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Molecular and Cellular Princples of Medicine > Unit 6 - Complex Lipids in Health and Disease > Flashcards

Unit 6 - Complex Lipids in Health and Disease Flashcards

1
Q

what are the 3 families of lipids, and their subgroups?

A
  1. glycerolipids: TGs, glycerophospholipids, and ether glycerolipids
  2. phospholipids: glycerophospholipids, ether glycerolipids, and sphingophospholipids
  3. sphingolipids: sphingophospholipids and glycolipids
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2
Q

structure of glycerophospholipids

A

predominant phospholipids/glycerolipids in cell membranes

  • amphipathic polar (alcohol) head group attached to DAG via phosphodiester bond to C3
  • 2 nonpolar FA chains form ester bonds to C1/2
  • -C2 FA often unsaturated
  • -embedded in hydrophobic core of bilayer
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3
Q

what is the simplest glycerophospholipid?

A

phosphatidic acid

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4
Q

what are the 3 major glycerophospholipids in cell membranes?

A

phosphatidylserine
phosphatidylethanolamine
phosphatidylcholine

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5
Q

what is cardiolipin (diphosphatidyl glycerol)? where is it found? what does it do?

A

2 molecules of phosphatidic acid are esterified thru phosphate to a glycerol

  • found in membranes of bacteria and eukaryotic cells, in IMM
  • supports structure and function of certain respiratory complexes in ETC
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6
Q

structure of plasmalogens

A

FA at C1 has unsaturated alkyl group via ether linkage (unsaturated ether glycerophospholipids)

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7
Q

what are the 2 major plasmalogens (unsaturated ether glycerophospholipids) in mammals?

A

phosphatidalcholine (enriched in heart muscle)

phosphatidalserine

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8
Q

what is platelet activating factor?

A

has saturated alkyl group linked by ether linkage to C1 (saturated ether glycerolipid) and acetyl group at C2
-made by many cells, and binds to specific surface receptors stimulating thrombotic and acute inflammatory responses

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9
Q

what is sphingomyelin structure? what is special about sphingomyelin?

A

backbone is amino alcohol sphingosine
-LCFA attached to amino group, to make ceramide
-alcohol group at C1 of sphingosine becomes esterified to phosphoryl choline to make sphingomyelin
(ceramide = sphingosine + LCFA)
(sphingomyelin = ceramide + choline)
-SM is the only major spingophospholipid in humans, and found in many membranes
-highly enriched in myelin sheath

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10
Q

structure of glycosphingolipids

A

similar to sphingomyelin, except don’t have a phosphate group, but a sugar attached by an O-glycosidic bond
-the sugar is the polar head group, and the ceramide is the hydrophobic tail that inserts into hydrophobic core of membranes

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11
Q

what are cerebrosides? where are they found most

A

simple uncharged glycosphingolipids with one galactose or glucose

  • found mostly in CNS and PNS tissue
  • -enriched in myelin sheath
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12
Q

what are globosides?

A 
ceramide oligosaccharides (attach monosaccharides to glucocerebroside)
-include substituted sugars like N-acetyl galactosamine
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13
Q

what are gangliosides? what is their structure? where are they found?

A

derivatives of globosides, in that they have negatively charged acidic glycosphingolipids

  • have one or more sialic acid residues and named M(ono), D(i), T(ri), Q(uatro), etc.
  • -additional numbers designate sequence of sugars attached to ceramide
  • found mostly in ganglion cells of CNS (enriched at nerve endings)
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14
Q

what are lipid rafts?

A

specialized choelsterol, sphingolipid, and glycolipid rich domains within membrane leaflets that regulate activity of membrane enzymes and receptors
-diverse assembly of signaling molecules, involvement in membrane PRO and receptor trafficking, regulating neurotransmission

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15
Q

what are the 2 pathways for phospholipid synthesis? where does it start?

A

both start with phosphatidic acid in SER

  1. Pi cleaved by phosphatase to make DAG, which reacts with activated CDP-head group to make glycerophospholipid and release CMP
  2. PA reacts with CTP to release PPi and CDP-DAG, which interacts with G3P (makes phosphatidylglycerol) or PG (makes cardiolipid or inositol to make phosphatidylinositol)
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16
Q

what are interconversions that can occur between phospholipids?

A
  • PS formed by base exchange RXN from PE, and converted back by decarboxylase with PLP (B6) coenzyme
  • PE converted to PC by 3 methylations of head group, by N-methyltransferase with SAM methyl donor
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17
Q

what is dipalmitoylphosphatidylcholine and how is it related to respiratory distress syndrome?

A

DPPC is PC with C1 and C2 esterified to palmitate

  • produced and secreted by type II pneumocytes, and major lipid component of surfactant (along with apo-PRO Sp-A/B/C, PG, and cholesterol
  • deficiency will caues RDS in neonates
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18
Q

how are cardiolipin and PI (glyceroPLs) made?

A

phosphatidic acid + CTP –> CDP-DAG

  • if inositol is added, PI is made, which can make PIP2
  • if phosphatidylglycerol is made, cardiolipin is made
19
Q

how is plasmalogen made?

A

DHAP (from glycolysis) C1 reacts with fatty acyl

  • FA exchanged for fatty alcohol made by reduction of FA by 2 NADPH to make ether linkage
  • keto gorup of C2 is reduced to alcohol, and FA esterified into C2
  • polar head groups added as normal
  • final reduction of alkyl group in ether linkage to C1 makes alkenyl group of plasmologen (DB between C1 and C2)
20
Q

what is Zellweger’s syndrome?

A

decreased plasmalogen causes decreased peroxisomes

21
Q

how is ceramide made?

A

serine + PCoA –> dihydrosphingosine + CoA + CO2

  • 22 C FA-CoA acylated at amino group to make amide bond
  • product is oxidized, DB is formed, and ceramide created
22
Q

what is ceramide the precursor of?

A

sphingolipids

23
Q

what do glycosyl transferases do?

A

add CHO monomers to ceramide to make globosides (more than 1 CHO)

24
Q

what do sulfotransferases do?

A

use sulfate carrier PAPS to convert galactocerebroside to sulfatide (negative charge)

25
Q

how are glycerophospholipids degraded?

A

phospholipases in all tissues and pancreatic juice (also snake/bee venom, pathogenic bacteria)

26
Q

where and what does phospholipase A1 do?

A

present in mammalian tissues

-cleaves off FA at C1 and C2, leaving behind lysophospholipids

27
Q

what are lysophospholipids?

A

phopsholipids that lack 1 acyl group

28
Q

where and what does phopsholipase A2 do? what does it act on and what inhibits it?

A

in mammalian tissues, pancreatic juice, snack, bee venoms

  • proenzyme is activated by trypsin, and needs bile salts for activity
  • acts on PI to release arachidonic acid
  • inhibited by glucocorticoids like cortisol
29
Q

where and what does phospholipase C do?

A

found in liver lysosomes and alpha-toxin of clostridia and other bacilli

  • membrane-bound is activated by PIP2, so plays role in making 2nd messengers
  • cleaves off phosphorylated head gropu to make DAG
30
Q

where and what does phospholipase D do?

A

in signal transduction to make phoshatidic acid from PC, and DAG from PA
-IOW, cleaves off head group

31
Q

how is phosphatidylinositol related in cell signaling?

A

PI most frequently has stearic acid associated with C1, and arachidonic acid on C2

  • serves as reservoir for AA, b/c released by phospholipase A2
  • phosphorylation of PI makes PIP2, which is cleaved after hormone binds to GPCR, to activate PLC
  • PIP2 –> DAG and IP3
  • -DAG stimulates PKC, and IP3 increases Ca++ release
32
Q

what does “last on, first off” mean?

A

specific lysosomal enzymes cleave specific glycosidic bonds in “last on, first off” order

33
Q

what happens when a specific lysosomal hydrolase is deficient or defective? what are these diseases called?

A

sphingolipids accumulate (only one per disease)

  • sphingolipidoses are lysosomal storage diseases caused by defects or diminishment
  • -cause premature death and neurologic problems, since nerve tissue are enriched in glycospohingolipids
34
Q

how are sphingolipidoses diagnosed?

A
  1. enzyme assays in cultured fibroblasts or peripheral leukocytes
  2. histologic examination of affected tissue
  3. analysis of DNA
35
Q

which diseases are more frequent in Ashkenazi Jewish population?

A

Gaucher, Tay-Sachs, and Niemann-Pick disease

36
Q

what are treatments for some sphingolipidoses?

A
  1. gene therapy (Gaucer, Fabry)
  2. bone marrow transplantation (Gaucher)
  3. substrate reduction therapy (Gaucher)
37
Q

what accumulates and happens in Tay-Sachs disease?

A

accumulation of gangliosides (GM2) due to deficiency of GM2 activator PRO or beta-hexosaminidase A

  • rapid, progressive, and fatal neurodegeneration
  • blindness
  • cherry-red macula
  • muscular weakness
  • seizures
38
Q

what accumulates and happens in Gaucher disease?

A

accumulation of glucocerebrosides due to deficiency of beta-glucosidase/glucocerebrosidase

  • most common lysosomal storage disease
  • hepatosplenomegaly
  • osteoporosis of long bones
  • CNS involvement in rare infantile and juvenile forms
  • enzyme replacement therapy as treatment
39
Q

what accumulates and happens in metachromatic leukodystrophy?

A

accumulation of sulfatides due to arylsulfatase A, or activator PRO saposin B, deficiency

  • cognitive deterioration (demyelination)
  • progressive paralysis and dementia in infantile form
  • nerves stain yellow-brown with cresyl violet
40
Q

what accumulates and happens in Krabbe disease (globoid cell leukodystrophy)?

A

accumulation of galactocerebrosides due to beta-galactosidase/galactocerebrosidase deficiency

  • mental/motor deterioration
  • blindness/deafness
  • near total loss of myelin
  • globoid bodies (glycolipid-laden macrophages) in white matter of brain
41
Q

what accumulates and happens in Farber disease?

A

accumulation of ceramide due to ceraminidase deficiency

  • painful and progressive joint deformity
  • subcutaneous nodules of lipid laden cells
  • hoarse cry
  • tissues show granulomas
42
Q

what accumulates and happens in Nieman-Pick disease

A

in both A and B type, accumulation of sphingomyelin due to deficiency in sphingomyelinase

  • hepatosplenomegaly
  • cherry red macula
  • neurodegeneration in A
43
Q

what accumulates and happens in Fabry disease?

A

X-linked accumulation of globosides

  • red-purple skin rash
  • kidney and heart failure
  • burning pain in lower extremeties
  • enzyme replacement therapy treatment
44
Q

what accumulates and happens in GM1 gangliosidosis?

A

accumulation of GM1 and keratan sulfate due to beta-galactosidase deficiency

  • neurologic deterioration
  • hepatosplenomegaly
  • skeletal deformities
  • cherry-red macula in infantile form

Molecular and Cellular Princples of Medicine (42 decks)

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