Chapter 21 Flashcards
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
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.
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 (farthest carbon from C-1).
D) no part of the molecule.
Which one of the following statements best applies to synthesis of fatty acids in E. coli extracts?
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 acetyl-CoA.
E) All of the above are true.
E) All of the above are true.
In comparing fatty acid biosynthesis with b oxidation of fatty acids, which of the following
statements is incorrect?
A) A thioester derivative of crotonic acid (trans-2-butenoic acid) is an intermediate in the synthetic
path, but not in the degradative path.
B) A thioester derivative of D-b-hydroxybutyrate is an intermediate in the synthetic path, not in the
degradative path.
C) Fatty acid biosynthesis uses NADPH exclusively, whereas b oxidation 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.
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 b-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 coenzymes.
D) The processes occur in different cellular compartments.
E) The processes occur in the mitochondrial matrix.
E) The processes occur in the mitochondrial matrix.
The rate-limiting step in fatty acid synthesis is:
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 b-hydroxybutyryl group.
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.
E) The immediate precursor of the added carbons is acetyl-CoA.
Which of these can be synthesized by plants but not by humans?
A) Linoleate [18:2(△9,12)]
B) Palmitate (16:0)
C) Phosphatidylcholine
D) Pyruvate
E) Stearate (18:0)
A) Linoleate [18:2(△9,12)]
The enzyme system for adding double bonds to saturated fatty acids requires all of the following
except:
A) a mixed-function oxidase.
B) ATP.
C) cytochrome b5
D) molecular oxygen (O2).
E) NADPH.
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
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.
B) humans after ingestion of excess carbohydrate.
The synthesis of both glycerophospholipids and triacylglycerols involves:
A) CDP-choline.
B) CDP-diacylglycerol.
C) phosphatidate phosphatase.
D) phosphatidic acid.
E) phosphoethanolamine.
D) phosphatidic acid.
Which of these statements about triacylglycerol synthesis is correct?
A) Humans can store more energy in glycogen than in triacylglycerols.
B) Insulin stimulates conversion of dietary carbohydrate into triacylglycerols.
C) It is not a hormone-sensitive process.
D) Mammals are unable to convert carbohydrates into triacylglycerols.
E) Phosphatidate is not on the pathway of triacylglycerol synthesis.
B) Insulin stimulates conversion of dietary carbohydrate into triacylglycerols.
A strategy that is not employed in the synthesis of phospholipids is:
A) condensation of CDP-alcohol with diacylglycerol.
B) condensation of CDP-diacylglycerol with alcohol.
C) condensation of CDP-diacylglycerol with CDP-alcohol.
D) exchange of free alcohol with head group alcohol of phospholipid.
E) remodeling of head group alcohols by chemical modification
C) condensation of CDP-diacylglycerol with CDP-alcohol.
