Phospholipids and Glycolipids Flashcards
1
Q
Phospholipids
A
- Amphipaths: polar head group and non-polar FA tails
- Phosphoglycerides
- Sphingomyelins
2
Q
Phosphoglycerides
structure
examples
A
- glycerol backbone, two FAs, a phosphorylated head group
- Phosphatidic acid (PA) is the simplest
- PS
- PC
- PE
- PI
- cardiolipin
3
Q
Sphingomyelins
structure
examples
A
- Sphingosine backbone
- one C of sphingosine attached to a phosphocholine
- one C of sphingosine attached to a FA via amide linkage
4
Q
Functions of Phospholipids
A
- structural components of cell membrane
- sources of arachidonic acid
- generate second messenger molecules
- modification of several membrane-associated proteins in their transit from the ER to the membrane
- isoprenoid
- Glycosylphosphatidylinositol(GPI) can serve as a membrane anchors for different proteins
5
Q
Biosynthesis of Phospholipids
A
- in liver, adipose tissue, and the intestine
- generated using components from TG synthesis
- Glycerol-3-P–>
- DHAP—> Plasmalogens OR PAF
- PA–>cardiolipin OR PI–>PIP2
- DAG–>TGsORPC,PE,PS
- Glycerol-3-P–>
6
Q
Two routes for phospholipid biosynthesis
A
- Activate DAG backbone with CDP–>add head group–>
- PI
- Phosphotidylglycerol
- cardiolipin
- Activate head group with CDP–>add DAG backbone–>
- PC
- PE
- PS
7
Q
CDP synthesis
A
- Synthesis of P-Choline
ATP + choline –(Choline kinase)–>P-Choline + ADP
- Activation of P-Choline
CTP + P-Choline –> CDP-choline + PPi
* CDP-ethanolamine is generated similarily
8
Q
Biosynthesis of PE, PC, and PS from PA
A
PA–>DAG—>
- DAG + CDP-ethanolamine–> PE + CMP
- PE + 3 SAM –> PC
- PE + Serine –> PS + Ethanolamine
- PS –> PE + CO2
- DAG + CDP-choline–> PC + CMP
9
Q
Biosynthesis of PI, phosphatidylglycerol and cardiolipin
A
- PA + CTP –> CDP-diacylglycerol + PPi
- CDP-diacylglycerol + inositol –> PI + CMP
- PI –(kinase)–>PIP–(kinase)–>PIP2
- CDP-diacylglycerol + glycerol –> phoshphatidylglycerol + CMP
- CDP-diacylglycerol + phosphatidylglycerol –> cardiolipin
- CDP-diacylglycerol + inositol –> PI + CMP
- PIP2: precursor for 2ndary messenger molecule
- PI anchors membrane proteins
10
Q
Respiratory Distress Syndroms (RDS)
A
- deficiency in lung surfactant
- surfactant: dipalmitoylphosphatidyl-choline, phosphatidylglycerol, apoproteins, and cholesterol
- Dipalmitoylphosphatidyl-choline is synthesized by type II granular pneumocytes of the lung
- In adults, RDS can result from the destruction of surfactant producing cells by immunosuppressive chemotherapeutic drugs
- PC=lecithin
- Lecithin/sphingomeylin ratio in amniotic fluid as an indicator of fetal lung maturity. Ratio <2.0, risk of RDS
- reduces surface tension
11
Q
Plasmalogens
A
Same as PC, PS, or PE EXCEPT
- acyl group in PC; alkenyl group in Plasmalogens
- attached via an ester bond in PC; attached via an ether bond in Plasmalogens
- Plasmalogens found in myelin and heart muscle
-
Platelet activating factor (PAF) is a plasmalogen in which an alkyl (not alkenyl) moietyis attached via an ether bond to carbon 1 of the glycerol
- C2 of the glycerol is esterified to an acetyl group
- PAF are released by phagocytes to
- aggregation
- edema, hypotension, and involvedin allergicrxn
12
Q
Degradation of Phospholipids
A
- Phospholipases A1, A2, C, and D hydrolyze phosphoglycerides
*
13
Q
Sphingomyelin synthesis
A
- Palmityl CoA + Serine –> CO2 + CoA –(3 ketosphinganine) + NADPH + H+–> NADP+ –(sphinganine) + FAD–> FADH2 + Sphingosine
- Sphingosine + Fatty acyl CoA —> Ceramide + CoA
- Ceramide + CDP-choline —> Sphigomyelin + CMP
14
Q
Sphingomyelin Degradation
A
- Sphingomyelin –(Sphingomyelinase)–> Ceramide + phosphorylcholine
- Ceramide –(Ceramidase)–>Sphingosine + free FA
15
Q
Glycospingolipids aka glycolipids
A
- derived from ceramides
- head group = monosaccharide (s) or oligosaccharides (via glycosidic linkage)
- no phosphate
16
Q
Neutral glycosphingolipid (glycolipid)
A
- head group is a monosaccharide or oligosaccharide–neutral
- Cereboside monosaccharides:
- galactocerebroside (ceramide + galactose)
- glucocerebroside (ceramide + glucose
- Cerebroside oligosaccharide (globosides)
- found in brain and peripheral nervous tissue
- highly concentrated in myelin sheath
17
Q
Acidic Glycospingolipids (glycolipids)
A
- At physiologic pH, carry a negative charge provided either by N-acetylneuraminic acid (NANA) or by sulfate group
-
gangliosides: found primarily in ganglion cells of CNS
- ceramide oliogosaccharides w/ one or more NANA
- GM1, GM2, GM3
- Accumulation can lead to lipid storage diseases
- ceramide oliogosaccharides w/ one or more NANA
- Sulfatides: galactocerebrosides in which galactose residue has been sulfated
- found in nervous tissue
-
gangliosides: found primarily in ganglion cells of CNS
21
Q
Degradation of Glycospingolipids
A
- degraded by lysosomal enzymes
- Ganglioside GM1 –(ß Galactosidase) –> Ganglioside GM2
- Ganglioside GM2 –(Hexosaminidase A)–> Hematoside GM3
- Hematoside GM3 –(Neuraminidase)–> Lactosyl ceramide
- Globoside –(Hexosaminidase B/A)–> Ceramide trihexoside
- Ceramide trihexoside –(alpha-galactosidase A)–> Lactosyl ceramide
- Lactosyl ceramide –(ß Galactosidase)–>Glc-Cer
- Glc-Cer –(ß Glucosidase)–> Cer
- Choline-P-Cer sphingomyelin –(sphingomyelinase)–>Cer
- Cer-Gal-SO3- –(Arylsulfatase A)–> galactocerebroside
- galactocerebroside –(ß galactosidase I)–>Cer
- Cer –(ceramidase)–>Sphingosine + FA
22
Q
Lipid Storage Diseases
A
23
Q
Tay Sach’s vs. Sandoff’s
A
