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IMS > S+F OF THE PLAMSA MEMBRANE > Flashcards

S+F OF THE PLAMSA MEMBRANE Flashcards

1
Q

what are the 4 components of the eukaryotic cell?

A

plasma memb
nucleus
memb-bound organelles
cytoskeleton

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2
Q

why does the interior of the cell need to be physically separated from the surrounding environment?

A

To keep desirable substances in

To keep undesirable substances out

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3
Q

what is the function of the plasma membrane?

A 
Barrier
Sites of metabolic activities 
Ion transport
Cell signalling 
Cell shape
Cell-cell interactions
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4
Q

what is hypotonic?

A

Cells swelling

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5
Q

what is hypertonic?

A

cell shrinking

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6
Q

what happens if the membrane is ruptured?

A

escape of cell contents

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7
Q

what is compartmentalisation?

A

Applies to most internal organelles

Needed for chemical activities

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8
Q

what is Robertson’s “unit membrane”?

A

Membranes found to have “railroad track” structure

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9
Q

what is the structure of the unit membrane?

A

Two dark lines separated by a lightly stained central zone: “A trilaminar (three-layered) staining pattern”

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10
Q

what does the Triliaminar staining pattern by TEM show?

A

2 dark lines: outer & inner layer (containing the polar head groups)
separated by light central space (containing the hydrophobic region of the lipid molecules which do not stain)

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11
Q

what does the Fluid Mosaic Model show?

A

2 fluid layers of lipid

Proteins within or on lipid layers

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12
Q

how are lipid molecules arranged in the plasma membrane?

A

asymmetrically distributed

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13
Q

what is amphiphilic?

A

hydrophilic & hydrophobic regions

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14
Q

what is the polar head?

A

a hydrophilic (water-loving)

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15
Q

what are non polar tail?

A

a hydrophobic (water-fearing)

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16
Q

give examples of membrane lipids

A

phospholipids
glycolipids
sterols

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17
Q

what are phospholipids?

A

2 hydrocarbon tails; usually fatty acids
Tails differ in length between 14 -24 C atoms long
Cis-double bonds in one tail creating a small kink

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18
Q

how are lipid molecules arranged in phospholipids?

A

spontaneously aggregate to keep their hydrophobic tails in the interior and expose their hydrophilic heads to water

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19
Q

what are the 2 ways lipids can be arranged?

A

cone-shaped

cylinder-shaped

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20
Q

what is cone-shaped?

A

lipid molecules (single chain) form micelles

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21
Q

what is cylinder-shaped?

A

phospholipid molecules (double tailed) form bilayers

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22
Q

what are phosphoglyceride?

A

glycerol-based phospholipid

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23
Q

give examples of phosphoglyceride in the PM

A

Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine (-)
Phosphatidylinositol

24
Q

what is the main sphingolipid in PM?

A

Sphingomyelin

25
Q

what is the structure o the phospholipid?

A

Polar head (such as choline, ethanolamine, serine, inositol)
Lipid backbone
Glycerol or sphinogosine based

26
Q

how are glycolipids formed?

A

by the addition of CHO group(s) to lipids

27
Q

what are glycolipids?

A

Glycerol-based

28
Q

what are sphingolipids?

A

Sphingosine-based

29
Q

what are Glycosphingolipids?

A

Combination of glycerol and sphingosine-based

30
Q

what are the most common glycosphingolipids?

A

cerebrosides

gangliosides

31
Q

what is the structure of the glycolipid?

A

Carbohydrate head group
Lipid backbone
Glycerol or sphinogosine based

32
Q

what are sterols?

A

Eukaryotic PM large amounts of cholesterol

33
Q

what do sterols effect?

A

PM fluidity
increase permeability barrier properties of PM
maintain stability+integrity of PM

34
Q

what does the fluidity of the plasma membrane depend on?

A

composition

temperature

35
Q

what is the composition of the PM?

A

shorter chain length

cis-double bonds

36
Q

what is the effect of having a shorter chain length?

A

reduces the tendency of the tails to interact with one another, in both the same and opposite monolayer

37
Q

what is the effect of cis-double bonds?

A

produce kinks in the hydrocarbon chains that make them more difficult to pack together.

38
Q

what is the effect of temperature on PM fluidity?

A

The movements decrease when temp drops and increase as it rises

39
Q

how do phospholipids molecules move within the memb?

A 
Rotation about its long axis
Lateral diffusion by exchanging places with neighbouring molecules in the same monolayer
Transverse diffusion, or “flip-flop” from one monolayer to 
the other (rare)
40
Q

what are the 3 classes of proteins?

A

integral
peripheral
lipid anchored

41
Q

where are integral proteins found?

A

Embedded within bilayer

42
Q

what do integral proteins contain?

A

Hydrophobic segments

Hydrophilic regions

43
Q

what is the function of hydrophobic segments in integral proteins?

A

have affinity for hydrophobic interior of bilayer

44
Q

what is the function of hydrophilic regions in integral proteins?

A

extend outward from the membrane into the aqueous phase

45
Q

what are peripheral proteins?

A

More hydrophilic, lack the hydrophobic segment

46
Q

where are peripheral proteins found?

A

Located on surface of PM / linked to polar head of phospholipids – glycosylphosphatidylinositol (GPI) anchors

47
Q

what are lipid anchored proteins?

A

Hydrophilic / on surface of memb

Attached to lipid molecules in bilayer

48
Q

what are Lipid rafts?

A

Transient clusters/associations of lipids and proteins within membrane

49
Q

what is the function of Lipid rafts?

A

Proposed to increase functional efficiency

50
Q

what is the barrier function of the PM?

A

Allow nutrients to enter & keep out harmful
Defines boundaries of cell & compartments
Separates organelles into discrete regions

51
Q

what is the transport function of the PM?

A

Controls the passage of substances into & out of the cell
Selectively permeable
Proteins in bilayer act as pore channels/carriers

52
Q

what can’t criss the lipid bilayer?

A

Large molecules, ions, hydrophillic substances

53
Q

what are the 2 proteins that allow transport to occur in the PM?

A

Transporter proteins

Ion channel proteins

54
Q

how does signal detection occur in the PM?

A

Cells receive info from their environment via signals

Chemical signals bind to specific receptor proteins

55
Q

what happens when the signal binds to receptor?

A

molecular event inside membrane

56
Q

give an example of signal detection in the PM?

A

PM of Liver & Muscle:

insulin receptors

IMS (52 decks)

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