MCQ Lipid Synthesis Flashcards
Which of the following is not required in the synthesis of fatty acids? A) Acetyl-CoA B) Biotin C) HCO–(CO) 32 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.
It requires acyl carrier protein (ACP).
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-β-hydroxybutyrate is an intermediate in the synthetic path, not in the degradative path.
C) Fatty acid biosynthesis uses NADPH exclusively, whereas β 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.
Fatty acid degradation is catalyzed by cytosolic enzymes; fatty acid synthesis by mitochondrial
enzymes.
Enzymes that catalyze the synthesis of long chain fatty acids in vertebrate cells:
A) act as seven separate proteins.
B) are encoded in mitochondrial genes.
C) are localized in the mitochondrial matrix.
D) are part of a single polypeptide chain containing several distinct enzyme activities.
E) have none of the characteristics above.
D) are part of a single polypeptide chain containing several distinct enzyme activities.
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 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 β-hydroxybutyryl gro
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.
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.
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.
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.
Cholesterol is synthesized from: A) acetyl-CoA. B) choline. C) lipoic acid. D) malate. E) oxalate.
A) acetyl-CoA.
Which of the following is derived from a sterol? A) Bile salts B) Gangliosides C) Geraniol D) Phosphatidylglycerol E) Prostaglandins
A) Bile salts
