WGU Biochem Module 3 Question

WGU Biochem Module 3 Questions Unit 3 Quiz 1. Which property of enzymes isillustrated in the final step of the enzymatic cycle? a. Enzymes increase the reaction rate for a reaction. b. Enzymes lower the activation energy for a reaction. c. Enzymes are reusable. d. Enzymes are specific. Answer: C. In the final step of the enzymatic cycle, the product is released and the enzyme is able to bind to a new substrate and begin the cycle again. 2. In the enzyme cycle, which step immediately followsinduced fit? a. Formation ofthe enzyme-substrate complex b. Release of the product and enzyme complex c. Formation of the enzyme-molecule complex d. Formation of the enzyme-product complex Answer: D. The induced fit refers to the conformational change that the enzyme undergoes when it binds to the substrate to form the enzyme-substrate complex. Therefore, the enzymatic cycle step that occurs after the induced fit is the formation of the enzyme-product complex. 3. Which type of inhibition occurs when a particular drug binds to the active site of an enzyme? a. Noncompetitive b. Irreversible c. Competitive d. Uncompetitive Answer: C. Competitive inhibitors compete with the substrate to bind to the active site of the enzyme. 4. Salivary amylase, an enzyme responsible for partial digestion of carbohydrates, has optimum activity at a pH value of 6.8. What is the impact on the activity if the pH is decreased to 4.0? a. Significantly increase b. Slightly decrease c. Slightly increase d. Significantly decrease Answer: D. A drop in pH from 6.8 to 4.0 is a significant change in pH. Recall that the hydrogen bonds and ionic bondsthat hold protein structurestogether can be broken by changes in pH. The disruption in protein structure due to this pH change will also significantly decrease amylase activity. 5. Low levels of glutathione are associated with certain types of ovarian and breast cancers. In the synthesis of glutathione, glutathione accumulates in the cell, binding to an enzyme in the pathway and temporarily preventing the synthesis of glutathione. Which type of inhibition is described by this scenario? a. Uncompetitive b. Allosteric c. Feedback d. Competitive Answer: C. The keywords here are that glutathione accumulates and bindsto an enzyme in the pathway to prevent synthesis. Feedback inhibition occurs when a product of a pathway turns into an inhibitor of an enzyme earlier in the pathway. 6. Lipase is an enzyme with an optimum temperature of 98.6°F and an optimum pH of 7.0 in the duodenum in the human body. If a person is experiencing a fever of 99.8°F, what will increase the activity of the lipase enzyme? a. Decrease in temperature b. Increase of pH of duodenum to 8.0 c. Increase in temperature d. Decrease of the substrate of the enzyme Answer: A. An enzyme will have the highest activity when it is under optimal conditions. In this case, the fever of 99.8 is above the optimal temperature,so lowering the temperature will increase activity. Decreasing the substrate of the enzyme would also decrease activity because the substrate is needed to initiate the reaction. 7. The enzyme glucokinase only bindsits substrate glucose and converts glucose into the product glucose-6-phosphate. Which property of enzymes is described by this scenario? a. Reaction rate b. Specificity c. Activation energy d. Induced fit Answer: B. Enzymes have a high degree of specificity. They will bind to one specific class of molecules and usually catalyze only one type of reaction. 8. Low levels of glutathione are associated with neurological, immunological, and cardiovascular impairments. Two enzymatic reactions are involved in the synthesis of glutathione. In the second enzymatic reaction, glutathione synthetase converts glycine to glutathione. What would potentially decrease risks associated with low levels of glutathione? a. Noncompetitive inhibitor of glutathione synthetase b. Uncompetitive inhibitor of glutathione synthetase c. Increasing the amount of glycine in the diet d. Decreasing the amount of glycine in the diet Answer: C. The desired outcome for this scenario is an increase in glutathione. One way to increase glutathione levels is to increase the activity of glutathione synthetase. Glutathione synthetase activity can be increased by increasing the amount of substrate, or glycine available. 9. Which class of enzymes impacts protein function by temporarily removing a phosphate? a. Synthetase b. Esterase c. Phosphatase d. Kinase Answer: C. 10. How doesthe activation energy of enzyme-catalyzed reactions compare to those of corresponding uncatalyzed reactions? a. The activation energy of the enzyme-catalyzed reactions only changesin response to temperature. b. The activation energy of enzyme-catalyzed reactions are lower than the uncatalyzed reaction c. The activation energy of enzyme-catalyzed reactions are the same as uncatalyzed reactions d. The activation energy of enzyme-catalyzed reactions are higher than uncatalyzed reactions Answer: B. The activation energy is the amount of energy needed to get the reaction started and over the energy hill to form products. Enzymes reduce the amount of energy needed to start the reaction or lower the amount of energy needed to climb the energy hill. 11. A final product of a four-step metabolic pathway serves as a noncompetitive inhibitor, binding to an enzyme in this pathway and temporarily turning off the pathway. Which enzyme is most likely to be targeted by the inhibitor? a. The final enzyme in the pathway b. The second enzyme in the pathway c. The first enzyme in the pathway d. Any enzyme in the middle of the pathway Answer: C. The final product’s structure is more unlike the substrate for the first enzyme in the pathway than any other, and thus the least likely to fit the active site of enzyme 1. Additional Practice Questions – Unit 3 1. Which one of the following pathsrequires less activation energy to convert the reactants into the products? The options include the path indicated by a bold line, and the path indicated by a dotted line. a. In presence of an enzyme-Dotted line b. In absence of an enzyme-Bold line Answer: A. The path with the bold line represents the one with the higher amount of energy needed to get the reaction started and over the energy hill to form products, or a higher activation energy. For the path represented by the dotted line, the reactants need less energy to climb the hill, or a lower activation energy, to get the reaction over the hill to form products. 2. Select True or False: the lower the activation energy for a reaction, the faster the reaction rate. True False Answer: True. If less energy is needed to get the reaction over the energy hill, it goes faster. Enzymes help bring all of the items needed for a reaction together in the best way, so less energy is needed for the reaction to get started. This lowers the activation energy for the reaction and speeds up the reaction so that it can go much faster than if the enzyme were not present. 3. How do enzymes eliminate the need for high temperatures to complete a reaction? a. The need for high temperatures is eliminated by increasing the thermal energy needed for the reaction b. The need for high temperatures is eliminated by lowering the activation energy needed for the reaction c. The need for high temperatures is eliminated by increasing the activation energy needed for the reaction d. The need for high temperatures is eliminated by increasing the kinetic energy needed for the reaction Answer: B. Increasing the thermal energy for the reaction would typically result in an increase in the temperature of the reaction. Enzymes function within a certain specific temperature range. The activation energy is the amount of energy the reaction needs to initiate the change of substrate into product. Without an enzyme present, this can be too much energy for the reaction to happen in the body. The enzyme lowers the amount of energy needed by positioning the right amino acids near the right substrate, so less energy is needed when the enzyme is present. This means that the enzyme can function at a lower temperature than would be needed for the reaction if the enzyme were not present. 4. An enzyme that adds a phosphate group is a . An enzyme that removes a phosphate group is known as a . a. phosphatase, kinase b. phosphatase, hydroxylase c. kinase, phosphatase d. kinase, hydroxylase Answer: C. To remember the correct terms, think 'kinases are kind and giving,' and phosphatases take away phosphate groups. 5. Which level of protein structure provides enzymes with theirsubstrate specificity? a. Tertiary structure b. Primary structure c. Quaternary structure d. Secondary structure Answer: A. The tertiary structure of the enzyme is the level that placesthe right amino acids into the right locations in 3D space so that the enzyme can act like a baseball glove and wrap itself around the correct substrate. A baseball glove is designed to catch baseballs, not other types of balls, so it is specific for baseballs. In this way, the enzyme is designed to catch one type of substrate, based on the locations of the R groups of the amino acids in 3D space (tertiary structure), when it wraps up just the right way around the substrate in the active site. 6. Which of the following characteristic of an enzyme is responsible forspeeding up the reaction? a. They can bind multiple substrates b. They catalyze a specific type of reaction c. They are reusable d. They decrease activation energy Answer: D. Enzymes are called catalysts, which means they help speed up a reaction, and they are not used up by the reaction. They have the right amino acids in the right places to help change the substrate into product, and they still have these amino acids when the reaction is over. All of these factors assist the enzyme in lowering the activation energy, which means that less energy isrequired to start the reaction (or get it over the energy hill) than when the enzyme is not present. Therefore, when the enzyme lowers the activation energy this results in a faster reaction. 7. A substrate bindsto an enzyme at a specific site, which is referred to as a(n) . a. Substrate site b. Active site c. Enzymatic site d. Allosteric site Answer: B. Although 'substrate site' seems like it could be a good name, imagine that the enzyme can be activated when the substrate binds in the active site. 8. Which of the following factors can affect the protein folding and activity of an enzyme? a. All of the options are correct b. pH c. Heat d. Reducing agents Answer: A. Heat can disrupt hydrophobic interactions at the center of the protein. pH can disrupt ionic interactions, and hydrogen bonds. Reducing agents can break disulfide bonds. Each of the individual options are correct statements. Therefore, the option 'All of the options are correct' must be chosen to demonstrate your understanding that any of these conditions could disrupt protein folding and activity. 9. Which of the following are possible effect(s) that phosphorylation/dephosphorylation can have on the activity of an enzyme? a. Turn the enzyme "on" or “off” b. Increase enzyme aggregation c. Alter the amino acid sequence of the enzyme d. Increase the amount ofsubstrate for the enzyme. Answer: A. Adding or removing a phosphate group islike 'flipping a switch' on an enzyme's activity. It is a way of modulating, or regulating, enzyme activity. 10. Induced fit describes which of the following? a. An enzyme slightly changesits shape to accommodate specific substrates b. A substrate changes shape to fit the enzyme c. An enzyme changesshape drastically to accommodate all kinds ofsubstrates d. A substrate bound to the enzyme undergoes a slight conformational change to form a product Answer: A. Enzymes have a high degree of specificity. They will bind to one specific class of molecules and usually catalyze only one type of reaction. The enzyme has the right amino acids in the right locations to be able to recognize a particular type of substrate. 11.11. In the figure provided, what component of the enzymatic cycle does the number 3 depict? a. Enzyme and Product b. Enzyme-Substrate Complex c. Enzyme-Product Complex d. Active site Answer: C. First, the substrate and the enzyme come near to each other, and then the substrate can bind to the active site. The binding of the enzyme to the substrate makes the enzyme-substrate complex. After the substrate is changed to product, but before the product's release, the enzyme is still bound to the product, which is called the enzyme-product complex. Last, the enzyme releases the product from its active site. The enzyme is now ready to accept a new substrate molecule and repeat the same steps. 12. What happens to the enzyme at the end of the cycle? a. Remains bound to the product. b. The enzyme is used again. The enzyme will bind to a substrate. c. The enzyme shape is altered and it cannot be re-used for another reaction d. The enzyme is destroyed. Answer: B. During the process of changing the substrate into product and product release, the amino acids in the active site where the chemistry occurred on the substrate are changed back into their original state. This means that, after the product is formed and then released, the same amino acids will then be available to accept the next substrate molecule and repeat the same chemistry. 13. The concept of the induced fit applies to which part of the enzymatic cycle? a. Substrate b. Enzyme-Substrate Complex c. Product d. Enzyme-Product Complex Answer: B. Recent studies on enzymes have shown that while the substrate and active site are somewhat complementary prior to substrate binding, many enzymes will adjust their active site conformation slightly when the substrate binds, and the Enzyme-Substrate complex is formed, to improve the fit. This is known as induced fit. Think about giving a friend a hug. Your arms are wide open as they come towards you, but only when they are next to you do you close your arms around them. Thus, their proximity causes an induced fit with your arms that is a better fit to their body shape than the initial posture of having your arms wide open. Just as you require recognition of your friend prior to embracing them, an enzyme will have some indication from the shape and properties of the molecule, whether it is the correct substrate or not. When the molecule is recognized as the substrate, the enzyme will adjust to form itself around the substrate more tightly to facilitate the reaction it catalyzes. 14. Inhibitors that have a similar structure to a substrate of an enzyme are most likely to bind to the enzyme’s and be a inhibitor. a. Active site, Competitive b. Allosteric site, Competitive c. Active site, Non-competitive d. Allosteric site, Non-competitive Answer: A. Since competitive inhibitors are able to bind the active site of the enzyme in place of the substrate, competitive inhibitors often have a similar structure to the substrate. 15. When an inhibitor binds reversibly to a site of the enzyme that is not the active site, what type of inhibition results? a. Anti-competitive b. Competitive c. Non-competitive d. None of the options Answer: C. Enzymes can be inhibited by substances called non-competitive inhibitors. Some non-competitive inhibitors attach to the enzyme at an allosteric site, which is a site other than the active site.The presence of the non-competitive inhibitor changes the shape of the enzyme enough to interfere with binding of the normal substrate. Some non-competitive inhibitors are used in the regulation of metabolic pathways, but others are poisons. Such inhibitors distort the tertiary protein structure and alter the shape of the active site. Any enzyme molecule thus affected can no longer bind its substrate, so the enzyme cannot catalyze a reaction. Although some non-competitive inhibitors bind reversibly, others bind irreversibly and permanently inactivate the enzyme molecules, thereby greatly decreasing the reaction rate. In non-competitive inhibition, increasing the substrate concentration does not increase the reaction rate as it does in the presence of a competitive inhibitor. 16. You are in charge of designing a drug that inhibits the activity of a specific enzyme. An important criteria for the drug selection is to ensure that the drug directly competes with the original substrate by binding to the active site of the enzyme. Which of the following kind of inhibitor would be an ideal choice? a. Non-specific inhibitor b. Uncompetitive inhibitor c. Competitive inhibitor d. Non-competitive inhibitor Answer: C. A competitive inhibitor is usually a molecule similar in structure to a substrate that can bind to an enzyme’s active site even though the molecule is unable to react. This non-substrate molecule competes with the substrate for the active site. When the inhibitor bindsto an active site, it prevents the substrate from binding and thereby inhibits the reaction. The answer choice 'non-specific', is incorrect because nonspecific is not a type of inhibition. 17. One way a cell can avoid overproduction of a molecule is by using a particular type of inhibition in which this same molecule acts as an inhibitor for an enzyme in its production pathway. This type of regulation is known as inhibition. a. Regulatory b. allosteric c. feedback d. specific Answer: C. Feedback inhibition, a kind of reversible non-competitive inhibition, regulates the rate of many metabolic pathways. When the end product of a pathway is needed by the cell and consumed by cellular reactions, the pathway remains active. When the end product is no longer needed by the cell, the end product ceases to be consumed and begins to accumulate. Upon accumulation of the end product, it binds to the first enzyme in the pathway and initiates the inhibition of the pathway. The inhibition of the first enzyme in the pathway decreases the activity of each subsequent pathway intermediate. When the product concentration falls, there would no longer be inhibition of the first enzyme in the pathway and the pathway could resume its production of the end product again. While feedback inhibition often targets the first step in a biochemical pathway, thistype of inhibition can occur for any step in the pathway. The end product will target the most important step in a biochemical pathway. The answer choice 'regulatory' inhibition, is incorrect because while feedback inhibition is used to regulate the activity of the pathway, it is not the name of the type of inhibition. 18.18. Identify the components for each letter in the diagram provided below. a. A: enzyme-product complex; B: product; C: enzyme; D: enzyme-substrate complex; E:substrate b. A: enzyme-substrate complex; B: product; C: enzyme; D: enzyme-product complex; E:substrate c. A: enzyme-product complex; B: enzyme; C: substrate; D: enzyme-substrate complex; E: product d. A: enzyme-substrate complex; B: product; C:substrate; D: enzyme-product complex; E: enzyme Answer: B. First, the substrate and the enzyme come near to each other, and then the substrate can bind to the active site. The binding of the enzyme to the substrate makes the enzyme-substrate complex. After the substrate is changed to product, but before the product's release, the enzyme is still bound to the product, which is called the enzyme-product complex. Last, the enzyme releases the product from its active site. 19.19. What type of inhibition isshown in the image provided below? a. Non-competitive b. Anti-competitive c. None of the options d. Competitive Answer: A. Non-competitive inhibitors attach to the enzyme at an allosteric site, which is a site other than the active site. The presence of the non-competitive inhibitor changes the shape of the enzyme enough to interfere with binding of the normal substrate. Such inhibitors distort the tertiary protein structure and alter the shape of the active site so the enzyme can no longer bind its substrate, so the enzyme cannot catalyze a reaction. Although some non-competitive inhibitors bind reversibly, others bind irreversibly and permanently inactivate the enzyme molecules, thereby greatly decreasing the reaction rate. In non-competitive inhibition, increasing the substrate concentration does not increase the reaction rate as it does in the presence of a competitive inhibitor. 20. What are differences between competitive and non-competitive inhibitors? a. Competitive inhibitors bind reversibly to the active site change the enzyme tertiary structure; noncompetitive inhibitors bind only reversibly to the allosteric site and change the enzyme tertiary structure. b. Competitive inhibitors bind only irreversibly to the allosteric site and do not change the enzyme tertiary structure; non-competitive inhibitors bind only irreversibly to the active site and change the enzyme tertiary structure. c. Competitive inhibitors bind reversibly to the active site and do not change the enzyme tertiary structure; non-competitive inhibitors bind reversibly or irreversibly to the allosteric site and change the enzyme tertiary structure. d. Competitive inhibitors bind reversibly to the active site and do not change the enzyme tertiary structure; non-competitive inhibitors bind only irreversibly to the allosteric site and do not change the enzyme tertiary structure. Answer: C. A competitive inhibitor is usually a molecule similar in structure to a substrate that can bind to an enzyme’s active site even though the molecule is unable to react. This non-substrate molecule competes with the substrate for the active site. Enzymes can also be inhibited by substances called non-competitive inhibitors. Some non-competitive inhibitors attach to the enzyme at an allosteric site, which is a site other than the active site. Competitive inhibitors bind to the active site so that the substrate cannot, thereby inhibiting the reaction. The presence of the non-competitive inhibitor changes the shape of the enzyme enough to interfere with binding of the normal substrate. Some non-competitive inhibitors are used in the regulation of metabolic pathways, but others are poisons. Non-competitive inhibitors distort the tertiary protein structure and alter the shape of the active site. Any enzyme molecule thus affected can no longer bind its substrate, so the enzyme cannot catalyze a reaction. Although some non-competitive inhibitors bind reversibly, others bind irreversibly and permanently inactivate the enzyme molecules, thereby greatly decreasing the reaction rate. In non-competitive inhibition, increasing the substrate concentration does not increase the reaction rate asit doesin the presence of a competitive inhibitor. 21.21. Using the hypothetical pathway, which molecule would accumulate if Enzyme Y stopped working? a. Triangle b. Heart c. Circle d. Star Answer: A. The molecule represented asthe “triangle” is the substrate of the enzyme Y. The levels of the substrate increase when an enzyme stops functioning, whereas the levels of the product decrease. In this case, when the enzyme Y stops functioning, the levels of the molecule represented as a “triangle” increase (accumulate), whereas the levels of the molecule represented as the “heart” decrease. 22.22. Using the hypothetical pathway, which molecule would decrease if Enzyme Z stopped working? a. Triangle b. Heart c. Star d. Circle Answer: C. The molecule represented as “heart” is the substrate for the enzyme Z. The levels the molecule represented by the “heart” shape increase rather than decrease when the enzyme Z stops working. The correct answer is the option representing the “star” molecule. The levels of the substrate increase when an enzyme stops functioning, whereas the levels of the product decrease. In this case, when the enzyme Z stops functioning, the levels of the molecule represented as a “heart” increase (accumulate), whereas the levels of the molecule represented as the “star” decrease. 23.23. Using the hypothetical pathway, which downstream product could inhibit Enzyme X due to feedback inhibition? Circle Star Heart Triangle Answer: B. The molecule represented as “triangle” is the product for the enzyme X, which is the first step of the reaction pathway. The productsfrom the earlierstepsin an enzymatic pathway do not act asfeedback inhibitors. The correct answer is the option “star.” The molecule represented as “star” is the last product of the pathway. Typically, the last product of the pathway when inhibits the enzymes of the earlier steps such as Enzyme X or Y, in this case, is known as feedback inhibition. 24.24. For the pathway below, which of the following statements istrue? a. Inhibition of Enzyme 1 will lead to increased levels of Molecule C b. Inhibition of Enzyme 2 will decrease levels of Molecule D c. Increased levels of molecule C will result in increased levels of molecule D d. Molecule C inhibits Enzyme 3 Answer: D. Increased levels of molecule C will not result in increased levels of molecule D. Note that molecule C inhibits enzyme 3, as a result, decreases the levels of Molecule D. The correct answer is the option “Molecule C inhibits Enzyme 3”. Molecule C, in this image inhibits enzyme 3, which would result in decreased levels of Molecule D. Thus, the production of Molecule C impedes the production of molecule D. 25.25. Below is a depiction of the enzyme cycle for sucrase. Which of the following is true? a. Glucose is a substrate of sucrose b. Water is a product of sucrose c. Fructose isthe substrate ofsucrose d. Sucrose isthe substrate ofsucrase Answer: D. Water is not the product of sucrase. Water is entering the reaction pathway, thus is one of the substrates of the enzyme. The correct answer isthe option “Sucrose isthe substrate of sucrase.” The substrate is at the beginning of the arrow, and the product at the tip of the arrow. Sucrose is a substrate for the enzyme sucrase. Sucrase catalyzes a reaction where it cleaves sucrose to glucose and fructose. 26.26. The diagram below illustrates the pathway thatsynthesizesisoleucine. When isoleucine levels drop, how would you describe the activity of threonine deaminase? 27. Threonine deaminase activity is high because of feedback inhibition b. Threonine deaminase activity is low because feedback inhibition is relieved c. Threonine deaminase activity is low because of feedback inhibition d. Threonine deaminase activity is high since feedback inhibition is relieved Answer: D. Threonine deaminase activity is not high because of feedback inhibition. If there were feedback inhibition from isoleucine, it would result in the inhibition of the threonine deaminase enzyme. The correct answer is the option “Threonine deaminase activity is high since feedback inhibition is relieved.” Threonine deaminase shown as enzyme 1 is the first enzyme of the pathway. The final product of the pathway is isoleucine. Isoleucine inhibits the enzyme threonine deaminase and is known as the feedback inhibition. When the levels of the isoleucine drop, it relieves or lifts off the inhibitory effect it has on the enzyme threonine deaminase. Thus, the threonine deaminase activity is high since feedback inhibition is relieved. 27. Based on the following representation, the molecule represented by the letter “F” inhibits and is a type of inhibitor. Enzyme 1, noncompetitive inhibitor Enzyme 1, competitive inhibitor Enzyme 3, noncompetitive inhibitor Enzyme 3, competitive inhibitor Answer: B. Notice that the active site of the Enzyme 1 appears to be a good fit for the molecule “F” and looks similar to its originalsubstrate “A,” represented by a triangular shape. Recall that the competitive inhibitors are structural analogs (similar in structure) of the original substrates. In this case, both molecules “A” and “F” are structural analogs and compete to bind to the same active site on the enzyme 1. 28.28. Considering the pathway below, which of the following occur when the levels of ‘D’ are high? a. Enzyme 1 will have low activity due to feedback inhibition b. The levels of ‘C’ will increase c. The levels of ‘E’ will increase d. Enzyme 2 will have high activity because of negative feedback. Answer: C. Product ‘D’ functions as a feedback inhibitor for enzyme 2, as indicated by the blunt-ended arrow. When enzyme 2 is inhibited, it will have low activity and the levels of ‘C’ will decrease. The pathway will then route through enzyme 4 and the levels of ‘E’ will increase. The activity of enzyme 1 will not be impacted by in increase in ‘D’. 29. If the enzyme 2 was defective, the amount of molecule C would , and the amount of the molecule B would . a. Increase, increase b. Increase, decrease c. Decrease, decrease d. Decrease, increase Answer: D. When enzyme 2 is defective, the product, which is the molecule C is not made. As a result, the levels of the substrate, which is the molecule B, will increase. 30.30. If molecule D acts as a feedback inhibitor for enzyme 1 in this pathway, what happens to the amount of molecule A following initiation of feedback inhibition? a. Decreases b. Increases Answer: B. When Molecule D inhibits enzyme 1, its substrate, Molecule A, will increase in levels because Molecule A would no longer be converted into Molecule B. Thus, the correct answer is the option “increases”. 31.31. Phenylalanine hydroxylase is an enzyme that breaks down phenylalanine in the body. When there are low levels of this enzyme, as seen in Phenylketonuria, what is the consequence? a. Tyrosine levelsincrease. b. Phenylalanine levels decrease. c. Phenylalanine levelsincrease. Answer: C. Phenylalanine isthe substrate of the enzyme phenylalanine hydroxylase. If the level of this enzyme is low, then the level of its substrate, phenylalanine, will increase. 32.32. Phenylalanine istoxic to the developing brain. Using the following schematic, propose a suggestion to alleviate the problems associated with Phenylketonuria. a. Increase activity of phenylalanine hydroxylase. b. Supplement tyrosine in the diet. c. Decrease activity of phenylalanine hydroxylase. d. Supplement phenylalanine in the diet. Answer: A. Increased phenylalanine levelslead to phenylketonuria, so symptoms can be relieved by decreasing the level of phenylalanine. By increasing the activity of the enzyme that uses phenylalanine, phenylalanine hydroxylase, we can decrease the phenylalanine levels. 33. The enzyme acetylcholinesterase breaks down acetylcholine in the brain leading to neuron degeneration. Which of the following strategiesrepresents the best way to increase acetylcholine levels? a. Competitive inhibition of acetylcholinesterase. b. Allosteric activation of acetylcholinesterase. c. Increase gene expression for acetylcholinesterase. d. Non-competitive inhibition of acetylcholinesterase. Answer: D. If acetylcholinesterase isinhibited, then the substrate, acetylcholinesterase, will increase. If the inhibitor is a competitive inhibitor, the substrate levels will eventually overcome the inhibition, which will be relieved. If the inhibitor is an inhibitor, the concentration of substrate does not affect the inhibition. Therefore, non-competitive inhibition of acetylcholinesterase is the best approach. The answer choice ‘Competitive inhibition of acetylcholinesterase’, is incorrect because competitive inhibition is affected by the concentration of the substrate. As acetylcholine levels build up due to inhibition of the enzyme they will reduce the amount of inhibition. 34. Alkaline phosphatase is produced by bone and liver in the human body. The amount of alkaline phosphatase in blood can help identify if a patient potentially has certain types of bone and/or liverrelated disease, including Paget disease, hepatitis, and certain types of cancer. The optimal pH range for alkaline phosphatase activity is a pH of 8.0 to 10.0. What happens to the activity of the alkaline phosphatase at a pH of 2.0. a. Slightly decreases b. Significantly decreases c. Significantly increases d. Slightly increases Answer: B. This particular enzyme's optimal pH, the pH where it will have the highest activity, is between 8.0 and 10.0. Putting it into a notably different pH, like 2.0, willsignificantly decrease the activity. 35.35. In the reaction provided, glucose-6-phosphate accumulates in the cell and bindsto hexokinase at a site that is distinct from the active site. This prevents hexokinase from binding to its substrate. What happens to the amount of glucose in the cell once hexokinase is inhibited? a. Increases b. Stays the same c. Decreases Answer: A. When hexokinase isinhibited, it can no longer convert the substrate, glucose, into the product, glucose6-phosphate. Glucose therefore accumulates when hexokinase is inhibited. 36.36. In the reaction provided, glucose-6-phosphate accumulates in the cell and bindsto hexokinase at a site that is distinct from the active site. This prevents hexokinase from binding to its substrate. What type of inhibition is occurring in this example? a. Competitive inhibition b. Non-competitive inhibition c. Anti-competitive inhibition Answer: B. Glucose-6-phosphate binds to a site other than the active site, indicating that it is binding an allosteric site. When an allosteric site is bound by an inhibitor, the active site is altered, preventing substrate binding. Thisis the definition of non-competitive inhibition. The answer choice ‘competitive inhibition’, is incorrect because a competitive inhibitor binds and enzyme at the active site. 37. Patients with chronic myelogenous leukemia (CML) have a mutation that resultsin the production of BCR-ABL, an enzyme that speeds up cell division using ATP as a substrate.The drug Gleevec impairs the activity of the enzyme by binding to BCR-ABL where ATP would normally bind. Which statement best describes how the drug exerts its effect? a. Gleevec is a non-competitive inhibitor that bindsto an allosteric site on the enzyme to prevent ATP from binding to the active site. b. Gleevec is a non-competitive inhibitor and prevents ATP from binding with the active site of an enzyme. c. Gleevec is a competitive inhibitor and prevents ATP from binding with the active site of the enzyme. d. Gleevec is a competitive inhibitor that bindsto an allosteric site on the enzyme to prevent ATP from binding to the active site. Answer: C. Competitive inhibitors bind to an enzyme in the active site. Gleevec is binding in the same site as ATP. ATP isthe substrate, so the site of ATP binding must be the active site. Therefore, Gleevec is binding the active site and is a competitive inhibitor. The answer choice ‘Gleevec is a non-competitive inhibitor…’, isincorrect because non-competitive inhibitors bind at a site different from the active site. 38.38. This is a schematic showing the synthesis and degradation of acetylcholine, an important neurotransmitter. If you were to design a drug to keep the acetylcholine concentration high, where would you target a drug inhibitor? a. Choline acetyltransferase b. Acetylcholine c. Acetylcholinesterase d. Acetate + Choline Answer: C. Acetylcholinesterase isthe enzyme that converts the substrate, acetylcholine, into the products, acetate and choline. Inhibition of acetylcholinesterase will decrease degradation of acetylcholine, therefore increasing the concentration of acetylcholine. The answer choice ‘choline acetyltransferase’, is incorrect because acetylcholine is the product of choline acetyltransferase. Inhibition of that enzyme will lead to a decrease in the product, acetylcholine, not an increase.