BCHS 3305 Fall 2009 Exam #4 (Answers at end) 12/02/09

Multiple-Choice. Choose one answer for each question. Each correct answer gets two points. Each wrong answer or no answer gets zero point but no extra penalty.

On the answer sheet, identify (a) your name AND (b) the last four digits of your UH student #.

· Adenosine is a structural component of (#1) _____.

[(A) tetrahydrofolate; (B) pyridoxal phosphate; (C) FMN; (D) FAD]

· The IMP synthetic pathway requires 11 enzymes: (1) ribose phosphate pyrophosphokinase, (2) amidophosphoribosyl transferase, (3) glycinamide ribotide synthetase, (4) glycinamide ribotide transformylase, (5) formylglycinamidine ribotide synthetase, (6) 5-aminoimidazole ribotide synthetase, (7) 5-aminoimidazole ribotide carboxylase, (8) 5-aminoimidazole-4-(N-succinylocarboxamide) ribotide synthetase, (9) adenylosuccinate lyase, (10) 5-aminoimidazole-4-carboxamide robitide transformylase, and (11) inosine monophosphate cyclohydrolase.

o For these 11 enzymes, (#2) ____ of them require ATP as a substrate.

[(A) 4; (B) 5; (C) 6; (D) 7; (E) 8]

o For these ATP-requiring enzymes, (#3) ____ of them produce(s) ADP as one of the products.

[(A) 2; (B) 3; (C) 4; (D) 5; (E) 6]

o For these 11 enzymes, (#4) ____ of them require(s) N⁵-Formyl-THF as a substrate.

[(A) none; (B) 1; (C) 2; (D) 3; (E) 4]

o For these 11 enzymes, (#5) ____ of them require an amino acid as a substrate.

[(A) 2; (B) 3; (C) 4; (D) 5; (E) 6]

· Ribose phosphate pyrophosphokinase is inhibited by (#6) ____.

[(A) AMP but not ADP or ATP; (B) ADP but not AMP or ATP; (C) ATP but not AMP or ADP; (D) AMP, ADP, and ATP]

· Amidophosphoribosyl transferase is inhibited by (#7) ____.

[(A) AMP but not ADP or ATP; (B) ADP but not AMP or ATP; (C) ATP but not AMP or ADP; (D) AMP, ADP, and ATP]

· In purine, the N at position 7 is derived from the (#8) ____, and the N at position 3 is derived from the (#9) ____.

[(A) amine group of glycine; (B) amine group of aspartate; (C) amine group of glutamine, (D) amide group of glutamine]

· The synthesis of AMP from IMP requires (A) adenylosuccinate synthetase and (B) adenylosuccinate lyase whereas the formation of GMP from IMP involves (C) IMP dehydrogenase and (D) GMP synthetase.

o ATP is required as substrate by the enzyme (#10) _____.

o AMP is a feedback inhibitor against the enzyme (#11) _____.

· For purine bio-degradations, (#12) ____.

[(A) AMP can be converted to IMP but adenosine cannot be converted to inosine; (B) adenosine can be converted to inosine but AMP cannot be converted to IMP; (C) neither AMP can be converted to IMP nor adenosine can be converted to inosine; (D) AMP can be converted to IMP and adenosine can be converted to inosine]

· For purine bio-degradations, (#13) ____ is a product of purine nucleotide phosphorylase.

[(A) ribose-1-P; (B) ribose-5-P; (C) Pi; (D) none of the above]

· Decreased activity of hypoxanthine-guanine phosphoribosyltransferase will step-wise lead to (#14) _____ synthesis of purine nucleotides.

[(A) increased; (B) decreased; (C) unaffected]

· The enzymes (A) carbamoyl phosphate synthetase II, (B) aspartate transcarbamoylase, (C) dihydroorotase, (D) dihydroorotate dehydrogenase, and (E) orotate phosphoribosyl transferase are involved in the synthesis of orotidine monophosphate (OMP).

o For these five enzymes, an oxidation of substrate to product is catalyzed by the enzyme (#15) ____.

· The enzyme orotate phosphoribosyl transferase catalyzes the conversion of a (#16) _____.

[(A) pyrimidine base to the corresponding nucleoside; (B) nucleoside to the corresponding nucleotide; (C) pyrimidine base directly to the corresponding nucleotide]

· The N donor for the synthesis of carbamoyl phosphate by carbamoyl phosphate synthetase II is (#17) ____.

[(A) NH₃; (B) glutamate; (C) the amine (or amino) group of glutamine; (D) the amide group of glutamine; (E) aspartate]

· For the pyrimidine as shown below, the N at position 1 is derived from the (#18) ____.

[(A) amine group of glycine; (B) amine group of aspartate; (C) amine group of glutamine, (D) amide group of glutamine]

· For the synthesis of CTP from UTP, an extra N is incorporated into the CTP product. This extra N is derived from the (#19) ____.

[(A) amine group of glycine; (B) amine group of aspartate; (C) amine group of glutamine, (D) amide group of glutamine; (E) NH₃]

· In animals, carbamoyl phosphate synthetase II is (#20) ____.

[(A) inhibited by ATP and UTP; (B) inhibited by ATP but activated by UTP; (C) inhibited by UTP but activated by ATP; (D) activated by ATP and UTP; (E) none of the above]

· In E. coli, aspartate transcarbamoylase is (#21) ____.

[(A) inhibited by ATP and UTP; (B) inhibited by ATP but activated by UTP; (C) inhibited by UTP but activated by ATP; (D) activated by ATP and UTP; (E) none of the above]

· Nucleotide diphosphate kinase can convert (#22) ____.

[(A) ribonucleoside diphosphate (NDP) to ribonucleoside triphosphate (NTP) but cannot convert deoxyribonucleoside diphosphate (dNDP) to deoxyribonucleoside triphosphate (dNTP); (B) dNDP to dNTP but cannot convert NDP to NTP; (C) NDP to NTP and also dNDP to dNTP; (D) neither NDP to NTP nor dNDP to d NTP]

· The enzyme thymidylate synthase catalyzes the conversion of (#23) ____.

[(A) dUMP + N⁵,N¹⁰-Methylene-THF à dTMP + tetrahydrofolate; (B) dUMP + N⁵,N¹⁰-Methylene-THF à dTMP + dihydrofolate; (C) dUDP + N⁵,N¹⁰-Methylene-THF à dTDP + tetrahydrofolate; (D) dUDP + N⁵,N¹⁰-Methylene-THF à dTDP + dihydrofolate]

· In bio-degradation of pyrimidine, (#24) _____ can be step-wise converted to uracil..

[(A) CMP but not UMP; (B) UMP but not CMP; (C) both CMP and UMP; (D) neither CMP not UMP]

· b-Aminoisobutyrate is a product from (#25) _____ through a single- or multiple-step of enzymatic degradative reaction(s).

[(A) dihydrouracil; (B) dihydrothymine; (C) β-ureidopropionate; (D) none of the above]

· Nitrogen fixation is the conversion of N₂ to 2 NH₃. This N₂ à 2 NH₃ process is (#26) ____ reaction.

[(A) an oxidative; (B) a reductive; (C) neither an oxidative nor a reductive]

· For the nitrogen fixation reaction catalyzed by nitrogenase, electron transfers take place in the direction of (#27) ____.

[(A) Fe- protein à MoFe-protein à N₂; (B) Mo-Fe-protein à Fe-protein à N₂; (C) N₂ à Fe- protein à MoFe-protein; (D) N₂ à Mo-Fe-protein à Fe-protein; (E) none of the above]

· The molecule H₂N-NH₂ is a (#28) ____. [(A) diimine; (B) hydrazine]

· In the nitrogenase-catalyzed nitrogen fixation, hydrolysis of ATP molecules takes place. As a consequence, the E^○’ of the Fe-protein (#29) ____.

[(A) is lowered; (B) is elevated; (C) remains the same] [Note: lowered = becomes more negative]

· In the nitrogenase-catalyzed nitrogen fixation, the transfer of one electron requires the hydrolysis of (#30) ____ molecule(s) of ATP.

[(A) 1; (B) 2; (C) 3; (D) 4]

· α-Ketoglutarate is (#31) ____ for the mammalian glutamine synthetase.

[(A) an activator; (B) an inhibitor; (C) neither an activator nor an inhibitor]

· For E. coli, higher concentrations of glutamine will result in (#32) ____ of glutamine synthetase activity.

[(A) higher levels; (B) lower levels; (C) no change in the level]

· For ammonification, the conversion of one molecule of nitrate to one molecule nitrite requires (#33) ____ electron(s), and the conversion of one molecule of nitrite to one molecule of NH₃ requires (#34) ____ electrons.

[(A) zero, (B) 1; (C) 2; (D) 4; (E) 6]

· In animals, pyruvate (#35) ____.

[(A) can be decarboxylated to acetyl-CoA but cannot be carboxylated to oxalloacetate; (B) can be carboxylated to oxalloacetate but cannot be decarboxylated to acetyl-CoA; (C) can be either decarboxylated to acetyl-CoA or carboxylated to oxalloacetate; (D) cannot be either decarboxylated to acetyl-CoA or carboxylated to oxalloacetate]

· Blood flow is essential to the supply of (#36) ____ to brain.

[(A) glucose but not oxygen; (B) oxygen but not glucose; (C) both oxygen and glucose; (D) neither oxygen nor glucose]

· The primary fuel for brain under conditions of extended fast is (#37) ____.

[(A) glucose; (B) glycogen; (C) fatty acids; (D) ketone bodies]

· Muscle tissue is active in (#38) ____.

[(A) glycolysis but not in gluconeogenesis; (B) gluconeogenesis but not in glycolysis; (C) both glycolysis and gluconeogenesis; (A) neither glycolysis nor gluconeogenesis]

· When heart is at a normal resting state, the primary fuel molecule(s) is/are (#39) ____.

[(A) glucose; (B) glycogen; (C) fatty acids; (D) ketone bodies]

· In adipose tissues, the metabolic fates of fatty acids are (#40) ____ the dihydroxyacetone phosphate level.

[(A) regulated by; (B) unrelated to]

· At a blood glucose level of ~2 mM in liver, (#41) ____.

[(A) both glucokinase and hexokinase should be operating at levels close to their respective maximal velocity V_max; (B) glucokinase should be operating near its V_max but hexokinase should be operating at a level substantially lower than its V_max; (C) hexokinase should be operating near its V_max but glucokinase should be operating at a level substantially lower than its V_max; (D) both glucokinase and hexokinase should be operating at levels substantially lower than their respective V_max]

· The acetyl-CoA generated from fatty acids in liver is used for the synthesis of (#42) ____.

[(A) ketone bodies to be released to peripheral tissues but not for the synthesis of ATP by TCA and oxidative phosporylation to support the energy need by liver; (B) ATP by TCA and oxidative phosporylation to support the energy need by liver but not for the synthesis of ketone bodies to be released to peripheral tissues; (C) ketone bodies to be released to peripheral tissues and for the synthesis of ATP byTCA and oxidative phosporylation to support the energy need by liver; (D) neither ketone bodies nor ATP]

· For the Cori cycle, the energy required for muscle contractions during heavy exercise is provided primarily through (#43) ____.

[(A) glycolysis and homolactic fermentation; (B) TCA cycle; (C) oxidative phosphorylation]

· For the glucose-alanine cycle, (#44) ____ in liver for gluconeogenesis.

[(A) pyruvate is converted to lactate; (B) lactate is converted to pyruvate]

· The adenylate cyclase system involves a trimeric Gs-protein (i.e. s_abg) and also an inhibitory trimeric Gi-protein (i.e. i_abg). An GTP hydrolytic activity is associated with (#45) ____.

[(A) only the s_a but not the i_a; (B) only the i_a but not the s_a; (C) both the s_a and the i_a; (A) neither the s_a nor the i_a]

· In the absence of cAMP, the cAMP-dependent protein kinase exists as an inactive tetramer R₂C₂. Upon binding by cAMP, the active species of protein kinase is released in the form of (#46) ____.

[(A) an R₂ dimer; (B) 2 of R monomers; (C) a C₂ dimer; (D) 2 of C monomers]

· As a consequence of hormone binding to a usual receptor tyrosine kinase RTK (such as human growth hormone receptor), RTK undergoes (#47) ____.

[(A) dimerization of RTK but not the cross phosphorylation of the C-terminal domains; (B) the cross phosphorylation of the C-terminal domains but not the dimerization of RTK; (C) dimerization of RTK and the subsequent cross phosphorylation of the C-terminal domains]

· For the insulin receptor (αβ)₂ dimer, the tyrosine kinase activity is located in the intracellular portion of β. Following the binding of insulin to the α subunit, the intracellular portion of the β undergoes (#48) ____.

[(A) both a conformational change and phosphorylation (B) a conformational change but not any phosphorylation; (C) phosphorylation but not any conformational change; (D)neither any conformational change nor any phosphorylation]

· When the β domain of the insulin receptor is activated to become an active tyrosine kinase, it (#49) ____ directly bind the SH2-domain of certain cellular proteins.

[(A) can; (B) cannot]

· In the phosphoinositide pathway, the activated membrane-bound phospholipase C catalyzes the hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2) to inositol-1,4,5-triphosphate (IP3) and 1,2-diacylglycerol (DAG). (#50) ____ lipid-soluble second messenger.

[(A) Both IP3 and DAG are; (B) IP3 is but DAG is not; (C) DAG is but IP3 is not; (D) Neither IP3 nor DAG is]

Answers: (1-D), (2-C), (3-D), (4-A), (5-C), (6-B), (7-D), (8-A), (9-D), (10-D), (11-A), (12-D), (13-A), (14-A), (15-D), (16-C), (17-D), (18-B), (19-D), (20-C), (21-E), (22-C), (23-B), (24-C), (25-B), (26-B), (27-A), (28-B), (29-A), (30-B), (31-A), (32-B), (33-C), (34-E), (35-C), (36-C), (37-D), (38-A), (39-C), (40-A), (41-C), (42-C), (43-A), (44-B), (45-C), (46-D), (47-C), (48-A), (49-B), (50-C)