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BIOCHEMISTRY > Oxidation of Fatty Acids: Ketogenesis > Flashcards

Oxidation of Fatty Acids: Ketogenesis Flashcards

1
Q

collectively as the ketone bodies

A

acetoacetate, D-3-

hydroxybutyrate, and acetone,

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2
Q

overproduction

of ketone bodies causes

A

ketosis

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3
Q

ketone bodies are acidic, when they are produced in excess

over long periods, as in diabetes, they cause

A

ketoacidosis,

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4
Q

any impairment in fatty acid oxidation can lead to

A

hypoglycemia

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5
Q

poison that inhibition of fatty acid oxidation

A

hypoglycin

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6
Q

Which statement is incorrect?
A. The separation of fatty acid
oxidation in mitochondria from biosynthesis in the cytosol allows each
process to be individually controlled and integrated with tissue
requirements.
B. It is an anaerobic process, not requiring the presence of oxygen.
C. Each step in fatty acid oxidation involves acyl-CoA
derivatives, is catalyzed by separate enzymes, utilizes NAD+ and FAD as
coenzymes, and generates ATP.
D. None of the above

A

B. It is an anaerobic process, not requiring the presence of oxygen.

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7
Q

Free fatty acids (FFAs)—also called unesterified (UFA) or nonesterified
(NEFA) fatty acids —are fatty acids that are in the what state?

A

unesterified state.

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8
Q

In plasma, longer-chain FFA are combined with

A

albumin

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9
Q

in the cell they are attached to a

A

fatty acid–binding protein,

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10
Q

Which is incorrect?
A. In plasma, longer-chain FFA are combined with albumin
B. In plasma they are attached to a fatty acid–binding protein
C. Shorter-chain fatty acids are
more water soluble and exist as the unionized acid or as a fatty acid anion
D. None of the above

A

B. In plasma they are attached to a fatty acid–binding protein

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11
Q

All are correct except:
A. Fatty acids must first be converted to an active intermediate before they
can be catabolized.
B. This is the only step in the complete degradation of a
fatty acid that requires energy from ATP.
C. ATP and coenzyme A is needed to catalyze the conversion of a fatty acid (or FFA) to an “active fatty acid” or acyl-CoA
D. The PPi undergo oxidation reduction by inorganic pyrophosphatase with the loss of a further high-energy phosphate

A

D. The PPi undergo oxidation reduction by inorganic pyrophosphatase with the loss of a further high-energy phosphate

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12
Q

What enzyme catalyzes the
conversion of a fatty acid (or FFA) to an “active fatty acid” or acyl-CoA,
using one high-energy phosphate and forming AMP and PPi

A

acyl-CoA synthetase (thiokinase)

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13
Q

This enzyme hydrolyzes the PPi with the loss of a further high-energy phosphate, ensuring that the overall reaction goes to
completion.

A

inorganic pyrophosphatase

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14
Q 
Acyl-CoA synthetases are found in theses areas except: 
A. endoplasmic
reticulum
B. peroxisomes
C. Inner membrane of mitochiondria 
D. Outer membrane of mitochondria.
A

C. Inner membrane of mitochiondria

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15
Q

Which is incorrect?
A. Long-chain acyl-
CoA formed by acyl-CoA synthetase enters the intermembrane space.
B. For transport across the inner membrane, acyl groups must be transferred from CoA to carnitine by carnitine palmitoyltransferase-I.
C. The acylcarnitine
formed is then carried into the matrix by a translocase enzyme in exchange for a free carnitine and acyl-CoA is reformed by carnitine palmitoyltransferase-II.
D. None of the above

A

D. None of the above

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16
Q

Which is correct?
A. Carnitine (β-hydroxy-γ-trimethylammonium butyrate), (CH3)3 N+—CH2 —CH(OH)—CH2—COO−, is widely distributed and is particularly
abundant in liver
B. Long-chain acyl-CoA (or FFA) can penetrate the inner membrane of mitochondria
C. In the presence of carnitine, carnitine palmitoyltransferase-I, located in the inner mitochondrial membrane, transfers the long-chain acyl group from CoA to carnitine, forming acylcarnitine and releasing CoA.
D. Acylcarnitine is able to penetrate the inner membrane and gain access to the β-oxidation system of enzymes via the inner membrane exchange transporter carnitineacylcarnitine translocase.

A

D. Acylcarnitine is able to penetrate the inner membrane and gain access to the β-oxidation system of enzymes via the inner membrane exchange transporter carnitineacylcarnitine translocase.

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17
Q

This transfers the long-chain acyl group from CoA to carnitine,
forming acylcarnitine and releasing CoA

A

carnitine palmitoyltransferase-I, located in outer mitochondrial membrane

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18
Q

Acylcarnitine is able to
penetrate the inner membrane and gain access to the β-oxidation system of
enzymes via the inner membrane exchange transporter called?

A

carnitineacylcarnitine translocase

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19
Q

Which is incorrect?
A. carnitine palmitoyltransferase-I: outer mitochondrial membrane
B. carnitine palmitoyltransferase-II: inner mitochondrial membrane
C. carnitineacylcarnitine
translocase: outer mitochondrial membrane
D. None of the above

A

C. carnitineacylcarnitine
translocase: outer mitochondrial membrane

the inner membrane exchange transporter carnitineacylcarnitine
translocase

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20
Q

This reaction is being catalyzed by:

The transporter binds acylcarnitine and
transports it across the membrane in exchange for carnitine.

The acyl
group is then transferred to CoA so that acyl-CoA is reformed and carnitine is liberated.

A

carnitine
palmitoyltransferase-II

which is located on the inside of the inner
membrane

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21
Q

how many carbons at a time that are being cleaved from acyl-CoA molecules,

A

two carbons

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22
Q

why the process is termed β-oxidation

A

The chain is broken between the α(2)- and β(3)-carbon atoms—

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23
Q

how many acety-CoA molecules can be produced from palmitoyl(C16)-CoA?

A

eight acetyl-CoA molecules

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24
Q

Several enzymes, known collectively as _______________ are found in
the mitochondrial matrix or inner membrane adjacent to the respiratory
chain.

A

“fatty acid oxidase,”

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25
Q

catalyze the oxidation of acyl-CoA to acetyl-CoA via the β-

oxidation pathway.

A

“fatty acid oxidase,”

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26
Q

Which is true of beta oxidation?
A. The system proceeds in cyclic fashion which results in the degradation of long fatty acids to acetyl-CoA.
B. Large quantities of the reducing equivalents FADH2 and NADH are generated and are used to form ATP by oxidative phosphorylation
C. All of the above
D. None of the above

A

C. All of the above

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27
Q

The first step is the removal of two hydrogen atoms from the 2(α)- and
3(β)-carbon atoms, catalyzed by what enzyme?

A

acyl-CoA dehydrogenase

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28
Q

acyl-CoA dehydrogenase requires what coenzyme

A

flavin adenine dinucleotide (FAD)

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29
Q

Product of 1st step of beta oxidation

A

This results in the formation of Δ2-

trans-enoyl-CoA and FADH2

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30
Q

Water is added to saturate the double bond and form 3-hydroxyacyl-CoA, catalyzed by

A

Δ2-enoyl-CoA hydratase

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31
Q

The 3-hydroxy derivative undergoes further dehydrogenation on the 3-
carbon catalyzed by __________
to form the corresponding 3-ketoacyl-CoA compound.

A

L-3-hydroxyacyl-CoA dehydrogenase

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32
Q

L-3 hydroxyacyl-CoA dehydrongenase needs what coenzyme?

A

NAD+

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33
Q

3-ketoacyl-CoA is split at the 2,3-position by what enzyme, forming acetyl-CoA

A

thiolase (3-ketoacyl-CoA-thiolase)

34
Q

Which statement is correct?
A. a new acyl- CoA two carbons shorter than the original acyl-CoA molecule
B. The shorter
acyl-CoA formed in the cleavage reaction reenters the oxidative pathway at reaction 2
C. long-chain fatty acid with an
even number of carbons may be degraded completely to acetyl-CoA
D. All of the above
E. None of the above

A

D. All of the above

35
Q

Which statement is incorrect?
A. Fatty acids with an odd number of carbon atoms are oxidized by the
pathway of β-oxidation producing acetyl-CoA until a three-carbon (propionyl-CoA) residue remains.
B. This compound is converted to malate, a constituent of the citric acid cycle
C. the propionyl residue from an odd-chain fatty acid is the only part of a fatty acid that is glucogenic
D. None of the above

A

B. This compound is converted to malate, a constituent of the citric acid cycle

(converted to oxaloacetate)

36
Q

Which is incorrect?
A. Each cycle of β-oxidation generates one molecule of FADH2 and one of
NADH.
B. The breakdown of 1 mol of the C16 fatty acid, palmitate, requires eight cycles and produces 8 mol of acetyl-CoA.
C. Oxidation of the reducing
equivalents via the respiratory chain leads to the synthesis of 28 mol of ATP
D. oxidation of acetyl-CoA via the
citric acid cycle produces 80 mol of ATP

A

B.

Should be:
The breakdown of 1 mol of the C16 fatty acid, palmitate, requires
SEVEN cycles and produces 8 mol of acetyl-CoA.

37
Q

A modified form of β-oxidation is found in _____ and leads to the
breakdown of very-long-chain fatty acids

A

peroxisomes

38
Q

Beta oxidation of very long fatty acid in peroxisomes produces acetyl CoA and ________ which is then broken down by catalase

A

H202

39
Q

Beta oxidation in peroxisomes sequence ends at formation of what compound?

A

octanoyl-CoA

40
Q

A hypolipidemic drug that induces peroxisomal enzymes

A

clofibrate

41
Q

True of the perixosomall beta oxidation?
A. peroxisomal β-oxidation is to shorten the side chain of cholesterol in bile acid formation
B. Peroxisomes also take
part in the synthesis of ether glycerolipids,
cholesterol, and steroids
C. All of the above
D. None of the above

A

B.

Peroxisomes also take
part in the synthesis of ether glycerolipids,
cholesterol, and dolichol

42
Q

This statement is true.
A. Ketogenesis occurs when there is a high rate of fatty acid oxidation in
The liver
B. Acetoacetate can
undergo spontaneous decarboxylation to yield acetone.
C. Under metabolic conditions associated with a high rate of fatty acid
oxidation, the liver produces considerable quantities of acetoacetate and
D-3-hydroxybutyrate (β-hydroxybutyrate).
D. All of the above

A

D. All of the above

43
Q

Which is incorrect?
A. Acetoacetate
and 3-hydroxybutyrate are interconverted by the mitochondrial enzyme D-
3-hydroxybutyrate dehydrogenase
B. The equilibrium is controlled by the mitochondrial [FAD+]/[FADH2] ratio
C. Acetone is a waste product which, as it is volatile, can be excreted via the lungs.
D. Extrahepatic tissues utilize acetoacetate and 3-
hydroxybutyrate as respiratory substrates

A

B.

the equilibrium is controlled by the
mitochondrial [NAD+]/[NADH] ratio, that is, the redox state.

44
Q

Which is correct of ketogenesis?
A. The enzymes responsible for ketone body formation (ketogenesis) are
associated mainly with the mitochondria
B. Condensation of
acetoacetyl-CoA with another molecule of acetyl-CoA by 3-hydroxy-3-
methylglutaryl-CoA (HMG-CoA) synthase forms HMG-CoA.
C. HMGCoA
lyase then causes acetyl-CoA to split off from the HMG-CoA,
leaving free acetoacetate.
D. All of the above
E. None of the above

A

D. All of the above

45
Q

Enzyme use for condensation of

acetoacetyl-CoA with another molecule of acetyl-CoA to forms HMG-CoA

A

3-hydroxy-3-

methylglutaryl-CoA (HMG-CoA) synthase

46
Q

Enzyme that causes acetyl-CoA to split off from the HMG-CoA,

A

HMGCoA lyase

47
Q

Product formed when HMGCoA

lyase cause acetyl-CoA to split off from the HMG-CoA,

A

free acetoacetate.

48
Q

This is ketone body is quantitatively the predominant present in
the blood and urine in ketosis.

A

D-3-

Hydroxybutyrate

49
Q

acetoacetate is activated to acetoacetyl-CoA by what enzyme?

A

succinyl-CoA-acetoacetate-CoA transferase.

50
Q 
preferred method of assessing the severity of ketosis
A. measurement of the ketonemia
B. measurement of the
ketonuria
C. All of the above 
D. None of the above
A

A. measurement of the ketonemia

51
Q

Which is incorrect of regulation of ketogenesis?
A. Ketosis does not occur in vivo unless there is an increase in the level of
circulating FFAs arising from lipolysis of triacylglycerol in adipose tissue.
B. FFAs are the precursors of ketone bodies in the liver
C. Both in fed and in fasting conditions, the liver extracts ~50% of the FFAs passing through it, so that at high concentrations the flux passing into the organ is substantial.
D. Factors regulating mobilization of FFA from adipose tissue are important in controlling ketogenesis

A

C.

Both
in fed and in fasting conditions, the liver extracts ~30% of the FFAs passing through it, so that at high concentrations the flux passing into the organ is substantial.

52
Q

Which is correct?
A. After uptake by the liver, FFAs are either oxidized to CO2 or ketone
bodies or esterified to triacylglycerol and phospholipid.
B. There is regulation of entry of fatty acids into the oxidative pathway by Malonyl-CoA
C. CPT-I activity is high
in the fed state, leading to depression of fatty acid oxidation, and low in starvation, allowing fatty acid oxidation to increase
D. In the fast state,
FFAs enter the liver cell in low concentrations and are nearly all esterified to acylglycerols and transported out of the liver in very-lowdensity
lipoproteins (VLDLs)

A

A.

There is
regulation of entry of fatty acids into the oxidative pathway by
carnitine palmitoyltransferase-I (CPT-I)

CPT-I activity is low
in the fed state, leading to depression of fatty acid oxidation, and high in starvation, allowing fatty acid oxidation to increase.

In the fed state,
FFAs enter the liver cell in low concentrations and are nearly all
esterified to acylglycerols and transported out of the liver in very-lowdensity
lipoproteins (VLDLs)

53
Q

This enzyme regulates the entry of fatty acids into the oxidative pathway, so that the remainder of the fatty acid taken up is esterfied

A

carnitine palmitoyltransferase-I (CPT-I)

54
Q

CPT-I activity is ______

in the fed state, leading to depression of fatty acid oxidation

A

low

55
Q

CPT-I activity is ______

in starvation, allowing fatty acid oxidation to increase.

A

high

56
Q

initial intermediate in fatty acid biosynthesis and is a

potent inhibitor of CPT-I

A

Malonyl-CoA

57
Q

In the fed state,
FFAs enter the liver cell in low concentrations and are nearly all esterified to acylglycerols and transported out of the liver in _________

A

very-low density

lipoproteins (VLDLs)

58
Q

This inhibits acetyl-CoA carboxylase

A

acyl-CoA

59
Q

Which is incorrect?
A. 1 mol of palmitate involves a net production of 106 mol of ATP via β-oxidation and the citric acid cycle
B. 26 mol of ATP are produced when acetoacetate is the end product
C. 16 mol of ATP are produced when acetoacetate is the end product
D. ketogenesis may be regarded as a mechanism that allows the liver to
oxidize increasing quantities of fatty acids within the constraints of a tightly coupled system of oxidative phosphorylation

A

C

only 16 mol when 3-hydroxybutyrate is the end product

60
Q

Which is correct?
A. A fall in the concentration of oxaloacetate, particularly within the mitochondria, can impair the ability of the citric acid cycle to metabolize
acetyl-CoA and divert fatty acid oxidation toward ketogenesis.
B. increase in the (NADH)/(NAD+) ratio caused
when increased β-oxidation alters the equilibrium between oxaloacetate
and malate so that the concentration of oxaloacetate is decreased, and also when gluconeogenesis is elevated due to low blood glucose levels
C. All of the above
D. None of the above

A

C. All of the above

61
Q

can occur particularly in the newborn—and
especially in preterm infants—owing to inadequate biosynthesis or renal
leakage.

A

Carnitine deficiency

62
Q

Symptoms of deficiency include hypoglycemia, which is a consequence of
impaired fatty acid oxidation, and lipid accumulation with muscular
weakness. Treatment is by oral supplementation with carnitine.

A

Carnitine deficiency

63
Q

affects only the liver, resulting in reduced

fatty acid oxidation and ketogenesis, with hypoglycemia.

A

Inherited CPT-I deficiency

64
Q

affects primarily skeletal muscle and, when severe, the liver.

A

CPT-II

deficiency

65
Q

The sulfonylurea drugs (glyburide [glibenclamide] and tolbutamide),
used in the treatment of type 2 diabetes mellitus, reduce fatty acid
oxidation and, therefore, hyperglycemia by inhibiting what enzyme?

A

CPT-I

66
Q

Can be a cause of acute fatty liver

of pregnancy

A

Defects in long chain 3-hydroxyacyl-CoA dehydrogenase enzyme

67
Q 
affect the degradation of leucine
A. deficiency in 3-Ketoacyl-CoA thiolase 
B. deficiency in HMG-CoA lyase
C. All of the above 
D. None of the above
A

C. All of the above

68
Q

caused by eating the unripe fruit of the

akee tree, which contains the toxin hypoglycin

A

Jamaican vomiting sickness

69
Q

characterized by the
excretion of C6—C10 ω-dicarboxylic acids and by nonketotic
hypoglycemia,

A

Dicarboxylic aciduria

70
Q

Dicarboxylic aciduria is caused by

A

lack of mitochondrial medium-chain

acyl-CoA dehydrogenase.

71
Q

Hypoglycin inactivates what chain of acyl-CoA dehydrogenase

A

medium and

short-chain

72
Q

rare neurologic disorder
caused by a metabolic defect that results in the accumulation of phytanic
acid, which is found in dairy products and ruminant fat and meat.

A

Refsum disease

73
Q

thought to have pathologic effects on membrane function, protein
prenylation, and gene expression

A

Phytanic acid

74
Q

occurs in individuals with a rare inherited absence of
peroxisomes in all tissues. They accumulate C26—C38 polyenoic acids in
brain tissue and also exhibit a generalized loss of peroxisomal functions.
The disease causes severe neurologic symptoms, and most patients die in
the first year of life.

A

Zellweger (cerebrohepatorenal)

syndrome

75
Q

Higher than normal quantities of ketone bodies present in the blood

A

ketonemia (hyperketonemia

76
Q

Higher than normal quantities of ketone bodies present in the urine

A

ketonuria

77
Q

ketonemia + ketonuria is called?

A

ketosis.

78
Q

Which is true of ketosis?
A. The basic form of ketosis occurs in starvation and involves depletion of available carbohydrate coupled with mobilization of FFA.
B. This pattern of metabolism is exaggerated to produce the pathologic states found in diabetes mellitus, the type 2 form
of which is increasingly common in Western countries; twin lamb
disease; and ketosis in lactating cattle.
C. Nonpathologic forms of ketosis
are found under conditions of high-fat feeding and after severe exercise in
the postabsorptive state
D. All of the above
E. None of the above

A

D. All of the above

79
Q

Which is incorrect?
A. Fatty acid oxidation in mitochondria leads to the generation of large
quantities of ATP by a process called β-oxidation that cleaves acetyl-
CoA units sequentially from fatty acyl chains. The acetyl-CoA is
oxidized in the citric acid cycle, generating further ATP

B.The ketone bodies (acetoacetate, 3-hydroxybutyrate, and acetone) are formed in hepatic mitochondria when there is a high rate of fatty acid
oxidation. The pathway of ketogenesis involves synthesis and
breakdown of HMG-CoA by two key enzymes: HMG-CoA synthase and HMG-CoA lyase.

C. Ketone bodies are important fuels in extrahepatic tissues.

D. All of the above

E. None of the above

A

E. None of the above

80
Q 
Diseases associated with impairment of fatty acid oxidation lead to
A. hypoglycemia
B. fatty infiltration of organs 
C. hypoketonemia
D. all of the above
A

D. all of the above

BIOCHEMISTRY (7 decks)

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