Microsoft Word - Assignment Biochem____.docx 1 Multiple Choice. Circle the single best answer choice XXXXXXXXXXpts total; 1.5 pts each) 1. What kind of intermolecular interaction would you expect to...

Please answer all of the questions, and briefly explain the reasoning next to each question answered.


Microsoft Word - Assignment Biochem____.docx 1 Multiple Choice. Circle the single best answer choice. (43.5 pts total; 1.5 pts each) 1. What kind of intermolecular interaction would you expect to form between side chains of valine and leucine in a protein? a) Salt bridges b) Hydrophobic interactions c) Disulfide bonds d) Hydrogen bonds e) Metal ion coordination 2. What is the [H+] concentration in a sample of lemon juice that has a pH of 2? a) 102 M b) 100.2 M c) 10-2 M d) 10-14 M e) 2 M 3. Which of the following is true of all allosteric enzymes? a) They consist of proteins only. b) They have a non-protein portion. c) They generally follow Michaelis-Menten kinetics. d) They have more than one active site on each subunit. e) They have sites at which binding affects protein function at another site. 4. Confirmation that an inhibitor is competitive would come from which of the following experimental findings? a) Vmax changes significantly b) Km changes, but Vmax remains the same c) Vmax and Km both change d) Vmax and Km do not change e) None of the above 5. The KM of hexokinase for glucose 0.15 mM and for fructose, KM = 1.5 mM. Which is expected to be the preferred substrate? a) Glucose b) Fructose c) Both are equally preferred. d) Neither glucose nor fructose are substrates of hexokinase. e) The answer cannot be determined from the data provided. 6. Which of the following is true of isozymes? a) Their amino acid sequences are mirror images of one another. b) They are a pair of enzymes that must both be present for enzyme activity to occur. c) They are different forms of the same enzyme, one of which is inactive and one of which is active. d) They are different forms of the same enzyme typically found in different tissues. e) None of the above. 7. How does the presence of cis double bonds in fatty acids affect membrane fluidity? a) They tend to increase the fluidity. b) They tend to decrease the fluidity. c) They don't have any specific effect on fluidity. d) Fatty acids don’t have cis double bonds. 8. Which statement best describes what the change in energy is when ATP is hydrolyzed to ADP? a) Energy is stored. b) Energy is released. c) There is no energy change. 9. The reduction of pyruvate to lactate. . . a) is the process that aids in the recovery of sore muscles after exercise. b) is accompanied by phosphorylation of ADP. c) does not occur in aerobic organisms. d) allows for recycling of NAD+. 2 10. Which enzymes in the citric acid cycle catalyze oxidative decarboxylation reactions? a) isocitrate dehydrogenase and the alpha-ketoglutarate dehydrogenase complex b) aconitase and succinate dehydrogenase c) the alpha-ketoglutarate dehydrogenase complex and succinate thiokinase d) fumarase and succinate dehydrogenase 11. NADPH used in lipid biosynthesis is produced in. . . a) the pentose phosphate pathway. b) the citric acid cycle. c) glycolysis. d) gluconeogenesis. e) None of the above 12. A biological reaction with a significantly positive ΔG under cellular conditions may proceed in the forward direction because a) the cell will change the concentrations of the substrates and products so that the reaction can occur. b) the cell will raise the temperature, thereby affecting the overall thermodynamics of the reaction. c) the reaction can be coupled to a reaction with a more significant negative ΔG. d) reactions with positive ΔG values always proceed in the forward direction. 13. Metabolic processes are regulated by. . . a) transcriptional regulation of the amount of enzyme. b) allosteric control of enzyme activity. c) accessibility of substrates by compartmentalization. d) covalent regulation of enzymatic activity. e) All of the above 14. Second messengers are advantageous to signaling pathways because. . . a) the signal can be amplified by making many second messengers. b) second messengers can freely diffuse to other sites within the cell. c) a few common second messengers can be used in multiple signaling pathways. d) All of the above e) None of the above 15. Which of the following statements explains why the biochemical pathway for the catabolism of a molecule is almost never the same as the pathway for the biosynthesis of the molecule? a) It would be extremely difficult to regulate the pathway if it served both functions. b) The reactions never take place in the same type of cell. c) All enzyme-catalyzed reactions are irreversible. d) None of the above 16. Which carrier molecule is used in beta-oxidation? a) ATP b) ACP c) Carnitine d) Coenzyme A e) Lipoic acid 17. Which of the following best describes carnitine? a) It's a precursor of cholesterol. b) It carries growing acyl chains during fatty acid synthesis. c) It transports acetyl-CoA to the cytosol for fatty acid synthesis. d) It transports fatty acids across the inner mitochondrial membrane for breakdown. e) None of these 18. How many cycles of beta-oxidation are required to convert stearic acid (18 carbons) to 9 acetyl-CoAs? a) 6 b) 8 c) 9 d) 10 e) 18 3 19. Which of the following is not true? a) One advantage of the beta-oxidation of fats compared to oxidation of sugars is that fatty acids produce more metabolic water. b) The oxidation of fats produces more energy per carbon than the oxidation of carbohydrates. c) Fat yields more energy than carbohydrates because it is more oxidized. d) For every cycle of oxidation of a fatty acid, one NADH and one FADH2 are produced. 20. When is propionyl-CoA carboxylase required for the complete oxidation of a fatty acid? a) When it has an even number of carbons. b) When it has an odd number of carbons. c) When it is a monounsaturated fatty acid. d) When it is a polyunsaturated fatty acid. 21. What effect do high concentrations of ketone bodies have on blood pH? a) They tend to lower blood pH. b) They tend to increase blood pH. c) They help to maintain homeostasis of blood pH. d) They have no effect on blood pH. 22. Which of the following mechanisms explains why fatty acid synthesis and breakdown do not compete with each other in the body? a) Synthesis and breakdown take place in two separate compartments of the cell. b) One process uses NADH/NAD+ and the other uses NADPH/NADP+. c) They are not attached to the same carrier molecule in the two processes. d) All of these mechanisms are in operation. e) None of these 23. Which of the following are not macronutrients? a) Carbohydrates b) Fats c) Proteins d) Vitamins 24. What happens to the nitrogen from excess protein? a) It is stored as carbohydrate. b) It is stored as fat. c) It is eliminated through the urea cycle. d) It is exhaled as N2 gas. e) It is stored to make future proteins. 25. What function do vitamins usually serve? a) Coenzymes or precursors of coenzymes b) Intermediates of the citric acid cycle c) Precursors of amino acids d) Hormones or second messengers 26. Which of the following is not a function of cholesterol in the human body? a) Precursor of steroid hormones b) Energy storage compound c) Component of LDL and HDL d) Component of cell membranes e) All of these are important function of cholesterol in humans. 27. The nitrogen-fixing enzyme system, nitrogenase, is found exclusively in. . . a) plants. b) bacteria. c) some viruses. d) eukaryotic organisms. e) mammals. 28. If an amino acid is ketogenic, then it: a) has a catabolic pathway that leads to acetyl-CoA or acetoacetyl-CoA b) has a one-step pathway to a fatty acid c) enters the citric acid cycle as pyruvate d) enters the citric acid cycle as fumarate e) None of these 4 29. When blood glucose is high, the pancreas releases a) epinephrine b) insulin c) ghrelin d) glucagon e) phospholipase Fill in the blank. Use the word bank below to fill in the blanks. Words may be used once, more than once, or not at all. (9 pts total) ADP enzyme-substrate complex(es) protease(s) allosteric site(s) exon(s) protein amino GTP replication AMP hydrolysis ribosome amphibolic hyperbolic RNA polymerase amphipathic intron(s) RNA primer ATP isomerase(s) rRNA condensation isomerization salvage deoxyribonucleotide kinase(s) sigmoidal dephosphorylation mRNA splicing disulfide oxidative decarboxylation substrate(s) DNA polymerase peptide transcription DNA primer phosphodiester transferase(s) electron phosphorolysis translation enzyme(s) phosphorylation tRNA 30. DNA polymerase requires a/an _________________________ for replication to take place in living cells. 31. The efficiency or strength of a promoter sequence serves to regulate _________________________. 32. The formation of _________________________ bonds between deoxyribonucleotides is catalyzed during _________________________. 33. Post-transcriptional processing of mRNA includes _______________________ in eukaryotes, which results in the removal of _______________________. 34. The _______________________ curves observed when studying the kinetics of allosteric proteins indicate cooperativity between the subunits. 35. _______________________ belong to a class of enzymes that catalyze the rearrangement of atoms in a molecule, which is typically a reversible process. 36. The glyoxylate cycle allows plants to skip over the _______________________ step(s) in the citric acid cycle to ultimately produce carbohydrates from fats. 5 37. Given the reaction drawn below, circle the most appropriate word(s) from the list below to describe it (2 pts): Exergonic Non-Spontaneous Endergonic Spontaneous 38. a)