Lecture 12 - Lipids and lipid membranes Flashcards

1
Q

what does lipid refer to?

A

-a large heterogeneous group of fat soluble biological compounds

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2
Q

what compounds are considered lipids? (7)

A
  1. fatty acids
  2. triglycerols
  3. glycerophospholipids
  4. sphingolipids
  5. steroids
  6. isoprenoids (terpenoids)
  7. eicosanoids
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3
Q

what are 4 major functions of lipids?

A
  1. membranes
  2. energy storage
  3. signaling (as hormones)
  4. vitamins
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4
Q

what are fatty acids?

A

-carboxylic acids with long hydrocarbon tail?

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5
Q

what are the most common types of fatty acids?

A

C16 or C18 fatty acids

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6
Q

what are saturated carbon bonds?

A

single C-C bonds

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7
Q

what are partially unsaturated?

A

some C=C double bonds

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8
Q

double C=C bonds on fatty acid tails are always ____

A

cis

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9
Q

where does the first C=C bond often start for unsaturated fatty acids?

A

C9

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10
Q

if there is more than one C=C bond, how often do they usually repeat?

A

-every 3 carbons

C9, C12, C15 etc.

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11
Q

what do cis double bonds create?

A

rigid kinks in the fatty acid tail

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12
Q

what are triglycerols?

A

esters made from attaching fatty acids to a glycerol

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13
Q

what are examples of triglycerols?

A
  • fats and oils in plants and animals

- usually complex mixtures

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14
Q

what do animals use triglycerols for?

A

-long-term energy storage

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15
Q

where is fat deposited in?

A

fat cells in side adipose tissues, mostly subcutaneous

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16
Q

what is a function of glucose?

A

-glucose stored in the form of glycogens can release energy rapidly

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17
Q

what is characteristic of glycogens and energy storage?

A
  • lower density

- highly hydrated and more oxidized

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18
Q

do fats contain O?

A
  • anhydrous

- contain almost no O

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19
Q

-typical fat content of humans allow them to survive starvation for ______

A

2-3 months

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20
Q

how are glycerophospholipids obtained?

A

-by replacing a fatty acid branch in triglycerol by a PO4-linked polar head group

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21
Q

what can cleave glycerophospholipids be cleaved by?

A

various phospholipase enzymes

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22
Q

what are the hydrolysis products of cleaved phospholipids used as? why?

A
  • signal transducers

- they are fat-soluble but easily distinguishable from membrane lipids

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23
Q

what are plasmalogens?

A
  • variation of a glycerophospholipid

- one of the ester is modified to an ether with an alpha C=C bond

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24
Q

plasmalogens are easily ______

A

oxidized

25
Q

why are plasmalogens easily oxidized?

A

-thought to act as oxygen free radical scavengers

26
Q

what is the parent of a sphingolipid?

A

sphingosine?

27
Q

what is a sphingosine?

A

-a glycerol modified by one amine substitution on C2 and a hydrocarbon chain on C3 instead of an H through a C=C bond

28
Q

what is a sphingomyelin?

A

-key component of electrically-insulating myelin sheath around nerve cells

29
Q

what is a sphingolipid?

A
  • glycerophospholipd modified by an amide (instead of an ester) linkate to one of the fatty acids
  • OH on C1
  • C=C double bond for other fatty acid
30
Q

what are gangliosides and cerebrosides classified as?

A

sphingolpids

31
Q

what are 4 functions of gangliosides?

A
  1. hormone binding sites
  2. cell recognition determinants
  3. cell signaling mediators
  4. receptors for small proteins
32
Q

gangliosides are usually ____ on the cell surface

A

exposed

33
Q

cerebrosides have only ______ linked to the ceramide

A

one sugar

34
Q

what is the structure of a steroid?

A

-4-fused ring

35
Q

what is cholesterol?

A

a cell membrane additive

36
Q

what is cholesteryl stearate?

A

esterified by a fatty acid

37
Q

what do many steroids act as?

A

hormones

38
Q

what is the function of cortisol?

A

reduce inflammatory reactions

39
Q

what is the function of aldosterone?

A

-regulates the excretio nf salt + water from the kidney

40
Q

what is the function of testosterone + estradiol?

A

affects sexual development

41
Q

What is vitamin D?

A

Ca2+ regulatio steroid hormone

42
Q

what does vitamin D do?

A
  • promotes intestinal absorption of Ca2+ from dietary calcium
  • increase calcium deposition into teeth + bone structures
43
Q

what is the signature of an isoprenoid?

A

C-C single and double bond structure

44
Q

where are isoprenoids found?

A
  • plants
  • fungus
  • bacteria
45
Q

what are the functions of isoprenoids?

A
  • signaling molecules (pheromones)
  • pigments
  • for defense (toxins)
46
Q

What is coenzyenzyme Q (coQ)/ubiquinone used for?

A

electron transport

47
Q

what is retinoic acid used for?

A

vision

-tissue repair

48
Q

what is vitamin E

A

an antioxidant

formed from beta carotene

49
Q

what are the functions of phylloquinone/menaquinone?

A

blood clotting

50
Q

where are Eicosanoids derived from?

A

-arachidonic acid

51
Q

what do eicosanoids do?

A

fever + pain

  • regulate blood pressure
  • blood coagulation
  • reproduction
52
Q

what are most lipids in the cell used for?

A

-form the plasma membrane or membranes separating cell compartments

53
Q

what are major components of the cell membrane?

A

-amphiphilic phospholipid molecules

54
Q

what do phospholipids form?

A

bilayers with small curvature

55
Q

what do phospholipids spontaneously form?

A

liposomes

56
Q

how are bilayers ordered?

A

they are inherently disordered

57
Q

the ordering of the phospholipids are _____ dependent

A

temperature

58
Q

how do phospholipids form function membranes?

A

they must stay above the ordering transition temperature

59
Q

what happens to lipid bilayers below the transition temperature?

A
  • stuck in a solid-like state

- lacks the fluidity needed for membranes to function properly