Overview Function de novo glucose synthesis effectively glycolysis in reverse can maintain blood glucose when glycogen stores are exhausted must supply brain and RBCs which utilize glucose for energy is NOT a source of energy for the liver hepatocytes use β-oxidation to supply the energy needed for gluconeogenesis potential substrates all amino acids except for leucine and lysine lactate produced in anaerobic glycolysis glycerol-3-phosphate produced in fat catabolism propionyl-CoA produced in odd-carbon fatty acid catabolism Pathway location hepatocytes (primary) kidney enterocytes NOT muscle no glucose-6-phosphatase cannot release free glucose enzymes involves both mitochondrial and cytosolic enzymes several steps of glycolysis are reversible the non-reversible steps must be bypassed with special gluconeogenic enzymes pyruvate carboxylase pyruvate → oxaloacetate requires biotin and ATP activated by acetyl-CoA oxaloacetate must be converted to malate to exit the mitochondria via the malate-aspartate shuttle in mitochondria PEP carboxykinase (PEPCK) oxaloacetate → phosphoenolpyruvate (PEP) requires GTP activated by glucagon and cortisol in both cytosol and mitochondria fructose-1,6-bisphosphatase fructose-1,6-bisphosphate → fructose-6-P important control point of gluconeogenesis activated by ATP, inhibited by AMP and fructose-2,6-bisphosphate in cytosol glucose-6-phosphatase (G6P) glucose-6-P → glucose in ER of hepatocytes clinical relevance von Gierke disease = G6P deficiency see Glycogen metabolism other enzymes lactate dehydrogenase lactate → pyruvate requires free NAD+ regulation stimulation glucagon acetyl CoA citrate inhibition high NADH/NAD+ ratio alcohol may cause elevated NADH/NAD+ ratio leading to hypoglycemia
QUESTIONS 1 of 6 1 2 3 4 5 6 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.BC.15.74) The balance between glycolysis and gluconeogenesis is regulated at several steps, and accumulation of one or more products/chemicals can either promote or inhibit one or more enzymes in either pathway. Which of the following molecules if increased in concentration can promote gluconeogenesis? Tested Concept QID: 106607 Type & Select Correct Answer 1 AMP 12% (14/118) 2 ADP 19% (22/118) 3 Insulin 5% (6/118) 4 Fructose-2,6-biphosphate 23% (27/118) 5 Acetyl-CoA 41% (48/118) M 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review tested concept Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.BC.14.1) To prepare for an endoscopy, a 27-year-old male was asked by the gastroenterologist to fast overnight for his 12 p.m. appointment the next day. Therefore, his last meal was dinner at 5 p.m. the day before the appointment. By 12 p.m. the day of the appointment, his primary source of glucose was being generated from gluconeogenesis, which occurs via the reversal of glycolysis with extra enzymes to bypass the irreversible steps in glycolysis. Which of the following irreversible steps of gluconeogenesis occurs in the mitochondria? Tested Concept QID: 106291 Type & Select Correct Answer 1 Glucose-6-phosphate to glucose 2% (1/48) 2 Fructose-1,6-biphosphate to fructose-6-phosphate 15% (7/48) 3 Pyruvate to oxaloacetate 65% (31/48) 4 Phosphoenolypyruvate to pyruvate 12% (6/48) 5 Glucose-6-phosphate to 6-phosphogluconolactone 2% (1/48) M 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review tested concept (M1.BC.13.2) A 65-year-old homeless man with a history of hospitalization for alcohol intoxication is brought in confused. His serum glucose is 39mg/dl. Which of the following is likely true? Tested Concept QID: 100067 Type & Select Correct Answer 1 He has also been using cocaine 1% (2/330) 2 He has decreased activity of alcohol dehydrogenase 9% (30/330) 3 Hepatic gluconeogenesis is elevated 7% (23/330) 4 The next step in management is glucose repletion 21% (68/330) 5 His hepatic NADH/NAD+ ratio is high 62% (203/330) M 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review tested concept