WGU Biochem Mod 2 Questions.

WGU Biochem Mod 2 Questions. Unit 2 Quiz 1. Which level of protein structure is disrupted through the hydrolysis of peptide bonds? a. Primary b. Tertiary c. Secondary d. Quaternary Answer: A. The primary structure of a protein is the sequence of amino acids held together by peptide bonds. Peptide bonds are formed by dehydration reactions and disrupted by hydrolysis. 2. A mutation in the beta-hemoglobin gene, which results in the replacement of the amino acid glutamate in position 6 with the amino acid valine, leads to the development of sickle cell anemia. The structures of glutamate and valine are shown below. Amino acid structures of glutamate and valine If the beta hemoglobin gene in a patient with sickle-cell anemia were to be edited so that the valine in position 6 wasreplaced with a different amino acid, which replacement for valine would be expected to have the best clinical outcome, in theory, for the patient? (Assume the valine can potentially be replaced with any amino acid other than glutamate.) A. b. c. d. Answer: B. The original amino acid in a healthy patient is glutamate, which is negatively charged. The mutated amino acid is valine, which is non-polar. Valine is causing sickle cell anemia. The best amino acid to replace valine so that the patient is healthy again would be the one most like glutamate, so any negatively charged amino acid. Amino acid structure C is non-polar, not charged. 3. Secondary, tertiary, and quaternary levels of protein structure can all be impacted by exposing a protein to which treatment? a. Increase in the concentration of the protein in solution b. Placement of the protein in a solution with a low pH c. Addition of a reducing agent d. Change of a hydrophobic amino acid to a different hydrophobic amino acid Answer: B. The correct answer is “Placement of the protein in a solution with a low pH”. The addition of a reducing agent would only affect disulfide bonds in the side chains of polar amino acids containing SH. These types of bonds are only found in the tertiary and quaternary structure, not secondary structure. 4. An increase in beta-pleated sheet structure in some brain proteins can lead to an increase in amyloid deposit formation, characteristic ofsome neurodegenerative diseases. What isthe primary biochemical process that follows the increase in beta-pleated sheet structure that leads to the development of the amyloid deposits? a. An increase in anaerobic metabolism of glucose in the brain b. Aggregation of the proteinsin the brain c. An increase in glycogen formation in the brain cells d. Secretion of glucagon, leading to excessive ketogenesis Answer: B. The correct answer is “Aggregation of the proteins in the brain”. This question is describing changes in protein structure. Glycogen is a carbohydrate, not a protein, and is stored in the liver and muscles, not the brain. See Unit 6 for more information on glycogen. 5. Which level of protein structure is determined by the sequence of amino acids? a. Secondary structure b. Tertiary structure c. Primary structure d. Quaternary structure Answer: C. The correct answer is “Primary structure”. The primary structure of a protein is simply the sequence of amino acids held together by peptide bonds. The quaternary structure of a protein is when two or more polypeptide chains(“subunits”) work together to perform the function of the protein. The two or more polypeptide chains are held together by side chain interactions, including the hydrophobic effect, ionic bonds, disulfide bonds, and hydrogen bonds. 6. Which force is most influential in determining the secondary structure of a protein? a. Disulfide bonding b. Hydrophobic effect c. Hydrogen bonding d. Electrostatic interactions Answer: C. The secondary structure of a protein is built by hydrogen bonds between the carboxyl groups and amino groups on the backbones of the amino acids. 7. Which amino acid would most likely participate in hydrogen bonds? a. b. c. d. Answer: C. This is a polar, uncharged amino acid due to the OH group on the side chain. Polar, uncharged amino acids containing oxygen or NH groups make hydrogen bonds. 8. Which portion of the amino acid isinside the box? a. Amino group b. Alpha carbon c. Side chain d. Carboxyl group Answer: C. The side chain is the variable group of the amino acid, also called the R group. Every amino acid has the same amino group, carboxylic acid group, and an alpha carbon, but the side chain is different. 9. Which pair of amino acids will most likely interact through hydrophobic forces between their side chains? a. b. c. d. Answer: D. “Pair of amino acids (3)”. In “Pair of amino acids (4)” the left is non-polar and therefore can make hydrophobic interactions, but it must do this with another non-polar amino acid. The amino acid on the right is polar, uncharged due to the SH group. Please note that the “S” in the amino acid on the left is non-polar, while the “SH” group is polar. The S must have an H to be polar and is otherwise non-polar. SH groups make disulfide bonds with other SH groups. 10. Which portion of the amino acid is inside the box? a. Alpha carbon b. Amino group c. Carboxyl group d. Side chain Answer: A. The alpha carbon is the central carbon on an amino acid that holds together the other groups of the amino acid. It is always attached to the amino group, the carboxyl group, the side chain, and a single hydrogen. It is part of the backbone of the amino acid and is found in every amino acid. 11. Given the following amino acid structure, what isthe strongest intermolecular force it would participate in to stabilize a protein structure? a. Hydrogen bond b. Hydrophobic interaction c. Disulfide bond d. Ionic bond Answer: B. The correct answer is “Hydrophobic interaction”. The amino acid pictured only has CH groups in its side chain, and therefore is non-polar. Non-polar amino acids make hydrophobic interactions. Hydrogen bonds occur between polar, uncharged amino acids containing oxygen or NH groups in their side chains. 12. Which change would most likely result in a permanent modification of an expressed protein’s function? a. An increase in the pH of a solution in which a protein is dissolved from 6.5 to 8.0, when it is known that the protein has an optimal activity of pH 7.8 b. A mutation of the gene for a protein that leads to the substitution of a hydrophobic amino acid with a nonpolar amino acid c. A mutation of the gene for a protein that leads to the substitution of a nonpolar amino acid with a charged amino acid d. The mutation of a gene for an enzyme involved in protein synthesisfollowing exposure to X-rays, causing the protein not to be synthesized Answer: C. The correct answer is “Mutation of the gene for a protein that leads to the substitution of a nonpolar amino acid with a charged amino acid”. A “hydrophobic amino acid” is the same thing as a “non-polar amino acid”. Therefore, the protein’s function will not be disrupted. Additional Practice Questions – Unit 2 1. Which kind of interaction can the following pair of amino acids form between their side chains (Rgroups)? a. Disulfide bond b. Hydrogen bond c. Ionic bond d. Hydrophobic interaction Answer: The correct answer is ‘hydrogen bonds’. Hydrogen bonds are made between R groups that have polar bonds within them N-H, O-H, C-O or C-N but do not display a visible charge (+/-) on their R group. The disulfide bond is a very specific interaction between two cysteine amino acids where their sulfur atoms (S) bond to each other covalently (S-S). 2. Which bond or interaction can the R group of this amino acid form to stabilize tertiary structure? a. Disulfide bond b. Hydrophobic interaction c. Ionic bond d. Van der Waalsinteraction Answer: Cysteine can also form a disulfide bond with its terminal S-H. van der Waals interactions form when atoms are close together, such as when hydrophobic interactions form in the core of the protein. Hydrophobic interactions are formed by non-polar amino acids that have R groups with C-H bonds. 3. A missense mutation resulting in a change from asparagine to leucine at a specific position on an enzyme leads to a neurodegenerative disease. Isthere an alternate amino acid substitution of a missense mutation listed below that would have less of an impact on the protein structure and consequently its function than the proposed leucine substitution would? a. b. c. d. Answer: The correct answer is ‘Glutamine’. Glutamine is a polar amino acid and the amino acid asparagine is a polar amino acid, which contain C-N, C-O, O-H or N-H bonds on the outside surface of their R groups. The most likely replacement for a polar amino acid that would have less of an impact on protein structure would be another polar amino acid. Glutamate is a charged amino acid. 4. Choose the answer that correctly labels the amino group, the carboxyl group, and the variable group on the amino acid from the image: a. A-carboxyl group, B-variable group, D-amino group b. A-amino group, B-carboxyl group, D-variable group c. A-variable group, B-amino group, C-carboxyl group Answer: C. A is a variable group and can be any one of 20 different things, B is an amine group that contains one nitrogen and three hydrogens, C is a carbonyl group consisting of one carbon and two oxygens and, D is a hydrogen atom found attached to the central carbon (carbon alpha). 5. Which characteristic correctly describes the amino acid image? a. Polar b. Charged c. Non-polar Answer: C. Non-polar amino acids have R groups with C-H bonds. 6. Which of the following interactions can occur between two positively charged amino acids? a. none of these b. hydrogen bond c. disulfide bond d. hydrophobic interaction e. ionic bond Answer: The correct answer is‘none of these’. Two positively charged amino acids would repel each other. Only opposite charges attract. Ionic bonds occur between two oppositely charged amino acids. 7. Antibodiesthat enable our body to fight bacterial infections must bind to antigens on the surface of the bacterial cell. If the antigen on the surface of the bacterial cell has several negatively charged amino acids, which of the following amino acids would you expect to find on the portion of the antibody that binds to the antigen? a. b. c. d. Answer: The correct answer is C. Positive charged amino acids will be attracted to the negatively charged amino acids. 8. What category does this amino acid belong to? a. Polar, uncharged b. Nonpolar c. Polar, charged Answer: C. The amino acid depicted is charged. There is a COO- group displayed as the R group of this amino acid with a visible charge. 9. This amino acid is polar. a. True b. False Answer: True. The amino acid depicted in this problem is polar/hydrophilic because the end of the amino acid R group has an oxygen bound to a hydrogen. Other polar amino acids can have nitrogen bound to hydrogen, carbons bound to oxygens or carbons bound to nitrogens. 10. This amino acid would prefer to interact with oil over water. a. True b. False Answer: False. The amino acid depicted in this problem is polar/hydrophilic because the end of the amino acid R group has a nitrogen bound to a hydrogen. Other polar amino acids can have oxygen bound to hydrogen, carbons bound to oxygens or carbons bound to nitrogens. Water is also polar and that is why this amino acid would like to interact with water and why the amino acid is categorized as hydrophilic (water loving). Oils are nonpolar and polar amino acids don't like nonpolar molecules. 11. Which of the following best describes the nature of protein primary structure? a. Amino acids linked together in a specific order by peptide bonds b. Two or more polypeptide chains coming together to form the final functional protein c. The overall three-dimensional shape of a chain of amino acids d. Structural elements such as alpha helices and beta-pleated sheets Answer: A. The correct answer is ‘Amino acids linked together in a specific order by peptide bonds’. The sequence of amino acids connected by peptide bonds in a specific order defines the protein primary structure. Two or more polypeptide chains coming together to form the final functional protein refers to a quaternary structure. 12. Which of the following statements about the different levels of protein structure istrue? a. The interactions between the side chains of the amino acids make up the secondary level structure of a protein b. Peptide bonds between amino acids make up the secondary structure of a protein c. The interactions between the side chains of the amino acids make up the tertiary level structure of a protein d. Two or more polypeptides each with their own secondary structures come together to form a single larger tertiary structure of a protein Answer: The correct answer is ‘The interactions between the side chains of the amino acids make up the tertiary level structure of a protein’. Two or more polypeptides each with their own tertiary structures come together to form a single larger quaternary structure of a protein. 13. Which type of bonding or interaction is correctly paired with a chemical or change in environment that will disrupt/break the interaction or bond? a. Hydrogen bonds/ionic bonds: Change in pH b. Hydrophobic interactions: Change in pH c. Peptide bonds: Reducing agents d. Peptide bonds: Change in pH Answer: A. Changes in pH instead disrupt hydrogen bonds and ionic bonds. 14. Which of the following statements about protein structure and stability istrue? a. Ionic bonds between the side chains of the charged amino acids stabilize the protein structure b. Protein structure is notstabilized by the hydrophobic effect c. Denaturation isthe loss of primary,secondary, and tertiary structure d. Denatured proteinsretain their tertiary structure Answer: A. Ionic bonds help stabilize both the tertiary structure of a protein chain and the quaternary structure of a protein with multiple subunits. 15. The negatively charged amino acid, Glutamate, isreplaced with the negatively charged amino acid Aspartate. Which level of protein structure is most significantly impacted by this change? a. Tertiary structure b. Secondary structure c. Quaternary structure d. Primary structure Answer: D. The correct answer is ‘primary structure’. The original and substitute amino acid both have a negative charge and can both form an ionic bond with a positively charged amino acid. The amino acid sequence, however, has been altered, and so the primary structure has certainly been changed. The secondary structure of a protein depends on backbone interactions, and these are probably unaffected. 16. Which of the following pairs of amino acids are NOT likely to interact with one another to stabilize tertiary structure? a. b. c. d. Answer: B (option 4). This is correct because the side-chains of aspartate and glutamate are both negatively charged, they will repel each other. Opposite charges attract and like charges repel. 17.17. Which portion of the amino acid above islikely to engage in a hydrogen bond with an oxygen in the carboxyl group of another amino acid as part of a beta pleated sheet? C D A B Answer: The correct answer is ‘A’. Secondary structures arise from hydrogen bonding between backbone atoms. The H attached to the more electronegative N can form a hydrogen bond to the carboxyl O. This H atom is attached to a C atom, which leads to a non-polarized bond and no capability for hydrogen bonding 18. Primary structure consists of the order of in a protein. These are held together with bonds that are formed by a reaction. a. Amino acids, peptide, dehydration b. Nucleotides, phosphodiester, dehydration c. Nucleotides, peptide, dehydration d. Amino acids, peptide, hydrolysis Answer: A. Protein primary structure is defined by the order of amino acids that make up the protein. The amino acids are linked together by peptide bonds, which are formed via dehydration reactions. 19. Which of the following statements describes the tertiary structure of a protein? a. It involves hydrogen bonding between the backbone atoms. b. It includes beta pleated sheets as a common form. c. It involves hydrogen bonding between amino acid side- chains. d. It includes alpha helices as a common form. Answer: C. The correct answer is‘It involves hydrogen bonding between amino acid side- chains’. Secondary structures arise from hydrogen bonding patterns between backbone atoms. The most common secondary structures are alpha-helices and beta sheets. 20. What type of reaction breaks peptide bonds apart? a. Oxidation/Reduction Reaction b. Condensation Reaction c. Methylation Reaction d. Hydrolysis Reaction Answer: D. The correct answer is‘hydrolysisreaction’. Peptide bonds are formed by dehydration reactions(named for the loss of water that occurs) and broken via hydrolysis (named for the addition of water). To break this down further, hydro- meaning water, and -lysis meaning cutting, the water cuts the peptide bond. For an oxidation/reduction, this reaction transfers electrons from one molecule to another. 21. A toddler mistakenly swallows a bathroom cleaning solution, containing a strong reducing agent. Which interaction is most likely to be disrupted within a glycoprotein in the lining of the toddler’s esophagus? a. Disulfide Bond b. Ionic Bonds c. Hydrogen Bond d. Hydrophobic interactions Answer: A. Reducing agents disrupt disulfide bonds. 22. A patient presents with a fever of 110°F. Which interaction(s) would be disrupted within a neuronal protein if the fever is not resolved quickly? a. Hydrophobic Interactions b. Hydrogen Bond c. Ionic Bonds d. Disulfide Bond Answer: A. The patient's temperature is much higher than normal. High temperatures disrupt hydrophobic interactions. 23. A diabetic patient issuffering from ketoacidosis. Which interaction(s) could be disrupted within the patient’s hemoglobin due to this condition? a. Disulfide Bonds b. Ionic Bonds and hydrogen bonds c. Hydrophobic Interactions and hydrogen bonds d. Hydrophobic interactions and ionic bonds Answer: B. Diabetic ketoacidosis leads to a lower pH than normal. Changes in pH can disrupt both hydrogen bonds and ionic bonds inside of a protein. Disulfide bonds are disrupted by reducing agents. 24. Which of the following forces can lead to aggregation as a result of protein misfolding? a. Hydrophobic Interactions b. Hydrogen Bond c. Ionic Bonds d. Disulfide Bond Answer: A. Misfolded proteins can have sections of hydrophobic amino acid residues exposed to water. This can lead to misfolded proteins to aggregate in order to form favorable hydrophobic interactions between nonpolar amino acids in adjacent protein chains and to keep these hydrophobic residues away from water. 25. Which of the following interactionsinvolve a covalent bond? a. Hydrophobic Interactions and ionic bond b. Disulfide bond and peptide bond c. Ionic bond and disulfide bond d. Hydrogen Bond and peptide bond Answer: B. A covalent bond is a bond between two atoms involving the electrons being shared between them. In proteins, these include peptide bonds and disulfide bonds. Hydrophobic interactions are very weak attractive forces between two non-polar groups, and do not involve the formation of covalent bonds between the two groups. In an ionic bond, there is no sharing of electrons. Instead, they are attracted to each other by opposite charges on the two sidechains. 26.26. The two amino acids below are part of the myosin protein. What interaction can these amino acids form, and where are they likely to be located in the protein? a. Hydrophobic interaction, the surface of the protein b. Hydrophobic interaction, the core of the protein c. Hydrogen bond, the surface of the protein d. Hydrogen bond, the core of the protein Answer: B. the two amino acids presented have side-chains comprised of only nonpolar C-C and C-H bonds. These amino acids belong to the nonpolar group and can form hydrophobic interactions. Because these amino acids cannot form hydrogen bondsthey are hydrophobic in nature. This hydrophobic nature leadsthese amino acidsto be in the interior/core of the protein, hidden away from the water surrounding the protein. The surface of the protein is surrounded by water molecules, which do not interact favorably with nonpolar amino acid sidechains. 27. Which of the following does not occur when a protein is misfolded? a. It can be degraded by the cell. b. It will lose its normal function. c. It loses its primary structure. d. It can cause protein aggregation. Answer: C. The primary structure is determined by the peptide bonds between amino acids in the protein, which are strong covalent bonds that are not broken by the protein changing shape or from conditions which cause the protein to misfold and denature. In addition to chaperone proteins being able to help misfolded protein refold, the cell also has mechanisms for identifying and breaking down misfolded proteins into amino acids to prevent these misfolded proteins from forming aggregates. 28. Which of the following amino acids would you expect to find in the interior of a protein rather than on its exterior? a. b. c. d. Answer: A. Option 1 represents a nonpolar amino acid, with a side-chain comprised of only nonpolar C-C and C-H bonds that is hydrophobic. This hydrophobic nature leads this amino acid to be in the interior of the protein, hidden away from the water surrounding the protein. 29. As a piece of bacon is heated in a skillet on the stove, you observe that the appearance of the bacon changes. You may even notice that the bacon becomes crispy if left in the skillet. What types of bonds or interactionsin proteins are susceptible to temperature changes? a. Hydrogen Bonds b. Disulfide Bonds c. Hydrophobic interactions d. Ionic Bonds Answer: C. Just as protein structure is stabilized primarily by the hydrophobic effect and hydrophobic interactions, disruption of hydrophobic interactionsisthe simplest way to denature a protein. Thisis generally done by applying heat. High temperatures cause the atoms in a protein to move so quickly that the structure loosens and causes the hydrophobic core to open up and expose the nonpolar residuesto water. Hydrogen bonds are stronger interactions than hydrophobic interactions and will not be easily disrupted by heat as hydrophobic interactions will. Hydrogen bonds are disrupted by changes in pH and by increasing the concentration of salts in the protein's environment. 30.30. If lysine isrequired at position #150 in the peptide chain in order for a protein to properly fold and function, what happens if amino acid #150 is mutated from lysine to leucine? a. The protein will not fold properly b. The protein will fold properly-no change Answer: A. Changing lysine (positively charged amino acid, forms ionic bonds, is hydrophilic) to leucine (a non-polar amino acid, does not form ionic bonds, is hydrophobic) eliminates one or more important interactions and will prevent the protein from properly folding. 31.31. Glutamine at position 16 forms an important interaction with Serine in a different location in the protein. How would the protein structure be affected if the Glutamine in position 16 were mutated to Leucine? Would this increase or decrease the stability of the protein? a. Decrease. Glutamine and Serine formed an ionic bond that stabilized the protein structure before the mutation. Serine and leucine do not interact. b. Decrease. Glutamine and Serine formed a hydrogen bonding that stabilized the protein structure before the mutation. Serine and Leucine do not interact c. Increase. Leucine and Serine form a stronger ionic bond together d. Approximately the same. The Glutamine-Serine interaction issimilar to the Leucine-Serine interaction Answer: B. GIutamine and serine are both polar, uncharged amino acids that can interact by forming a hydrogen bond. Leucine is a nonpolar amino acid that would participate in hydrophobic interactions. Since both glutamine and serine are polar, neither of which would form an ionic bond. With this mutation, a hydrogen bond would not form and protein stability would decrease. 32.32. When Estrogen binds to the binding pocket of the Estrogen Receptor, it is stabilized by hydrogen bonds. Which amino acidslisted could stabilize the interaction with Estrogen in the binding pocket of the Estrogen Receptor? a. Amino Acid 1 b. Amino Acid 10 c. Amino Acid 13 d. Amino Acid 3 Answer: C. The correct answer is‘amino acid 13’ which is a polar, uncharged amino acid that can participate in hydrogen bonds. Amino Acid 1, is hydrophobic, as evidenced by their chains consisting of hydrocarbons. Hydrophobic amino acids do not participate in hydrogen bonds. 33.33. The amino acid at position 150 (not shown) helps to stabilize the protein by forming disulfide bonds. What amino acid islikely located at position 150? Could this amino acid form a disulfide bond with any of the amino acids in the provided sequence above? a. Cysteine is at position 150. No, there are no amino acids shown that can form a disulfide bond. b. Methionine is at position 150. No, there are no amino acids shown that can form a disulfide bond. c. Cysteine is at position 150. Yes, amino acid 9 can form a disulfide bond. d. Methionine is at position 150. Yes, amino acid 9 can form a disulfide bond. Answer: A. Cysteine is at 150. Cysteine only forms a disulfide bond with itself and it is the only amino acid with -SH and there are no Cysteines in the sequence above. 34.34. If all of the Arginine amino acids (positions 2, 5, 8 and 12) in the sequence are mutated to Lysine, would there be a significant effect on the protein’s stability? a. Yes, Lysine and Arginine would repel one another because they are both positively charged b. No, not significant, Lysine and Arginine would have all the same interactions c. Yes, mutations always destabilize the protein Answer: B. The side chains of Lysine and Arginine are both long with a positive charge at the end. If Lysine is forming an ionic bond with another amino acid elsewhere in the protein, Arginine would be able to make that same ionic bond. The protein would, therefore, be stable, even with this mutation. The answer choice ‘Lysine and Arginine would repel one another because they are both positively charged,’ isincorrect because Arginine replaces Lysine. Since it is a replacement, the two amino acids would never interact. 35. Aggregation of proteinsisthe main reason behind many neurodegenerative diseases. Which one of the following mutations will likely cause a neurodegenerative disease? a. Replacing a positively charged amino acid with a negatively charged amino acid b. Replacing a negatively charged amino acid with a negatively charged amino acid c. Replacing a polar amino acid with a nonpolar amino acid d. Replacing a polar amino acid with another polar amino acid Answer: C. Protein aggregation is caused by disruptions in hydrophobic interactions. Replacing a polar amino acid with a nonpolar amino acid can lead to aggregation due to the introduction of a nonpolar amino acid. The answer choice ‘replacing a positively charged amino acid with a negatively charged amino acid’, is incorrect because this particular mutation will cause disruption of an ionic bond, resulting in tertiary structure destabilization. However, it does not encourage aggregation, as non-polar amino acids are not involved. 36. A mutation in the protein A gene results in a negatively charged amino acid, Glutamate, being replaced with the nonpolar amino acid Leucine. This is an example of a mutation that could potentially interrupt . a. nonsense, a hydrophobic interaction b. nonsense, a hydrogen bond c. missense, an ionic bond d. missense, a disulfide bond Answer: C. Changing the amino acid sequence is a missense mutation, whereas a nonsense mutation causes a stop codon to be introduced, thus shortening the protein. Additionally, Glutamate is a negatively charged amino acid, which participates in an ionic bond. Hydrophobic interactions occur between non-polar amino acids. 37.37. Diabetic ketoacidosis can lower blood pH, which affects the structure of important proteins like hemoglobin. For the following interactionsshown in the image, which pairs are most likely to be disrupted by a change in pH? A only B only B and C C only A and B Answer: The correct answer is ‘A and B’. Interaction A isshowing an ionic bond between a positive and negatively charged amino acid while interaction B is showing a hydrogen bond between two polar, uncharged amino acids. Both ionic and hydrogen bonds can be disrupted by a change in pH. 38. In order to fulfill their function, proteins must fold in proper, three-dimensional conformations. Which one of the following molecules, available in a cell, is likely to help a protein fold properly? a. Chaperone b. Cysteine c. Glycine d. Polymerase Answer: A. A chaperone functions to help proteins fold into the correct structure. 39. Alzheimer disease is caused by aggregation of the Amyloid beta peptide and tangle formation by the tau protein. What kinds of amino acids are likely to drive the formation of these protein aggregates? a. Hydrophilic b. Hydrophobic c. Cysteine d. Polar Answer: B. The Amyloid-beta plaque and tau protein become misfolded, exposing hydrophobic amino acids on their exterior. When hydrophobic amino acids are exposed to water, they actively seek out ways to avoid that water. One way to do this isto find other exposed hydrophobic amino acids, located on other misfolded proteins. When misfolded proteins begin to gather, they form aggregates, ultimately resulting in neuronal cell death. Hydrophilic isincorrect because these amino acids are water-loving. Since cells are an aqueous environment, proteins tend to have hydrophilic/polar amino acids on their exterior to interact with that water. 40. As a piece of bacon is heated in a skillet on the stove, you observe that the appearance of the bacon changes. You may even notice that the bacon becomes crispy if left in the skillet. What type of bonds or interactions in proteins are susceptible to temperature changes? Why? a. Disulfide bonds. Disulfide bonds are associated with the smell of cooking bacon. b. Hydrophobic interactions. As the temperature increases, as it does in the skillet, the atoms in the proteins in bacon begin to move more rapidly. This causes the hydrophobic areas of the protein to become exposed. c. Hydrophobic interactions. Hydrophobic interactions are oily when the bacon grease cooks away from the bacon it takes away the hydrophobic interactions. d. Ionic bonds. As the bacon cooks, charged amino acids become neutral causing proteins to aggregate. This aggregation causes the characteristic look of crispy bacon. Answer: B. Only reducing agents can disrupt disulfide bonds. Disruption of disulfide bonds is associated with the smell of rotten eggs, a distinctly different smell from cooked bacon.