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Biochemistry Session 2 - Protein Structure and Function
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Questions in this quiz (43)
1There are thousands of protein possibilities within the human body, but their functions tend to fall under broad categories. For example, enzymes are catalysts. What is an example of a protein that would fall under the regulation-signaling-communication category?
- AMyosin
- BGrowth factor
- CCollagen
- DGlucose transporter
2A protein that normally contains one serine was incorrectly translated from a mutated mRNA strand and now it contains one alanine in its place. No other amino acids in the chain were affected. What could we expect to result?
- AA minor structural change, no change in function.
- BA major structural change, a significant change in function.
- CNo change in structure or function.
- DNo structural change, but a significant change in function.
3Which of the following are true regarding peptide bonds? (Select all that apply)
- APeptide bonds are flat.
- BPeptide bonds are nonpolar.
- CPeptide bonds have freedom of rotation and they are not structurally restricted.
- DPeptide bonds have partial double bond character.
4Which of the following successfully describes the primary structure of a polypeptide chain?
- ALocalized region of structural symmetry.
- BThree dimensional conformation of an entire intact covalently bonded polypeptide chain.
- CThree dimensional interactions of protein subunits in oligomeric protein complexes.
- DThe amino acid sequence from N-terminal to C-terminal end of a single covalently linked polypeptide chain.
5Bovine insulin consists of a primary structure of an A polypeptide chain and a B polypeptide chain. The total structure is being structurally stabilized by cysteines forming reversible covalent linkages. What is the term for this bond?
- ADisulfide bond
- BPeptide bond
- CPhosphodiester bond
- DHydrogen bond
6The alpha helix is one of the most common secondary structures. All peptide bonds in the helical domain are engaged in _____________, contributing to an overall very stable structure.
- AIntra-chain hydrogen bonding
- BDisulfide bonding
- CMetallic bonding
- DSteric hindrance
7A beta sheet is a super secondary structure consisting of multiple beta-strands lined up next to one another in flat, planar arrays. Which bond listed below is responsible for the for this structure's conformation and stability?
- AHydrogen bonds between amide hydrogens and carbonyl oxygens in adjacent peptide bonds.
- BPeptide bonds between amide hydrogens and carbonyl oxygens in adjacent peptide bonds.
- CHydrogen bonds from amino acid residue side-chains positioned perpendicular to the plane of the beta-sheet.
- DPeptide bonds from amino acid residue side-chains positioned perpendicular to the plane of the beta-sheet.
8Myoglobin is a product of combined inter-helix interactions between 7 alpha-helix domains. This is an example of _________ structure.
- APrimary
- BSecondary
- CTertiary
- DQuaternary
9Which of the following inter-subunit interactions are responsible for precisely stabilizing the quaternary structure? (Select all that apply)
- AHydrogen bonds
- BElectrostatic interactions
- CHydrophobic interactions
- DVan der Waal contacts
10Generally, protein structure orients hydrophobic amino acids to the interior of the protein and hydrophilic amino acids to the exterior. However, exceptions do exist, and hydrophilic amino acids can be found in the interior. What could happen to the protein if water came into contact with the interior hydrophilic amino acids?
- ANothing, water binding to the hydrophilic proteins would promote stabilization.
- BNothing, it is impossible for water to penetrate the interior of a protein.
- CThe overall structure could be denatured.
- DThe structural conformation would change, but function would be maintained.
11Where are "the instructions" for folding a protein into its native functional structure?
- AThe amino acid sequence
- BThe molten globule
- CThe secondary structure
- DThe tertiary structure
12Which of the following is NOT true regarding chaperone assisted protein folding?
- AChaperone proteins convert unstable proteins into properly folded proteins.
- BChaperone proteins can aid in folding unstructured or denatured proteins.
- CChaperone proteins are found solely near the exit portals of ribosomes.
- DChaperone proteins can escort partially folded proteins to large protein complexes that will assist in folding newly synthesized chains.
13A stable protein, RNaseA, is very stable. It is denatured by exposing it to a chaotrophic agent, a disulfide bond reducing agent, and then subjected to elevated heat. At this point, it was no longer functional. However, function returned when environmental conditions were returned to normal. Which of the following is true about the aforementioned reaction? (Select all that apply)
- AThe primary structure of RNaseA was preserved.
- BThe primary structure of RNaseA determined its overall structure.
- CThe primary structure was irreversibly damaged, but function was preserved.
- DThe structure forming process is random.
14You have been asked to quickly denature a fairly stable protein. You have tried heating it up, dissolving it in an organic solvent, and shaking it. What is another method you could try? (Select all that apply)
- AExposing it to hydrochloric acid
- BExposing it to dithiotheritol
- CPutting it in a cool, dark drawer
- DHeating it to a higher temperature
15A modified protein with an added acetyl group is denatured. What could we expect to see in terms of functionality?
- AAs this was a minor modification, the protein will still spontaneously refold and maintain function.
- BIt cannot renature appropriately and it is garbage.
- CThe protein will partially refold spontaneously, but function will be negatively affected.
- DDenatured proteins function more efficiently than original conformations. It will be faster.
16You have two febrile patients in your clinic. Patient A has had a sustained fever of 104 degrees Fahrenheit for three days. Patient B has had a sustained fever of 101 degrees Fahrenheit for one day. Which of the following statements are correct? (Select all that apply)
- APatient A is at serious risk of denaturing their own replication, transcription, and protein synthesis complexes.
- BPatient B is keeping their infection in check by denaturing bacterial proteins.
- CPatient A is at risk of brain damage.
- DPatient B requires immediate medical intervention.
17Many serious diseases can arise from the accumulation of plaques as a direct result of protein folding missteps. Which of the following is NOT a step that could ultimately lead to the accumulation of aggregates?
- AExposed hydrophobic domains of certain proteins.
- BProtein misfolding
- CProtein denaturing
- DControlled protein degradation
18The ubiquitinylation system is analagous to what scenario?
- APutting an old, broken chair with a clear sign that says "take me" on your curb that you would like the garbage truck to pick up.
- BBuilding a complicated piece of IKEA furniture.
- CTaking an old, broken chair out of the garbage because one day you'll have the energy to fix it up.
- DDestroying a complicated piece of IKEA furniture with a hammer.
19If a protein is entering the S26 proteosome, what can you correctly assume? (Select all that apply)
- AThe protein will be degraded into individual peptides.
- BThe protein has been brought to the proteosome by a chaperon protein.
- CThe protein has been ubiquitinylated.
- DThe protein's quaternary structure will be restored with the addition of ATP.
20Glycosylation of cell surface proteins helps to coordinate a layer of water molecules to act as an external lubricant for the cell. Which of the following examples accurately utilizes this mechanism?
- AGlycophorin A protecting the external surface of a red blood cell from frictional forces that may be encountered in circulation.
- BThe alpha-helix domain of a membrane protein spanning the phospholipid bilayer, stabilizing the protein's position.
- CGlycophorin A protecting the external surface of a red blood cell from an invading bacteria.
- DThe alpha-helix domain of a membrane protein spanning the phospholipid bilayer, destabilizing the protein's position and allowing for the increased passage of water out of the cell.
21Which of the following is NOT true regarding the Na+/K+ ATPase pump?
- AGenerates the electrical potential across membrane surfaces to drive nerve and muscle function.
- BRegulates cell volume and osmotic pressure.
- COnly supports kidney filtration functions, the Na+/K+ ATPase pump is highly specialized.
- DMost energy in the body is spent maintaining sodium and potassium gradients.
22The Na+/K+ ATPase pump is an active transport system, meaning energy is expended to support its function. Which of the following steps involves the phosphorylation of ATP?
- ABinding cytoplasmic sodium ions to the protein.
- BThe protein changing its conformation to permit potassium ions to bind to the receptor.
- CBinding extracellular potassium ions to the protein.
- DThe protein changing its conformation to permit potassium ions to release from the receptor.
23You have a heart failure patient that has clinically improved after being prescribed digoxin, a digitalis derivative. Which of the following could explain the mechanism of this improvement?
- AThe digoxin has inhibited the Na+/K+ ATPase pump, decreasing the sodium ion concentration needed to pump calcium ions back into the heart tissue. This has led to an increased calcium ion concentration in the cytosol, increasing contractility of the heart.
- BThe digoxin has inhibited the Na+/K+ ATPase pump, increasing the sodium ion concentration needed to pump calcium ions back into the heart tissue. This has led to a decreased calcium ion concentration in the cytosol, increasing contractility of the heart.
- CThe digoxin has increased the activity of the Na+/K+ ATPase pump, decreasing the sodium ion concentration needed to pump calcium ions back into the heart tissue. This has led to an increased calcium ion concentration in the cytosol, increasing contractility of the heart.
- DThe digoxin has increased the activity of the Na+/K+ ATPase pump, increasing the sodium ion concentration needed to pump calcium ions back into the heart tissue. This has led to a decreased calcium ion concentration in the cytosol, increasing contractility of the heart.
24The lung airway of a healthy human has a balance of sodium and chloride ion transport through the CFTR channel. A cystic fibrosis patient has an absent or defective CFTR channel, leading to what implications? (Select all that apply)
- AThe movement of chloride ions out of the cell will be impaired or nonexistent.
- BExtracellular osmotic water retention and extracellular lubrication will both be reduced.
- CMucus will chronically build up in the airways.
- DA decrease in salt release in sweat will occur.
25There are two major CFTR mutations found in cystic fibrosis. Which of the following mechanisms could explain the impaired ion transport process?
- AAn abnormal channel formation, causing altered CFTR structure resulting in poor membrane binding and partial denaturing. The CFTR protein is degraded.
- BA normal channel formation, but promotion of incorrect ubiquitinylation. The CFTR protein is degraded.
- CThe formation of a stable ionic bridge across the channel, partially blocking it and repelling chloride ions.
- DThe formation of an unstable ionic bridge across the channel, partially blocking it and attracting chloride ions.
26What is the main function of collagen?
- AStructural support
- BVascularization
- CNeural output
- DFormation of red blood cells
27Which of the following is NOT true regarding the structure of collagen?
- ACollagen is very tightly packed and stabilized by interchain hydrogen bonding between centrally located glycine peptide bonds.
- BThe structural stability is highly dependent on glycosylation.
- CProline turns the collagen chain back on itself, resulting in a right handed chain.
- DThe structure contains repeated sequences of glycine, alanine, proline, and hydroxyproline.
28Scurvy is a deficiency of vitamin C, resulting in a destabilization of collagen at normal body temperature. Which of the following is the mostly likely reason for this denaturation?
- AKey proline and lysine residues do not undergo hydroxylation.
- BKey proline and alanine residues do not undergo hydroxylation.
- CKey proline and lysine residues do not undergo phosphorylation.
- DKey proline and alanine residues do not undergo phosphorylation.
29Which step directly leads to the formation of a pervasive collagen cross-linked matrix (fibril)?
- AThe twisting of collagen fibers around one another, establishing tight H-bonding contacts. The N-terminal end forms a globular trimeric structure.
- BExcretion from the fibroblast cell and processing by an extra-cellular pair of proteases.
- CThe formation of complex covalent bonds between lysine residues on adjacent subunits.
- DThe formation of disulfide bonds between chains.
30In osteogenesis imperfecta, point mutations to the COL1A1 and COL1A2 genes can result in unstable collagen fibers. Which of the following could be an explanation for this instability? (Select all that apply)
- AExchanging out glycine for any other amino acid.
- BMutated hydroxylation enzymes.
- CMutation in processing sequences at the N and C-terminal domains.
- DSubstituting bulky amino acids into the collagen structure.
31Myoglobin primarily stores oxygen, whereas hemoglobin allows for oxygen transport and delivery. What is the main explanation for this variance in function?
- AHemoglobin tightly binds to oxygen, allowing it to successfully carry oxygen through the turbulent bloodstream. Myoglobin has a lower affinity.
- BBoth myoglobin and hemoglobin have a low affinity for oxygen, but the structure of both enables unequal binding.
- CThe structure of myoglobin is significantly altered when bound to oxygen, making it almost impossible to dissociate. Hemoglobin is only slightly altered, allowing for easy dissociation and binding.
- DMyoglobin and hemoglobin are significantly altered when bound to oxygen, but hemoglobin is able to electrochemically react with capillary walls, permitting oxygen release to the tissues.
32Each hemoglobin subunit can bind to one oxygen molecule. What happens after the first oxygen molecule binds to the first deoxyhemoglobin subunit?
- AThree other oxygen molecules bind at the same rate of the first molecule.
- BConformational changes induced by the binding of the first molecule permit much faster binding of the other three.
- CIt depends on the amount of atmospheric oxygen available.
- DConformational changes induced by the binding of the first molecule inhibit faster binding of the other three.
33As oxygen tension drops in peripheral tissues, hemoglobin tends to switch to which conformation?
- ADeoxy - 8 salt bridges
- BDeoxy - 6 salt bridges
- COxy - 8 salt bridges
- DOxy - 6 salt bridges
34Hemoglobin subunits have two primary histidines, a proximal and a distal. What are the functions of the distal histidine? (Select all that apply)
- ALinking the protein structure to heme dynamics on oxygen binding and release.
- BPromoting angular binding geometry of ligands.
- CProtecting oxygen binding valence of heme iron by sterically blocking the site.
- DActing as a "sweep" to clear the heme iron of ligands in the deoxy conformation.
- EBlocking the linear association of CO with heme iron at normal environmental levels of oxygen.
35Which of the following scenarios would heme exhibit the lowest affinity for oxygen?
- ApH of 7.4, carbon dioxide partial pressure of 0
- BpH of 7.2, carbon dioxide partial pressure of 0
- CpH of 7.4, carbon dioxide partial pressure of 40 torr
- DpH of 7.2, carbon dioxide partial pressure of 40 torr
36Which of the following promotes oxygen ejection from hemoglobin? (Select all that apply)
- ARapoport-Luebering shunt - stabilization of deoxy form of hemoglobin
- BRapoport-Luebering shunt - stabilization of oxy form of hemoglobin
- CFormation of 6 additional salt-bridges between the beta subunits
- DFormation of 6 additional salt-bridges between the alpha subunits
37Which of the following is NOT true regarding fetal hemoglobin?
- AThe gamma subunit in fetal hemoglobin has one less histidine than adult beta hemoglobin.
- BFetal deoxy hemoglobin is less stable than the mother's.
- CFetal red blood cells have a lower oxygen affinity.
- DThere is a net flow of oxygen across the placental barrier.
38At what age would we expect to see a baby's gamma hemoglobin have a higher percentage than beta hemoglobin?
- A1 week of age
- B1 year of age
- C8 weeks of age
- D9 months of age
39Which of the following accurately describes Hb-S sickle cell anemia? (Select all that apply)
- ALysis of red blood cells.
- BBeta chain 6 position glutamate to valine substitution mutation.
- CBeta chain 6 position glutamate to lysine substitution mutation.
- DAnemia through reduced oxygen transport.
40A peptide bond:
- AHas a partial double-bond character.
- BIs ionized at physiologic pH.
- CIs stable to heating in strong acids.
- DIs cleaved by agents that denature proteins, such as organic solvents and high concentrations of urea.
41Which of the following statements about protein structure is correct?
- AProteins consisting of one polypeptide can have quaternary structure.
- BThe formation of a disulfide bond in a protein requires that the two participating cysteine residues be adjacent to each other in the primary sequence of the protein.
- CThe denaturation of proteins always leads to irreversible loss of secondary and tertiary structure.
- DThe information required for correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain.
42An 80-year old man present with impairment of higher intellectual function and alterations in mood and behavior. His family reported progressive disorientation and memory loss over the last 6 months. There is no family history of dementia. The patient was tentatively diagnosed with Alzheimer disease. Which one of the following best describes the disease?
- AIt is associated with beta-amyloid - an abnormal protein with an altered amino acid sequence.
- BIt results from accumulation of denatured proteins that have random conformations.
- CIt is associated with the deposition of neurotoxic amyloid peptide aggregates.
- DIt is associated with the accumulation of amyloid precursor protein.
43Which of the following statements concerning the binding of oxygen by hemoglobin is correct?
- AThe Bohr effect results in a lower affinity for oxygen at higher pH values.
- BCarbon dioxide increases the oxygen affinity of hemoglobin by binding to the C-terminal groups of the polypeptide chains.
- CThe oxygen affinity of hemoglobin increases as the percentage saturation increases.
- DOxyhemoglobin and deoxyhemoglobin have the same affinity for protons (H+).
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- Biochemistry Quiz on Biochemistry Session 2 - Protein Structure and Function, created by Kathleen Lonergan on 07/06/2019.
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- Kathleen Lonergan
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- Created on 7 Jun 2019 · updated on 9 Jun 2019
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