MCAT gluconeogenesis and glycogen metabolism
High-yield flashcards for MCAT review focusing on gluconeogenesis and glycogen metabolism, crucial biochemistry concepts tested in the exam.
Quiz(72 questions)
1. Which of the following is NOT a substrate for gluconeogenesis?
Terms in this Study Set(72)
Gluconeogenesis Pathway(16)
Key substrates for gluconeogenesis?
1. Lactate 2. Glycerol 3. Glucogenic amino acids 4. Propionate
Enzyme converting pyruvate to oxaloacetate?
Pyruvate carboxylase (PC) - requires biotin and ATP.
True or False: Gluconeogenesis occurs in muscle cells.
False - occurs primarily in liver and kidney.
Which enzyme bypasses pyruvate kinase?
Fructose-1,6-bisphosphatase (F1,6BPase) - removes a phosphate.
Key regulatory enzyme in gluconeogenesis?
Fructose-1,6-bisphosphatase - regulated by AMP and fructose-2,6-bisphosphate.
What is the role of glucose-6-phosphatase?
Converts glucose-6-phosphate to glucose - allows release of glucose into the bloodstream.
Fill in the blank: Gluconeogenesis is mainly stimulated by ________.
Glucagon - promotes glucose production.
Gluconeogenesis energy requirements?
6 ATP equivalents required to synthesize one glucose molecule.
Key regulator that inhibits F1,6BPase?
AMP - signals low energy status.
What are the final products of gluconeogenesis?
Glucose (or glucose-6-phosphate) - primary output for maintaining blood sugar.
Enzyme converting oxaloacetate to phosphoenolpyruvate?
Phosphoenolpyruvate carboxykinase (PEPCK) - requires GTP.
True or False: All amino acids can be converted to glucose.
False - only glucogenic amino acids can.
Comparison: Gluconeogenesis vs. Glycolysis?
Gluconeogenesis: anabolic, uses ATP; Glycolysis: catabolic, produces ATP.
What activates pyruvate carboxylase?
Acetyl-CoA - essential for gluconeogenesis initiation.
Cause → Effect: Increased glucagon levels?
Stimulates gluconeogenesis - raises blood glucose levels.
What is the relationship between fructose-2,6-bisphosphate and gluconeogenesis?
Fructose-2,6-bisphosphate inhibits gluconeogenesis and promotes glycolysis.
Glycogen Metabolism(20)
What is glycogenesis?
The process of converting glucose to glycogen for storage in liver and muscle.
Enzyme that initiates glycogenesis?
Glycogen synthase catalyzes the addition of glucose units to the growing glycogen chain.
Key substrate for glycogenesis?
UDP-glucose is the activated form of glucose used in glycogen synthesis.
Glycogenolysis process?
The breakdown of glycogen into glucose-1-phosphate for energy release.
Main enzyme in glycogenolysis?
Glycogen phosphorylase cleaves glucose units from glycogen.
Hormones that regulate glycogenesis?
Insulin promotes glycogenesis by activating glycogen synthase.
Hormones that regulate glycogenolysis?
Glucagon and epinephrine stimulate glycogenolysis by activating glycogen phosphorylase.
True or False: Glycogen is stored primarily in muscle tissue.
False. Glycogen is primarily stored in the liver and muscle.
Fill in the blank: Insulin activates ________ to promote glycogenesis.
glycogen synthase.
Comparison: Glycogenesis vs. Glycogenolysis?
Glycogenesis builds glycogen; glycogenolysis breaks it down.
Energy requirement in glycogenesis?
Glycogenesis requires energy in the form of ATP.
What does glucagon do to glycogen?
Glucagon stimulates glycogen breakdown to increase blood glucose levels.
Key regulator of glycogen phosphorylase?
AMP activates; ATP and glucose-6-phosphate inhibit glycogen phosphorylase.
What molecule acts as a signal for glycogen breakdown?
Epinephrine activates glycogenolysis during stress or exercise.
The role of debranching enzyme?
It removes oligosaccharides from the branch points during glycogenolysis.
Short example: Glycogen synthesis after a meal?
After eating, insulin increases, activating glycogen synthase to store glucose as glycogen.
True or False: Glycogen can be converted directly to glucose.
False. Glycogen is broken down to glucose-1-phosphate before conversion.
Regulatory effect of glucose on glycogenesis?
High glucose levels promote glycogenesis by stimulating glycogen synthase.
What is the function of protein phosphatase-1 (PP1)?
PP1 dephosphorylates glycogen synthase, activating it and promoting glycogenesis.
Key difference between liver and muscle glycogen?
Liver glycogen maintains blood glucose; muscle glycogen provides energy for muscle contraction.
Energy and Regulation(20)
Energy source for gluconeogenesis?
Lactate, glycerol, and certain amino acids serve as key substrates.
True or False: Glycogen metabolism is energy-efficient.
True - Glycogen provides a quick energy source and requires less ATP than gluconeogenesis.
Fill in the blank: Gluconeogenesis primarily occurs in the ______.
Liver and to a lesser extent in the kidney.
Key regulatory enzyme in gluconeogenesis?
Fructose-1,6-bisphosphatase; it is a major control point.
Role of ATP in gluconeogenesis?
ATP provides energy for converting pyruvate to phosphoenolpyruvate.
Cause → Effect: High acetyl-CoA levels?
Stimulates gluconeogenesis, as it indicates fat metabolism.
Comparison: Gluconeogenesis vs. glycolysis?
Gluconeogenesis uses ATP, while glycolysis produces ATP; opposite pathways.
Primary allosteric inhibitor of fructose-1,6-bisphosphatase?
Fructose-2,6-bisphosphate; it inhibits gluconeogenesis when glucose is plentiful.
Key substrate derived from triglycerides?
Glycerol; it can be converted to glucose during gluconeogenesis.
What regulates glycogen phosphorylase?
AMP activates it; ATP and glucose-6-phosphate inhibit it.
Energy cost of gluconeogenesis?
6 ATP equivalents are used to synthesize one glucose molecule.
True or False: All amino acids can be used for gluconeogenesis.
False - Only glucogenic amino acids can contribute.
Fill in the blank: Glycogen is primarily stored in the ______ and ______.
Liver and muscle tissues.
What initiates glycogen synthesis?
Glucose-6-phosphate activates glycogen synthase, promoting glycogenesis.
Glycogen metabolism regulation by insulin?
Insulin promotes glycogenesis by activating glycogen synthase and inhibiting glycogenolysis.
Key enzyme in glycogenolysis?
Glycogen phosphorylase; it breaks down glycogen into glucose-1-phosphate.
Cause → Effect: Low blood glucose levels?
Stimulate gluconeogenesis and glycogenolysis to increase glucose availability.
Role of glucagon in metabolism?
Glucagon promotes glycogen breakdown and gluconeogenesis, raising blood glucose levels.
Energy substrate during fasting?
Body relies on gluconeogenesis from amino acids and glycerol when glucose is low.
What is the role of biotin in gluconeogenesis?
Biotin serves as a cofactor for pyruvate carboxylase, essential for converting pyruvate.
Clinical Relevance(16)
Glycogen storage disease type I
Also known as Von Gierke's disease. Deficiency in glucose-6-phosphatase leads to hypoglycemia and accumulation of glycogen.
Glycogen storage disease symptoms
Symptoms include: - Hypoglycemia - Lactic acidosis - Hyperlipidemia - Growth retardation
True or False: Gluconeogenesis is primarily active in muscle tissue.
False. Gluconeogenesis primarily occurs in the liver, not in muscle tissue.
Cause of hypoglycemia in fasting
Inadequate gluconeogenesis due to liver dysfunction or glycogen storage disease can cause hypoglycemia during fasting.
McArdle's disease
A glycogen storage disease due to deficiency in muscle glycogen phosphorylase. Results in exercise intolerance.
Effect of prolonged fasting
Prolonged fasting increases gluconeogenesis to maintain blood glucose levels, especially from amino acids and glycerol.
Difference between Type I and Type II Glycogen Storage Diseases
Type I: Glucose-6-phosphatase deficiency. Type II: Acid alpha-glucosidase deficiency, leading to Pompe disease.
Glycogen storage disease type III
Cori disease due to debranching enzyme deficiency. Symptoms include hypoglycemia and liver enlargement.
Gluconeogenesis dysregulation implications
Dysregulation can lead to diabetes mellitus, metabolic acidosis, or hypoglycemia due to impaired glucose release.
True or False: Gluconeogenesis uses the same enzymes as glycolysis.
False. Gluconeogenesis uses unique enzymes like pyruvate carboxylase and fructose-1,6-bisphosphatase.
Fill in the blank: Gluconeogenesis primarily occurs in the _____ and _____.
Liver and kidneys.
Symptoms of von Gierke's disease
Symptoms include: - Severe fasting hypoglycemia - Lactic acidosis - Hyperlipidemia - Kidney disease
Impact of insulin on gluconeogenesis
Insulin inhibits gluconeogenesis. In diabetes, this regulation is impaired, leading to hyperglycemia.
Glycogen synthesis disorder
Andersen's disease: caused by branching enzyme deficiency, leads to abnormal glycogen structure and liver failure.
Key metabolic pathway for glucose during starvation
Gluconeogenesis synthesizes glucose from non-carbohydrate sources like amino acids and glycerol during fasting.
Fructose-1,6-bisphosphatase regulation
It is activated by ATP and inhibited by AMP and fructose-2,6-bisphosphate, which regulates gluconeogenesis.
Questions in this Study Set(72)
1. Which of the following is NOT a substrate for gluconeogenesis?
2. What enzyme deficiency is associated with Glycogen storage disease type I?
3. What process involves converting glucose into glycogen for storage in the body?
4. Which of the following molecules can serve as an energy source for gluconeogenesis?
5. What enzyme plays a critical role in converting pyruvate to oxaloacetate in gluconeogenesis?
6. Which of the following symptoms is NOT associated with glycogen storage disease type I?
7. Which enzyme is responsible for adding glucose units to glycogen during glycogenesis?
8. True or False: Glycogen metabolism requires more ATP than gluconeogenesis.
9. True or False: Gluconeogenesis primarily occurs in muscle tissue.
10. True or False: Gluconeogenesis occurs mainly in the brain.
11. Which molecule is the activated form of glucose used in glycogen synthesis?
12. Fill in the blank: Gluconeogenesis is primarily regulated by ______.
13. Which enzyme bypasses the irreversible step catalyzed by pyruvate kinase?
14. In the context of fasting, inadequate gluconeogenesis can lead to what condition?
15. What is the primary function of glycogen phosphorylase?
16. What is the primary allosteric activator of gluconeogenesis?
17. Which enzyme is considered a key regulatory step in gluconeogenesis?
18. What is the primary defect in McArdle's disease?
19. Which hormone promotes glycogenesis?
20. Which enzyme is responsible for converting pyruvate to phosphoenolpyruvate in gluconeogenesis?
21. What is the primary function of glucose-6-phosphatase in gluconeogenesis?
22. Prolonged fasting primarily stimulates gluconeogenesis using which substrates?
23. Which hormones stimulate glycogenolysis?
24. What is the energy cost of synthesizing one glucose molecule through gluconeogenesis?
25. Fill in the blank: Gluconeogenesis is stimulated by ________.
26. Which of the following correctly describes the difference between Type I and Type II Glycogen Storage Diseases?
27. True or False: Glycogen is primarily stored in the liver and muscle.
28. Which of the following statements is NOT true regarding glycogen metabolism?
29. How many ATP equivalents are required for the synthesis of one glucose molecule in gluconeogenesis?
30. Cori disease is caused by a deficiency in which enzyme?
31. Insulin activates which enzyme to promote glycogenesis?
32. Which hormone primarily promotes gluconeogenesis?
33. Which molecule acts as a key inhibitor of the enzyme fructose-1,6-bisphosphatase?
34. What condition can arise from the dysregulation of gluconeogenesis?
35. What is the main difference between glycogenesis and glycogenolysis?
36. What is the effect of high blood glucose levels on gluconeogenesis?
37. What is the main product of gluconeogenesis?
38. True or False: Gluconeogenesis and glycolysis share all the same enzymes.
39. Which of the following is required for glycogenesis?
40. Which of the following is a substrate for gluconeogenesis derived from triglycerides?
41. Which enzyme converts oxaloacetate to phosphoenolpyruvate in gluconeogenesis?
42. Fill in the blank: Gluconeogenesis primarily occurs in the _____ and _____.
43. What does glucagon do to glycogen?
44. Which molecule inhibits glycogen phosphorylase?
45. True or False: All amino acids can be converted to glucose through gluconeogenesis.
46. Which of the following is NOT a symptom of Von Gierke's disease?
47. Which molecule activates glycogen phosphorylase?
48. What initiates glycogen synthesis?
49. Compare gluconeogenesis and glycolysis: which is anabolic?
50. What effect does insulin have on gluconeogenesis?
51. True or False: Glycogen can be converted directly to glucose.
52. In which organ does gluconeogenesis primarily occur?
53. What activates pyruvate carboxylase in gluconeogenesis?
54. Andersen's disease is caused by a deficiency in which enzyme?
55. Which enzyme removes oligosaccharides from branch points during glycogenolysis?
56. Cause → Effect: Low blood glucose levels will lead to what metabolic response?
57. What effect do increased glucagon levels have on gluconeogenesis?
58. Fructose-1,6-bisphosphatase is regulated by which of the following?
59. What role does protein phosphatase-1 (PP1) play in glycogen metabolism?
60. Which of the following is NOT a substrate for gluconeogenesis?
61. What is the relationship between fructose-2,6-bisphosphate and gluconeogenesis?
62. What is the primary metabolic consequence of untreated Von Gierke's disease during fasting?
63. What is a key difference between liver and muscle glycogen?
64. What is the role of biotin in gluconeogenesis?
65. Which of the following statements is NOT true about glycogen metabolism?
66. Which enzyme is a key regulatory point in gluconeogenesis?
67. What happens to glycogen synthesis after a high-carbohydrate meal?
68. What effect does insulin have on glycogen metabolism?
69. Which hormone is primarily responsible for inhibiting glycogenesis?
70. What type of amino acids can contribute to gluconeogenesis?
71. Which of the following statements correctly describes the role of glycogen in the liver?
72. Which of the following molecules acts as a primary allosteric inhibitor of gluconeogenesis?
Related Study Sets
Kohlenhydrate Fette Proteine Prüfung
Glucose Fischer- und Haworth-Projektion fürs Abi
Aminosäuren und Peptidbindung Lernzettel
Abiturwissen: Proteinstruktur und Denaturierung
Harnstoffzyklus Biochemie Karteikarten
Glykolyse Regulation Biochemie Karteikarten
Gluconeogenese Biochemie Prüfungsfragen
Enzyme im Stoffwechsel
Create Your Own Study Set
Upload a PDF, paste your notes, or describe a topic – AI generates flashcards, quizzes and more in seconds.
