Review session for exam-III

1. Review session for exam-III

2. Q1. Which of these is able to cross the inner mitochondrial membrane? • fatty acyl-CoA • malonyl-CoA • acetyl-CoA • fatty acyl-carnitine • none of the above can cross

3. Q2. The normal sequence of action of these components of the hormonal hierarchy is: • adrenal cortex  hypothalamus  anterior pituitary • anterior pituitary  adrenal cortex  hypothalamus • anterior pituitary  hypothalamus  adrenal cortex • hypothalamus  adrenal cortex  anterior pituitary • hypothalamus  anterior pituitary  adrenal cortex

4. Q3. Describe five possible fates for glucose 6-phosphate in the liver.

5. Q3 answer • (1) conversion to liver glycogen; (2) dephosphorylation and release of glucose into bloodstream; (3) oxidation via the pentose phosphate pathway; (4) oxidation via glycolysis and the citric acid cycle; (5) oxidation to acetyl-CoA, which then serves as precursor for synthesis of triacylglycerols, phospholipids, and cholesterol.

6. Q4. What is leptin? How does it function in the long-term maintenance of body mass?

7. Q4 Answer Leptin is a small polypeptide that is produced in adipocytes and is carried by the blood to the brain. It is produced when there are adequate stores of lipid in the adipocytes and interacts with a receptor in the hypothalamus. This interaction produces a cascade of effects that tend to suppress appetite and increase energy expenditure.

8. Q5. Which of the following cannot be used as an energy source by the brain? • glucose • ketone bodies • fatty acids • acetoacetate

9. Q6. . Which of the following is a major effect of insulin binding to its receptor? • a. autophosphorylation of tyrosineb. dephosphorylation of substrates such as IRS-1c. binding of phosphatidylinositol-3-kinase to the receptor

10. Q7. What hormone(s) is (are) a signal of the "fed state"? • Insulin • Glucagon • both insulin and glucagon • aldosteron

11. Q8. Which of the following is NOT true of acetoacetate and β-hydroxybutyrate? • They can provide energy for brain cells. • They allosterically modify other enzymes. • They are produced from the acetyl CoA of fats. • They cannot be used in liver.

12. Q9. During prolonged starvation, what is the last cellular material to be utilized? • Glycogen • Fats • Proteins • Cholesterol

13. Q10. Which of these can be synthesized by plants but not by humans? • palmitate (18:0) • stearate (20:0) • linolenate [18:3(D9,12,15)] • Arachidonic acid • phosphatidylcholine

14. Q11. Type 2 Diabetes is a disease characterized by overproduction of glucose by the liver and its underutilization by other organs. Which of the following is NOT a cause of diabetes? • inability to produce insulin • loss of ability to respond to insulin when it is produced • the generation of enzymes in the blood that rapidly degrade insulin after release from the pancreas

15. Q12. What are plasma lipoproteins? What is their general role in mammalian metabolism?

16. Q13. The synthetic compound mevinolinic acid, also called lovastatin, is a potent competitive inhibitor of HMG-CoA reducdase (hydroxymethylglutaryl-CoA reductase). Predict and explain the effect of this drug on serum cholesterol levels in humans.

17. Q14. The glycerol produced during the lipolysis of triglycerides A. is a waste product that is excreted from cells. B. is stored within the cell for future synthesis of tryglycerides. C. can be used as either a source of energy or for gluconeogenesis.

18. Q15. Write additional enzymes to oxidize fatty acids that have double bonds.

19. Q16. The degradation of an 18-carbon saturated fatty acid would be expected to yield how many NADH and FADH2 per fatty acid molecule? • A. 6 • B. 10 • C. 7 • D. 8 • E. 9

20. Q17. The NADPH used in the reductive steps of fatty acid biosynthesis comes from • one NADPH being generated per citrate leaving the mitochondria. • the degradation of glucose via the pentose phosphate pathway exclusively • both a and b.

21. Q18. Ubiquitin is added to …………. residues on proteins targeted for degradation. • Lysine • Asp • Gln • all of the above • none of the above

22. Q19. Cholesterol is synthesized from: • acetyl-CoA. • choline. • lipoic acid. • malate. • oxalate.

23. Q 20. Which of these statements about the regulation of cholesterol synthesis is not true? • Cholesterol acquired in the diet has essentially no effect on the synthesis of cholesterol in the liver. • Failure to regulate cholesterol synthesis predisposes humans to atherosclerosis. • High intracellular cholesterol stimulates formation of cholesterol esters. • Insulin stimulates HMG-CoAreductase. • Some metabolite or derivative of cholesterol inhibits HMG-CoAreductase.

24. Q21. The synthesis of fatty acids and their breakdown by b oxidation occur by separate pathways. Compare the two paths by filling in the blanks below. (Some blanks may require more than one answer.) Synthesis b oxidation ————————————————— Activating group _______________ ___________ Electron carrier coenzyme(s) _______________ ___________ Basic units added or removed _______________ ____________ Cellular location of process _______________ ____________

25. Q21. Answer Synthesis b oxidation ————————————————— Activating group acyl carrier protein CoA—SH Electron carrier coenzyme(s) NADPH NAD+ Basic units added or removed malonyl- and acetyl acetyl- Cellular location of process cytosol in animals mitochondrial matrix

26. Q22. Which of the following metabolic pathways and intracellular localization of the pathway are correctly paired a. b oxidation of fatty acids; mt. matrix b. Citric acid cycle; cytoplasm c. Fatty acid synthesis; cytoplasm d. Glycolysis; mitochondrial matrix e. Pentose phosphate pathway; peroxisomes

27. Q23. Which of the following statements about metabolism in the mammalian liver is false? • Most plasma lipoproteins are synthesized in the liver. • The enzymatic complement of liver tissue changes in response to changes in the diet. • The liver synthesizes most of the urea produced in the body. • The presence of glucose 6-phosphatase makes liver uniquely able to release glucose into the bloodstream. • Under certain conditions, most of the functions of the liver can be performed by other organs.

28. Q24. The Cori cycle is: • the conversion of lactate to pyruvate in skeletal muscle to drive glycogen synthesis. • the interconversion between glycogen and glucose l-phosphate. • the production of lactate from glucose in peripheral tissues with the resynthesis of glucose from lactate in liver. • the synthesis of alanine from pyruvate in skeletal muscle and the synthesis of pyruvate from alanine in liver. • the synthesis of urea in liver and degradation of urea to carbon dioxide and ammonia by bacteria in the gut.

29. Q25. The largest energy store in a well-nourished human is: • ATP in all tissues. • blood glucose. • liver glycogen. • muscle glycogen. • triacylglycerols in adipose tissue.

30. Q26. What distinguishes eicosanoids from other potent biological signaling molecules such as epinephrine?

31. Q26 answer Eicosanoids are paracrine hormones: they generally do not move long distances between their points of release and their points of action.

32. Q27. In animals, the carbon backbone of glucose _____ be metabolically converted and stoichiometrically utilized for synthesis of fatty acids; in animals, the carbon backbone of fatty acids _____ be metabolically converted and stoichiometrically utilized for synthesis of glucose. • Can; can • Can; cannot • Can only; can only • Cannot; can • Cannot; cannot

33. Q28. Which of the following intermediate in cholesterol biosynthesis is the substrate for the enzyme at the key regulatory step of the pathway • Dimethylallyl pyrophosphate • 3-hydroxy-3-methylglutaryl-CoA • 3-isopentyl pyrophosphate • Malonyl-CoA • Mevalonate

34. Q29. Which of the following best describes, in order, the complete series of catalyzed reactions that occurs as a molecule of acyl-CoA is shortened by one two-carbon unit during fatty acid degradation • Hydration; oxidation; thiolysis • Oxidation; hydration; oxidation; thiolysis • Oxidation; hydration; reduction; thiolysis • Oxidation; hydration; thiolysis • Reduction; hydration; oxidation; thiolysis

35. Q29 Answer • Hydration; oxidation; thiolysis • Oxidation; hydration; oxidation; thiolysis • Oxidation; hydration; reduction; thiolysis • Oxidation; hydration; thiolysis • Reduction; hydration; oxidation; thiolysis

36. Q30. During b oxidation, the carbon backbone of fatty acids is converted into which of the following • Carbon dioxide • Pyruvate • Acetyl groups • Malonyl groups • Succinyl groups

37. Q30 answer • Carbon dioxide • Pyruvate • Acetyl groups • Malonyl groups • Succinyl groups