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IMS > Membranes & Proteins > Flashcards

Membranes & Proteins Flashcards

1
Q

Function of membranes

A
  • functional barrier
  • energy source
  • organise & regulate enzyme activity
  • facilitate signal transduction
  • supply substrates for biosynthesis
  • protein recruitment platform
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2
Q

What do membranes consist of

A
  • lipids

- proteins

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3
Q

What are the three types of membrane lipids

A
  • glyceropphospholipids (phospholipids)
  • sphingolipids –> glucoshpingolipids (glycolipids)
  • sterols
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4
Q

What are fatty acid chains

A
  • long aliphatic carbon chains

- terminal carboxylic acid

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5
Q

How does hydrophobic affect water molecules

A

Reorganise

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6
Q

What happens if hydrophobic molecules cluster together

A
  • smaller no. of water molecules affected —> lower energy cost
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7
Q

What could lipids form

A
  • bilayers

- micelles

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8
Q

How are fatty acids named

A

XX:Y n-y

XX: C atoms
Y: =s
n-y: position of 1st double bond (starting at methyl terminus)

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9
Q

Describe saturated lipids

A
  • no =

- straight

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10
Q

Describe unsaturated lipids

A
  • contains =
  • cis = —> 30 degrees kink
  • trans = —> no effect
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11
Q

What does diff. in length and saturation of fatty acids influence

A

How phospholipids pack against one another

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12
Q

Where does chemical diversity in glycerophospholipids arise from

A
  • combination of two fatty acids
  • sn-1 position linkage
  • head group linkage
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13
Q

Describe sn-1 fatty acid (in glycerophospholipids)

A
  • saturated

- monounsaturated

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14
Q

Describe sn-2 fatty acid (in glycerophospholipids)

A
  • more monounsaturated

- polyunsaturated

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15
Q

What are the anaionic phospholipids

A
  • PS
  • PI
  • PG
  • CL
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16
Q

What is the charge of zwitterionic phospholipids

A

Zero

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17
Q

What do PS & PE glycerophospholipids contain and what does that help towards

A

Reactive amines

H-bonds

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18
Q

Which glycerophospholipids are bulky and what does that help with

A
  • PI, PC & CL

- their packing

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19
Q

What lipids are found in mitochondria

A

PG & cardiolipins

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20
Q

How are PIPs generated

A

Head group phosphorylation at positions 3, 4 & 5 of phosphatidylinositol

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21
Q

How many different PIP species are there

A

7

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22
Q

How saturated are the tails of PIP

A

Saturated

Polyunsaturated

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23
Q

What is the most abundant PIP in mammalian plasma membrane, where is it found

A

PI(4,5)P2

Inner leaflet of plasma membrane

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24
Q

What does PTEN protein do

A

Convert PI(3,4,5)P3 to PI(4,5)P2

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25
Q

What do sphingolipids consist of

A
  • sphingolipids base
  • N-acyl chain
  • head group
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26
Q

What is the most common sphingolipid

A

Sphingomyelin (SM)

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27
Q

What head group does sphingomyelin have

A

PC

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28
Q

The amide gp on sphingolipids have the ability to h bond, what does that help with

A

Interactions of sphingolipids with cholesterol and polar parts of proteins

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29
Q

Describe N-acyl chain in sphingolipids

A
  • more saturated

- longer than acyl chains of glycerophospholipids

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30
Q

What are the different head groups of glycosphingolipids

A

Oligosaccharides

sugar building blocks

31
Q

Where are glycosphingolipids found

A

Outer leaflet of membrane, 5% of membrane

32
Q

Which groups are exposed to cell surface in glycosphigolipids

A
  • sugar
  • help with cell-cell adhesion
  • membranes act as recognition sites
33
Q

Name 3 components of glycolipids

A

Ganglioside GM1, 2, 3

34
Q

Where do h bonds form in glycolipids

A

Between sugars and lipids tail

35
Q

What is self-aggregation of GM1 driven by

A

Sugars

36
Q

What groups do sterol have

A
  • hydroxyl group

- hydrocarbon tail

37
Q

What is the most common sterol in animals

A

Cholesterol

38
Q

What sterols is found in yeast & fungi membrane

A

Ergosterol

39
Q

What sterols are found in plants

A
  • sitosterol

- stigmasterol

40
Q

What can cholesterol shape allow it to do

A

Align better with saturated site chains

41
Q

Cholesterol interaction with POPC

A

OH group is not buries in complex

42
Q

Describe interaction between cholesterol and sphingomyelin

A
  • H bond: OH of cholesterol & NH of sphingolipid

- OH of cholesterol masked by polar head of sphingomyelin

43
Q

What are the three different membrane curvatures

A
  • cylindrical (flat membrane)
  • conical (negative membrane)
  • inverted-conical (positive membrane)
44
Q

What lipids are cylindrical

A
  • PC

- PS

45
Q

What lipids are conical

A
  • PE

- PA

46
Q

What lipids are inverted-conical

A
  • lysosome-GPLs

- phosphoinositides

47
Q

What does -ve curvature of PE lead to

A
  • generation of non-bilayer

- eg fusion

48
Q

What are the types of lipid diversity

A
  • chemical/structural

- compositional

49
Q

Describe the lipid asymmetry in erythrocytes membranes

A
  • 50% cholesterol
  • high conc. of PC & SM in outer leaflet
  • high conc. of PS & PE in inner leaflet
50
Q

Give an example of functional importance of lipid asymmetry in cell signalling

A
  • PS translocate to extra cellular layer when cell dies
  • signals neighbouring cells, macrophages
  • phagocytise dead cell
51
Q

How does movement of PS occur

A

Via scramblases

52
Q

What direction are secondary signalling messengers oriented towards

A

Interior of cell

53
Q

When does lipid interdigitation occur & what does it do

A
  • Lipid length asymmetry in membranes

- Coupled two leaflets together

54
Q

What are the directions of lipid movement

A
  • rotational
  • lateral
  • transverse
55
Q

What is rotational movement

A
  • spinning of lipids around axis
  • doesn’t alter positions
  • affects interactions with neighbouring molecules
56
Q

What is lateral movements

A
  • neighbouring lipids exchange places

- lipids change position within bilayer

57
Q

What is transverse movement

A
  • exchange of molecules between leaflets

- lipids move across bilayer by transverse diffusion or proteins

58
Q

What is the difference between lipids composition of tumour tissues (lung cancer) and normal tissues

A
  • PI higher in tumour

- SM lower in tumour

59
Q

What is different about lipid composition in tumour tissues in breast cancer

A

PI, PE, PC and SM sig. higher in tumour

60
Q

Which lipid is increased in type ii diabetes, Alzheimer’s and CF

A

Ceramide

61
Q

What lipids are increased in outer leaflet of thalassaemic and diabetic red cells

A
  • PS

- PE

62
Q

What phases are covered by lamellar phase

A
  • lamellar liquid crystalline (liquid disorder)
  • solid gel
  • liquid-ordered
63
Q

What does the adopted phase depend on

A

Lipid structure

64
Q

What are lipid droplets

A
  • storage organelles
  • maintain lipid
  • maintain energy homeostasis
65
Q

What are hydrophobic cores of neutral lipids enclosed by (droplets)

A

Phospholipid monolayer

- has specific proteins

66
Q

Where do lipid droplets originate from

A
  • ER
67
Q

When are lipid droplets initiated

A

Neutral lipids are produced

68
Q

What do neutral lipids result from

A
  • esterification of a fatty acid to triacylglycerol or sterol to sterol ester
69
Q

Where are neutral lipids dispersed at low concs.

A

Between leaflets of ER bilayer

70
Q

What can impairment of fatty acid storage in lipid droplet result in

A
  • type 2 diabetes

- non-alcoholic fatty liver disease

71
Q

Describe spontaneous transverse movement

A
  • bidirectional
  • no energy
  • non-specific
72
Q

describe P-type flippase transverse movement

A
  • inward movement
  • ATP
  • specific
73
Q

Describe ABC flippase transverse movement

A
  • outward
  • ATP
  • specific
74
Q

Describe scramblase transverse movement

A
  • bidirectional
  • no energy
  • non-specific
  • Ca2+ dependent

IMS (18 decks)

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