38. Which one is   not   the limiting step in lipid metabolism?
(A) Fatty acyl CoA + Carnitine → Fatty acyl carnitine
(B) Palmitoyl CoA + Serine → Sphinganine
(C) Acetyl CoA → Malonyl CoA
(D) HMG COA → Mevalonate
(E) Mevalonate → Cholesterol

34. Consider the reaction below, which of the following statement is   false  ? (A) When M is acetaldehyde, enzyme 1 is pyruvate decarboxylase. (B) When M is oxaloacetate, enzyme 1 is pyruvate carboxylase. (C) When M is phosphoenopyruvate, enzyme 2 is pyruvate kinase. (D) When M is malate, enzyme 2 is malic enzyme. (E) None of above is false.

35. Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic conditions in animal cells is   correct  ? (A) The process occurs in the cytosolic compartment of the cell. (B) The methyl group is eliminated as CO2. (C) One of the products of the reactions of the pyruvate dehydrogenase complex is a thioester of acetate. (D) The pyruvate dehydrogenase complex uses all of the following as cofactors: , lipoic acid, pyridoxal phosphate (PLP), and FAD. (E) The reaction is so important to energy production that pyruvate dehydrogenase operates at full speed under all conditions.

36. 2,4-dinitrophenol and oligomycin inhibit mitochondrial oxidative phosphorylation. 2,4-dinitrophenol is an uncoupling agent； oligomycin blocks the ATP synthesis reaction itself. Therefore,2,4-dinitrophenol will: (A) allow electron transfer in the presence of oligomycin. (B) allow oxidative phosphorylation in the presence of oligomycin. (C) block electron transfer in the presence of oligomycin. (D) diminish O2 consumption in the presence of oligomycin. (E) do none of the above.

37. Which one   directly   regulates fatty acid breakdown? (A) Succinyl CoA. (B) Myristoyl CoA. (C) Acetyl CoA. (D) Malonyl CoA. (E) Fatty acid synthase.

39. If an ATP synthase contains 12 c subunits, 3 a subunits and 3 ẞ subunits, how many protons must pass through this complex for every ATP molecule synthesized and transported to the cytosol, assuming that each ATP synthesized requires one proton for transport to the cytosol. (A) 3. (B) 4. (C) 5. (D) 12. (E) 13.

40. It is crucial that regulation occur at pyruvate dehydrogenase because: (A) pyruvate kinase is reversible. (B) lactate dehydrogenase is the only other enzyme to use pyruvate. (C) the product acetyl-CoA is committed to oxidation in the citric acid cycle or fatty acid biosynthesis. (D) alanine aminotransferase would use the pyruvate. (E) All of the above.

41. An essential feature of the glyoxylate cycle, which is not associated with the TCA cycle is: (A) it utilizes condensation of acetyl-CoA with glyoxylate. (B) each complete cycle produces a net gain of two 4-carbon molecules. (C) it occurs in chloroplasts and the mitochondria of plant seeds. (D) mammals use the glyoxylate cycle for gluconeogenesis. (E) it is a reductive pathway that utilizes NADPH as an electron source.

42. Which of the coenzyme is   not   involved in the one-carbon metabolism: (A) Tetrahydrofolate. (B) S-adenosylmethione. (C) Vitamin B12 (cabalamin). (D) Pyridoxal phosphate. (E) None of the above.

43. Otto Warburg observed that, in conditions of normal oxygen tension, normal cells produced most of their energy via mitochondrial respiration. In contrast, over 50% of cancer cell energy was generated in the cytosol via glycolysis, with the remainder from the mitochondrial respiratory chain. This is termed the Warburg effect. The Warburg effect may be beneficial to cancer cells because it provides precursors for many biosynthetic pathways. These precursors include the followings,   except  : (A) amino acid precursors. (B) NADPH. (C) ribose sugars for DNA and RNA synthesis. (D) fatty acids for lipid synthesis.

44. Purinosome is a: (A) bacteria relying on the metabolism of purine for energy. (B) multi-enzyme complex that carries out de novo purine biosynthesis within the cell. (C) multi-enzyme complex degrading purine nucleotides within the cell. (D) membrane transporter for cells to uptake purine base from the cell medium. (E) nutrient formula promoting muscle growth.