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biochem block 3 > phospholipids > Flashcards

phospholipids Flashcards

1
Q

2 main classes of phospholipids

A
  • glycerophospholipids (glycerol backbone)

- sphingolipids (sphingosine backbone)

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2
Q

4 components of glycerophospholipid

A

backbone- glycerol
Head group- variable, esterified via OH to PO4
FA1- saturated (palpitate or stearate)
FA2- unsaturated (arachidonic acid)

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3
Q

where is the site of glycerophospholipid synthesis? how distributed in cell?

A

cytosolic face of ER, following synthesis will travel to golgi for distribution

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4
Q

what is the simplest glycerophospholipid?

A

phosphatidic acid (head group = H)

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5
Q

what results when FA1 or FA2 are removed from a glycerophospholipid?

A

lysophosphoglyceride

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6
Q

what are the functions of lysophosphoglyceride in the cell?

A

signaling or pro-inflammatory

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7
Q

what are the sources of glycerol-3-p?

A
  • from DHAP (liver and adipose)

- free glycerol phosphorylated by glycerol kinase (liver only)

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8
Q

in the synthesis of phosphatidic acid, what is the required activator of the polar head group and hydrophobic tail?

A

CTP (cytidylyl triphosphate)

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9
Q

phosphatidic acid is the precursor for the synthesis of what 2 things?

A
  • glycerophospholipids

- triglycerides

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10
Q

what is the only antigenic human phospholipid?

A

cardiolipin

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11
Q

what is the structure of cardiolipin?

A

2 molecules of esterified phosphatidic acid

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12
Q

where is cardiolipin found?

A

inner mito membrane

bacterial membranes

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13
Q

what is the physiologic role of cardolipin in the mitochondria?

A

cardiolipin contains an ionized “bridge” that acts as a buffer to trap H+ in the inner mito membrane and maintain electron flux in the ETC

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14
Q

what is the action of cardiolipin oxygenate? consequences?

A

cardiolipin oxygenase causes per oxidation of unsaturated acyl chains on cardiolipin, triggers apoptosis

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15
Q

describe apoptosis caused by cardiolipin peroxidation

A

when cardiolipin in peroxidized, a large pore forms in the inner mito membrane that allows for the passage of cytochome C into the cytosol, while in the cytosol, cytochome C binds IP3 to trigger Ca release from SER that induces more cytochrome c movement into cytosol

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16
Q

2 types of ether phospholipids

A
  • alkyl (saturated)

- alkenyl (unsaturated)

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17
Q

2 biologically important alkenyl ether phospholipids

A
  • ethanolamine plasmogen (in myelin)

- choline plasmogen (in heart mm)

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18
Q

main phospholipid component of PAF?

A

phosphatidylcholine

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19
Q

2 reactions mediated by PAF

A

1- acute inflammation

2- anaphylactic shock

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20
Q

what cells are acted on by PAF to produce inflammation/anaphylaxis?

A
  • neutrophils/macrophages = superoxide anions

- platelets = aggregation and degranulation

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21
Q

how does PAF affect the cell membrane?

A

will bind to external PAF receptor, activate transmembrane signaling domain that will trigger phospholipases = phospholipid degradation

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22
Q

main phospholipid component of surfactant

A

dipalmitoylphosphatidylcholine

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23
Q

cells that produce surfactant

A

type II granular pneumocytes

24
Q

purposes of surfactant (3)

A
  • decrease alveolar surface tension
  • prevent alveolar collapse
  • reduce susceptibility for free radial oxidation
25
Q

RDS/hyaline membrane disease

A

in premature infants due to inadequate lung maturity at birth, assess risk with phos-choline:sphingomyelin ratio

26
Q

respiratory failure related to surfactant

A

in adults, caused by damage to type II pneumocytes, commonly asdic with immunosuppressive medication or chemotherapy

27
Q

how is phosphatidylserine synthesized?

A

from phosphatidylethanolamine: serine is exchanged for free serine

28
Q

how is phosphatidylcholine synthesized from phosphatidylserine in the membrane?

A
  • Phos-serine is decarboxylated to phos-ethanolamine
  • PE undergoes 3 successive methylations (donor = SAM)
  • Phos-choline formed
29
Q

after SAM donates methyl group, what is formed?

A

SAH (s-adenosylhomocysteine)

30
Q

what is SAM?

A

s-adenosylmethionine

31
Q

what limits the ability to perform de novo synthesis of phos-choline?

A

availability of methionine

essential aa, often deficient in diet

32
Q

besides de novo synthesis, what is another way that cells can make phis-choline?

A

using the salvage pathway (CDP-choline pathway) that will activate free choline for reincorporation into lipid membranes

33
Q

choline sources (3)

A
  • synthesis in the liver
  • dietary intake (meats, eggs, some veggies)
  • recycling (Phos-choline, sphingomyelin, ACH)- using salvage pathway
34
Q

what can result from deficiency of choline?

A

impairment of brain development and memory

35
Q

general type of enzyme that degrades glycerophospholipids

A

phospholipases

36
Q

phospholipase A1

A

removes FA from sn1 position

37
Q

phospholipase A2

A

removes FA from sn2 position to yield free FA + lysophospholipid; release arachidonic acid that is used for eicosanoid synthesis and removes damaged PUFA from membrane

38
Q

phospholipase C

A

cleaves phosphodiester bond between C3 and phosphate

39
Q

phospholipase D

A

cleaves phosphodiester bond between phosphate and polar head group

40
Q

4 types of phospholipase A2

A

1- cytosolic
2- Ca-independent intracellular
3- secretory
4- pancreatin

41
Q

cytosolic phospholipase A2

A

activated by increased Ca and by phosphorylation by MAP kinase, will release arachidonic acid for eicosanoid synthesis

42
Q

calcium independent intracellular A2

A

involved in turnover and remodeling of phospholipids

43
Q

secretory A2

A

active extracellularly, role in sepsis and inflammation

44
Q

pancreatic A2

A

digestive enzyme, released as zymogen

45
Q

3 components of sphingolipids

A
  • backbone= sphingosine
  • one fatty acid- usually saturated
  • polar head group
46
Q

what is the polar head group in sphingomyelin?

A

choline

47
Q

ABO group determinants are:

A

sphingolipids (specifically glycolipids)

48
Q

what is ceramide?

A

a sphingolipids that is a 2nd messenger and is important for cell differentiation or apoptosis

49
Q

what is the result of interaction between cholesterol and sphingomyelin in the cell membrane?

A

assoc with cholesterol promotes the transition from gel phase to liquid state

50
Q

what are the membrane domains assoc with sphingolipids?

A

caveolae and lipid rafts

51
Q

what enzyme will degrade sphingolipids?

A

sphingomyelinase

52
Q

what disease has a deficiency of sphingomyelinase?

A

Niemann-Pick type 1

53
Q

what are the sx of niemann-pick type 1?

A

enlarged liver and spleen due to accumulation of lipids, mental retardation, death in childhood

54
Q

what are glycolipids?

A

sphingolipids with sugar as the polar head group

55
Q

2 types of glycolipids

A
  • cerebroside- ceramide + one sugar

- ganglioside- ceramide + branched sugar

biochem block 3 (7 decks)

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