37. Shown is the purine catabolism. What is the chemical structure of the compound ( A )?
(A)① 
(B)②
(C)③
(D) ④
(E)⑤

33. The enzymes of the citric acid cycle are listed in the following. 1. Pyruvate dehydrogenase 2. Succinate dehydrogenase 4. Citrate synthase 5. a-ketoglutarate dehydrogenase 7. Succinyl-CoA synthase 8. Fumarase 3. Aconitatse 6. Isocitrate dehydrogenase 9. Malate dehydrogenase Which of the following descriptions is correct? (A) Enzyme 7 catalyzes the reaction that produces FADH2. (B) Enzymes 1, 5, and 9 catalyze the reactions that release CO2. (C) Enzymes 4 and 8 catalyze reactions consume H2O. (D) Enzymes 2 and 4 catalyze the reactions that consume double-bond-containing molecules. (E) Enzymes 3 and 6 catalyze the reactions that are bypassed in the glyoxylate cycle.

34. Which of the following statements about oxidation of fatty acids (FAs) is correct?  1. The energy yield per gram of FA oxidized is lesser than that per gram of carbohydrate oxidized. 2. Carnitine is used to shuttle acyl groups across the inner mitochondrial membranes.  3. Oxidation of acyl-CoA to unsaturated acyl-CoA is catalyzed by NAD-dependent acyl-CoA dehydrogenase.  4. Cleavage of the B-ketoacyl-CoA is catalyzed by thiolase. (A) 1 and 3 are correct. (B) 2 and 4 are correct. (C) 1 and 4 are correct. (D) 2 and 3 are correct. (E) All of above are correct.

35.Which of the following statements about amino acid biosynthesis is incorrect?  1. The conversion of a-ketoglutarate to glutamate is an amidation reaction. 2. Pyridoxal phosphate is a coenzyme frequently encountered in transamination reactions.  3. In animals, conversion of cysteine from serine use 3'-Phospho-5'adenylylsulfate as a sulfur donor. 4. Pyruvate generated from glycolysis can be used to synthesize alanine. (A) 1 and 3 are incorrect. (B) 2 and 4 are incorrect. (C) 1 and 4 are incorrect. (D) 2 and 3 are incorrect. (E) All of above are incorrect.

36. Which of the following statements about urea cycle is correct? 1. The urea cycle is linked to the citric acid cycle by arginine. 2. Aspartic acid is the main amino acid precursor for the carbon chain in arginine.  3. Citrulline is synthesized in the cytosol and transported to the mitochondrial matrix for subsequent reaction.  4. Ornithine is synthesized in the mitochondrial matrix and transported to the cytosol for subsequent reaction. (A) All of above are incorrect. (B) 1 and 3 are correct. (C) 2 and 4 are correct. (D) 1 and 2 are correct. (E) 3 and 4 are correct.

38. How many ATPs are produced by the complete metabolization of the saturated fatty acid shown below? (D) 50 (A) 32 (B) 36 (C) 38 (E) 52

39. ne pyrophosphate (TPP), derived from vitamin B1, is a coenzyme of pyruvate decarboxylase. Regar the functional role of TPp, which atom will be converted into a nucleophile? (A) No. 1. (B) No. 2. (C) No. 3. (D) No. 4. (E) No. 5.

40. Which of the following enzymes catalyzes the conversion shown below in the glycolysis pathway? (A) Hexokinase (B) Phosphofructokinase-1 (PFK-1) (C) Phosphohexose isomerase (D)Phosphoglucose mutase (E) Phosphohexose epimerase

41. The reaction, 1,3-bisphosphoglycerate→ 2,3-bisphosphoglycerate, is catalyzed by: (A) bisphosphoglycerate phosphatase (B) bisphosphoglycerate mutase (C) 2,3-bisphosphoglycerate synthetases (D) 3-phosphoglycerate isomerase (E) 1,3-bisphosphoglycerate hydrolase

42. All are uses of glucose-6-phosphate in liver except: (A) catabolized to acetyl-CoA for fatty acid biosynthesis. (B) generate NADPH and pentoses. (C) released as glucose to blood stream. (D) converted to glycogen. (E) All are true.

43. In the citric acid cycle, succinate is dehydrogenated by succinate dehydrogenase, which yields fumarate. The dehydrogenation of two of the four hydrogens in succinate (labeled as H1~H4 in the figure shown below) is stereospecific, with the pro-S hydrogen removed from one carbon atom and the pro-R hydrogen removed from the other.  Which of the following two hydrogens could be abstracted in the four hydrogens of the succinate molecule in the reaction catalyzed by succinate dehydrogenase? a. H1 and H2 b. H1 and H3 c. H1 and H4 d. H2 and H3 e. H2 and H4 f. H3 and H4 (A) b and e (B) c and d (C) a and f (D) Only c could occur. (E) Only d could occur.