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Metabolism of Lipids II - Coggle Diagram
Metabolism of Lipids II
Fatty Acid Synthesis Is Tightly Regulated via ACC
Additional Modes of Regulation in Fatty Acid Synthesis
Changes in gene expression
peroxisome proliferator-activated receptors (PPARS)
Reciprocal regulation
Desaturation of a Fatty Acid by
Fatty Acyl-CoA Desaturase
Plants Can Desaturate Positions Beyond C-9
Polyunsaturated fatty acids (PUFAs) help control membrane fluidity.
Eicosanoids Are Potent Short-Range
Hormones Made from Arachidonate
Eicosanoid hormones
prostaglandins
leukotrienes
thromboxanes
incorporated into the phospholipids of membranes
PGH2 Synthase Has Two Isoforms
COX-1
catalyzes synthesis of prostaglandins
that regulate gastric mucin secretion.
COX-2
catalyzes synthesis of prostaglandins
that mediate pain, inflammation, and fever
NSAIDs (aspirin, ibuprofen, acetaminophen) inhibit COX-2.
Synthesis of Backbone of TAGs and Phospholipids
Synthesis of Phosphophatidic Acid Occurs Before TAGs
Phosphatidic acid is the precursor to TAGs and phospholipids.
Regulation of Triacylglycerol Synthesis by Insulin
Triacylglycerol Breakdown and
Resynthesis create a Futile Cycle
75% free fatty acids (FFAs)
reesterified to form TAGs
25% free fatty acids (FFAs)
be used for fuel
The Triacylglycerol Cycle
Glyceroneogenesis Makes DHAP for Glycerol
3-Phosphate Generation During TAG Cycle
During lipolysis (stimulated by glucagon or epinephrine),
glycolysis is inhibited.
Attaching Phospholipid Head Group
Requires Activation by CDP
Synthesis and Transport of
Cholesterol, Steroids, and Isoprenes
biosynthesis using 5-carbon isoprene unit
Three acetates condense to form mevalonate.
Mevalonate converts to phosphorylated 5-C isoprene.
Six isoprenes polymerize to form the 30-C linear squalene.
Squalene cyclizes to form the four rings that are modified to produce cholesterol
Fates of Cholesterol After Synthesis
Activation and Mobilization of
Lipoprotein Contents
Chylomicrons
fuel
adipose tissue
heart
skeletal muscle
VLDL
Contains
TAG
cholesteryl esters
LDL
ApoB-100
cholesterol/chloesteryl esters
removal of TAG from VLDL
HDL
high in protein
picks up cholesterol from the cells and returns to liver
Cardioprotective
Regulation of Cholesterol Synthesis and Transport
Covalent modification of HMG-CoA reductase
Glucagon, epinephrine
phosphorylation, low activity
Insulin
dephosphorylation,gain activity
Transcriptional regulation of HMG-CoA gene
Sterol regulatory element-binding proteins (SREBPs)
Proteolytic degradation of HMG-CoA reductase
Activation of ACAT, which increases esterification for storage
Transcriptional regulation of the LDL receptor
Cardiovascular Disease (CVD) Is Multifactorial
Very high LDL-cholesterol levels tend to
correlate with atherosclerosis.
Low HDL-cholesterol levels are negatively
associated with heart disease.
Statin Drugs Inhibit HMG-CoA Reductase
to Lower Cholesterol Synthesis
Statins resemble mevalonate
competitive inhibitors of HMG-CoA reductase
