S+F OF THE PLAMSA MEMBRANE

Question 1

what are the 4 components of the eukaryotic cell?

Answer 1

plasma memb
nucleus
memb-bound organelles
cytoskeleton

Question 2

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

Answer 2

To keep desirable substances in

To keep undesirable substances out

Question 3

what is the function of the plasma membrane?

Answer 3

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

Question 4

what is hypotonic?

Answer 4

Cells swelling

Question 5

what is hypertonic?

Answer 5

cell shrinking

Question 6

what happens if the membrane is ruptured?

Answer 6

escape of cell contents

Question 7

what is compartmentalisation?

Answer 7

Applies to most internal organelles

Needed for chemical activities

Question 8

what is Robertson’s “unit membrane”?

Answer 8

Membranes found to have “railroad track” structure

Question 9

what is the structure of the unit membrane?

Answer 9

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

Question 10

what does the Triliaminar staining pattern by TEM show?

Answer 10

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)

Question 11

what does the Fluid Mosaic Model show?

Answer 11

2 fluid layers of lipid

Proteins within or on lipid layers

Question 12

how are lipid molecules arranged in the plasma membrane?

Answer 12

asymmetrically distributed

Question 13

what is amphiphilic?

Answer 13

hydrophilic & hydrophobic regions

Question 14

what is the polar head?

Answer 14

a hydrophilic (water-loving)

Question 15

what are non polar tail?

Answer 15

a hydrophobic (water-fearing)

Question 16

give examples of membrane lipids

Answer 16

phospholipids
glycolipids
sterols

Question 17

what are phospholipids?

Answer 17

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

Question 18

how are lipid molecules arranged in phospholipids?

Answer 18

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

Question 19

what are the 2 ways lipids can be arranged?

Answer 19

cone-shaped

cylinder-shaped

Question 20

what is cone-shaped?

Answer 20

lipid molecules (single chain) form micelles

Question 21

what is cylinder-shaped?

Answer 21

phospholipid molecules (double tailed) form bilayers

Question 22

what are phosphoglyceride?

Answer 22

glycerol-based phospholipid

Question 23

give examples of phosphoglyceride in the PM

Answer 23

Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine (-)
Phosphatidylinositol

Question 24

what is the main sphingolipid in PM?

Answer 24

Sphingomyelin

Question 25

what is the structure o the phospholipid?

Answer 25

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

Question 26

how are glycolipids formed?

Answer 26

by the addition of CHO group(s) to lipids

Question 27

what are glycolipids?

Answer 27

Glycerol-based

Question 28

what are sphingolipids?

Answer 28

Sphingosine-based

Question 29

what are Glycosphingolipids?

Answer 29

Combination of glycerol and sphingosine-based

Question 30

what are the most common glycosphingolipids?

Answer 30

cerebrosides | gangliosides

Question 31

what is the structure of the glycolipid?

Answer 31

Carbohydrate head group Lipid backbone Glycerol or sphinogosine based

Question 32

what are sterols?

Answer 32

Eukaryotic PM large amounts of cholesterol

Question 33

what do sterols effect?

Answer 33

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

Question 34

what does the fluidity of the plasma membrane depend on?

Answer 34

composition | temperature

Question 35

what is the composition of the PM?

Answer 35

shorter chain length | cis-double bonds

Question 36

what is the effect of having a shorter chain length?

Answer 36

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

Question 37

what is the effect of cis-double bonds?

Answer 37

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

Question 38

what is the effect of temperature on PM fluidity?

Answer 38

The movements decrease when temp drops and increase as it rises

Question 39

how do phospholipids molecules move within the memb?

Answer 39

``` 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) ```

Question 40

what are the 3 classes of proteins?

Answer 40

integral peripheral lipid anchored

Question 41

where are integral proteins found?

Answer 41

Embedded within bilayer

Question 42

what do integral proteins contain?

Answer 42

Hydrophobic segments | Hydrophilic regions

Question 43

what is the function of hydrophobic segments in integral proteins?

Answer 43

have affinity for hydrophobic interior of bilayer

Question 44

what is the function of hydrophilic regions in integral proteins?

Answer 44

extend outward from the membrane into the aqueous phase

Question 45

what are peripheral proteins?

Answer 45

More hydrophilic, lack the hydrophobic segment

Question 46

where are peripheral proteins found?

Answer 46

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

Question 47

what are lipid anchored proteins?

Answer 47

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

Question 48

what are Lipid rafts?

Answer 48

Transient clusters/associations of lipids and proteins within membrane

Question 49

what is the function of Lipid rafts?

Answer 49

Proposed to increase functional efficiency

Question 50

what is the barrier function of the PM?

Answer 50

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

Question 51

what is the transport function of the PM?

Answer 51

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

Question 52

what can't criss the lipid bilayer?

Answer 52

Large molecules, ions, hydrophillic substances

Question 53

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

Answer 53

Transporter proteins | Ion channel proteins

Question 54

how does signal detection occur in the PM?

Answer 54

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

Question 55

what happens when the signal binds to receptor?

Answer 55

molecular event inside membrane

Question 56

give an example of signal detection in the PM?

Answer 56

PM of Liver & Muscle: | insulin receptors