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Lipids (Lipid Signals, Cofactors, Pigments (Steroid Hormones (Structure…
Lipids
Lipid Signals, Cofactors, Pigments
Phosphatidylinositols
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Function
- PIP2 in inner membrane is a messenger molecule reservoir
vasopression activates phospholipase C
- inositol phospholipids are points of nucleation for proteins to form multi-enzyme signaling complexes
- signaling proteins bind PIP3
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Eicosanoids
Structure
- FA derivatives of arachidonate/arachidonic acid and eicosapentaenic acid
- 20:4 (delta5,8,11,14) and 20:5 (delta5,8,11,14,17) #
Function
- reproductive function, fever, pain, inflammation, blood clotting, gastric acid secretion
- paracrine hormones that act on nearby cells instead of distal ones
Prostaglandins, PG
Structure
- contain a 5 C ring
- PGE2 and other series 2 PGs come from arachidonate
- series 3 come from EPA
Function
- series 3 elevate body temp, inflammation, and pain
- contract smooth muscle (uterus), stimulate blood flow to organs, sleep-wake cycle, tissue response to hormones
Thromboxanes, TX
Structure
- 6 C ring with ether bridge
Function
- produced by platelets
- act in blood clotting and reduce blood flow
- NSAIDs inhibit PH H2 synthase
- catalyzes arachidonate to PGE2s and TXs
Leukotrienes, LT
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Function
- LT D4 from LT A4 induces smooth muscle contraction of airways
Lipoxins, LP
Structure
- linear eicosanoids with several hydroxyls on chain
Function
- anti-inflammatory agents that are stimulated by aspirin
Steroid Hormones
Structure
- oxidized sterol derivatives
- have sterol nucleus but lack alkyl chain on D ring of cholesterol
- more polar than cholersterol
Function
- move through blood on protein carriers to distal tissue
- bind tightly to highly specific receptors to change gene expression and metabolism
Lipophilic Compounds
- volatile substances secreted by plants
- attract pollinators, repel herbivores, communicate with other plants
- made from FAs or isoprene condensations
Fat-Soluble Vitamins
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E & K: Redox Cofactors
E
- class of lipids called tocopherols
- substituted aromatic ring and isoprenoid side chain
- hydrophobic association with cell membrane, lipid deposits, and lipoproteins in blood
- biological antioxidants
- aromatic ring destroys ROSs
- deficiency causes scaly skin, muscle wasting, sterility
K
- has an aromatic ring that undergoes a redox cycle during prothrombin formation
- K1 = phylloquinone
- K2 - menaquinone
- ubiquinone and plastoquinone are electron carriers
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Oddballs
Dolichols
- isoprenoid alcohols are added to sugars to activate them before their addition to glycoproteins/lipids
Conjugated Dienes
- easily excited by visible light
- synthesized from isoprene
Polyketides
- secondary metabolites that act as antibiotics, antifungals, or cholesterol synthesis inhibitors
Sphingosine Derivatives
Structure
- ceramides and sphingolipids #
Function
- ceramide and sphingomyelin are protein kinase regulators
- involved in cell division, differentiation, migration, apoptosis
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Storage Lipids
Fatty Acids
Structure
- carboxylic acid with carbon chain 4-36 C
- double bonds, commonly at C9, C12 and C15
- cis DBs almost always unconjugated
Triacylglycerols
Structure
- three FAs in an ester linkage with glycerol
- simple all have same FA, complex have different ones
- most natural ones are mixed
*nonpolar hydrophobic with low water solubility
- melting point depends on mix of FAs
- more long-chain FAs = higher MP
Function
- form fat droplets in cells
- store twice as much energy than carbs
- unhydrated, saves space
- require lipases to release FAs
Nomenclature
- 20:2 (delta^9,12) = 20-C chain with two DBs at 9 & 12
- cis-cis-9,12-icosadienoic acid
- n-whatever acid = saturated
- PUFAs are named from the last (omega) C
Waxes
Structure
- esters of long chain FAs with long chain alcohols
- high melting points
Function
- protect hair and skin
- prevent water saturation or evaporation
Properties
- longer saturated chains decrease solubility
- unsatured DBs have a lower melting point
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