Lipid Structure and 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. the different sites in the molecule where they cleave the
phospholipids
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. hydrolyzing them.
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. All of these
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. a thioester.
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.Activation is accompanied by hydrolysis of ATP to ADP and Pi.
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. Carnitine.
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. both of these
Which of the following is not true regarding catabolism of triacylglycerols?
a.Control of release of fatty acids from triacylglycerols in adipocytes involves cyclic
AMPasasecond 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 protein kinase, once activated, cleaves fatty acids from the triacylglycero
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. True
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. Initiation occurs at the methyl end of the fatty acid.
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. a thioester
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. Mitochondrial matrix.
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. CPT-I: Carnitine Translocase: CPT-II
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. It transports fatty acids across the inner mitochondrial membrane for breakdown.
Carnitine acyltransferase is located in the mitochondrial
a. intermembrane
space.
b. outer membrane.
c. inner membrane.
d. matrix.
c. inner membrane
(see picture)
16. The enzyme activity catalyzing the reaction shown is best termed a
a. reductase
b. hydratase
c. dehydratase
d. dehydrogenase
d. dehydrogenase
(see picture)
17. Which group of small molecules best fit the boxes associated with the reaction shown?
a. I
b. II
c. III
d. IV
b. II
he 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. one mole each of NADH and FADH2
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. ADP
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. True
Palmitic acid, with 16 carbons, requires 8 cycles of β-oxidation to produce 8 acetyl-CoA.
a. True
b. False
b. False
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. 8
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:
3 →2→4→1
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. Biotin
. 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. 7
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. FAD is the cosubstrate when the oxidation creates a double bond
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. requires 8 cycles of β-oxidation and produces 9 molecules of acetyl-CoA.
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. 80 < ATPs ≤ 120
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. 120
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. both of these
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.Fat yields more energy than carbohydrates because it is more oxidized
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. Storage of fats in muscle tissue makes it readily available for use during activity.
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 cis-trans isomerase and a reductase.
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. propionyl-CoA
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. True
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. When it has an odd number of carbons.
The conversion of methylmalonyl-CoA to succinyl-CoA involves which of these cofactors?
a. thiamine
pyrophosphate
b. Vitamin B12
c. NAD
d. biotin
b. Vitamin B12
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 double bond results in the bypassing of the first oxidation step of the pathway,
thereby eliminating one FADH product
The cis double bonds of naturally-occurring fatty acids react well with the hydratase enzyme.
a. True
b. False
b. False
The β-oxidation of unsaturated fatty acids requires additional enzymes to isomerize the
double bonds.
a. True
b. False
a. True
The unsaturated fatty acids that are intermediates in the β-oxidation cycle have what
orientation around the double bond?
a. the cis orientation
b. the trans orientation
c. can have either orientation
d. the orientation is not
known
b. the trans orientation
Isomerization of the double bonds of polyunsaturated fatty acids involves both cis-trans
isomerization and changing the position of the double bonds.
a. True
b. False
a. True
The yield of ATP from oxidation of an unsaturated fatty acid has what relationship to the yield
from the oxidation of a saturated fatty acid with the same number of carbon atoms?
a. less
b. greater
c. the same
d. not possible to determine from the information in this
chapter
a. less
A key intermediate in the formation of “ketone bodies” is
a. succinyl-CoA
b. methyl malonyl-CoA
c. propionyl-CoA
d. acetoacetyl-CoA
d. acetoacetyl-CoA
“Ketone bodies” are formed when
a. oxaloacetate is converted to acetoacetyl-CoA.
b. there is a deficiency of acetyl-CoA.
c. there is not enough oxaloacetate to react with available acetyl-CoA.
d. an organism consumes excessive amounts of carbohydrate compared to its lipid
intake.
e. none of these
c. there is not enough oxaloacetate to react with available acetyl-CoA.
What effect do high concentrations of ketone bodies have on blood pH?
a. They tend to lower blood pH.
b. They tend to increase blood pH.
c. They have no effect on blood
pH.
a. They tend to lower blood pH.
Which of the following is not true regarding ketone bodies?
a.Ketone bodies form during the catabolism of fats.
b.Ketone bodies are an effective means for weight loss, since the body will excrete them
in the urine.
c.The first enzyme used in the production of ketone bodies is thiolase
d.Ketone bodies are always an alternative fuel in all tissues
d.Ketone bodies are always an alternative fuel in all tissues
Which are the three most common ketone bodies?
a. Acetone, formaldehyde, acetoacetate.
b. Acetone, butyric acid and oxaloacetate.
c. Acetone, β-hydroxybutyrate and acetoacetate.
d. Acetone, β-hydroxybutyrate and oxaloacetate.
c. Acetone, β-hydroxybutyrate and acetoacetate.
Acetyl-CoA carboxylase uses which of these cofactors?
a. thiamine
pyrophosphate
b. Vitamin B12
c. NAD
d. biotin
d. biotin
Where in the cell does fatty acid synthesis occur?
a. Cytoplasm.
b. Outer mitochondrial membrane.
c. Mitochondrial intermembrane
space.
d. Inner mitochondrial membrane.
e. Mitochondrial matrix.
a. Cytoplasm.
Of the processes listed below, which is not an important source of acetyl-CoA?
a. pentose phosphate
pathway
b. amino acid degradation
c. glycolysis
d. fatty acid oxidation
a. pentose phosphate
pathway
How is acetyl-CoA transported from the mitochondria to the cytosol for fatty acid synthesis?
a.directly as acetyl-CoA
b.through a temporary linkage to carnitine
c.as citric acid
d.There is no reason to transport acetyl-CoA from the mitochondria to the cytosol, since
it is produced primarily in the cytosol.
c.as citric acid
Reduction reactions during fatty acid synthesis utilize
a. FADH2.
b. NADH.
c. NADPH.
d. FADH2 and NADH.
c. NADPH.
If the bicarbonate used in malonyl-CoA synthesis were labeled with 14C in the biosynthesis of
palmitate, where would the label be found in the reaction products?
a. CO2
b. C−16 of palmitate
c. C−1 of palmitate
d. evenly distributed in
palmitate
a. CO2
The addition of two-carbon units to a growing fatty acid chain is directly driven by
a. reduction of NADP+
b. oxidation of NADPH
c. decarboxylation of
malonyl-CoA
d. hydrolysis of ATP
c. decarboxylation of
malonyl-CoA
Which of the following statements concerning the anabolism and catabolism of fatty acids is
true?
a.Biotin is required for oxidation of fatty acids but not for anabolism.
b.NADPH is required for anabolism of fatty acids and not for catabolism.
c.Anabolism occurs in the intermembrane space of mitochondria while catabolism takes
place in the mitochondrial matrix.
d.Acetyl-CoA is not required for anabolism.
b.NADPH is required for anabolism of fatty acids and not for catabolism.
The primary function of biotin in metabolism is:
a. to allow for the addition of CO2 to other molecules.
b. to inhibit acetyl-CoA carboxylase
c. to inhibit carnitine palmitoyltransferase
d. all of these
e. none of these
a. to allow for the addition of CO2 to other molecules.
Since acetyl-CoA carboxylase is key to the synthesis of fatty acids, inhibitors of this enzyme
may be useful for weight loss or treatment of obesity.
a. True
b. False
a. True
Synthesis of fatty acids involves simple reversal of the β-oxidation cycle.
a. True
b. False
b. False
Fatty acid synthase binds growing fatty acids
a. by an ester linkage to a side chain of serine.
b. by a thioester linkage to a side chain of cysteines.
c. as a Schiff base to a side chain of lysine.
d. by a thioester linkage to a phosphopantetheine linked to a serine.
d. by a thioester linkage to a phosphopantetheine linked to a serine.
(see picture)
61. Which group of small molecules best fit the boxes associated with the reaction shown?
a. I
b. II
c. III
d. IV
c. III
(see picture)
62. The enzyme activity catalyzing the reaction shown is best termed a
a. reductase
b. ketothiolase
c. transferase
d. dehydratase
a. reductase
(see picture)
63. The enzyme activity catalyzing the reaction shown is best termed a
a. reductase
b. ketothiolase
c. transferase
d. dehydratase
d. dehydratase
The acyl carrier used in fatty acid synthesis is similar to coenzyme A.
a. True
b. False
a. True
During fatty acid synthesis, the growing fatty acid is always bound to a protein.
a. True
b. False
a. True
Which of the following mechanisms explains why fatty acid synthesis and breakdown do not
compete with each other in the body?
a. Synthesis and breakdown take place in two separate compartments of the
cell.
b. One process uses NADH/NAD+ and the other uses NADPH/NADP+.
c. They are not attached to the same carrier molecule in the two processes.
d. All of these mechanisms are in operation.
e. None of these
d. All of these mechanisms are in operation.
How many NADPHare oxidized in the synthesis of palmitoyl-CoA from eight molecules of
acetyl-CoA?
a. 1
b. 7
c. 8
d. 14
e. 16
d. 14
Compared to β-oxidation, fatty acid synthesis requires this extra vitamin or cofactor.
a. Biotin
b. Riboflavin
c. Niacin
d. Pantothenic acid
e. All of these are used in both pathways.
a. Biotin
Which of the following reactants is involved in both fatty acids synthesis and breakdown?
a. CO2.
b. Malonyl-CoA
c. NADPH.
d. Pantothenic acid.
e. All of these reactants are involved in both fatty acid synthesis and breakdown.
d. Pantothenic acid.
ACP used in fatty acid synthesis is an abbreviation for:
a. Acetyl-CoA phosphate.
b. Adenosine
cyclo-phosphate.
c. Acyl Carnitine Protein
d. Acyl Carrier Protein.
e. None of these is correct.
d. Acyl Carrier Protein.
Which of the following enzyme types is involved in both fatty acid synthesis and breakdown?
a. Carboxylase.
b. Transferase.
c. Synthase.
d. Both carboxylase and synthase.
e. All three of these enzymes are used in fatty acid
synthesis.
b. Transferase
Biosynthesis of compound lipids typically takes place
a. in the mitochondrial matrix
b. in the cytosol
c. on the endoplasmic reticulum
d. in the Golgi apparatus
e. none of these
c. on the endoplasmic reticulum