Lipid Metabolism Flashcards
Phospholipases are designated A, B, etc, based on
a. the different sites in the molecule where they cleave the phospholipids.
b. whether they are phosphorylases or hydrolases.
c. whether they use NAD as a cofactor.
d. whether they use ATP as a cofactor.
a
Phospholipases break down fats by
a. adding a phosphate group to them.
b. reducing the double bonds to single bonds.
c. hydrolyzing them.
d. removing acetyl-CoA units.
e. none of these
c
Which of the following is true concerning phospholipases?
a. Many snake venoms contain phospholipases
b. Phospholipase D is a component in some spider venoms
c. Phospholipases in snake venoms can lead to the lysing of blood cells
d. All of these
d
The bond linking a fatty acid to coenzyme A is
a. an ester.
b. a thioester.
c. an anhydride.
d. an ether.
e. none of these
b
Which of the following statements below about the activation of fatty acids is false?
a. Activation involves the formation of a high energy thioester bond.
b. Activation is accompanied by hydrolysis of ATP to ADP and Pi.
c. Activation includes the formation of an acyl-adenylate intermediate.
d. Activation includes hydrolysis of ATP to produce AMP and PPi, with the further hydrolysis of PPi to drive the reaction to completion
b
The carrier molecule which transports fatty acids through the inner mitochondrial membrane is
a. ATP.
b. Carnitine.
c. Coenzyme A.
d. Lipoic Acid.
e. none of these
b
Which of the following reactions is catalyzed by carnitine acyltransferase?
a. carnitine + acyl-CoA –> CoASH + acylcarnitine
b. CoASH + acylcarnitine –> carnitine + acyl-CoA
c. both of these
d. none of these
c
Which of the following is not true regarding catabolism of triacylglycerols?
a. Control of release of fatty acids from triacylglycerols in adipocytes involves cyclic AMP as a second
messenger.
b. When cAMP is a second messenger in the catabolsim of triacylglycerols, it activates a protein kinase
c. The protein kinase, once activated, cleaves fatty acids from the triacylglycerol
d. The phosphorylated form of triacylglycerol lipase is the active form
e. All of these are true
c
The use of cyclic AMP to mobilize fatty acids from adipose tissue is analogous to cyclic AMPs role in mobilization of
sugars from glycogen in the liver.
a. True
b. False
a
Which of the following statements concerning β-oxidation of fatty acids is false?
a. Initiation occurs at the methyl end of the fatty acid.
b. β-oxidation is the primary route for degradation of fatty acids.
c. β-oxidation takes place in the mitochondrial matrix.
d. Two-carbon units are successively eliminated with each round.
a
The metabolically activated form of a fatty acid is
a. an ester
b. a Schiff base
c. a phosphate ester
d. a thioester
e. none of these
d
Where in the cell does β-oxidation occur?
a. Cytoplasm.
b. Outer mitochondrial membrane.
c. Mitochondrial intermembrane space.
d. Inner mitochondrial membrane.
e. Mitochondrial matrix.
e
When an acyl group is being transferred from the cytosol to the mitochondria for oxidation, the order of the enzymes it
encounters is:
a. CPT-I: Carnitine Translocase: CPT-II
b. Carnitine Translocase: CPT-I: CPT-II
c. CPT-II: Carnitine Translocase: CPT-I
d. none of these
a
Which of the following best describes carnitine?
a. It transports fatty acids across the inner mitochondrial membrane for breakdown.
b. It transports acetyl-CoA to the cytosol for fatty acid synthesis.
c. It’s a precursor of cholesterol.
d. It carries growing acyl chains during fatty acid synthesis.
e. none of these
a
Carnitine acyltransferase is located in the mitochondrial
a. intermembrane space.
b. outer membrane.
c. inner membrane.
d. matrix.
c
- The enzyme activity catalyzing the reaction shown is best termed a
(picture)
a. reductase
b. hydratase
c. dehydratase
d. dehydrogenase
d
- Which group of small molecules best fit the boxes associated with the reaction shown?
(picture)
a b I. ATP ADP II. NAD+ NADH III. NADP+ NADPH IV. FAD FADH2
b
The first three reactions of the β-oxidation cycle of fatty acids produce
a. two moles of NADH
b. two moles of FADH2
c. one mole each of NADH and FADH2
d. two moles of ATP
c
Which of the following is not a product of the activation of fatty acids?
a. A thioester
b. ADP
c. Pyrophosphate
d. Phosphate
e. All of these are products of the activation of a fatty acid.
b
Fatty acid catabolism is called β-oxidation, since the second or β carbon from the carboxyl group is the site of
oxidation.
a. True
b. False
a
Palmitic acid, with 16 carbons, requires 8 cycles of β-oxidation to produce 8 acetyl-CoA.
a. True
b. False
b
How many cycles of β-oxidation are required to convert stearic acid (18 carbons) to 9 acetyl-CoAs?
a. 6
b. 8
c. 9
d. 18
e. none of these
b
The reactions involved in β-oxidation of fatty acids include the following:
1. Cleavage of acetyl-CoA from the fatty acid.
2. Hydration of a double bond.
3. Formation of a C−C double bond.
4. Oxidation of an alcohol.
The correct order of these reactions is:
a. 1 → 2 → 3 → 4
b. 4 → 3 → 2 → 1
c. 3 → 2 → 4 → 1
d. 2 → 4 → 3 → 1
e. 1 → 4 → 3 → 2
c
Which of the following vitamins and cofactors is not used in β-oxidation?
a. Biotin
b. Niacin
c. Pantothenic acid
d. Riboflavin
e. All of these are important in the β-oxidation of fatty acids.
a
How many NAD+
are reduced in the degradation of palmitoyl-CoA to form eight molecules of acetyl-CoA?
a. 1
b. 7
c. 8
d. 14
e. 16
b
Which of the following is true about the oxidation steps in β-oxidation of fatty acids?
a. NAD+
is the cosubstrate when the oxidation creates a double bond
b. FAD is the cosubstrate when the oxidation produces a carbonyl group
c. FAD is the cosubstrate when the oxidation creates a double bond
d. either NAD+
or FAD can be used to create a double bond
e. none of these
c
The processing of one molecule of stearic acid (18 carbons) by β-oxidation
a. requires 8 cycles of β-oxidation and produces 9 molecules of acetyl-CoA.
b. requires 8 cycles of β-oxidation and produces 8 molecules of acetyl-CoA.
c. requires 9 cycles of β-oxidation and produces 8 molecules of acetyl-CoA.
d. requires 9 cycles of β-oxidation and produces 9 molecules of acetyl-CoA
a
How many ATPs can be netted from the complete oxidation of palmitate (C16) to CO2 & H2O?
a. ATPs ≤ 40
b. 40 < ATPs ≤ 80
c. 80 < ATPs ≤ 120
d. 1200 < ATPs
c
Approximately how many ATP molecules are netted from the complete oxidation of stearic acid (C−18)?
a. 2
b. 4
c. 32
d. 88
e. 120
e
Lipids yield more ATP than sugars because
a. they have more carbon atoms than sugars.
b. their carbon atoms are more highly reduced.
c. both of these
d. neither of these
c
Which of the following is not true?
a. One advantage of the β-oxidation of fats compared to oxidation of sugars is that fatty acids produce more
metabolic water.
b. The oxidation of fats produces more energy per carbon than the oxidation of carbohydrates
c. Fat yields more energy than carbohydrates because it is more oxidized
d. For every cycle of oxidation of a fatty acid, one NADH and one FADH2 are produced
c
Which of the following is not an advantage of fatty acids as a form of energy storage?
a. Fatty acids contain more highly reduced carbons than carbohydrates.
b. Their hydrophobic nature allows close packing in adipose tissue.
c. Storage of fats in muscle tissue makes it readily available for use during activity.
d. Fats contain more energy per gram than sugars.
e. They do not require water for storage.
c
The oxidation of unsaturated fatty acids specifically requires
a. a cis-trans isomerase and a reductase.
b. a cis-trans isomerase and a dehydrogenase.
c. a dehydrogenase and a reductase.
d. a dehydrogenase and a hydrase.
e. none of these
a
A key intermediate in the catabolism of fatty acids with uneven numbers of carbon atoms is
a. malonyl-CoA
b. propionyl-CoA
c. oxaloacetate
d. phosphoenolpyruvate
b
The β-oxidation of fatty acids with an odd number of carbons requires additional enzymes to allow all the products to
enter the citric acid cycle .
a. True
b. False
a
When is propionyl-CoA carboxylase required for the complete oxidation of a fatty acid?
a. When it has an even number of carbons.
b. When it has an odd number of carbons.
c. When it is a monounsaturated fatty acid.
d. When it is a polyunsaturated fatty acid.
e. Never
b
The conversion of methylmalonyl-CoA to succinyl-CoA involves which of these cofactors?
a. thiamine pyrophosphate
b. Vitamin B12
c. NAD
d. biotin
b
The oxidation of an unsaturated fatty acid leads to the production of fewer ATPs than a saturated fatty acid with the same number of carbons because ____
a. the oxidation of the fatty acid stops when it reaches the double bond
b. unsaturated fatty acids cannot be metabolized
c. the double bond results in the bypassing of the first oxidation step of the pathway, thereby eliminating one
FADH product
d. none of these
c
The cis double bonds of naturally-occurring fatty acids react well with the hydratase enzyme.
a. True
b. False
b
The β-oxidation of unsaturated fatty acids requires additional enzymes to isomerize the double bonds.
a. True
b. False
a