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Energy economy of the cells
Glucose --- ready cash
Lipids --- savings account
Fatty acids (from triacylglycerols)
catabolization
Acetyl-CoA
synthesis
Lipids
Citric acid cycle
ATP
Catabolism of Lipids
Phospholipiase D
in spider and snake venom
Lipid products of hydrolysis
Lyse red blood cells
Prevent clot formation
Hormone-dependent
hydrolysis of
triacylglyerols
The formation of an acetyl-CoA in cytosol
(activation step requires two ATP)
Role of carnitine in the transfer of acyl groups to the mitochondrial matrix
Carnitine
translocase
Carnitine
acyltransferase
b-oxidation of saturated fatty acids
One cycle:
2 C shorten
1 acetyl-CoA formed
1 FADH2 formed
1 NADH formed
Degradation of stearic acid (18 C) through b-oxidation
The energy yield from the oxidation of fatty acids
O
CH3(CH2)16C-S-CoA + 8FAD + 8NAD+ + 8H2O + 8CoA-SH
O
9CH3-C-S-CoA + 8FADH2 + 8NADH + 8H+
O
9CH3-C-S-CoA + 9FAD + 27NAD + + 9GDP + 9Pi + 27 H2O
18CO2 + 9CoA-SH + 9FADH2 + 27NADH + 9GTP + 27H+
17FADH2 + 8.5O2 + 25.5ADP + 25.5Pi
17 FAD + 25.5 ATP + 17 H2O
35NADH + 35H+ + 17.5 O2 + 87.5ADP + 87.5Pi
35NAD+ + 87.5ATP + 35H2O
O
CH3(CH2)16C-S-CoA + 26O2 + 122 ADP + 122Pi
18CO2 + 17H2O + 122ATP + CoA-SH
one 18C fatty acid
120 ATP
one 6C glucose
32 ATP
The balance sheet for oxidation of one molecule
of stearic acid
Cytosol
Matrix in mitochondia
Citric acid cycle
Electron transport chain
O
CH3(CH2)16C-S-CoA + 26O2 + 122 ADP + 122Pi
18CO2 + 17H2O + 122ATP + CoA-SH
Metabolic water
The oxidation of a fatty acid containing an odd number
of carbon atoms
b-oxidation of unsaturated fatty acids
The oxidation pathways for polyunsaturated fatty acids
The anabolism of fatty acids
●
Oxaloacetate
and acetyl-CoA
can not cross through
mitochondria membrane
but citrate can.
fatty acid synthesis
in cytosol
The formation of malonyl-CoA --the first step in anabolism of fatty acids
Acetyl-CoA carboxylase
Three proteins making up acetyl-CoA carboxylase
The first cycle of palmitate synthesis
ACP: acyl carrier protein
Fatty acid synthase
ACP has a functional group that is structurally similar
to coenzyme A
The second cycle of palmitate synthesis in E. coli
16C saturated fatty acid (palmitate)
In E. coli,
multienzyme system
In eukaryotes,
multifunctional enzyme
A comparison of fatty acid degradation and biosynthesis
Chain lengthening beyond 16C
Pathways for the biosynthesis of triacylglycerols
Pathways for the biosynthesis of phosphoacylglycerols (I)
In E. coli
Pathways for the biosynthesis of phosphoacylglycerols (II)
In mammals
The interconversion of PE and PS in mammals
The anabolism of cholesterol
C2
C6
C5
C30
C27
● Most
of the cholesterol formed in the smooth ER of the liver in mammals
The biosynthesis of mevalonate
●This
step is inhibited by high levels of cholesterol
and is the major control point of cholesterol synthesis
●A
target for drugs to lower cholesterol levels in the body
●lovastatin
an inhibitor of HMG-CoA reductase
2 acetyl-CoA
The synthesis of Squalene
The synthesis of bile acids from cholesterol
The synthesis of
steroid hormones
from cholesterol
The role of cholesterol in heart disease
● Deposition
of cholesterol plaques
atherosclerosis
● Cholesterol
is transported by lipoproteins in bloodstream
● Lipoprotein
aggregates are classified by their densities
LDL (low-density lipoproteins) particles
Lipids:
cholesterol
triacylglycerols
cholerserol esters
phospholipids
The fate of cholesterol
in the cell
lysosomes
Proteins in LDL
Cholesterol ester
amino acids
fatty acids +
cholesterol
ACAT
(acyl-CoA cholesterol acyltransferase)
HMG-CoA reductase
Synthesis of LDL receptors