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5.3 Glycogen Metabolism β Test 1
Q1. Identify the correct statements: I. Sucrose and Pi are inhibitors of sucrose-phosphate synthase; II. Fructose-6-P and Pi are activators of fructose-2,6-bisphosphatase; III. Fructose-6-P and Pi are activators of fructose-6-phosphate 2-kinase; IV. Fructose-2,6-bisphosphate and Pi are inhibitors of fructose-1,6-bisphosphatase.β III and IV
Q2. The process in which lactate formed in skeletal muscle is transported to the liver and kidney, where it reforms glucose, is called:β Cori cycle
Q3. After intense exercise, lactate from skeletal muscle is transported to the liver and converted into glucose. These reactions constitute:β Cori cycle
Q4. In human liver, the initial step in the utilization of fructose is its phosphorylation to fructose-1-phosphate. This is followed by:β Cleavage of fructose-1-phosphate to glyceraldehyde and dihydroxyacetone phosphate
Q5. Which of the following stimulate glycogenolysis?β Glucagon and epinephrine
Q6. Which liver enzyme, absent from other tissues, gives the liver an advantage in taking up glucose after a meal?β Glucokinase
Q7. Glucokinase:β Has a high Km for glucose
Q8. Identify the correct statements: 1) Glucokinase and hexokinase phosphorylate hexoses; 2) Hexokinase has a higher affinity for glucose than glucokinase; 3) Glucokinase has a higher affinity for glucose than hexokinase; 4) Glucokinase is a liver isozyme of hexokinase.β 1, 2 and 4 only
Q9. In muscle, the first product generated in the breakdown of glycogen is:β Glucose-1-phosphate
Q10. During fasting, liver glycogen is a glucose source but muscle glycogen is not, because:β Muscle lacks glucose-6-phosphatase
Q11. During fasting, liver glycogen is the source of glucose for other tissues, but muscle glycogen is not. The explanation is:β Muscle lacks glucose-6-phosphatase
Q12. Glucose-6-phosphate is a substrate or product in all of the following pathways EXCEPT:β Ξ²-oxidation
5.3 Glycogen Metabolism β Test 2
Q13. Identify the correct statements about glycogen synthase and glycogen phosphorylase: (i) Both are active upon phosphorylation; (ii) Active glycogen synthase is dephosphorylated; (iii) Phosphorylated glycogen phosphorylase is active; (iv) Both are inactive upon phosphorylation.β ii & iii
Q14. Glycogen is received in the blood circulation from all tissues except:β Adipose
Q15. Which of the following denotes the active form of the enzyme?β Dephosphorylated glycogen synthase
Q16. Glycogen synthase, the key regulatory enzyme for glycogenesis, is inactivated by:β Phosphorylation
Q17. Which of the following is the donor of new glucose molecules in glycogen synthesis?β UDP-glucose
Q18. The priming function in glycogen synthesis is carried out by:β Glycogenin
Q19. The first step in glycogen breakdown releases glucose units as:β Glucose-1-phosphate
Q20. Which of the following statements about the control of glycogen synthase by insulin is/are correct?β Phosphorylation by GSK3 is inhibited by insulin
Q21. Which statement about the control of glycogen synthase regulation by insulin is/are correct? (variant)β The phosphorylation by GSK3 is inhibited by insulin
Q22. ______ refers to glycogen synthesis; ______ refers to glycogen breakdown; ______ refers to glucose-to-pyruvate production.β Glycogenesis, glycogenolysis, glycolysis
Q23. Hexokinase-II is present predominantly in myocytes whereas hexokinase-IV (glucokinase) is primarily in liver. Choose the most appropriate statement:β Km of hexokinase-II is lower than Km of hexokinase-IV