lipids metabolism

1
Chapter 5 lipids metabolism
2
LIPIDS

• Water-insoluble substances that can be extracted
  from cells by nonpolar organic solvents
• Characteristics of fat
• Hydrophobic because of nonpolar FA chain
• Lipids store large amounts of energy
• 9 kcal/gram due to energy rich fatty acid chain

3
Outline

• Classification of FA and Nomenclature
• Digestion of Triacylglycerols
• Metabolism of TAG
• Metabolism of phospholipids
• Metabolism of cholesterol
• Lipoproteins metabolism

4
Section 1 Classification of FA and
Nomenclature(??)

• According to the number of carbon atom
• short chain(24C), medium chain (610C) long
  chain(1226C) fatty acid
• According to whether it contains double bond or
  not
• (saturate unsaturate fatty acid)
• According to the number of carbon atom, the
  source property. such as Butyric acid,
  Arachidonic acid
• systemic nomination
• (? catalogue, ? or n catalogue)

5
Classification and Functions of Lipids

• 1. Triglyceride, TG(Variable lipids)
• - As storage and transport form of metabolic
  fuel
• - To keep the body temperature
• - Fats are solids oils are liquids
• - To protect the visceras
• 2. Lipoid(Basic lipids)Cholesterols,
  Phospholipids, Glycolipids et al
• - As structural components of biological
  membranes.
• - Cholesterol serves the precursor of bile
  salt and steroid hormones
• 3. Lipid ramification to involve the different
  functions

6
Fatty AcidsAcids obtained by the hydrolysis of
fats and oils

• Saturated (have only single bonds)
• Unsaturated (have double bonds)
• Essential
• -must originate from dietary sources
• -the body cannot synthesize
• -Polyunsaturated fatty acids
• linoleic (182,?9,12)
• linoleinic(183, ?9,12,15)
• arachidonic acid (204, ?5,8,11,14)

7
Omega-3 / Omega-6 Fatty Acids

• Sources of omega-3 fatty acid soybean, salmon
• Eicosapentaenoic acid(EPA,fish oil) found in
  oils of shell fish, cold-water tuna, sardines,
  and sea mammals

• Sources of omega-6 fatty acids
• Vegetable oils
• Nuts and seeds

8
Triglyceride

• Triglycerides(triacylglycerols),Called
  Neutral Fats
• - made of 3 free fatty acids and 1
  glycerol
• - FFA 4-22 Carbons long (mostly 16-20)
• - 95 of dietary lipids (fats oils)

9
Section 2Digestion of Triacylglycerols
10
6 Steps of Digestion and absorption of lipids

• Minor digestion of triacylglycerols in mouth
  and stomach by lingual lipase
• Major digestion of all lipids in the lumen of
  the duodenum(????) / jejunum (??)by Pancreatic
  lipases
• Bile acid facilitated formation of mixed micelles
  that present the lipolytic products to the
  mucosal surface, followed later by
  enterohepatic(??)bile acid recycling
• Passive absorption of the lipolytic products from
  the mixed micelle into the intestinal epithelial
  cell,Glycerol FAs lt 12 carbons in length pass
  thru the cell into the blood without
  modification. 2-monacylglycerols and FAs gt 12
  carbons in length are re-synthesized into TGs in
  the endoplasmic reticulum TGs then form large
  lipid globules in the ER called nascent
  chylomicrons (????).Several apolipoproteins are
  required
• Re-esterification of 2-monoacylglycerol,
  lysolecithin(?????), and cholesterol with free
  fatty acids inside the intestinal enterocyte
• Assembly and export from intestinal cells to the
  lymphatics of chylomicrons coated with Apo B48
  and containing triacylglycerols, cholesterol
  esters and phospholipids

11
Section 3 Metabolism of TAG

• Synthesis of TAG
• Catabolism of TAG
• - Fatty acid bata oxidation
• -Ketogenesis and Ketone Bodies
• Lipogenesis Fatty Acid Synthesis
• Some poly-unsaturated FA ramification

12
The synthesis of TAG

• Mono-acylglycerol pathway (MAG pathway)
• (for dietary fat digestion and
  absorption)

FA
FA
13
2. Diacylglycerol pathway (DAG pathway)
(for TAG synthesis of in adipose tissue, liver
and kidney)
ADP
ATP
HSCoA
HSCoA
HSCoA
phosphatase
acyl CoA transferase
acyl CoA transferase
14
Catabolism of TAG
15
Mobilization of triacylglycerols

• Mobilization of triacylglycerols
• in the adipose tissue, breaks
• down triacylglycerols to free
• fatty acids and glycerol (fatty
• acids are hydrolyzed initially
• from C1or C3 of the fat)
• hormone sensitive lipase
• cleave a fatty acid from a
• triglyceride, then other lipase
• complete the process of lipolysis,
• and fatty acid are released into
• the blood by serum albumin

16

• The glycerol is absorbed by the liver and
  converted to glycolytic intermediates

17
Fatty acid bata oxidation
18
CAPILLARY
CYTOPLASM
FA fatty acid
LPL lipoprotein lipase
cell membrane
FABP fatty acid binding protein
ACS acyl CoA synthetase
Overview of fatty acid degradation
19
Steps in Beta Oxidation

• Fatty Acid Activation by esterification with
  CoASH
• Membrane Transport of Fatty Acyl CoA Esters
• Carbon Backbone Reaction Sequence
• Dehydrogenation
• Hydration
• Dehydrogenation
• Thiolase Reaction (Carbon-Carbon Cleavage)

20
1. Activation of Fatty Acids

• Acyl CoA synthetase reaction occurs on the
  mitochondrial membrane

21
2.Transport into Mitochondrial Matrix

• Carnitine carries long-chain activated fatty
  acids into the mitochondrial matrix

22

• Carnitine carries long-chain activated fatty
  acids into the mitochondrial matrix

23
3. Fatty acid Beta oxidation
? ?

• Each round in fatty acid degradation involves
  four reactions
• 1. oxidation to
• trans-?2-Enoly-CoA
• Removes H atoms from the
• ? and ? carbons
• -Forms a trans CC bond
• -Reduces FAD to FADH2

24

• 2. Hydration to L3Hydroxylacyl CoA
• Adds water across the trans CC bond
• Forms a hydroxyl group (OH) on the ? carbon

25

• 3. Oxidation to
• 3Ketoacyl CoA
• Oxidizes the hydroxyl group
• Forms a keto group on the ? carbon

26

• 4. Thiolysis to produce AcetylCoA
• acetyl CoA is cleavedBy splitting the bond
  between the ? and ? carbons.
• To form a shortened fatty acyl CoA that repeats
  steps 1 - 4 of ?-oxidation

27
?-Oxidation of Myristic(C14) Acid
28
?-Oxidation of Myristic (C14) Acid
7 Acetyl CoA
6 cycles
29
Cycles of ?-Oxidation

• The length of a fatty acid
• Determines the number of oxidations and the total
  number of acetyl CoA groups
• Carbons in Acetyl CoA ?-Oxidation Cycles
• Fatty Acid (C/2) (C/2 1)
• 12 6 5
• 14 7 6
• 16 8 7
• 18 9 8

30
?-Oxidation and ATP
Activation of a fatty acid requires
2 ATP One cycle of oxidation of a fatty
acid produces 1 NADH 3 ATP 1
FADH2 2 ATP Acetyl CoA entering the citric
acid cycle produces 1 Acetyl CoA 12 ATP
31
ATP for Myristic Acid C14
ATP production for Myristic(14 carbons) Activati
on of myristic acid -2 ATP 7 Acetyl CoA 7
acetyl CoA x 12 ATP/acetyl CoA 84 ATP 6
Oxidation cycles 6 NADH x 3ATP/NADH 18
ATP 6 FADH2 x 2ATP/FADH2 12
ATP Total 102 ATP
32
Oxidation of Special Cases (monounsaturated
fatty acids)
33
Odd Carbon Fatty Acids
5 Cycles
5 CH3COSCoA CH3CH2COSCoA
Propionyl CoA Carboxylase ATP/CO2
Propionyl CoA
TCA Cycle
Epimerase
Mutase Vit. B12
Succinyl CoA
L-Methylmalonyl CoA
D-Methylmalonyl CoA
34
Ketogenesis (Ketosis) formation of Ketone
Bodies
Thiolase
CH3COSCoA
2 CH3COSCoA CH3COCH2COSCoA
Acetoacetyl CoA
HMG CoA Synthase
Several steps
Cholesterol (in cytosol)
OH
HO2C-CH2-C-CH2COSCoA
CH3
(in liver mitochon- drial matrix)
?-Hydroxy-?-methylglutaryl CoA (HMG CoA)
Ketogenesis
35
Ketogenesis formation of Ketone Bodies
OH
HMG CoA lyase
HO2C-CH2-C-CH2COSCoA
CH3COCH2CO2H
- CH3COSCoA
Acetoacetic Acid
CH3
HMG CoA
NADH H
- CO2
Dehydrogenase
NAD
OH
CH3COCH3
CH3CHCH2CO2H
Acetone (volatile)
?-Hydroxybutyrate
Ketone bodies are important sources of energy,
especially in starvation
36
Oxidation of ketone bodies in brain, muscle,
kidney, and intestine
37
The significance of ketogenesis and ketogenolysis

• Ketone bodies are water soluble, they are
  convenient to transport in blood, and readily
  taken up by non-hepatic tissues
• In the early stages of fasting, the
  use of ketone bodies by heart, skeletal muscle
  conserves glucose for support of central nervous
  system. With more prolonged starvation, brain can
  take up more ketone bodies to spare glucose
  consumption
• High concentration of ketone bodies can induce
  ketonemia and ketonuria, and even ketosis and
  acidosis
• When carbohydrate catabolism is
  blocked by a disease of diabetes mellitus or
  defect of sugar source, the blood concentration
  of ketone bodies may increase,the patient may
  suffer from ketosis and acidosis

38
Overview Catabolism of TAG
39
Lipogenesis Fatty Acid Synthesis

• Fatty acid are synthesized and degraded by
  different pathways
• from acetyl CoA
• in the cytosol
• intermediates are attached to the acyl carrier
  protein (ACP)
• the activated donor is malonylACP
• reduction uses NADPH H
• stops at C16 (palmitic acid ???)

40
Reactivity of Coenzyme A
Nucleophilic acyl substitution

HSCoA

• Acetyl coenzyme A is a source of an acetyl group
  toward biological nucleophiles(it is an acetyl
  transfer agent)

41
Reactivity of Coenzyme A
can react via enol(??)
E

• Acetyl coenzyme A reacts with biological
  electrophiles at its ? carbon atom

42
Formation of Malonyl Coenzyme A

• Formation of malonylCoA is the committed step in
  fatty acid synthesis

O CH3CSCoA HCO3- ATP
Acetyl CoA
O O
-OCCH2CSACP ADP
Pi Malonyl (???) CoA
43
Formation of Acetyl and Malonyl ACP

• The intermediates(acetyl-ACP and malonyl-ACP) in
  fatty acid synthesis are covalently linked to the
  acyl carrier protein (ACP)

44

• In bacteria the enzymes that are involved in
  elongation are separate proteins
• In higher organisms the activities all reside on
  the same polypeptide
• To start an elongation cycle, AcetylCoA and
  MalonylCoA are each transferred to an acyl
  carrier protein

O CH3CSACP (
Acetyl-ACP) O O
-OCCH2CSACP (Malonyl-ACP)
45
Condensation and Reduction

• In reactions 1 and 2 of fatty acid synthesis
• Condensation by a synthase combines acetyl-ACP
  with malonyl-ACP to form acetoacetyl-ACP (4C) and
  CO2 (reaction 1)
• Reduction converts a ketone to an alcohol using
  NADPH (reaction 2)

46
Dehydration and Reduction

• In reactions 3 and 4 of fatty acid synthesis
• Dehydration forms a trans double bond (reaction
  3)
• Reduction converts the double bond to a single
  bond using NADPH (Reaction 4)

47
Lipogenesis Cycle Repeats

• Fatty acid synthesis continues
• Malonyl-ACP combines with the four-carbon
  butyryl-ACP to form a six-carbon-ACP.
• The carbon chain lengthens by two carbons each
  cycle

48
Lipogenesis Cycle Completed

• Fatty acid synthesis is completed when palmitoyl
  ACP reacts with water to give palmitate (C16) and
  free ACP.

49
Summary of Lipogenesis
50
Elongation and Unsaturation

• Endoplasmic reticulum(???) systems introduce
  double bonds into long chain acylCoA's
• Reaction combines both NADH and the acylCoA's to
  reduce O2 to H2O

• convert palmitoylCoA to other fatty acids
• Reactions occur on the cytosolic face of the
  endoplasmic reticulum.
• MalonylCoA is the donor in elongation reactions

51
? Oxidation and Fatty Acid Synthesis
52
Fatty Acid Formation

• Shorter fatty acids undergo fewer cycles
• Longer fatty acids are produced from palmitate
  using special enzymes
• Unsaturated cis bonds are incorporated into a
  10-carbon fatty acid that is elongated further
• When blood glucose is high, insulin stimulates
  glycolysis and pyruvate oxidation to obtain
  acetyl CoA to form fatty acids

53
Stoichiometry of FA synthesis

• The stoichiometry of palmitate synthesis
• Synythesis of palmitate from MalonylCoA
• Synthesis of MalonylCoA from AcetylCoA
• Overall synthesis

54
Sources of NADPH

• The malate dehydrogenase and NADPlinked malate
  enzyme reactions of the citrate shuttle exchange
  NADH for NADPH

55
Citrate Shuttle

• AcetylCoA is synthesized in the mitochondrial
  matrix, whereas fatty acids are synthesized in
  the cytosol
• AcetylCoA units are shuttled out of the
  mitochondrial matrix as citrate

56
Regulation of Fatty Acid Synthesis

• Regulation of Acetyl carboxylase(?????)
• Global
• () insulin
• (-) glucagon
• (-) epinephrine
• Local
• ()Citrate
• (-) PalmitoylCoA
• (-) AMP

57
Eicosanoid Hormones(????????)

• Eicosanoid horomones are synthesized from
  arachadonic acid (204,???-???)
• Prostaglandins(????)
• 20-carbon fatty acid containing 5-carbon ring
• Prostacyclins
• Thromboxanes(????)
• Leukotrienes(???)
• contain three conjugated double bonds

58
Eicosanoid Hormones
59
Eicosanoid Hormones
60
Eicosanoid Hormones
61
Section 4

• Metabolism of phospholipids(??)

62
Phospholipids

• Structure
• Glycerol 2 fatty acids phosphate group
• Functions
• Component of cell membranes
• Lipid transport as part of lipoproteins
• Food sources
• Egg yolks, liver, soybeans, peanuts

63
Phospholipids

• Phospholipids are intermediates in the
  biosynthesis of triacylglycerols
• The starting materials are glycerol 3-phosphate
  and the appropriate acyl coenzyme A molecules

64
Biosynthesis of glycerophospholipids
1. DAG shunt is the major pathway for
biosynthesis of phosphatidyl choline (lecithin)
and phosphatidyl ethanolamine (cephalin)
65
CDP-DAG shunt
2. CDP-DAG shunt is the major pathway for the
synthesis of phosphatidyl serine, phosphatidyl
inositol and cardiolipin - in this pathway,
DAG is activated as the form of CDP-DAG
Phosphatidic acid
66
Degradation of glycerophospholipids
67
Metabolism of sphingolipids
Sphingolipids are a class of lipids containing
sphingosine instead of glycerol include
glycosphingolipids phosphosphingolipids
The structure of phosphosphingolipids
???
?????
??????
The structure of glycosphosphingolipids
?????
???
N-??????
68
Section 5

• Metabolism of cholesterol

69
Structure of Cholesterol
Fundamental framework of steroids
CH3
CH3
CH3
CH3
CH3
H
H
H
HO
Structure of Cholesterol
70
Cholesterol Biosynthesis 1. Formation of
Mevalonate
Liver is primary site of cholesterol biosynthesis
Thiolase
CH3COSCoA
2 CH3COSCoA CH3COCH2COSCoA
Acetoacetyl CoA
HMG CoA Synthase
OH
OH
HMGCoA reductase
HO2C-CH2-C-CH2COSCoA
HO2C-CH2-C-CH2CH2OH
CoASH
CH3
CH3
?-Hydroxy-bata-methyl- glutaryl CoA (HMG CoA)
3R-Mevalonic acid ????
Key control step
71
Cholesterol Biosynthesis 2. processing of
Squalene
OH
OH
-O2C-CH2-C-CH2CH2OH
-O2C-CH2-C-CH2CH2OPOP
2 Steps
CH3
CH3
ATP
Mevalonate
5-Pyrophospho(???)- mevalonate
- CO2 - H2O
CH3
Isomerase
CH2C-CH2CH2OPOP
CH3-CCH2CH2OPOP
Isopentenyl(???) pyrophosphate
Dimethylallyl pyrophosphate
CH3
72
Isoprenoid(????)Condensation
Tail
Dimethylallyl pyrophosphate
Head to tail Condensation
Head
Tail
Head
Tail
Isopentenyl Pyrophosphate (IPP)
Geranyl (?????) Pyrophosphate (GPP)
Head
Isoprenes????
Head to tail condensation of IPP and GPP
Tail to tail condensation of 2 FPPs
Squalene??
Head
Tail
Farnesyl(???) Pyrophosphate (FPP)
73
3. Conversion of Squalene to Cholesterol
Squalene- 2,3-epoxide
Squalene monooxygenase
O2
2,3-Oxidosqualene lanosterol cyclase
Squalene??
20 Steps
Lanosterol????
Cholesterol
74
Transformations of Cholesterol

• Cholesterol is the biosynthetic precursor to a
  large number of important steroids
• Bile acids Vitamin D3 Corticosteroids
  Sex hormones

75
Section 6

• Lipoproteins metabolism

76
General Features of Lipoproteins

• Apolipoproteins specific lipid-binding proteins
  that attach to the surface
• intracellular recognition for exocytosis of the
  nascent particle after synthesis
• activation of lipid-processing enzymes in the
  bloodstream,
• binding to cell surface receptors for
  endocytosis and clearance
• Main lipid components triacylglycerols,
  cholesterol esters, phospholipids.
• Major lipoproteins
• chylomicrons
• very low density lipoproteins (VLDL)
• low density lipoproteins (LDL)
• high density lipoproteins (HDL)
• Subfraction intermediate density lipoproteins
  (IDL)
• Electrophoretic mobility (charge)
• HDLs ? ?lipoproteins
• LDLs ?-?lipoproteins
• VLDLs pre-? lipoproteins (intermediate
  between ? and ? mobility)

Plasma lipoproteins
77
Model of low density lipoprotein. Other
lipoproteins have a similar structure differing
in the core content of lipid and the type of
apoproteins on the surface of the molecule
78
Functions of apolipoproteins
Protein (Enzyme) Site of Action Activator Function
LPL (Enzyme) capillary walls apo CII excises FFA from TAGs in chylomicrons and VLDLs for adipose and muscle
CERP plasma membrane apo A1 (choles. Induced) flips cholesterol (and lecithin) to outer layer of lipid bilayer for LCAT action in blood
Apo A1 blood, plasma membrane none activates LCAT and CERP binds to apo A1 receptors on cells requiring cholesterol extraction
Apo B48 Gut none export of chylomicrons from intestinal cells
Apo B100 Various cells none ligand for LDL receptor export of liver VLDL
Apo CII capillary walls none activates lipoprotein lipase
Apo E liver none receptor ligand - clears remnants, IDL, and HDL
79
composition of lipoproteins
80
Lymph system Chylomicrons to capillaries via
lymph
non-hepatic tissues
intestine
ApoB48 aids with chylomicron assembly
Chylomicrons carry dietary fatty acids to tissues
liver
81
Triacylglycerol in core
Chylomicron (or VLDL)
To Liver
Apo CII
Lipoprotein lipase
Glycerol
Free fatty acids
Polysaccharide Chain
Endothelial Surface of cell
Capillary
In cellulo (muscle adipose)
Free fatty acids
Lipoprotein lipase action on chylomicron
triacylglycerol (an identical reaction occurs
with VLDL)
82
non-hepatic tissues
ApoB48
LIVER
Exogenous pathway of lipid transport Chylomicrons
carry dietary fatty acids to tissues and the
remnants take cholesterol to the liver
83
LPL hydrolyze TAGs FFA uptake LDL circulate to
tissues
non-hepatic tissues
LIVER
CII and E release to HDL
Cholesterol uptake excreted as bile acids
apo B100 on LDL bind to receptor
LDL taken into the cell to deliver cholesterol
Apo E binds liver receptor
HDL scavenge cholesterol
The liver-directed endogenous pathway of
lipoprotein metabolism
84
Chylomicrons Exogenous Pathway
Chylomicron Processing and Interface with HDL
HDL Both Pathways

• Nascent HDL
• Assembled in liver
• Loans apo E/ apo CII to nascent chylomicrons

• Nascent Chylomicron
• Assembly in Gut
• Mediated by B48

• Mature Chylomicron
• Apo E and CII added from HDL

• Mature Chylomicron
• Apo E and CII added from HDL
• CII activates LPL

• Lipoprotein Lipase
• capillary walls
• hydrolyzes TAG
• deliver FFA into adipose/muscle

• Mature HDL
• CE from peripheral cells
• activated by apo A1
• Apo CII returned by
• chylomicrons

• Chylomicron Remnant
• from mature chylomicron
• apo CII returned to HDL

85
VLDL/LDL Endogenous Pathway
VLDL/LDL Processing and Interface with HDL

• Nascent VLDL
• Assembly in Liver
• Mediated by B100

HDL Both Pathways
apo CII E from HDL

• Mature VLDL
• Apo E and CII added from HDL

• Mature VLDL
• Apo E and CII added from HDL
• CII activates LPL

• Lipoprotein Lipase
• capillary walls
• hydrolyzes TAG
• deliver FFA into adipose/muscle

Mature HDL Apo CII/E returned by VLDL

• LDL
• from mature VLDL

86
Clearance of Cholesterol by Liver from
Chylomicron Remnants, HDL and LDL
Mature HDL
Chylomicron Remnant
LDL
E Receptor
B100 receptor
E Receptor
CE Metabolism
87
Consequence of Oxidized LDL Formation
LDL
Oxidation of LDL
Oxidized LDL 1. Uptake by "scavenger receptors"
on macrophages that invade artery walls become
foam cells 2. Elicits CE deposition in artery
walls
Atherosclerosis ??????
88
LDL receptor
sorting endosome ligand/receptor dissociation
lysosome
Golgi
late endosome
free pool of cholesterol
ACEH CE ? cholesterol
ACAT (stimulated by cholesterol)
endocytosis
CE stored in droplets
CE
CE
LDL CE
Cholesterol metabolism to bile acids or steroids
CERP
Membrane Cholesterol
L CA T
Reverse CholesterolTransport
Mature HDL Cleared by liver
89
Lipoprotein classes
Lipo-protein Source Apo Proteins ProteinLipid/ Major (minor) Lipid Transported Function
Chylo-microns gut B48, CII, E 149triacylglycerol (CE) Dietary FFA ? Adipose/muscle CE ? Liver via remnants
VLDL liver B100, CII, E 19 triacylglycerol (CE) Synthesized FFA? adipose/muscle CE ? LDL
LDL blood B100 13 cholesterol ester CE to liver (70) and peripheral cells (30)
HDL liver A1, CII, E("ACE") 11 cholesterol ester supplies apo CII, E to chylomicrons and VLDL mediates reverse cholesterol transport
90
hypercholesterolemia
???????????
91
Guidelines for Appropriate Intake of Fat

• reduce fat in diet to lt30
• avoid saturated fat (animal fat)
• avoid margarine(??), baked goods, fried food
• mono/polyunsaturated cooking oils are best
  (olive, corn)
• eat foods rich in ?-3 polyunsaturated fatty
  acids
• (e.g, soybean,salmon)

92
????? ???
93
1. ?????????( )
A ????????(HSL) B ??? C ?????? D ????? E ???
94
2. ??????????????( )
A ????? B ???? C ACTH D ????? E ???
95
3. ????????????,??????????( )
A ??? B ?? C ?? D ??? E ???
96
4. ????????????( )
A ??CoA??? B ???????I C ???????II D
??CoA??? E ?-????
97
5. ??????-??????????( )
A ??,??,???,?? B ??,??,???,?? C ??,???,??,
?? D ??,??,??,??? E ??,??,??,???
98
6. ?????,???????????( )
A ???? B ?????? C ?????? D ???? E ????
99
7. ?????????????( )
A ??? B ??? C ??? D ???? E ??
100
8. ????HMG-CoA????????????( )
A ?????????? B ????????????? C ??????????? D
?????????? E ???????????
101
9. ?????????????????????( )
A ??????B B ?VLDL??LDL?? C ???LDL?????? D
??HMG-CoA??????? E ??????????(ACAT)????
102
10. ????????????????( )
A ????????????? B ?????????????????CoA C
???????? D ??ATP E ??NADPH??
103
11. The organ having the strongest ability of
fatty acid synthesis is ( )
A fatty tissue B lacteal gland C liver D
kidney E brain
104
12. Which one transports cholesterol from outer
to inner of liver?
A CM B VLDL C LDL D HDL E IDL
105
13. Which one is essential fatty acid?
A palmitic acid B stearic acid C oleinic acid D
octadecadienoic acid E eicosanoic acid
106
14. The main metabolic outlet of body
cholesterol is ( )
A change into cholesterol ester B change into
vitamine D3 C change into bile acid D change
into steroid hormone E change into
dihydrocholesterol
107
15. ????????????????( )
A ??? B ?????? C ???????? D ??? E ??

108
16. ??????????????( )
A ?? B ??? C ?? D ??? E ???
109
17. ?????????????( )
A ????????(HSL) B ??????(LPL) C ????(HL) D
???????????(LCAT) E ???????????(ACAT)

110
18. ???????( )

A ???????? B ?????????????? C ???????? D CM
VLDL?????????? E LDL HDL??????????
111
19. Which can be the source of acetyl CoA?

A glucose B fatty acid C ketone body D
cholesterol E citric acid
112
20. The matters which join in synthesis of
cholesterol directly are ( )
A acetyl CoA B malonyl CoA C ATP D NADH E
NADPH