S+F OF THE PLAMSA MEMBRANE Flashcards Preview

IMS > S+F OF THE PLAMSA MEMBRANE > Flashcards

Flashcards in S+F OF THE PLAMSA MEMBRANE Deck (56):
1

what are the 4 components of the eukaryotic cell?

plasma memb
nucleus
memb-bound organelles
cytoskeleton

2

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

To keep desirable substances in
To keep undesirable substances out

3

what is the function of the plasma membrane?

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

4

what is hypotonic?

Cells swelling

5

what is hypertonic?

cell shrinking

6

what happens if the membrane is ruptured?

escape of cell contents

7

what is compartmentalisation?

Applies to most internal organelles
Needed for chemical activities

8

what is Robertson’s “unit membrane"?

Membranes found to have “railroad track” structure

9

what is the structure of the unit membrane?

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

10

what does the Triliaminar staining pattern by TEM show?

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)

11

what does the Fluid Mosaic Model show?

2 fluid layers of lipid
Proteins within or on lipid layers

12

how are lipid molecules arranged in the plasma membrane?

asymmetrically distributed

13

what is amphiphilic?

hydrophilic & hydrophobic regions

14

what is the polar head?

a hydrophilic (water-loving)

15

what are non polar tail?

a hydrophobic (water-fearing)

16

give examples of membrane lipids

phospholipids
glycolipids
sterols

17

what are phospholipids?

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

18

how are lipid molecules arranged in phospholipids?

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

19

what are the 2 ways lipids can be arranged?

cone-shaped
cylinder-shaped

20

what is cone-shaped?

lipid molecules (single chain) form micelles

21

what is cylinder-shaped?

phospholipid molecules (double tailed) form bilayers

22

what are phosphoglyceride?

glycerol-based phospholipid

23

give examples of phosphoglyceride in the PM

Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine (-)
Phosphatidylinositol

24

what is the main sphingolipid in PM?

Sphingomyelin

25

what is the structure o the phospholipid?

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

26

how are glycolipids formed?

by the addition of CHO group(s) to lipids

27

what are glycolipids?

Glycerol-based

28

what are sphingolipids?

Sphingosine-based

29

what are Glycosphingolipids?

Combination of glycerol and sphingosine-based

30

what are the most common glycosphingolipids?

cerebrosides
gangliosides

31

what is the structure of the glycolipid?

Carbohydrate head group
Lipid backbone
Glycerol or sphinogosine based

32

what are sterols?

Eukaryotic PM large amounts of cholesterol

33

what do sterols effect?

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

34

what does the fluidity of the plasma membrane depend on?

composition
temperature

35

what is the composition of the PM?

shorter chain length
cis-double bonds

36

what is the effect of having a shorter chain length?

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

37

what is the effect of cis-double bonds?

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

38

what is the effect of temperature on PM fluidity?

The movements decrease when temp drops and increase as it rises

39

how do phospholipids molecules move within the memb?

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

what are the 3 classes of proteins?

integral
peripheral
lipid anchored

41

where are integral proteins found?

Embedded within bilayer

42

what do integral proteins contain?

Hydrophobic segments
Hydrophilic regions

43

what is the function of hydrophobic segments in integral proteins?

have affinity for hydrophobic interior of bilayer

44

what is the function of hydrophilic regions in integral proteins?

extend outward from the membrane into the aqueous phase

45

what are peripheral proteins?

More hydrophilic, lack the hydrophobic segment

46

where are peripheral proteins found?

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

47

what are lipid anchored proteins?

Hydrophilic / on surface of memb
Attached to lipid molecules in bilayer

48

what are Lipid rafts?

Transient clusters/associations of lipids and proteins within membrane

49

what is the function of Lipid rafts?

Proposed to increase functional efficiency

50

what is the barrier function of the PM?

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

51

what is the transport function of the PM?

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

52

what can't criss the lipid bilayer?

Large molecules, ions, hydrophillic substances

53

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

Transporter proteins
Ion channel proteins

54

how does signal detection occur in the PM?

Cells receive info from their environment via signals
Chemical signals bind to specific receptor proteins

55

what happens when the signal binds to receptor?

molecular event inside membrane

56

give an example of signal detection in the PM?

PM of Liver & Muscle:
insulin receptors