Topic 5 - chapter 11 Membrane structure Flashcards Preview

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Flashcards in Topic 5 - chapter 11 Membrane structure Deck (46)
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1

The lipid bilayer is a ...-dimensional fluid

two-dimensional

2

The fluidity of a lipid bilayer depends on its ...? Which 3 factors?

composition
- phospholipid tail length
- phospholipid saturation level
- presence of cholesterol

3

T or F - the lipid bilayer is symmetrical

false - asymmetrical

4

What are the most abundant lipids in cell membranes? Whatis the most common membrane lipid?

phospholipids (head linked to rest of lipid via phosphate group)
phosphatidylcholine

5

In the membrane lipid phosphatidylcholine, what makes up the hydrophilic & hydrophobic regions?

hydrophilic (polar head) - phosphate & choline
hydrophobic (non-polar tail) - hydrocarbon tail

6

What are 3 different types of membrane lipids? egs...

phospholipid - phosphatidylserine
sterol - cholesterol
glycolipid - galactoserebroside

7

Which polar molecule can dissolve in water?

acetone

8

Which polar molecule can not dissolve in water?

2-methylpropane

9

What is the difference between amphipathic and hydrophobic?

amphipathic molecules will always form a bilayer in water and spontaneously form sealed compartments

10

Lipid asymmetry is preserved during ...?

membrane transport

11

Why is the lipid bilayer considered two-dimensional?

- phospholipids form spherical liposomes in water
- membrane behaves like a fluid
- temperature-dependant
- not much 'flip-flopping'

12

Approximate thickness of lipid membrane?

5nm

13

3 main functions of plasma membranes...

- receiving info from from environment via receptor proteins
- import & export of small molecules via transport proteins
- cell growth & movement due to flexibility of membrane

14

What is the hydrophilic/hydrophobic part of phosphatidylserine?

hydrophilic - serinephosphate
hydrophobic - hydrocarbon chain

15

What is the hydrophilic part of cholesterol?

OH group

16

What is the hydrophilic part of galactocerebroside?

sugar (galactose) & -OH group

17

Size range of cell vesicles membranes can form?

25nm - 1mm

18

Which ways can phospholipids move within the plane of the membrane?

lateral diffusion
flexion
rotation
'flip-flopping' (rarely)

19

What is meant by fluidity of a cell?

the ease with which lipid molecules move within the plane of the bilayer

20

Which structure(s) mainly affect membrane bilayer fluidity? Which 2 factors of those structures?

nature of the hydrocarbon tails:
- length (the shorter, the more fluid)
- number of double bonds (the more, the more fluid)

21

What is saturated and unsaturated?

based on number of hydrogen bonds attached to the carbon tail
saturated - fatty acid tail with no double bonds and full complement of hydrogen atoms
unsaturated - has at least one double bond thus does not have maximal hydrogen atoms

22

Usual hydrocarbon tail length?

18 - 20 carbon atoms

23

How does cholesterol fit into the lipid bilayer?

in animal cells, cholesterol fits in between the kinked gaps left by double bonds thus stiffening the bilayer and making it less permeable

24

Why is membrane fluidity so important?

- enables rapid diffusion of proteins
- enables protein interactions with one another
- enables membrane lipids & proteins to diffuse to other regions of the cell
- allows membranes to fuse with one another & mix their molecules
- ensures membrane molecules are distributed evenly between daughter cells during cell division

25

In eukaryotic cells, what are phospholipids made from?

enzymes bound to ER membrane

26

What enables the transfer of phospholipid molecules from one monolayer to another ('flip-flopping')?

flippases (enzymes)

27

Glycolipids are mainly located where? Their sugar groups?

in the plasma membrane and are found ONLY in the noncytosolic half of the bilayer
their sugar groups are exposed to the exterior of the cell forming a protective carb coating surrounding most animal cells

28

List 4 functions that membrane proteins serve

transporters
anchors
receptors
enzymes

29

Transporters - protein example & function...?

transporters - Na+ pump: actively pumps Na+ out of cells and K+ into cells

30

Anchors - protein example & function...?

anchors - integrins: link intracellular actin filaments with extracellular matrix proteins