Biochemistry Practice Exam IV Answer Key PDF

Practice Exam IV, 31 questions, 50 points Name (Please Print): _____________________________ 1. What reaction does amylase catalyze? breakdown of starch/endoglucoside that cleaves alpha-1,4 linkages in polysaccharides 2. Which of the following groups of people is most likely to suffer from lact...

Practice Exam IV, 31 questions, 50 points Name (Please Print): _____________________________ 1. What reaction does amylase catalyze? breakdown of starch/endoglucoside that cleaves alpha-1,4 linkages in polysaccharides 2. Which of the following groups of people is most likely to suffer from lactase deficiency? a. Danes b. Swedes c. African Americans d. Dutch e. All of the above f. None of the above 3. (2 points) The enzymes required for synthesis of glycogen from glucose-1 phosphate in the liver are: a. UDP-glucose phosphorylase b. glycogen synthase * could also add 4:6 transferase (branching enzyme) 4. (2 points) During gluconeogenesis, fructose-1,6-bisphosphate is converted to fructose-6-phosphate by fructose-1,6 bisphosphatase and glucose-6-phosphate is converted to glucose by glucose-6 phosphatase. 5. (3 points) In the process of glycolysis in the liver, there are 3 reactions that are irreversible under physiological conditions that have to be bypassed in the process of gluconeogenesis, starting with pyruvate. Name either the enzymes involved or the reactants and products of each of these 3 reactions. a. glucokinase (glucose + ATP  glucose-6-P + ADP b. phosphofructokinase-1 (fructose-6-P + ATP  fructose 1,6-P + ADP) c. pyruvate kinase (phosphophenolpyruvate + ADP  pyruvate + ATP) 1 6. One way insulin regulates glycolysis and gluconeogenesis in the liver is by: a. increasing cAMP concentration, thereby activating protein kinase A, which leads to phosphorylation of the glycolytic enzyme pyruvate kinase, thereby decreasing activity of pyruvate kinase. b. increasing the concentration of fructose-2,6-bisphosphate, thereby increasing the activity of the glycolytic enzyme phosphofructokinase-1 and decreasing the activity of the gluconeogenic enzyme fructose bisphosphatase-1. c. increasing cAMP concentration, thereby activating protein kinase A, which leads to the phosphorylation of the glycolytic enzyme glucokinase, thus increasing the activity of glucokinase. d. doing all of the above. 7. Which of the following statements is not true? a. Glycogen phosphorylase a is inactive in the phosphorylated form. NOT TRUE b. Glycogen phosphorylase a is inactive in the non-phosphorylated form. TRUE c. Glycogen synthase is inactive in the non-phosphorylated form. NOT TRUE d. Glycogen synthase is inactive in the phosphorylated form. TRUE e. none of the above is true 8. One major metabolic function of the pentose phosphate pathway is: a. to act as a source of ADP. b. to provide intermediates of the citric acid cycle. c. the generation of NAD+ for use in oxidative reactions. d. the generation of NADPH for reductive reactions. e. to participate directly in reactions in which ATP is produced from fuel oxidation. 9. The enzyme transketolase in the pentose phosphate pathway in the liver: a. recycles pentose-P to 6-phosphogluconate. b. converts NADP+ to NADPH. c. transfers a 2-carbon fragment to form fructose-6-phosphate. d. transfers a 3-carbon fragment to form fructose-6-phosphate. e. none of the above is true. 2 10. Which of the compounds below is a product of the metabolism of fructose in the liver and an intermediate of glycolysis? a. glycerol b. glycerate c. glyceraldehyde-3-P d. dihydroxyacetone e. fructose-2,6-bisphosphate 11. Which of the statements below best describes the events that occur after ingesting a carbohydrate- rich meal? a. Blood glucose concentration decreases. b. Insulin concentration in the blood decreases. c. Glucagon concentration in the blood increases. d. Glucose uptake by skeletal muscle decreases dramatically. e. None of the events listed above occur. 12. UDP-glucose is a precursor for: a. ribose-5-P b. glycolipids c. glyceraldehyde-3-P d. all of the above 13. Which of the steps below occur in the process of triacylglycerol digestion, absorption, transport and clearance from the blood? a. Secretion of chylomicrons. b. Hydrolysis of triacyglycerol by lipoprotein lipase. c. Hydrolysis of tiracylglycerol by pancreatic lipase. d. Synthesis of triacyglycerol in the intestinal mucosa. e. All of the above. f. None of the above. 14. Bile acids are derived from: cholesterol 3 15. Which of the steps below occur in the synthesis of fatty acids. a. Reduction of a keto derivative to give a hydroxy derivative. b. Removal of water. c. Addition of 2 carbons from malonyl-CoA. d. Reduction of a double bond. e. All of the above. f. None of the above. 16. A major factor in the short-term inhibition of fatty acid synthesis involves: a. the dephosphorylation of the enzyme Acetyl CoA Carboxylase. active when dephosphorylated b. the inhibition of formation of CDP derivatives of malonyl-CoA. not relavant c. the inhibition of formation of malonyl-carnitine. not relevant d. the phosphorylation of carnitine:palmitoyl acytransferase-I. not relavant e. none of the above. 17. The process of the elongation of palmitic acid (16:0) to stearic acid (18:0) requires: a. malonyl-CoA b. conversion of palmitate to palmitoyl-CoA c. NADPH d. all of the above e. none of the above 18. Which of the following statements about triacylglycerol (TAG) synthesis in adipose cells is INCORRECT? a. Decreased blood glucose concentration brings about an increase in TAG synthesis in adipose cells. b. TAG synthesis is enhanced by glucagon. c. Insulin decreases the movement of the enzyme lipoprotein lipase (LPL) to the cell surface, thereby increasing the rate of hydrolysis of TAG in chylomicrons and VLDL to fatty acids and glycerol. d. All of the above are incorrect. 19. (2 points) Draw the generalized structure of a sphingolipids. 4 20. The backbone of glycolipids is: sphingosine 21. Name the enzyme that is the rate limiting and major regulated step in cholesterol synthesis. HMG-CoA Reductase 22. (5 points) List the 5 types of lipoproteins and order them according to their relative size. chylomicrons, VLDL, IDL, LDL, HDL 23. Which of the following statements best applies to the cholesterol? a. They are formed from eicosanoids. b. They are formed from acetyl-CoA. c. They are formed from arachidonic acid. d. None of the above is true. 24. (2 points) Prostaglandin E1 (PGE1), which is shown below, is derived from arachidonic acid. In the diagram below, circle the differences between PGE1 and arachidonic acid. 25. (2 points) Progesterone, which is shown below, is derived from cholesterol. In the diagram below, circle the differences between progesterone and cholesterol. 26. Which statement is NOT CORRECT? a. Asprin and NSAIDS inhibit COX-2, but not COX-1. b. Asprin and NSAIDS inhibit COX-1 and COX-2. c. Asprin irreversibly inhibits COX-1 and COX-2 d. Ibuprofen reversibly inhibits COX-1 and COX-2. 5 27. During the fasting state, a. the insulin/glucagon ratio will be high. b. in the liver, the rate of glycogen synthesis will be increased and glycogen degradation will be decreased. c. the rate of fatty acid and triacyglycerol synthesis in the liver will be increased. d. the rate of fat storage in adipose tissue will be increased. e. none of the above are true. 28. (4 points, 1 point for each letter) What is the effect of glucagon on each of the following processes. Use an up arrow to indicate increase, a down arrow to indicate decrease, a dash to indicate no effect. a. Glycogen synthesis in the liver. arrow down b. Triacyglcyerol degradation in fat cells. arrow up c. Glycogen synthesis in skeletal muscle. no effect d. Gluconeogenesis in liver. arrow up 29. (4 points, 1 point for each letter) What is the effect of insulin on each of the following processes. Use an up arrow to indicate increase, a down arrow to indicate decrease, a dash to indicate no effect. a. Glycogen degradation in liver. arrow down b. Tiracylglycerol synthesis in fat cells. arrow up c. Glycolysis in liver. arrow up d. Fatty acid synthesis in liver. arrow up 30. Hexokinase in the muscle: a. has a lower Km than glucokinase in liver. b. has a higher Km than glucokinase in liver. c. has a nearly identical Km to glucokinase in liver. d. none of the above statements is true. 31. (3 points) The products of malic enzyme are: a. pyruvate b. NADPH c. CO2 6