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.

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.

45. In a number of species calorie restriction without malnutrition may slow the biological aging process, resulting in longer maintenance of youthful health and an increase in both median and maximum lifespan. Which of the followings is   not   involved in the underlying mechanism? (A) Reduced levels of insulin and IGF-1. (B) Increased gluconeogenesis. (C) Activation of AMPK. (D) Reduced production of reactive oxygen species. (E) Activation of Sirt-1.

46. Predict the prodcut of the following trasamination reaction via the enzyme using pyridoxal phosphate as cofactor. (A)(B)(C)(D)(E)

47. What is the essential ingredient for biosynthesis of fatty acid? (A)(B)(C)(D)(E)

48. Which of the following statements is   true  ? (A) Non-coding RNAs are known to promote RNA silencing. (B) Ribozymes are more efficient catalysts than protein-based enzymes. (C) 5' end of prokaryotic mRNA are protected from degradation. (D) The sequences in eukaryotic DNA known as introns are those included in the final sequence of messenger RNA. (E) The β-barrel structure motif in transcription factor CREB is responsible for protein-DNA interaction.

49. Which of the following is   not true   concerning silent mutations? (A) Silent mutations refer to base sequence differences that do not change the amino acid coded for. (B) Only changes in base sequence that lead to a different amino acid can have an effect on the organism. (C) Changes in the sequence of an exonic splicing enhancers can lead faulty removal of introns. (D) Silent mutations in a gene for pain tolerance have been correlated with human differences in perception of pain. (E) Translation kinetics and protein folding can be affected by silent mutations.

50. There is no codon for the amino acid hydroxyproline, but this amino acid is a prominent feature of collagen structure. Which of the following is a likely explanation? (A) Hydroxyproline is substituted for proline after translation by a cut and patch mechanism. (B) Proline is covalently modified to give hydroxyproline after translation. (C) There is an alternative mechanism for synthesis of proteins that contain hydroxyproline. (D) All of above are likely explanations. (E) It is not possible to form a hypothesis from the information given.