2. You will need a Scantron and a pencil for this exam.

Transcription

1 Exam III Chemistry 306 Fall 2009 Roper Name Exam Number Instructions: 1. Please turn in your chapter 21 and 23 homework. 2. You will need a Scantron and a pencil for this exam. 3. Please bring your backpacks to the front of the room before you begin the exam. Please turn off your cell phone. 4. Please sit in alternate seats. That means that the seat on either side of you should be empty. 5. You may write on this exam. No notes, tables, or memory aids may be used on the exam. 6. When you are finished, please turn in your exam, Scantron, and scratch paper. 7. Good luck and good thinking!!!!!!!! 1

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3 Mulitple Choice (3 pts each) 1. Which is not true of enzyme behavior? a. They lower the activation energy for a chemical reaction. b. They speed up the rate of a chemical reaction. c. They do not affect the equilibrium position of a process. d. All enzymes exhibit substrate specificity. e. All of the above are true. 2. Vitamin C is a non-protein component of the enzyme lysine hydroxylase, an enzyme involved in the synthesis of collagen. This enzyme is a conjugated protein that requires the presence of vitamin C for its catalytic function. Vitamin C would be considered a(n) a. substrate b. inhibitor c. active site d. cofactor e. zymogen 3. You are taking a drug that could damage your liver. A good indicator of liver health is the activity of liver enzymes such as alanine transaminase (ALT) and aspartate transaminase (AST). The laboratory method for determining ALT and AST enzymatic activity is called a. an assay b. a titration c. electrophoresis d. turnover number e. None of these 4. The theory of enzyme mechanism that suggests a flexible molecule whose shape is altered by the reactions conditions is the model. a. coenzyme b. lock and key c. induced fit d. active site e. substrate specific 5. Which factor(s) is (are) not important an feature of how enzymes work? a. i only b. i and iv c. i and iii d. iii and iv e. ii and iii i. After catalysis, the structure of the enzyme has fundamentally changed. ii. Substrates are forced into the correct orientation for interaction. iii. Substrates are at an isoelectric ph. iv. Substrates are placed near acidic or basic sites. 3

4 6. A multi-step biochemical process in which the rate of an early step is affected by the concentration of products of a later step is said to be subject to a. decomposition b. hydrolysis c. ph control d. feedback control e. all of the above 7. The mechanism of enzyme control that is similar to noncompetitive inhibition because both involve interactions with the enzyme at locations other than the active site is a. zymogen production b. feedback inhibition c. zymogen activation d. allosteric interaction e. genetic control 8. What is the major class of enzyme that catalyzes the reaction below? O CO 2 - C + - CO 2 HC NH 3 + CO 2 - CH NH O - CO 2 C CH 3 CH 2 - CO 2 CH 3 CH 2 - CO 2 a. transferase b. oxidoreductase c. isomerase d. ligase e. lyase 9. Competitive inhibition of enzyme activity can best be described as a. a type of enzyme regulation that requires an inactive form of an enzyme called a proenzyme. b. a process that occurs when a molecule similar to the correct substrate interacts with the active site of an enzyme. c. a process that occurs when a molecule other that the correct substrate interacts with some part of the enzyme to alter the shape of the active site. d. an alteration of the tertiary structure via covalent modification of the enzyme. e. the removal of a non-protein component that is essential for the enzyme s catalytic activity. 4

5 10. Which is the correct term for the inactive form of an enzyme that is often used for storage or transport? a. inhibitor b. coenzyme c. zymogen d. cofactor e. apoenzyme 11. Which mechanism of enzyme control determines the amount of enzyme available in cell? a. genetic control b. allosteric control c. covalent modification d. competitive inhibition e. zymogen production 12. The only substrate for the enzyme succinate dehydrogenase (an important player in the citric acid cycle and electron transport) is succinate. Succinate dehydrogenase exhibits a. relative specificity b. absolute specificity c. catalytic specificity d. stereochemical specificity e. specific specificity 13. Protein kinases are a family of enzymes whose activity is dependent on the level of cyclic AMP in the cell. These enzymes have several functions in the cell, including regulation of glycogen, sugar, and lipid metabolism. Protein kinases are enzymes that catalyze which of the following reactions? a. Hydrolysis of peptide bonds b. Reduction of protein carboxyl groups c. Phosphorylation of proteins d. Transfer of amino groups to proteins e. Decarboxylation of proteins 14. Which statement about hormones is not correct? a. Hormones can affect biochemical reactions by activating enzymes. b. Hormones can affect biochemical reactions by inhibiting enzymes. c. Hormones are usually produced by the endocrine glands. d. Hormones are very specific, affecting only one chemical reaction. e. Hormones are transported in the bloodstream. 15. The major chemical structures of hormones include a. polysaccharides, esters, and steroids b. steroids, amino acid derivatives, and polypeptides. c. steroids, esters, and amides d. enzymes, amino acid derivatives, and steroids e. receptors, second messengers, and steroids 5

6 16. A molecule within a cell that is released in response to the interaction of a hormone or neurotransmitter with a receptor outside of the cell is a a. agonist b. secondary messenger c. activator d. allosteric regulator e. More than one of the above. 17. Nerves that use acetylcholine as their neurotransmitter are said to be a. Cholinergic b. Cholinesterases c. Adrenergic d. Antagonized e. unreasonable 18. Arrange the steps of the chemical response of a cell to epinephrine in the correct order. a. conversion of ATP to cyclic AMP b. activation of the enzyme adenylate cyclase c. hydrolysis of glycogen to form glucose d. activation of a G protein in the cell membrane e. epinephrine binds to the cell receptor A. c,e,d,b,a B. e,c,d,b,a C. e,d,b,a,c D. e,b,d,a,c 19. Which of the following hormones does not require a secondary messenger? A. B. C. D. e. More than one of the above. 6

7 20. One example of a amino acid derivative that acts as both a hormone and a neurotransmitter is a. estrogen b. testosterone c. thyroxine d. epinephrine e. growth hormone 21. Proteins that exert a morphine-like suppression of pain are known as a. enkephalins b. monoamines c. cholinergic d. agonists e. zymogens 22. The three monoamine neurotransmitters most studied in relation to moods and emotions are a. tryptophan, serotonin, and melatonin b. histamine, testosterone, and acetylcholinesterase c. cortisone, testosterone, and androsterone d. amitriptyline, phenelzine, and fluoxitine e. serotonin, norepinephrine, and dopamine 23. The drug Abilify (aripiprazole) is a novel antipsychotic drug with a complicated mechanism of action. It is hypothesized that this drug has agonist activity at certain dopamine and serotonin receptors. This means that the drug Abilify a. enhances the normal biochemical response of dopamine and serotinin b. reduces the normal biochemical response of dopamine and serotonin c. acts as a competitive inhibitor of monoamine oxidase. d. acts as a non-competitive inhibitor of monoamine oxidase e. None of the above. 24. Steroid hormones are chemically described as a. molecules whose structure is clearly related to an amino acid, usually tyrosine. b. molecules containing a nucleus of four interconnected cyclic structures. c. molecules composed of four interconnected hydrophobic amino acids. d. polypeptides with a high degree of secondary and tertiary structure e. large hydrophobic structures with two aromatic rings and an alkene chain 25. According to the National Institute on Drug Abuse, substance abuse in middle school includes inhaling solvents like the toluene in spray paint. Researchers have now confirmed that toluene increases the release of a neurotransmitter in brain regions associated with reward and addiction. This neurotransmitter is most likely a. dopamine b. histamine c. acetylcholine d. norepinephrine e. melatonin 7

8 26. Which of the following will prevent symptoms associated with an allergic response by acting as an antagonist to histamine receptor sites? Histamine a. b. c. d. 27. All of the following statements about free energy are true except. a. The free energy change (ΔG) for a reaction is the change in total overall energy. b. A negative change in ΔG indicates that a reaction is spontaneous and will proceed in the direction written c. A reaction with a ΔG = -11 kcal will have a larger concentration of reactants at equilibrium that a reaction with a ΔG = -3 kcal. d. In an endergonic reaction the free energy of the products is greater than the free energy of the reactants. e. Endergonic reactions are those that are non-spontaneous and that do not liberate free energy. 28. Which of the following brings to an end a nerve impulse initiated by acetylcholine? a. Synaptic vesicles containing acetylcholine move to the cell membrane. b. Reuptake of acetylcholine c. Acetylcholinesterase catalyzes the decomposition of acetylcholine. d. Reuptake of choline e. Acetylcholine crosses the synapse and binds to the receptors on the postsynaptic neuron. 8

9 29. A metabolic pathway in which a series of steps, each using different enzymes, regenerates one of the early reactants, is a(n) pathway. a. anabolic b. catabolic c. cyclic d. linear e. spiral 30. Which sequence illustrates the order of the steps from food to biochemically useful energy? a. digestion, citric acid cycle, acetyl-scoa production, ATP production b. digestion, ATP production, acetyl-scoa production, citric acid cycle c. citric acid cycle, digestion, ATP production, acetyl-scoa production d. acetyl-scoa production, digestion, ATP production, acetyl-scoa production e. digestion, acetyl-scoa production, citric acid cycle, ATP production 31. Which class of vitamins is incorporated into the structure of reduced coenzymes? a. fat soluble b. water soluble c. antioxidants d. B vitamins e. Flinstone chewables 32. In order for two chemical reactions to be energetically coupled, they must a. occur simultaneously b. share a common reaction intermediate c. both be endergonic d. both be exergonic e. be friends 33. ATP is the molecule most often used for energy transport because a. A large amount of energy is released upon its hydrolysis b. An intermediate amount of energy is released upon hydrolysis and the hydrolysis is relatively slow except in the presence of the appropriate enzymes. c. It can only be produced in the citric acid cycle. d. It can only be produced as a result of reactions in the electron transport chain e. It has polar bonds. 34. All of the following are energy strategies used in biochemical reactions except a. ATP is produced as a means of transferring energy. b. The G of a chemical reaction can be changed by pairing it with another more favorable reaction. c. Exergonic reactions are used to drive unfavorable reactions. d. Coenzymes which can exist in oxidized or reduced forms are used to transfer electrons. e. ADP is transformed into a higher energy molecule when coupled with an exergonic reaction. 9

10 35. Which statements concerning coenzymes and redox reactions is incorrect? a. Oxidation can be considered as a loss of hydrogen and/or a loss of electrons. b. NAD+ is the oxidized form of NADH c. When an NADPH coenzyme participates in a chemical reaction, the reaction is most likely a reduction. d. NAD+ is often involved in the oxidation of a ketone to an alcohol e. An oxidation reaction cannot occur unless a reduction reaction also occurs. 36. All of the following molecules are directly involved in the electron transport chain except a. coenzyme Q b. FADH 2 c. Cytochrome c d. Acetyl SCoA e. H 2 O 37. Cyanide, a potent human toxin, blocks electron flow in electron transport by binding to Fe 2+. The Fe 2+ ion is found in which of the following? a. coenzyme Q b. FADH2 c. Cytochrome c d. Acetyl SCoA e. Catalase 38. Which of the following is a two-electron carrier in the electron transport chain? a. coenzyme Q b. FADH 2 c. Cytochrome c d. Acetyl SCoA e. H 2 O 39. After O 2 has been in the electron transport chain, the oxygen atoms are a part of. a. reduced; water b. oxidized; water c. reduced; ATP d. oxidized; ATP e. oxidized; coenzyme Q 40. The electrons that are transferred from one electron carrier to another in the electron transport chain originate from a. NAD and FADH b. NADH and FADH 2 c. ADP and ATP d. O 2 and H 2 0 e. Coenzyme Q 10

11 41. The name of the protein complex that facilitates ATP synthesis is a. ATPase b. ATP synthase c. ATP hydrolase d. NADH dehydrogenase e. None of the above 42. Which of the following is not a product of digestion? a. amino acids b. fatty acids c. glucose d. glycerol e. pyruvate 43. The most important goal of glucose metabolism is a. synthesis of oxidized coenzymes b. synthesis of glycogen for later use c. production of ATP as an energy source for all cells. d. production of acetyl SCoA for synthesis of lipids e. synthesis of carbon skeletons for amino acid production 44. Which chemical is produced from pyruvate when it is metabolized in muscle cells under aerobic conditions? a. lactate b. ethanol c. acetyl SCoA d. phosphoenol pyruvate e. glucose 45. Which chemical is produced from pyruvate when it is metabolized in muscle cells under anaerobic conditions? a. lactate b. ethanol c. acetyl SCoA d. phosphoenol pyruvate e. glucose 46. The products of glycolysis important in metabolism are a. acetyl-scoa and ATP b. pyruvate, ATP, and NADH c. CO 2, ATP, and NADH d. pyruvate, ADP, and NAD+ e. CO 2 and H 2 O 11

12 47. Glycolysis occurs mainly in the a. cytosol of all cells b. mitochondria of all cells c. muscle d. brain e. liver 48. Look at the citric acid cycle diagram on the last pages of this exam. Which of the following steps in the citric acid cycle is an oxidation and a decarboxylation? a. 2 b. 3 c. 5 d. 6 e Look at the citric acid cycle diagram on the last pages of this exam. Which of the following steps in the citric acid cycle requires acetyl S CoA? a. 1 b. 2 c. 3 d. 4 e Look at the citric acid cycle diagram on the last pages of this exam. Which of the following steps in the citric acid cycle requires FAD? a. 1 b. 2 c. 3 d. 4 e Look at the diagram of glycolysis on the last pages of this exam. Which step(s) produce pyruvate? a. 1 b. 4 c. 7 d. 10 e. More than one of the above. 52. Look at the diagram of glycolysis the last pages of this exam. Which of the following steps require ATP? a. 1 and 3 b. 1, 3, and 6 c. 3 and 6 d. 6 and 10 e. 1, 3, 6, and 10 12

13 53. Look at the diagram of glycolysis the last pages of this exam. Which of the following steps require NAD+? a. 2 b. 3 c. 6 d. 9 e Look at the diagram of fatty acid oxidation the last pages of this exam. Which steps of this series of reactions are catalyzed by an oxidoreductase enzyme? a. 1 and 3 b. 1 and 2 c. 3 and 4 d. 1, 2, and 3 e. 2,3 and Which of the following statements is incorrect regarding ATP? a. The life span of an ATP molecule is relatively short in the cell. b. The ester bonds in ATP release more energy than the anhydride bonds in ATP when hydrolyzed. c. The resonance stabilization of the products of ATP hydrolysis contributes to the large free energy difference between reactants and products.. d. Approximately 30% of the energy released from the complete oxidation of glucose is stored in the bonds of the ATP produced by this process with the remaining energy released as heat. e. All of the statements are correct. 56. In addition to producing ATP, the citric acid cycle produces as high energy molecules and as its major chemical waste product. a. oxidized coenzymes; H 2 O b. oxidized coenzymes, CO 2 c. reduced coenzymes; H 2 O d. reduced coenzymes; CO 2 e. ADP; CO Which of the following would most likely act as an inhibitor of the enzymes of the citric acid cycle? a. A high concentration of ADP b. A high concentration of ATP c. A low concentration of NADH d. A high concentration of NAD e. More than one of the above. 13

14 58. The driving force which provides the synthesis of ATP in oxidative phosphorylation is a. the concentration difference of hydrogen ions between the two sides of the inner mitochondrial membrane. b.the concentration of reduced coenzymes outside the mitochondrial matrix c.the energy difference between reduced carbon atoms and oxidized carbon atoms. d.the hydrolylsis of ADP to form AMP and Pi. e.more than one of the above. 14

15 Short Answer 1. (10 pts) T or F T or F T or F T or F All of the steps in glycolysis are reversible. Name Under anaerobic conditions, the NAD+ needed for glycolyisis comes from the reduction of pyruvate to lactate by NADH. The citric acid cycle occurs in the cytosol of the cell. The anti-ulcer drug cimetidine blocks both H1 and H2 receptors. T or F The electron carriers in the electron transport chain are found in the inner mitochondrial membrane and are arranged in increasing electron affinity. 2. Fructose 6 phosphate, whose structure is given below, is a compound with a free energy of hydrolysis of -3.3 kcal/mol a. (8 pts) Write the equation for the hydrolysis of the phosphate ester in fructose 6 phosphate (ΔG = -3.3 kcal/mol). Clearly show the structures of all participants. b. (8 pts) Write the word equation for the hydrolysis of the phosphate ester in fructose 6 phosphate (reaction above) coupled with the phosphorylation of ADP (ADP + P ATP, ΔG = 7.3 kcal/mol). (Use words or symbols instead of actual chemical structures). Calculate the overall free energy change for this coupled process. 30 pts c. (4 pts) Would the hydrolysis of fructose 6 phosphate be a good candidate for driving the phosphorylation of ADP? Why or why not? Clearly explain your reasoning. 15

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