hydrolysis D. single displacement

A. oxidation

The bonding of atoms of very different electronegativity is the source of ______. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. polarity B. van der Waals forces C. hydrophobic interactions D. ionic bonding

A. polarity

Which level of protein structure describes the covalent backbone of a protein, including the sequence of amino acids? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. primary B. secondary C. tertiary D. quaternary

A. primary

Choose the functions of amino acids (free or in a bound form) A. protein components B. metabolic intermediates C. hormones D. neurotransmitters E. carriers of genetic information

A. protein components B. metabolic intermediates C. hormones D. neurotransmitters

The purpose of adding SDS (sodium dodecyl sulfate) during the electrophoresis of proteins, is to make it possible to _____. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. separate proteins exclusively on the basis of molecular weight B. preserve a protein's native structure and biological activity C. determine an enzyme's specific activity D. determine a protein's isoelectric point

A. separate proteins exclusively on the basis of molecular weight

The Ramachandran plot A. shows combinations of permissible dihedral angles in a polypeptide chain. B. excludes proline residues. C. shows the amino acid sequence of a protein. D. shows values of Δ𝐺 for each combination of dihedral angles.

A. shows combinations of permissible dihedral angles in a polypeptide chain.

A regular secondary structure occurs in a protein chain segment when _______. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. the φ and ψ angles are the same, or nearly so, throughout the segment B. the dihedral angle ω is near 0° C. the pH is near 7.0 D. the segment is primarily composed of aromatic amino acids

A. the φ and ψ angles are the same, or nearly so, throughout the segment

What order of magnitude is the upper limit of the number of amino acids for the largest known proteins? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. thousands of amino acids B. hundreds of amino acids C. millions of amino acids D. billions of amino acid

A. thousands of amino acids

Which does not apply to β turns? A. usually involves three amino acids B. makes a 180° turn in the protein chain C. often occurs near the surface of a protein D. has a hydrogen bond between the first and last amino acids in the turn

A. usually involves three amino acids

Classify each phrase as a description of alpha helices, beta sheets, beta turns, or all 1 st residue hydrogen bonded to 4th residue hydrogen (that is residue n is bonded to residue n + 3) Succesive R groups point in opposite direction all -NH groups point in the same direction. 1st residue hydrogen bonded to 5th residue (that is residue n is H-bonded to residue n+4) Contains -NH hydrogen bonded to C = O

Alpha Helices : - -1st residue hydrogen bonded to 5th residue (that is residue n is H-bonded to residue n+4) -all -NH groups point in the same direction. Beta Sheets : -Succesive R groups point in opposite direction Beta Turns : -1 st residue hydrogen bonded to 4th residue hydrogen (that is residue n is bonded to residue n + 3) All -Contains -NH hydrogen bonded to C = O

hich of the following combinations of φ and ψ dihedral angles would be allowed in a poly-Alanine polymer? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. +180°, -180° B. -120°, + 120° C. +120°, -120° D. -120°, -120° E. +120°, +120°

B. -120°, + 120°

at is the [OH-] in a 0.010 M sulfuric acid (H2SO4) aqueous solution at 25 °C? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 0.020 M B. 5.0 x 10-13 M C. 1.0 x 10-12 M D. It cannot be determined from the information given.

B. 5.0 x 10-13 M

Which is true about the melting temperature, Tm, for ribonuclease? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. At Tm the protein is completely denatured. B. At Tm ribonuclease exhibits half the activity of a sample in its native conformation. C. At Tm the disulfide bonds and all hydrogen bonding are overcome by the heat. D. At Tm ribonuclease is resistant to treatment with urea.

B. At Tm ribonuclease exhibits half the activity of a sample in its native conformation.

Which statement is false? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Glycine does not have L and D configurations. B. By the Fischer assignment, the L amino acids are levorotatory. C. The active sites of enzymes that synthesize amino acids are asymmetric. D. The absolute configuration of a molecule specifies a particular enantiomer.

B. By the Fischer assignment, the L amino acids are levorotatory.

Which of the following best defines a signature sequence? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. An amino acid sequence consisting of the residues that most commonly occur at each position in a set of similar sequences B. Certain segments of a protein sequence that are found in the organisms of one taxonomic group but not in other groups C. The regions of a protein sequence that are identical in the organisms within one taxonomic group D. The random sequence that results when the amino acids of a known sequence are shuffled by a common computerized test

B. Certain segments of a protein sequence that are found in the organisms of one taxonomic group but not in other groups

Which substance is commonly used to salt out proteins during fractionation procedures? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. coomassie blue B. ammonium sulfate C. sodium chloride D. sodium dodecyl sulfate

B. ammonium sulfate

Which amino acid repeat is present in collagen? (X is often Pro; Y is often 4-Hyp) A. X-X-Y B. Gly-X-Y C. Ala-Lys-X D. Gly-Ala-Y-X

B. Gly-X-Y

Which statement does not describe a characteristic of a peptide bond? A. It is an amide bond. B. It causes resonance stabilization of each backbone bond. C. It is rigid and planar. D. It is a linkage between amino acids in a protein

B. It causes resonance stabilization of each backbone bond.

Which of the following statements is false with regard to specific activity? A. It is a measure of the purity of an enzyme. B. It refers to the total units of enzyme in a solution. C. It increases during the purification of an enzyme. D. It refers to the number of enzyme units per milligram of total protein.

B. It refers to the total units of enzyme in a solution.

What is unique about proline that is part of a β turn? A. Its ring structure is broken. B. Its N-terminal peptide bond is cis. C. It is in the D configuration. D. It is more protonated than other prolines.

B. Its N-terminal peptide bond is cis.

__________ are the polymers of amino acids. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Lipids B. Proteins C. Polysaccharides D. DNA and RNA

B. Proteins

Affinity chromatography can be used to purify proteins such as growth factor receptors. The ligand of the growth factor receptor can be linked to resin, and then an extract containing membrane proteins can be poured over the resin. If a high concentration of free ligand were poured over the resin next, what would you expect to happen? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. The excess ligand will attach to the resin. B. The excess ligand will compete with the ligand attached to the resin, releasing the growth-factor receptor from the resin. C. The growth-factor receptor will bind both the excess ligand and the ligand attached to the resin at the same time. D. none of the above

B. The excess ligand will compete with the ligand attached to the resin, releasing the growth-factor receptor from the resin.

What can be said about a single polypeptide containing: 5 Ala, 2 Glu, 1 Lys, 1 Gly, and 1 Cys? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. The peptide contains two carboxylic acid groups. B. The peptide will be charged at pH 7. C. The peptide is not redox active. D. The peptide contains three amino groups. E. All of these are true.

B. The peptide will be charged at pH 7.

In order for a solute to be soluble in water, which situation must be true? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. The solute is ionic. B. The water-solute interactions are more favorable energetically than water-water interactions. C. The undissolved solute particles must only be attracted to each other by van der Waals interactions. D. The solute must be able to hydrogen bond with water.

B. The water-solute interactions are more favorable energetically than water-water interactions.

Which factor is not associated with amino acids found in proteins? A. They are L enantiomers (with few exceptions). B. There are disulfide bonds between methionine side chains. C. Some have aromatic rings in their R groups. D. Hydrophobic side chains tend to cluster to the proteins interior.

B. There are disulfide bonds between methionine side chains.

In aqueous solution proteins will tend to fold and bury the hydrophobic amino acids toward the protein's interior. In the process, a great deal of conformational entropy is lost by the protein as it adopts a more ordered shape. If so much entropy is lost by the protein, why does it fold? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Loss of entropy is thermodynamically favorable. B. There is a larger entropic gain for the surrounding water molecules. C. The entropic loss is usually offset by the formation of interior salt bridges and hydrogen bonds. D. The folding process is also strongly exothermic.

B. There is a larger entropic gain for the surrounding water molecules.

Which statement is true about salt bridges? A. They tend to destabilize protein structures. B. They are stronger in the hydrophobic interior of a folded protein than on the surface. C. They very readily associate and dissociate in proteins. D. They generally contribute little to the conformation of a protein.

B. They are stronger in the hydrophobic interior of a folded protein than on the surface.

Of the 20 common amino acids, only one lacks a chiral α-carbon. Likewise, there is one amino acid that has a second chiral carbon within its side chain. Which amino acid is it? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Leu B. Thr C. Pro D. Arg E. Ser

B. Thr

Consider two weak acids (acid 1 and acid 2) that have pKa values of 4 and 5, respectively. Which statement below is true? A. Weak acid 2 is stronger than weak acid 1. B. Weak acid 1 has a tendency to donate protons 10-fold that of weak acid 2. C. Weak acid 1 has a lower Ka than weak acid 2. D. both B and C above

B. Weak acid 1 has a tendency to donate protons 10-fold that of weak acid 2.

Which amino acid has the greatest tendency to form an α helix? A. histidine B. alanine C. proline D. aspartate

B. alanine

Which of the following best defines the term bioinformatics? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. the study of the complete protein set that is encoded by an organism's genome B. an area of research focusing on the computerized analysis of biological data C. the name of a specific computer program used by researchers to analyze protein sequences D. the study of the complete set of small-molecule metabolites present in a given cell or tissue under specific conditions

B. an area of research focusing on the computerized analysis of biological data

Eukaryotic cells A. are heterotrophs and cannot perform photo synthetic processes B. apparently obtained their mitochondria via a symbiotic relationship with ancient bacterium C. first appeared about 3.5 billion years ago D. have orthologs, but no homologs

B. apparently obtained their mitochondria via a symbiotic relationship with ancient bacterium

All organisms A. use O2 as their final electron acceptor B. Are either heterotrophs or autotrophs C. Are either photoautotrophs or chemoautotrophs D. use H2O to reduce CO2

B. are either heterotrophs or autotrophs

Which does not apply to the most common kind of α helix? A. is stabilized by hydrogen bonding B. can be a mixture of L and D amino acids C. is right-handed D. has about 3.6 amino acid residues per helix turn

B. can be a mixture of L and D amino acids

The p𝐾a of a weak acid A. is <0 at pH>7. B. can be determined from its titration curve. C. is the pH at which it has no net charge. D. is a function of its concentration.

B. can be determined from its titration curve.

Proteins A. all have similar amino acid compositions. B. can consist of more than one polypeptide chain. C. consist solely of polymerized amino acids. D. can, by definition, consist of no more than 2000 amino acid residues.

B. can consist of more than one polypeptide chain.

Weak noncovalent interactions A. always involve water. B. can have a large cumulative effect. C. do not include ionic interactions. D. combine to form covalent interactions.

B. can have a large cumulative effect.

The carboxymethyl (CM) group is a common functional group attached to what type of chromatography material? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. affinity resin B. cation exchange resin C. anion exchange resin D. gel filtration resin E. None of these use the CM function.

B. cation exchange resin

A change in ___________ changes the spatial arrangement of atoms in a protein, but does not involve the breaking of covalent bonds. A. configuration B. conformation C. primary structure D. stereoisomer

B. conformation

If under a given set of conditions the reaction A->B occurs with DELTA G = -14 kJ/mol, and the reaction C->B occurs with DELTA G = +16 kJ/mol, then A. conversion of C to A is freely reversible B. conversion of A to C is exergonic D. conversion of A to C is entropically driven E. A and C can never be at equilibrium, even under different reaction conditions

B. conversion of A to C is exergonic

Which statement describes the hydrolysis of a peptide bond? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. exergonic with a low activation energy B. exergonic with a high activation energy C. endergonic with a low activation energy D. endergonic with a high activation energy

B. exergonic with a high activation energy

Sequencing of entire genomes A. has demonstrated that very few genes in humans are of unknown function B. has revealed that differences in genes between individual humans are few C. is unlikely to reveal the underlying causes of very complex genetic diseases D. has demonstrated that the more complicated an organism, the fewer regulatory housekeeping genes it has

B. has revealed that differences in genes between individual humans are few

Paralogs are always ______, but _________. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. homologs; usually are found in different species B. homologs; homologs are not always paralogs C. orthologs; orthologs are not always paralogs D. homologs; never exist in the same species

B. homologs; homologs are not always paralogs

Numerous weak interactions are responsible for stabilizing protein conformation. Of the following, ____ are the major contributors to stabilizing the conformation of most soluble proteins. A. hydrogen bonds B. hydrophobic interactions C. van der Waals interactions D. ionic interactions

B. hydrophobic interactions

The hydrophobic effect A. only occurs with amphipathic molecules. B. is driven by an increase in entropy of water molecules. C. results from attractive forces between hydrophobic molecules. D. does not occur in biological membranes.

B. is driven by an increase in entropy of water molecules.

When H2O ionizes, A. its concentration (7 M) does not appreciably change. B. it has a measurable 𝐾eq. C. free H+ ions are present in solution. D. the Δ𝐺∘=0 kJ/mol.

B. it has a measurable 𝐾eq.

In size-exclusion chromatography _____. A. smaller protein molecules appear in earlier fractions. B. larger protein molecules appear in earlier fractions. C. proteins with a more positive charge appear in earlier fractions. D. proteins with a more negative charge appear in earlier fractions.

B. larger protein molecules appear in earlier fractions.

the molecular weight range is not too broad in SDS-PAGE (electrophoresis), which plot will be linear? A. log(Mr) versus log(Relative migration) B. log(Mr) versus Relative migration C. Mr versus Relative migration D. Mr versus log(Relative migration)

B. log(Mr) versus Relative migration

Small molecules that are universal in all cells (common amino acids, nucleotides, sugars and their phosphorylated derivatives, and mono-, di-, and tricarboxylic acids) are called _______________. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. fundamental substances B. metabolites C. monomers D. basis set molecules

B. metabolites

Which does not involve a gain in entropy? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. evaporation of a liquid B. the formation of a hydrogen bond between water molecules C. the dissolving of an ionic compound, such as NaCl, in water D. the formation of a micelle

B. the formation of a hydrogen bond between water molecules

Ehlers-Danlos syndrome and osteogenesis imperfecta are caused by ____ in collagen. A. chemical toxins causing the formation of carbon-carbon double bonds B. the substitution of glycine with larger residues such as cysteine or serine C. insufficient hydroxylation of proline residues D. an increase in dehydrohydroxylysinonorleucine cross-links

B. the substitution of glycine with larger residues such as cysteine or serine

By definition, quaternary structure is exhibited by proteins that have ___________. A. an internal layering of β sheets B. two or more separate, but associating, protein chains C. more than one type of secondary structure D. an unusually high number of disulfide bonds

B. two or more separate, but associating, protein chains

All fibrous proteins _________. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. lack quaternary structure B.are insoluble in water C. are stabilized by disulfide bonding D. have a high content of polar amino acids

B.are insoluble in water

What is the pH of a 0.150 M solution of acetic acid at 25 °C? (pKa = 4.75) Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 5.2 B. 0.8 C. 2.8 D. 4.75

C. 2.8

stimate the number of of amino acids in a typical α helix that is 30 Å long. A. 5800 B. 45 C. 20 D. The number of amino acids cannot be estimated because of the irregularity of α helices.

C. 20

A typical range for the ΔG separating the folded (active) and unfolded states in typical proteins under physiological conditions is ________. The magnitude of this ΔG indicates that the folded state is _______________ relative to the unfolded state. A. 20 to 65 kJ/mol; extremely stable B. 2000 to 6500 kJ/mol; extremely stable C. 20 to 65 kJ/mol; marginally stable D. 2000 to 6500 kJ/mol; marginally stable

C. 20 to 65 kJ/mol; marginally stable

The complementarity between the two strands is useful for determining base composition. If guanine makes up 14% of the nucleotides in a DNA sample, what percentage of nucleotides in this sample will be adenine? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 14 B. 28 C. 36 D. 43 E. 72

C. 36

Estimate the number of amino acids in a protein with a molecular weight (Mr) of 43,000 (in daltons)? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 336 B. Cannot estimate without more information about the amino acid content. C. 391 D. 312

C. 391

The Ka of acetic acid is 1.74 x 10-5. Calculate the equilibrium constant (Kb) for the following equilibrium. (Ac- = acetate ion; HAc = acetic acid) Ac- + H2O ⇄ HAc + OH- Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. 1.74 x 109 B. 5.7 x 104 C. 5.7 x 10-10 D. 1.74 x 10-19

C. 5.7 x 10-10

Which of the statements about peptide bonds are true? A. Peptide bonds form from nucleophilic attack by an ALPHA carboxyl carbon atom on an electron pair of an ALPHA amino nitrogen atom of another amino acid B. Peptide bond formation is a hydrolysis reaction C. A tripetide contains three amino acid residues D. Peptide bonds are ester linkages E. Peptides are polymers of amino acids

C. A tripetide contains three amino acid residues E. Peptides are polymers of amino acids

Consider the equation H2O → H+ + OH-. Which of the following statements is false? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. The H+ and OH- molecules that form from the dissociation of water are very reactive. B. This is a reversible reaction. C. At equilibrium, the concentration of water molecules equals the concentration of H+ and OH-. D. The H+ shown in this equation will immediately bind to a water molecule, forming a hydronium ion, H3O+.

C. At equilibrium, the concentration of water molecules equals the concentration of H+ and OH-.

Which of the following bonds limits the range of conformations available for a polypeptide chain? A. N-Cα B. Cα-C C. C-N D. None of the above

C. C-N

Which statement is true regarding an acid dissociation reaction in water? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. The conjugate base form will always be the ionized species. B. The un-dissociated acid is always ionized. C. For a carboxylic acid, the conjugate base is the ionized form. D. An acid dissociation reaction does not involve ionization. E. For an amino group, the conjugate base is the ionized form.

C. For a carboxylic acid, the conjugate base is the ionized form.

lthough most amino acids follow general rules regarding structure, there are a few exceptions. _______ does not have a chiral α-carbon, while _______ is a cyclic amino acid. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Proline; alanine B. Proline; glycine C. Glycine; proline D. Alanine; proline

C. Glycine; proline

Halophiles are a group of organisms that flourish in high salt conditions. Which of the following is not true of halophiles? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Halophiles are single-celled organisms. B. Halophiles belong to the domain Archaea. C. Halophiles are eukaryotes. D.Halophiles are more closely related to slime molds than to animals.

C. Halophiles are eukaryotes.

What is a likely cause for limiting the size of cells? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. The plasma membrane cannot hold together if the cell is too large. B. Cell division time increases dramatically as cell size increases. C. Insufficient amounts of small molecules (e.g. O2) can diffuse into the cell's interior if the cell is too large. D. all of the above

C. Insufficient amounts of small molecules (e.g. O2) can diffuse into the cell's interior if the cell is too large.

Which statement is true about a living E. coli cell? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. All of its cellular processes are in equilibrium. B. It is in a state of high entropy. C. It is in a dynamic steady state that is far from equilibrium. D. It is in a dynamic steady state that is close to equilibrium.

C. It is in a dynamic steady state that is far from equilibrium.

Which statement is true for the dihedral angle, ω, in the protein backbone? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Because of the restricted rotation of the peptide bond ω is always 0°. B. The most common values of ω are -120°, -60°, +60° and +120°. C. It usually equals either -180° or +180° because the of the trans orientation about the peptide bond. D. It may take on any value between -180° and 180° in normal proteins.

C. It usually equals either -180° or +180° because the of the trans orientation about the peptide bond.

If the following secondary structures, which has not been observed in a protein before? A. Type I β turn B. Type II β turn C. Left-handed α helix D. Antiparallel β conformation

C. Left-handed ALPHA helix

Which of the following generalizations about methodologies that determine three-dimensional structure of proteins is correct? A. X-ray crystallography is performed on macromolecules that are in solution. B. NMR is limited to molecules that can be crystallized. C. NMR can generate information about protein conformational changes, protein folding, and interactions with other molecules. D. NMR is used to determine structure of proteins that are too large to be determined by x-ray crystallography.

C. NMR can generate information about protein conformational changes, protein folding, and interactions with other molecules.

A possible electron acceptor for Earth's earliest cells is _____; modern organisms use ____as the major electron acceptor for metabolism. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. H2; H2O B. H2O; H2 C. SO42-; O2 D. O2; SO42

C. SO42-; O2

hich statement about the amino acid Cys is not true? A. The Cys side chain contains a redox active thiol group. B. The Cys side chain is a nucleophile in its unprotonated form. C. The Cys side chain can act as an acid in its unprotonated form. D. The Cys side chain is ionizable. E. All of these are true.

C. The Cys side chain can act as an acid in its unprotonated form.

Which statement is true about the side chains (R groups) of amino acids in an α helix? A. They are randomly oriented along the helix. B. They alternating between pointing to the interior and exterior of the helix. C. They extend radially out from the helix. D. They point to the interior of the helix.

C. They extend radially out from the helix.

Which statement about buffers is false? A. [A−]=[HA] when pH=p𝐾a. B. They are weak acids and bases. C. They have maximum buffering capacity at pH=7. D. They can sometimes be biological macromolecules.

C. They have maximum buffering capacity at pH=7.

Which statement about hydrogen bonds is false? A. They cause acid-base reactions in aqueous solutions to be very rapid. B. They have an optimal geometry. C. They only occur between water molecules. D. They are weak compared with covalent bonds.

C. They only occur between water molecules.

What information can be gained by comparing the sequences of proteins that have the same or similar function in different species? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. to predict similarity in protein folding B. to determine evolutionary relationships and relatedness of species C. all of the above D. to determine sequences that are conserved among species since they are likely to be important to the function and stability of the proteins

C. all of the above

Sheets of continuous β conformation with 180° turns are ____________ and the hydrogen bonds between adjacent segments are ____________. A. parallel; in-line B. parallel; not in-line C. antiparallel; in-line D. antiparallel; not in-line

C. antiparallel; in-line

n the cation exchange chromatography of amino acids where the elution buffer is applied as a gradient from low pH to high pH, what is the order of elution (first to last) of a mixture of glycine, aspartate and arginine? A. glycine; aspartate; arginine B. glycine; arginine; aspartate C. aspartate; glycine; arginine D. arginine; glycine; aspartate

C. aspartate; glycine; arginine

Osmosis occurs A. because osmotic pressure is applied. B. because cells need H2O. C. because diffusion of H2O from high concentration to low is thermodynamically spontaneous. D. when a cell is in an isotonic solution relative to its cytosol.

C. because diffusion of H2O from high concentration to low is thermodynamically spontaneous.

Which does not apply to circular dichroism (CD) spectroscopy? A. examines the fraction of a protein that is folded B. in the far UV, measures the absorbance of the peptide bond C. determines the aromatic content of a protein D. examines structural asymmetry

C. determines the aromatic content of a protein

The strength of an acid _____. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. is directly proportional to the strength of its conjugate base B. is directly proportional to its pKa value C. is inversely proportional to the strength of its conjugate base D. has no relation to the strength of its conjugate base E. has no relation to its pKa

C. is inversely proportional to the strength of its conjugate base

Generally, physiological pH A. is between 9.35 and 9.45. B. is determined from its titration curve. C. is near 7. D. must be within one pH unit of its p𝐾a.

C. is near 7.

Which amino acid would tend to stabilize a protein through the hydrophobic effect? A. glutamate B. arginine C. leucine D. all of the above

C. leucine

Proteins are _____________ polymers of _____________. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. branched; nucleotides B. branched; amino acids C. linear; amino acids D. linear; nucleotides

C. linear; amino acids

Which defines denaturation of a protein? A. degradation to free amino acids B. aggregation of misfolded proteins with loss of native function C. loss of tertiary structure sufficient for loss of function D. complete unfolding and randomization of conformation

C. loss of tertiary structure sufficient for loss of function

MALDI MS analysis is used to determine the _______ of the protein. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. sequence B. 3-dimensional shape C. mass D. pI

C. mass

Because human and mouse α-globin genes are thought to have evolved from a common ancestor, they are considered to be _____. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. homologs B. paralogs C. orthologs D. none of the above

C. orthologs

Chemical synthesis of peptides by the Merrifield method A. is nearly as efficient as peptide bond synthesis in biochemical systems. B. has a practical upper limit of a polymer of about 500 amino acid residues. C. proceeds from the carboxyl terminus to the amino terminus. D. involves synthesizing the peptide and then attaching it to a solid support.

C. proceeds from the carboxyl terminus to the amino terminus.

In a glycoprotein the ______________ groups are _____________. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. subunit; glucose units B. protomer; chains of glycine C. prosthetic; carbohydrates D. conjugate; derivatives of glyceraldehyde

C. prosthetic; carbohydrates

Paralogs are _____. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. different conformations of a protein B. proteins with different signature sequences C. proteins from one species with the same function D. genes transferred from one species to another

C. proteins from one species with the same function

Quaternary structure A. refers to proteins with identical subunits. B. refers to proteins with four subunits. C. refers to an arrangement of tertiary protein subunits in a three‑dimensional complex. D. describes how oligomers are assembled into protomers.

C. refers to an arrangement of tertiary protein subunits in a three‑dimensional complex.

Which describes the proteins in hair? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. right-handed helix; forms triple-stranded fibers wrapped in a left-handed fashion B. left-handed helix; forms triple-stranded fibers wrapped in a right-handed fashion C. right-handed helix; forms double-stranded fibers wrapped in a left-handed fashion D. left-handed helix; forms double-stranded fibers wrapped in a right-handed fashion

C. right-handed helix; forms double-stranded fibers wrapped in a left-handed fashion

he pH of blood is not affected by A. consuming large amounts of sodium bicarbonate. B. fasting and starvation. C. the p𝐾a of acetic acid or acetate. D. hyperventilation.

C. the p𝐾a of acetic acid or acetate.

Most cells are microscopic, ranging from about 5-100 ____ in diameter, which can also be expressed as 0.005-0.1___. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. mm; μm B. nm; μm C. μm; mm D. μm; cm E. μm; nm

C. μm; mm

Which statement about buffers is false? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Buffers contain approximately equal amounts of a weak acid and its conjugate base. B. Buffers do change pH when an acid or base is added, but the change is small. C. A buffer cannot maintain pH if large amounts of acid or base are added. D. A combination of HCl and NaOH can make a good buffer.

D. A combination of HCl and NaOH can make a good buffer.

Ramachandran plots describe the combinations of Φ and Ψ dihedral angles that are or are not permitted in a peptide backbone. Which of the following statements is INCORRECT regarding Φ and Ψ angles? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Ψ involves the N-Cα-C-N bonds. B. Steric hindrance between atoms in the polypeptide backbone and amino acid side chains limit the values of Φ and Ψ. C. Φ involves C-N-Cα-C bonds. D. Both angles are defined as +/- 90 degrees when the polypeptide is fully extended and all peptide groups are in the same plane.

D. Both angles are defined as +/- 90 degrees when the polypeptide is fully extended and all peptide groups are in the same plane.

Describe what is occurring in the following reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. C6H12O6 and CO2 are oxidized. B. C6H12O6 is reduced and O2 is oxidized. C. O2 is oxidized and CO2 is reduced. D. C6H12O6 is oxidized and O2 is reduced.

D. C6H12O6 is oxidized and O2 is reduced.

Which statement about DNA is false? A. It is a double helix of two polymeric strands twisted about each other B. Each strand serves as a template for copying the DNA sequence C. Deoxyguanylate is complementary to deoxycytidylate D. Covalent interactions between complementary basses occur between the strands

D. Covalent interactions between complementary basses occur between the strands

A nonapeptide was determined to have the following amino acid composition: two Lys, two Gly, two Phe, one each of His, Leu, and Met. When the native peptide was exposed to cyanogen bromide, a heptapeptide and a dipeptide were recovered. Incubation of the native peptide with trypsin gave a pentapeptide and a tetrapeptide. Cyanogen bromide cleaves at Met (C); whereas trypsin cleaves at Lys and Arg (C). Which sequence is compatible with this data? A. Gly-Phe-Lys-Lys-Gly-Leu-Met-Phe-His B. Gly-Leu-Phe-His-Lys-Lys-Phe-Met-Gly C. His-Leu-Gly-Lys-Lys-Phe-Phe-Met-Gly D. Gly-Met-Leu-Lys-His-Phe-Gly-Phe-Lys

D. Gly-Met-Leu-Lys-His-Phe-Gly-Phe-Lys

Which statement applies to the following sequence's α helix formation at pH 7? AIVDAEDVEID A. Helices are favored due to high hydrophobic character. B. Helices are favored due to strong capacity for hydrogen bonding. C. Helices are not favored due to the bulkiness of side chains. D. Helices are not favored due to repulsion of negative charges.

D. Helices are not favored due to repulsion of negative charges.

Which of the following statements regarding β conformation is false? A. R groups of adjacent amino acids protrude from the structure in opposite directions. B. Individual segments of a β sheet are not required to be near one another in the linear sequence of the polypeptide. C. In this conformation, the polypeptide chain is extended into a zigzag rather than a helical structure. D. Interstrand H bonds are in-line for the parallel β sheet and not in-line for the antiparallel variant.

D. Interstrand H bonds are in-line for the parallel β sheet and not in-line for the antiparallel variant.

Freediving is an activity in which a person dives, sometimes to great depth, without the use of scuba gear. The diver must hold his or her breath for the duration of the dive. The record depth, with no equipment such as diving fins, is 101 m; the official record time is over 11 minutes. Historically, freediving has been used by pearl divers and sponge divers. Some freedivers hyperventilate (breathe rapidly and deeply) before diving. Hyperventilation can change the concentration of CO2 in the blood and may increase the length of time that a person feels like he or she can hold his or her breath. How does hyperventilation affect blood pH? A. It increases CO2 and H+ in the blood, decreasing pH B. It decreases CO2 and increases H+ in the blood, increasing pH C. It increases CO2 and decreases H+ in the blood, increasing pH D. It decreases CO2 and H+ in the blood, increasing pH

D. It decreases CO2 and H+ in the blood, increasing pH

What does it mean for a particle to be amphipathic? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. It can act as an acid or a base. B. Van der Waals forces are the only potential attractive forces for this particle. C. has more than one pKa. D. It has both polar (or charged) and nonpolar parts in the same particle

D. It has both polar (or charged) and nonpolar parts in the same particle

Which statement is true about alanine? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Only the zwitterion form provides buffering. B. It is a good buffer near neutral pH. C. It cannot buffer at any pH. D. It has two pH regions where it can act as a buffer.

D. It has two pH regions where it can act as a buffer.

Which statement about protein folding is false? A. It is a stepwise process. B. It is sometimes assisted by proteins known as chaperones. C. It is driven by changes in free energy. D. It requires protein disulfide and peptide prolyl cis-trans isomerases.

D. It requires protein disulfide and peptide prolyl cis-trans isomerases.

Which shows the order appearance of organism on Earth? (The earliest organisms are listed first.) Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Methanogens → Protists → Cyanobacteria → Aerobic Bacteria B. Protists → Cyanobacteria → Methanogens → Aerobic Bacteria C. Cyanobacteria → Methanogens → Aerobic Bacteria → Protists D. Methanogens → Cyanobacteria → Aerobic Bacteria → Protists

D. Methanogens → Cyanobacteria → Aerobic Bacteria → Protists

Which amino acid does not have an aromatic side chain? Please choose the correct answer from the following choices, and then select the submit answer button. A. tyrosine B. histidine C. phenylalanine D. None of the above, all have aromatic side chains.

D. None of the above, all have aromatic side chains.

Which statement is false? A. The function of a protein is a result of its amino acid sequence. B. It is possible to change the amino acid sequence of a protein and have no effect on its function. C. Protein structure is commonly described at four levels. D. Orthologs are homologs found in the same species.

D. Orthologs are homologs found in the same species.

For a polyprotic acid, which statement is true? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Polyprotic acids are stronger acids than monoprotic acids. B. A polyprotic acid has a single associated pKa value. C. A polyprotic acid can only react with one equivalent of base. D. The conjugate base of a polyprotic acid can also act as an acid itself. E. All of these statements are true.

D. The conjugate base of a polyprotic acid can also act as an acid itself.

An active protein was purified to homogeneity using gel filtration and analyzed for its amino terminal residue using dabsyl chloride as described in Chapter 3. After multiple tries, the researcher gave up because there appeared to be four different amino terminal residues in the protein. What would you conclude about this protein? A. The protein had not been purified properly. B. The protein had Lys, Arg, and His residues that were reacting in the dabsyl chloride. C. The protein had been degraded. D. The protein was made of four unique subunits. E. none of the above

D. The protein was made of four unique subunits.

Do any of these statement not apply to a reaction with a large equilibrium constant? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. No, all of the above apply. B. The products are favored and the reaction tends to go to completion. C. The standard free-energy change is negative. D. The reaction proceeds rapidly toward equilibrium.

D. The reaction proceeds rapidly toward equilibrium.

Which of the following generalizations about globular proteins is incorrect? A. The globular structure derives stability from hydrophobic interactions. B. Globular proteins have a more compact shape than fibrous proteins. C. They tend to have a dense hydrophobic core. D. They generally have quaternary structure.

D. They generally have quaternary structure.

Circular dichroism measures the difference between _____. A. absorbance by a linear peptide vs. absorbance by a circular peptide B. total light absorbed by an α-helix vs. total light absorbed by a β-sheet C. the dipole moment of the amino end of an α-helix vs. the carboxyl end D. absorption of right circular polarized light vs. left circular polarized light E. visible light absorption vs. ultraviolet light absorption

D. absorption of right circular polarized light vs. left circular polarized light

Which of the following properties of RNA suggest it or its related precursors may have been the first genes and catalysts? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. RNA-like molecules can form abiotically. B. RNA molecules can catalyze their own formation. C. The process of RNA self-replication is not perfect, enabling the formation of RNA variants. D. all of the above

D. all of the above

Which amino acids are particularly common in β turns? A. alanine and proline B. glycine and alanine C. serine and threonine D. glycine and proline

D. glycine and proline

Collagen A. has a primary structure of repeating -Glu-X-Y-. B. consists of α‑helical subunits. C. does not have quaternary structure. D. has fibrils consisting of cross‑linked triple helices of polypeptide chains.

D. has fibrils consisting of cross‑linked triple helices of polypeptide chains.

All cells A. Are approximately the same size B. Have mitochondria C. are at least partially aerobic D. Have a plasma membrane

D. have a plasma membrane

Peptides A. are not biologically active. B. do not have isoelectric points. C. have no α‑carboxyl groups. D. have their amino acid sequences written from the N‑terminus.

D. have their amino acid sequences written from the N‑terminus.

A good way to predict whether an amino acid side chain is on the outside or inside of a protein is to consider its ______. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. molecular weight B. three-letter abbreviation C. one-letter abbreviation D. hydropathy (polarity) E. none of the above

D. hydropathy (polarity)

The cell has a number of mechanisms to protect against the accumulation of misfolded proteins when the endoplasmic reticulum's capacity to fold proteins is overwhelmed. Which of the following does not describe the way a cell would respond during that situation? A. increase the number of chaperone proteins B. degrade misfolded proteins by autophagy C. degrade proteins by the ubiquitin-proteasome system D. increase the rate of overall protein synthesis

D. increase the rate of overall protein synthesis

Which describes collagen? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. left-handed helix; forms double-stranded fibers wrapped in a right-handed fashion B. right-handed helix; forms double-stranded fibers wrapped in a left-handed fashion C. right-handed helix; forms triple-stranded fibers wrapped in a left-handed fashion D. left-handed helix; forms triple-stranded fibers wrapped in a right-handed fashion

D. left-handed helix; forms triple-stranded fibers wrapped in a right-handed fashion

A researcher has isolated an enzyme with an optimal pH of 3 and needs to select a buffer to perform experiments with the enzyme. Which of the following would be the best buffer choice for the researcher? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. bicine, pKa 8.04 B. PIPES, pKa 6.6 C. HEPES, pKa 7.31 D. MES, pKa 5.97 E. none of the above

D. none of the above

Which of the following serve as hydrogen acceptors during the formation of a hydrogen bond? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. oxygen B. nitrogen C. carbon D. oxygen and nitrogen E. oxygen, nitrogen, and carbon

D. oxygen and nitrogen

The first step in two-dimensional gel electrophoresis generates a series of protein bands by isoelectric focusing. In a second step, a strip of this gel is turned 90 degrees, placed on another gel containing SDS, and electric current is again applied. In this second step _____. A. the proteins in the bands separate more completely because the second electric current is in the opposite polarity to the first current B. the individual bands undergo a second, more intense isoelectric focusing C. the individual bands become stained so that the isoelectric focus pattern can be visualized D. proteins with similar isoelectric points become further separated according to their molecular weights

D. proteins with similar isoelectric points become further separated according to their molecular weights

If a disulfide bond connects two polypeptide chains in a protein, the highest level of protein organization this protein has is _____. A. primary structure. B. secondary structure. C. tertiary structure. D. quaternary structure.

D. quaternary structure.

Water A. is a buffer. B. has a pH=0 when pure. C. is a reactant in condensation reactions. D. reacts with CO2 in a reaction catalyzed by carbonic anhydrase.

D. reacts with CO2 in a reaction catalyzed by carbonic anhydrase.

Computer algorithms have been generated to help determine the pathway proteins take to arrive at their native conformation when folding. Which of the following is thought to be the first region to be assembled during this process? A. supersecondary structures B. long-range interactions between segments C. domains D. secondary structures

D. secondary structures

The C−N bond in the peptide backbone of a protein would have a bond that is ______ the C−N bond in CH3−NH3+. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. the same length as B. weaker than C. identical to D. shorter than E. longer than

D. shorter than

Which convention is not used when working with amino acids? A. numbering of carbons B. one‑letter abbreviations of the amino acids C. Greek letter designations of some carbons D. superscripts on the amino acid names corresponding to the five main classes

D. superscripts on the amino acid names corresponding to the five main classes

Which of the following is true regarding Keq? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. Equilibrium constants do not have units. B. The equilibrium constant is fixed for a given reaction at a specific temperature. C. It can be determined by the following equation [reactants]/[products]. D. all of the above E. the first two options only

D. the first two options only

What role does vitamin C play in the synthesis of collagen? A. the assembly of the three-stranded superhelix B. the formation of disulfide bonds C. Vitamin C has no role in the synthesis of collagen. D. the hydroxylation of proline and lysine

D. the hydroxylation of proline and lysine

Important functional groups in biomolecules include A. carbons B. nucleic acids C. lipids D. thioesters

D. thioesters

Which disease is not associated with protein misfolding? A. Parkinson disease B. amyloidosis C. cystic fibrosis D. type 1 diabetes mellitus

D. type 1 diabetes mellitus

The DNA sequence of a gene for a protein A. is a polymer of four ribonucleotides B.. mutates at a high rate C. is a non-linear code D. ultimately determines the amino acid sequence of a protein

D. ultimately determines the amino acid sequence of a protein

If a cell homogenate were subjected to centrifugation at increasingly higher speeds, in which order would you expect to see the following components in the pellet? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. microsomes, mitochondria, whole cells B. nucleus, microsomes, mitochondria C. mitochondria, whole cells, chloroplasts D. whole cells, chloroplasts, mitochondria E. none of the above

D. whole cells, chloroplasts, mitochondria

If a reaction is at equilibrium, which is true? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. ΔG = ΔG° B. ΔG = Keq C. ΔG = ΔH D. ΔG = 0

D. ΔG = 0

All of the common secondary structural elements fall within allowed combinations of φ and ψ dihedral angles except _____. A. α-helix B. β-helix C. triple helix D. antiparallel β-sheets E. They all have allowed angles.

E. They all have allowed angles.

Which of the following can be obtained through the process of SDS gel electrophoresis? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. estimation of the purity of a protein sample B. estimation of protein molecular weight C. protein purification D. all of the above E. estimation of the purity and molecular weight of a protein sample

E. estimation of the purity and molecular weight of a protein sample

Which of the following groups can ionize and contribute to the total acid-base behavior of a peptide? Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices A. some R-groups B. terminal alpha-amino groups C. alpha-carboxyl groups involved in peptide bonds D. all of the above E. some R-groups and terminal alpha-amino groups

E. some R-groups and terminal alpha-amino groups

A sample (511 mg) of an oligomeric protein of 𝑀r 133,000 was treated with an excess of 1‑fluoro‑2,4‑dinitrobenzene (Sanger's reagent) under slightly alkaline conditions until the chemical reaction was complete. The peptide bonds of the protein were then completely hydrolyzed by heating it with concentrated HCl. The hydrolysate was found to contain 4.35 mg of DNP‑Val. 2,4‑Dinitrophenyl derivatives of the α‑amino groups of other amino acids could not be found. Calculate the number of polypeptide chains in this protein. Give the answer as a whole number. number of polypeptide chains:? A second oligomeric protein of 𝑀r 230,000 was shown by a similar endgroup analysis to consist of five polypeptide chains. SDS polyacrylamide gel electrophoresis in the presence of a reducing agent shows three bands: α (𝑀r 30,000), β (𝑀r 40,000), and γ (𝑀r 60,000), indicating three distinct polypeptides. SDS electrophoresis without reducing agent also yields three bands, with 𝑀r of 30,000, 40,000, and 120,000. Which oligomeric structures is consistent with this data? αβ2γ2 α2β2γ α2βγ2 α2β2γ2

From the given data -concentration of oligomeric protein = 511 mg or 0.525 g -Mol wt of oligomeric protein = 133,000 -Concentration of DNP-Val= 4.35 mg or 0.00435 g -Mol wt of DNP-Val=(C11H13O6N3)= 283 g/mol The moles of the protein: Moles of Protein=(0.511g/133,000g/mol)=3.84 x10^-6 mol The moles of DNP-Val: Moles of DNP-Val= (0.00435g/283g/mol)= 1.5x10^-5 mol Ratio= (1.5x10^-5 mol /3.84x10^-6 mol)= 4 aB2Y2 IDK WHY

Consider the partial sequence of a peptide. I L W A N R M S H V L F A V E A Select all amino acidresidues likely to be on the solvent‑exposed surfaceonce the peptide folds into its native conformation. H N F A S L I R M E V

N, R, S, H, E The non-polar amino acids are neutral in charge as they have equal number of amino and carboxyl groups. They are uncharged amino acids and hydrophobic in nature. The polar amino acids are charged and are hydrophilic in nature. The amino acids with polar charge are grouped as amino acids with no charge, positive charge and negative charge. • The amino acids with no charge are serine, threonine, glutamine, cysteine, asparagine, and tyrosine. • The polar amino acids with positive charge have more amino groups than the carboxylic groups. They are lysine, histidine, and arginine. • The polar amino acids with negative charge have more carboxylic groups than the amino groups. They are aspartic acid and glutamic acid. The polar amino acids are mostly exposed on the surface as they are hydrophilic in nature and non-polar amino acids are embedded inside and exhibit the hydrophobic nature.

What functional groups that are common to all amino acids?

NH3+ and COO-

Classify each phrase as a description of α helices, β sheets, β turns, or, "All" if it describes all three Successive R groups point in opposite directions peptide bond of reside n is hydrogen-bonded to residue n+4 peptide bond of residue n is hydrogen-bonded to residue n+3 electric dipole of peptide bonds generates a net dipole backbone NH groups are hydrogen-bonded to a backbone C=O groups

Successive R groups point in opposite directions BETA SHEETS peptide bond of reside n is hydrogen-bonded to residue n+4 ALPHA HELICES peptide bond of residue n is hydrogen-bonded to residue n+3 BETA TURNS electric dipole of peptide bonds generates a net dipole ALPHA HELICES backbone NH groups are hydrogen-bonded to a backbone C=O groups ALL

Based on the chemical properties of the residues, determine which sequences would exhibit which structural properties. List them as -Most likely an amphipathic α helix -Most likely an amphipathic β sheet -Most likely a turn/loop -Not amphipathic 1. Asn−Leu−Ala−Asp−Ser− Phe−Arg−Gln−Ile 2. Lys - Gln - Asn - Glu - Pro - Arg - Ala - Asn - Glu 3. Arg-Phe-Gln-Ile-His-Val-Gln-Phe-Glu 4. Ala-Phe-Leu-Val-Ile-Trp-Phe-Val-Ala

The given sequences would form different protein structure as mentioned below: 1. The sequence Asn - Leu - Ala - Asp - Ser - Phe - Arg - Gln - Ile α−helix. 2. The sequence Lys - Gln - Asn - Glu - Pro - Arg - Ala - Asn - Glu would form turn. 3. The sequence Arg-Phe-Gln-Ile-His-Val-Gln-Phe-Glu would form a B sheet 4. Ala-Phe-Leu-Val-Ile-Trp-Phe-Val-Ala would not be amphipathic The amino acids namely, methionine, alanine, leucine, glutamate and lysine are likely to form an alpha helix. The presence of glycine in a structure weakens the possibility of a chain to form an alpha helix. The aromatic amino acids, tryptophan, tyrosine, phenylalanine and along with beta branched amino acids, leucine, threonine, and valine tend to form a beta sheet. Furthermore, the amino acid proline is considered to be chain breaker and tends to form a turn in the polypeptide chain. Once the polypeptide chains with above propensities have been categorized, the remaining sequence would likely be forming a non-amphipathic ch

You are performing site‑directed mutagenesis to test predictions about which residues are essential for protein function. Choose the amino acid replacements that would be expected to cause the largest disruption of protein structure. Val is replaced by Ala. OR Phe. Lys is replaced by Arg. OR Asp. Gln is replaced by Asn. OR Glu. Ala is replaced by His. OR Gly.

Val is replaced Phe. Lys is replaced by Asp. Gln is replaced by Glu. Ala is replaced by His.

When performing site‑directed mutagenesis to test predictions about which residues are essential for protein function, which amino acid substitution would disrupt protein structure the most. Val replaced by Ala OR Phe Lys replaced by Asp OR Arg Gln replaced by Asn OR Glu Ala replaced by Gly OR His

Val replaced by Ala OR Phe Lys replaced by Asp OR Arg Gln replaced by Asn OR Glu Ala replaced by Gly OR His

The proton concentrations of three solutions at 25 °C are given. Classify the solutions as acidic, basic, or neutral. [H+]= 0.00001 M [H+]= 1.0x10^-4 M [H+]= 1.0x10^-9 M

[H+]= 0.00001 M ACIDIC [H+]= 1.0x10^-4 M ACIDIC [H+]= 1.0x10^-9 M BASIC

Polylysine and polyglutamate are two examples of synthetic polypeptides which can assume an ALPHA-helical structure under appropriate conditions. Identify which of these two synthetic polypeptides can form an ALPHA-helix at the indicated pH values. polylysine at pH 2 polyglutamine at pH 13 polyglutamate at pH 7 polylysine at pH 7 polylysine at pH 13 polyglutamate at pH 2

polylysine at pH 13 polyglutamate at pH 2 Polylysine is protonated and carries a positive charge below the pK of the side chain amino groups, which is approximately 10.5. At pH 13, the side chains are less than 1% protonated. Thus, repulsive positive charges would disrupt the ordered ALPHA helix at pH 2 and 7 but not at pH 13 Polyglutamate is deprotonated and carries a negative charge above the pK value of the side chain carboxyl groups, which is approximately 4.2. At pH 2, it is more that 99% protonated and predominantly neutral. Repulsive negative charges would disrupt the ordered ALPHA helix at pH 7 and 3 but not at pH 2

Which peptide segment is most likely to be part of a stable α helix at physiological pHpH ? −Gly−Arg−Lys−His−Gly− −Glu−Leu−Ala−Lys−Phe− −Gly−Gly−Gly−Ala−Gly− −Lys−Lys−Ala−Arg−Ser− −Tyr−Trp−Phe−Val−Ile− −Glu−Glu−Glu−Glu−Glu− −Pro−Leu−Thr−Pro−Trp−

−Glu−Leu−Ala−Lys−Phe− Interactions can destabilize the structure. Interactions between two charged side chains can destabilize the structure. For example, a segment of Glu residues, which are negatively charged at physiological pH, repel each other. Lys and Arg have positively charged side chains whose charges may interfere with formation of a stable helix Gly, with the side chain -H, has great conformational flexibility. Segments with glycine residues do not favor ALPHA helix formation, and glycine is not a major component of ALPHA helices Pro is structurally constrained, and there is no rotation about the N-C ALPHA bond. Proline also does not take part in hydrogen bonding. Therefore, Pro is not common in ALPHA helices Bulky or large residues (e.g., Tyr, Ile, or Trp) can aslo strain the structure if they are close together