Ferchmin Review 2018 If you still find errors, please, let me know.

Use this sketch to follow the movement of labeled carbons from one metabolic pathway to another. A question you could find later in this course might be: Starting fatty acid synthesis from glucose-3-C14. In which positions of a newly synthesized fatty will the C14 be found?

Disease Deficiency Subject Hereditary fructose intolerance   Deficiency Subject Hereditary fructose intolerance Fructose-1-phosphate aldolase (aldolase B) deficiency fructose metabolism Galactosemia (mild form) Galactokinase deficiency galactose metabolism Galactosemia (severe form) Hexose-1-phosphate uridylyltransferase deficiency Galactosemia Type III. UDP-glucose-4-epimerase Lactose intolerance (milk intolerance) Intestinal lactase deficiency lactose metabolism Hypoglycemia secondary to ethanol ingestion Cytoplasmic NAD depletion Gluconeogenesis Von Gierke disease (glycogen storage disease Glucose-6-phosphatase deficiency glycogen metabolism Pompe's disease Lysosomal acid maltase deficiency Cori's disease Glycogen debranching enzyme deficiency Andersen's disease Glycogen branching enzyme deficiency McArdle's Disease Muscle glycogen phosphorylase deficiency glycogen storage disease Tarui disease Muscle phosphofructokinase deficiency Primaquine-induced hemolytic anemia Glucose-6-phosphate dehydrogenase deficiency Pentose phosphate pathway Beriberi Chronic thiamine deficiency vitamins Wernicke encephalopathy in a chronic alcoholic. Acute thiamine deficiency

Which of the following participates directly in the synthesis of glucosamine-6-phosphate from fructose-6-phosphate?   a. phosphofructokinase-2 b. glutamine c. ATP d. glutamine:fructose-6-phosphate transaminase e. glycine

Different cell types regulate their plasma membrane transport of glucose differently. Some cell types display insulin-dependent transport of glucose while others transport glucose independent of insulin levels. In the table below, insulin-dependent membrane transport of glucose is indicated by (+) and glucose transport independent of insulin is indicated by (–). Which answer is correct for the five cell types shown? Answer D

40. Which of the following processes can produce net gluconeogenesis in humans? a. synthesis of glucose from acetylCoA b. formation of glucose from galactose synthesis of glucose from glucogenic α-amino acids d. synthesis of glucose from ethanol e. release of glucose from glycogen

41. Insulin binds to which of the following molecules on the plasma membrane of its target cells? a. a membrane receptor that transfers insulin into the nucleus where insulin directly modulates gene expression b. a membrane receptor that activates adenylate cyclase and increase the cytoplasmic cyclic AMP level c. a membrane receptor that has protein tyrosine kinase activity in its cytosolic domain a membrane receptor that opens Na+ and Ca2+ channels through the plasma membrane e. the GluT4 membrane glucose transporter

42. High cytoplasmic levels of citrate reduce the activity of which of the following pathways? the pentose phosphate pathway b. glycolysis c. gluconeogenesis d. fatty acid synthesis e. glycogenesis

44. The enzyme phosphofructokinase-2 is indirectly inhibited by which of the following? a. ATP b. insulin c. UDP-glucose Citrate e. cyclicAMP

45. The blood of a patient who has an inherited deficiency of pyruvate kinase shows: a. erythrocytes with abnormally high affinity for oxygen. b. erythrocytes with abnormally low affinity for oxygen. c. erythrocytes with abnormally low levels of 2,3-bisphosphoglycerate (BPG). d. erythrocytes with abnormally high levels of ATP. e. a high concentration of plasma lactate.

46. Inhibition of hepatic glycolysis by either glucagon or epinephrine is mediated by: a. inhibition of glucokinase by phosphorylation. b. binding of cyclicAMP to a G-protein. c. inhibition of liver pyruvate kinase by phosphorylation. d. activation of phosphofructokinase-2 directly by cyclic AMP. e. activation of cyclic-AMP-specific phosphodiesterase (PDE).

47. Tissue hypoxia (a shortage of oxygen) may occur in shock or in conditions that impair blood flow. The lack of oxygen leads to the increased production of lactic acid and to lactic acidosis. Which of the following statements explaining how deficient oxygenation causes increased lactate production is TRUE? a. Low O2 levels increase the activity of phosphofructokinase-2 which stimulates glycolysis. b. High ATP levels directly stimulate lactate dehydrogenase to convert pyruvate into lactate. c. Low O2 levels directly stimulate pyruvate kinase to convert pyruvate into phosphoenolpyruvate. d. Low O2 levels limit the formation of ATP by oxidative phosphorylation which stimulates glycolysis. e. High ATP levels directly inhibit the activity of glyceraldehyde-3-phosphate dehydrogenase.

48. The carbohydrate response element-binding protein (ChREBP) regulates both glycolysis and lipogenesis. A high intracellular concentration of xylulose-5-phosphate acts through ChREBP to increase the synthesis of which of the following hepatic enzymes? a. fumarase b. hexokinase c. aldose reductase d. pyruvate kinase e. phosphofructokinase-1

49. With glycogen as the source of glucose, the oxidation of 1 mole of glucose by anaerobic glycolysis produces a theoretical net maximum yield of: a. 3 moles of lactate, 2 moles of NADH and 3 moles of ATP. b. 2 moles of pyruvate, 4 moles of NADH and 2 moles of ATP. c. 2 moles of pyruvate, 3 moles of NAD and 4 moles of ATP. d. 2 moles of lactate and 3 moles of ATP. e. 2 moles of lactate and 2 moles of ATP.

50. An increased concentration of AMP in muscle cells activates which of the following enzymes? a. fructose-1,6-bis-1-phosphatase b. glycogen synthase c. enolase d. glycogen phosphorylase e. phosphofructokinase-2

51. Carbon 2 of lactic acid is the carbon that carries the hydroxyl group. In anaerobic glycolysis, carbon 2 of lactic acid comes from which carbon(s) of glucose? a. carbons 1 and 6 b. carbons 2 and 5 c. carbons 3 and 4 d. carbons 5 and 6 e. only carbon 1

52. Fructose can be metabolized via glycolysis without the regulatory restrictions of hexokinase and phosphofructokinase-1. Its uptake does not depend on insulin and fructose does not increase glycemia. Because of this, intravenous fructose administration to diabetics and other patients was once practiced but was promptly abandoned due to the development of life-threatening hypoglycemia and hypophosphatemia. These bad effects of fructose occur because one enzyme of fructose metabolism is more active than a second enzyme of fructose metabolism. Which answer below identifies these two enzymes? a. aldolase A (fructose-1,6-bisphosphate aldolase) is more active than hexokinase b. phosphofructokinase-1 is more active than fructose-1,6-bisphosphatase c. fructose-1-phosphate kinase is more active than glucose-6-phosphatase d. fructokinase is more active than aldolase B (fructose-1-phosphate aldolase) e. glucokinase is more active than aldolase B (fructose-1-phosphate aldolase)

53. [5-14C]-Glucose was given to a healthy, well-fed 40 year-old white male after supper. After 6 hours of sleep a biopsy sample of abdominal fat was taken and the fatty acids were analyzed. Which carbons of the newly synthesized palmitate were labeled with 14C? a. Only carbon 1 of palmitate was labeled with 14C. Only the odd-numbered carbons of palmitate were labeled with 14C. c. Only the even-numbered carbons of palmitate were labeled with 14C. d. All of the carbons of palmitate were labeled with 14C. e. No 14C was found in palmitate.

54. Which of the following molecules can be a precursor for net gluconeogenesis during fasting? a. acetylcoenzyme A b. a free fatty acid c. ethanol d. lactate e. fructose

55. Gluconeogenesis is an anabolic pathway that requires energy in the form of nucleotide triphosphates. During a prolonged fast, which of the following metabolic pathways is the major source of high-energy molecules needed to produce ATP for gluconeogenesis? a. anaerobic glycolysis b. fatty acid β-oxidation c. amino acid metabolism d. the hexose monophosphate pathway e. aerobic oxidation of pyruvate

56. The biosynthesis of which of the following compounds from pyruvate requires both acetylCoA and ATP? a. lactate b. alanine c. oxalate d. citrate e. oxaloacetate

57. How many moles of high-energy nucleotide triphosphates (ATP + GTP) are needed in gluconeogenesis for the synthesis of 1 mole of glucose from 2 moles of pyruvate? a. 8 b. 6 c. 4 d. 2 e. 0 pyruvate carboxylase PEPCK Phosphoglycero kinase

58. What is one consequence of fructose-1,6-bisphosphatase deficiency? a. failure of cells to metabolize glucose-6-phosphate via the glycolytic pathway b. accumulation of fructose phosphates in the liver c. inability to produce pyruvate from lactate d. hypoglycemia between meals e. pentosuria

59. Which of the following molecules is an intermediary metabolite in the gluconeogenesis pathway that is synthesized in the mitochondria but that cannot be directly transported into the cytosol? a. dihydroxyacetone phosphate b. phosphoenolpyruvate c. oxaloacetate d. aspartate e. malate

60. Ingestion of ethanol decreases the replenishment of muscle glycogen after exercise because of increased the formation of NADH. This increase in NADH formation inhibits gluconeogenesis from lactate because: a. the formation of NADH consumes the NADPH that is produced by the pentose phosphate shunt. b. NADH competes with phosphoenolpyruvate for phosphoenolpyruvate carboxykinase. c. the formation of NADH consumes the NAD+ that is needed to convert lactate into pyruvate. d. ethanol metabolism exhausts the intracellular stores of lactate. e. phosphoenolpyruvate carboxykinase is allosterically inhibited by NADH.

61. During lipogenesis from carbohydrates, which of the following hepatic enzymes is NOT activated? a. fructose-1,6-bis-phosphate-1-phosphatase b. pyruvate dehydrogenase complex c. pyruvate kinase d. acetylCoA carboxylase e. phosphofructokinase II

68. The ability of the liver to release glucose during starvation requires, among others, the activity of one of the following enzymes? a. glucokinase b. citrate synthase c. phosphofructokinase-1 d. fructose-l,6-bisphosphatase e. glycogen synthase

69. Which enzyme of the pentose phosphate pathway requires thiamine pyrophosphate (TPP) as a cofactor? a. glucose-6-phosphate dehydrogenase b. 6-phosphogluconate dehydrogenase c. phosphopentose isomerase d. transketolase e. transaldolase

70. The table below describes the effects of glucagon, insulin, glucose intake, overnight fasting and exercise on glycogenesis and glycogenolysis in muscle and in liver. Only one of these descriptions is correct. Answer this question by selecting the letter from the first column corresponding to the row that gives the correct description of the metabolic changes. Answer A