BCH 3025 Exam 4 Questions With Correct
Answers
Which of the following is not required in the synthesis of fatty acids?
A) Acetyl-CoA
B) Biotin
C) HCO3- (CO2)
D) Malonyl-CoA
E) NADH - answerE) NADH
Which of the following is not true of the reaction producing malonyl-CoA during fatty acid
sy...
EXAM STUDY MATERIALS July 26, 2024 9:30 AM BCH 3025 Exam 4 Questions With Correct Answers Which of the following is not required in the synthesis of fatty acids? A) Acetyl -CoA B) Biotin C) HC O3- (CO2) D) Malonyl -CoA E) NADH - answer✔✔E) NADH Which of the following is not true of the reaction producing malonyl -CoA during fatty acid synthesis? A) It is stimulated by citrate. B) It requires acyl carrier protein (ACP). C) It requires CO2 (or bicarbonate). D) One mole of ATP is converted to ADP + Pi for each malonyl -CoA synthesized. E) The cofactor is biotin. - answer✔✔B) It requires acyl carrier protein (ACP). If malonyl -CoA is synthesized from 14CO2 and unlabeled acetyl -CoA, and the labeled malonate is then used for fatty acid synthesis, the final product (fatty acid) will have radioactive carbon in: A) every C. B) every even -numbered C -atom. C) every odd -numbered C -atom. D) no part of the molecule. E) only the omega -carbon atom (farth est carbon from C -1). - answer✔✔D) no part of the molecule. Which one of the following statements best applies to synthesis of fatty acids in E. coli extracts? EXAM STUDY MATERIALS July 26, 2024 9:30 AM A) Acyl intermediates are thioesters of a low molecular weight protein called acyl carrier protein. B) CO2 or HCO3 - is essential. C) Reducing equivalents are provided by NADPH. D) The ultimate source of all the carbon atoms in the fatty acid product is a cetyl -CoA. E) All of the above - answer✔✔E) All of the above In comparing fatty acid biosynthesis with β oxidation of fatty acids, which of the following statements is incorrect? A) A thioester derivative of crotonic acid (trans -2-butenoic acid) is an i ntermediate in the synthetic path, but not in the degradative path. B) A thioester derivative of D -β-hydroxybutyrate is an intermediate in the synthetic path, not in the degradative path. C) Fatty acid biosynthesis uses NADPH exclusively, whereas β oxida tion uses NAD+ exclusively. D) Fatty acid degradation is catalyzed by cytosolic enzymes; fatty acid synthesis by mitochondrial enzymes. E) The condensation of two moles of acetyl -CoA in the presence of a crude extract is more rapid in bicarbonate buffer than in phosphate buffer at the same pH; the cleavage of acetoacetyl -CoA proceeds equally well in either buffer. - answer✔✔D) Fatty acid degradation is catalyzed by cytosolic enzymes; fatty acid synthesis by mitochondrial enzymes. Which of the following is not true of the fatty acid synthase and the fatty acid β -oxidation systems? A) A derivative of the vitamin pantothenic acid is involved. B) Acyl -CoA derivatives are intermediates. C) Double bonds are oxidized or reduced by pyridine nucleotide coenzyme s. D) The processes occur in different cellular compartments. E) The processes occur in the mitochondrial matrix. - answer✔✔E) The processes occur in the mitochondrial matrix. The rate -limiting step in fatty acid synthesis is: EXAM STUDY MATERIALS July 26, 2024 9:30 AM A) condensation of acetyl -CoA and malonyl -CoA. B) formation of acetyl -CoA from acetate. C) formation of malonyl -CoA from malonate and coenzyme A. D) the reaction catalyzed by acetyl -CoA carboxylase. E) the reduction of the acetoacetyl group to a β -hydroxybutyryl group. - answer✔✔D) the reaction catalyzed by acetyl -CoA carboxylase. Which of the following is not true of the fatty acid elongation system of vertebrate cells? A) It involves the same four -step sequence seen in the fatty acid synthase complex. B) It is located in the smooth endoplasmic reticulum. C) It produces stearoyl -CoA by the extension of palmitoyl -CoA. D) It uses malonyl -CoA as a substrate. E) The immediate precursor of the added carbons is acetyl -CoA. - answer✔✔E) The immediate precurs or of the added carbons is acetyl -CoA. Which of the following is not true about precursors required for fatty acid synthesis in animal cells? A) NADPH is produced in the cytosol by the pentose phosphate pathway. B) NADPH is produced in the nucleus by mali c enzyme. C) Acetyl -CoA is transported out of the mitochondrion via the citrate shuttle. D) CoA is not transported across the mitochondrial membrane. E) Malonyl -CoA is formed in the cytosol. - answer✔✔B) NADPH is produced in the nucleus by malic enzyme. Which of these can be synthesized by plants but not by humans? A) Linoleate [18:2(Δ9,12)] B) Palmitate (16:0) C) Phosphatidylcholine EXAM STUDY MATERIALS July 26, 2024 9:30 AM D) Pyruvate E) Stearate (18:0) - answer✔✔A) Linoleate [18:2( Δ9,12)] The enzyme system for adding double bonds to satura ted fatty acids requires all of the following except: A) a mixed -function oxidase. B) ATP. C) cytochrome b5. D) molecular oxygen (O2). E) NADPH. - answer✔✔B) ATP. Which of these statements about eicosanoid synthesis is true? A) An early step in the path to thromboxanes is blocked by ibuprofen. B) Arachidonate is derived mainly by hydrolysis of triacylglycerols. C) Aspirin acts by blocking the synthesis of arachidonate. D) Plants can synthesize leukotrienes, but humans cannot . E) Thromboxanes are produced from arachidonate via the "linear" path. - answer✔✔A) An early step in the path to thromboxanes is blocked by ibuprofen. The biosynthesis of triacylglycerols from acetate occurs mainly in: A) animals but not in plants. B) humans after ingestion of excess carbohydrate. C) humans with low carbohydrate intake. D) plants but not in animals. E) None of the above - answer✔✔B) humans after ingestion of excess carbohydrate. The synthesis of both glycerophospholipids and triacyl glycerols involves: A) CDP -choline.
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