43. Which of the following metabolic enzymes is NOT directly regulated by the ATP level?
(A) Pyruvate kinase M2
(B) Phosphofructokinase
(C) Pyruvate dehydrogenase
(D) Isocitrate dehydrogenase
(E) a-Ketoglutarate dehydrogenase

39. Regarding the degradation of purine, all of the following molecules are the product of purine degradation EXCEPT: (A) hypothanthine (B) beta-alanine (C) xanthine (D) uric acid (E) guanine

40. 5-Bromouracil is a brominated derivative of uracil that acts as an anti-proliferation activity, which of the following statement is incorrect for 5-Bromouracil? (A) 5-Bromouracil acts as a base analog, substituting for thymine in DNA (B) 5-Bromouracil causes transition mutation of DNA (C) 5-Bromouracil used mainly as an experimental mutagen (D) The keto form of 5-Bromouracil is complementary to guanine, so it can be present in DNA either opposite adenine or guanine during DNA replication (E) 5-Bromouracil induces a point mutation via base substitution

41. Which of the following amino acids will migrate to the positive electrode on the electrophoresis paper at pH 6.0? (A) Lysine (B) Arginine (C) Tyrosine (D) Asparagine (E) Proline

42. Which chemical classification does proline belong to? (A) Amphipathic amino acid (B) Aromatic amino acid (C) Imino acid (D) Basic amino acid (E) Acidic amino acid

44. A sample containing three proteins (A, B, and C) was analyzed by SDS-PAGE, as shown below. Size exclusion chromatography (also known as gel filtration) was utilized for their separation. Which protein will elute first through size exclusion chromatography? (A)A (B)B (C)C (D) It depends on the shape and oligomerization state of the proteins. (E) It depends on the isoelectric point (pI) of the proteins.

45. Which of the following statements accurately describes the Warburg effect? (A) It involves the preferential use of oxidative phosphorylation over glycolysis in cancer cells. (B) It describes the upregulation of gluconeogenesis in normal cells under hypoxic conditions. (C) It signifies the increased reliance of cancer cells on glycolysis, even in the presence of oxygen. (D) It indicates the decreased glucose uptake in tumors compared to healthy tissues. (E) The net effect is to increase the level of ATP.

46. The following plot is for an enzyme with multiple ligand binding sites. Which statement is True for this enzyme? (x: ligand concentration; y: fractional saturation)  (A) This enzyme is a non-allosteric oligomer. (B) The Hill coefficient for this enzyme is 2. (C) ligand binding favors another ligand binding. (D) ligand binding disfavors another ligand binding. (E) The Hill coefficient for this enzyme is -0.5.

47. The diagram depicts the mechanism of a protease inhibitor. What is the target of this inhibitor?  (A) Papain (B) Chymotrypsin (C) Pepsin (D) Carboxypeptidase A (E) Chymosin

48. Scientists covered an affinity chromatography column with microtubules for protein purification. Which of the following proteins would most likely be separated in this method? (A) Tubulin (B) Kinesin (C) Myosin (D) Actin (E) Lamin

49. Electrophoresis mobility shift assay (EMSA) is a sensitive method to detect protein-DNA interactions. The proteins and fluorescent DNA were combined as indicated and electrophoresed under native conditions, as shown below. Which of the following statements would be most likely?  (A) Protein B binds to the DNA independent of protein A. (B) Protein A binds to the DNA only in the presence of protein B. (C) Protein A and protein B compete for DNA binding. (D) Protein A and protein B form a protein complex before binding to the DNA. (E) Protein B binds to the protein A-DNA complex, resulting in a ternary complex.