47. Which of the following is   NOT   a ketone body?
(A) Acetyl-CoA
(B) Acetone
(C) β-hydroxybutyrate
(D) Acetoacetate

43. The human red blood cells burst when they are placed in the water. Which of the following will cause Escherichia coli ((E) coli) to burst completely in it? (A) Isotonic solution (B) Hypertonic solution (C) Hypotonic solution (D) None of above

44. The phosphate buffer system is maximally effective at a pH close to its pKa of 6.86 and thus tends to resist pH changes in the range between about 5.9 and 7.9. What is the pH of a mixture of 0.05 M NaH2PO4 and 0.5 M Na2HPO4? (A) 5.86 (B) 6.86 (C) 7 (D) 7.86

45. How many cycles of β-oxidation are required to completely process a saturated stearic acid (C18)? (A) 7 (B) 8 (C) 9 (D) 18

46. The β-oxidation of saturated fatty acids has four basic steps. The important enzymes involved in the reaction are listed below: 1. enoyl-CoA hydratase 2. acyl-CoA dehydrogenase 3. β-hydroxyacyl-CoA dehydrogenase 4. acyl-CoA acetyltransferase Which of the following is the correct order that they react in the β-oxidation pathway? (A) 1234 (B) 4321 (C) 2134 (D) 3421

48. Which description is   NOT   correct about the catabolism of amino acids? (A) An early step in the catabolism of amino acids is the separation of the amino group from the carbon skeleton. (B) The amino group is transferred to α-ketoglutarate to form glutamate. (C) The amino group transamination reaction requires the coenzyme pyridoxal phosphate. (D) Glutamate dehydrogenase liberates the amino group as ammonium ion (NH4+) in the liver peroxisome.

49. Which of the following hormones is derived from cholesterol? (A) Progesterone (B) Androgens (C) Estrogens (D) All of the above

50. Which description is   NOT   correct about the nitrogen excretion? (A) Ammonia is highly toxic to animal tissues. (B) In the urea cycle, ornithine combines with ammonia and regenerate in each turn of the cycle. (C) The urea cycle results in a net conversion of fumarate to oxaloacetate. (D) Both of fumarate and oxaloacetate are intermediates in the TCA cycle.

51. Which of the following enzymes is regulated by allosteric regulation in the urea cycle? (A) Carbamoyl phosphate synthetase I (B) Glutamine synthetase (C) Glutamate dehydrogenase (D) Aspartate aminotransferase

52. Which of the following is an alternative electron donor to the mitochondrial electron transport chain? (A) H2O (B) Succinate (C) Fumarate (D) All of the above

53. Which of the following metabolic reactions mainly occur in the mitochondrial matrix? (A) Gluconeogenesis (B) Pentose phosphate pathway (C) Citric acid cycle (D) Glycolysis