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FunMed Week 2 > Lipids and Membranes > Flashcards

Lipids and Membranes Flashcards

1
Q

lipids are found in which compartments in the body?

A
  1. plasma
  2. adipose tissue
  3. biological membranes
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2
Q

what forms the boundaries of cells?

A

biological membranes - proteins float in a sea of lipids.

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3
Q

:)

A

:)

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4
Q

what are membrane lipids?

A

small molecules that have hydrophilic and hydrophobic elements:

the head of of lipids are hydrophilic and are polar… tails are hydrophobic fatty acyl chains.

together get lipid bilayer

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5
Q

how big is lipid bilayer?

A

5nm

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6
Q

describe the characteristic of membrane proteins with regards to their hydrophobic / hydrophilic structure

A

amphiphilic

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7
Q

what are fatty acids?

A

long hydrocarbon chains of different lengths WITH a terminal carboxyl group

can be saturated (only single bonds) or unsaturated (contains double bond)

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8
Q

what is a monounsaturated fatty acid?

A

fatty acid with a single double bond

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9
Q

what is a polyunsaturated fatty acid?

A

fatty acid with two or more double bonds

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10
Q

why are essential fatty acids (EFA) essential?

A
  1. cant be synthesised by own bodies - have to ingest.

2. important for maintaining homeostatic balance

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11
Q

what are EFA and NEFA used for?

A 
integrity of cell membrane
function of NS
vision
cognition and memory
nutrient metabolism
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12
Q

what is fatty acid synthesis?

A

coming together of acetyl CoA and NADPH via enzyme action

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13
Q

where does fatty acid synthesis occur?

A

in the cytoplasm of cell

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14
Q

how are fatty acids stored in the body?

A

as triglycerides - three fatty acids bound to a glycerol molecule.

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15
Q

why is good that fatty acids are stored as triglycerides?

A
  1. theyre hydrolysable (used in aerobic resp)

2. efficient energy stores

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16
Q

what do cis-double bonds do for structure of fatty acid?

A

produces a kink in the linear structure of fatty acid chain

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17
Q

e.g. of NEFA?

A

oleic acid

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18
Q

oleic acid is most abundant fatty acid in which human tissue?

A

human adipose tissue

second overall

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19
Q

how do u make oleic acid?

A

stearic acid + desaturase -> oleic acic

baso stearic acid (18C bit no double bond), oleic acid (18C but DOUBLE BOND

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20
Q

what are the only two EFA?

why are they EFA?

A
  1. alpha - linolenic acid (an omega 3 FA)
  2. linoleic acid. (an omega 6 FA).

bc no desaturase enzyme needed to remove H from omega 3/6

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21
Q

what are micelle molecules?

A

Micelles are lipid molecules that arrange themselves in a spherical form in aqueous solutions

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22
Q

what are micelle molecules?

A

molecules that have hydrophobic hydrocarbon tails and polar, hydrophilic heads.

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23
Q

what are leaflets?

what happens to them?

A

the two opposing sheets of phospholipid bilayer

lipid bilayers tend to close in on themselves and self seal as it is more energetically feasible to do so

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24
Q

what do lipids do with regards to biomolecular sheets?

why do they do this?

A

spontaneously form closed biomolecular sheets (spheres), that are barriers to the flow of most solute.

why?
MORE ENERGETICALLY FAVOURABLE

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25
Q

what do most lipids owe their hydrophobic properties to?

A

their fatty acids

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26
Q

what is a liposome?

A

small spherical sac of phospholipid molecules enclosing an aq. compartment

can be loaded with molecules such as DNA or drugs

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27
Q

what is the favoured structure for most phospholipids and glycolypids in aq media?

why?

A

bimolecular sheet (rather than micelle)

WHY:
two fatty acid chains are too bulky to fit into interior of micelle

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28
Q

what causes lipid bilayers to be formed?

what does this mean the structure is like of lipid bilayers?

A

hydrophobic interactions:

  1. van der Waals attractive forces of tails cause them to fit closely together
  2. electrostatic and hydrogen bonding attraction between the polar head groups and water molecules
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29
Q

where do you find long circulating lipsomes?

A

concentrate in regions of increased blood circulation - e.g. tumours / inflammation

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30
Q

what are exosomes?

A

liposomes containing a cargo. use cell to cell communication

31
Q

what is the fluid mosaic model?

A

model that presents the membrane as a fluid like phospholipid bilayer into which proteins and lipids are embeded

32
Q

what does the enzyme flippase do?

A

allows the movement of lipids between the outer and inner bilayers leaflets

33
Q

what is lateral diffusion?

A

the movement of lipids and proteins between the membrane surface

34
Q

in order to perform physiological functions, what do membrane proteins do?

A

membrane proteins rotate and diffuse laterally in 2D

35
Q

what is Flip-Flop movement? how often does it occur?

A

movement of membrane lipid from one leaflet to another - RARE

36
Q

what can acyl chains do within the bilayer?

A

can flex within the bilayer

37
Q

what influences membrane fluidity?

A
  1. the properties of the fatty acid chain of the membrane

2. the motions of the lipids and proteins

38
Q

what is mosaicity?

A

describe the membrane proteins embedded in the bilayer

39
Q

how deep is the lipid bilayer?

A

50A deep

40
Q

what are the three major classes of membrane lipids?

A
  1. phospholipids - have phosphate group
  2. glycolipids - have a sugar group
  3. cholesterol
41
Q

how else can you further classify phospholipids?

A
  1. glycerolphospholipids - link between FA is glycerol

2. sphingolipids - link between FA is sphingosene

42
Q

how would you describe the symmetry of lipid bilayer ?

A

phospholipids and glycolipids are ASYMMETRICALLY distributed

43
Q

what is structure of phospholipid?

A
  1. fatty acid (one or more)
  2. platform to which fatty acid is attached
  3. phosphate
  4. alcohol attached to phosphate
44
Q

what can phospholipid platforms be?

A

glycerol
three C alcohol
sphingosine

45
Q

what are the common alcohols of glycerophospholipids ?

A

ethanolamine
choline
inositol

46
Q

describe structure of glycolipid

A

sugar + lipids

47
Q

what are glycolipids derived from?

A

sphingosine

48
Q

what is structure of cholesterol?

A

steroid built from four linked hydrocarbon rings. a HC tail is linked to steroid at one end and hydroxyl group at the other

49
Q

what makes kink in fatty acid tail of phospholipids?

A

2 C bond

50
Q

where are sugar residues of glycolipid found in lipid bilayer?

A

extracellular side of the membrane

51
Q

sphingolipids contain covalently bound sugars are aka as?

A

glycolipids

52
Q

what is function of the glycolipid? give two e.gs

A

recognition site for cell to cell interaction.

  1. immune response - selectins on surface of leukocytes and endothelial cells bind to carbs of glycolipids to start cell repsonse
  2. blood types - determined by the oligosaccaharide attached to a specific surface on rbc
53
Q

describe the structure of cholesterol

A

bulky steroid nucleus with a hydroxyl group at one end and flexible HC tail

54
Q

cholesterol is a key regulator of ….. …..?

A

membrane fluidity -

55
Q

where are the hydroxyl group and HC tail of cholesterol located in bilayer?

A

hydroxyl group: H bond with with phospholipid head group

HC tail: non-polar core of the bilayer

56
Q

the different X of cholesterol compared to phospholipid causes cholesterol to Y?

A

X - shape of cholesterol c.f. phospolipid

Y - disrupt the regular interactions between fatty acid chains

57
Q

what increases / decreases membrane fluidity?

A

DUE TO NATURE OF CHOLESTEROL:

drop in temp - decreases fluidity

increase in temp - increases fluidity

58
Q

Hoe does cholesterol integrate with glycerophospholipids?

A
  1. head of hydroxyl of chol. associates with head of neighbouring glycerophospholipids (HEAD TO HEAD)
  2. steroid ring and acyl chain intercalate (TAIL TO TAIL)
59
Q

what is effect of cholesterol and glycerophospholipid together on bilayer?

A

= more densely packed / less fluid and perm

60
Q

what does cholesterol do to sphingolipids? why is it important?

A

sphingolipids have long straight FA that are densely packed.

chol reduces the packing density - makes the membrane more fluid = IMPORTANT FOR ENDOCYTOSIS

61
Q

chol + X = less fluid?

chol + Y = more fluid?

A

X - glycerophospolipids

Y - sphingolipids

62
Q

chol is a precursor for? and where is each precursor made?

A
  1. steroid hormones - ADRENAL GLANDS
  2. sex hormones - TESTES AND OVARIES
  3. vit. D - SKIN
  4. bile acids - LIVER
63
Q

how much do humans normally synthesise of chol per day? how much absorbed per day?

A

1g

30 - 60% absorbed

64
Q

which membrane transporter absorbs dietary chol? need to know this???chol. homeostasis?

A

NPC1L1

65
Q

what is best way to reduce chol? what does it cause if dont?

A

eat less chol. or eat more phytosterols

have more circulating chol -> lead to atherosclerosis

66
Q

how can stop chol. in blood/

A

take statins - inhibits intracelllar synthesis of chol in body by stopping the HMG-CoA reductase enzyme (key enzyme in pathway)

67
Q

what is membrane surrounding a fat droplet like? why is it like this?

A

fat contents are hydrophobic. only need phosphoL monolayer

68
Q

what are lipid rafts?

A

highly dynamic complexes formed between chol and specific lipids.

HAVE DIFFERENT LIPID AND PROTEIN CONTENT FOR SPECIALISED FUNCTION

69
Q

function of lipid rafts?

A

bring together proteins that work together

70
Q

the outer and inner surfaces of all known bio membranes have…

A

different components and enzymatic activities - depends on function of cell.

(ALL ASYMMETRICAL)

71
Q

what are the limitations to fluid mosaic model?

A

although some proteins can diffuse laterally within the membrane, others are anchored in protein complexes or tied to ECM

the lipid content of rafts important for raft integrity

lipids can also be signally molecules

lipids can also modulate membrane protein activity

72
Q

why do different chem structure of alcohols have different effect on membrane structure?

A

short chain alcohols have an amphiphillic character and do less damage to the cell c.f. long chain

73
Q

omega3 and 6 are important precursors of …

A

paracrines (involved in cell signalling)

74
Q

cox-2 enzyme in the paracrine pathway is a target for ?

A

NSAIDS

FunMed Week 2 (10 decks)

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