Boc membranes L1

Question 1

What percent of membrane is lipid by weight

Answer 1

30-50

Question 2

polysaccharides less than…

Answer 2

10%

Question 3

Draw phosphoglyceride

Answer 3

see notes

Question 4

What kind of bonds are there

Answer 4

ester OH c1 and c2 to CARBOXYL groups of long fatty acid chains
ester OH C3 to phosphoric acid
ester link phosphate to amino acid/alcohol

Question 5

How named?

Answer 5

phosphatidyl + charged group eg. phosphatidylserine

Question 6

What is sphingophospholipid

Answer 6

see notes

Question 7

Major fatty acids how many carbons long

Answer 7

14-24

Question 8

in eukaryotes how many usually saturated

Answer 8

1

Question 9

glycolipid describe and draw

Answer 9

see notes

Question 10

sterol describe and draw

Answer 10

see notes

Question 11

at physiological pH…

Answer 11

most phospholipids zwitterions ie no net charge repulsion allows close packing

Question 12

Thylakoid membrane enriched in?

Answer 12

glycolipids to allow sharp bends in stacks

Question 13

how can you look at membrane fluidity?

Answer 13

x-ray diffraction and differential calorimetry (difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature)

Question 14

when T low state is…

Answer 14

gel

Question 15

what is phase transition temp and what is state here

Answer 15

at this temp bilayer interior becomes more fluid but head groups still closely associated, bilayer in liquid crystal state

Question 16

at high T state is….

Answer 16

disordered liquid

Question 17

v saturated lipid phase transition temp?

Answer 17

40-50 degrees

Question 18

what happens when more cis kinks introduced in lipid fatty acid tails?

Answer 18

lower phase transition temp bc weaker VdW

Question 19

what do sterols do below and above transition temp?

Answer 19

below: prevent close packing and maintain fluidity
above: sterol restricts hydrocarbon chain movement and prevents chains coming apart

Question 20

sterols make up what max percent of lipid bilayer?

Answer 20

50

Question 21

what is homeoviscous adaptation?

Answer 21

when plants change proportion of unsaturated fatty acids depending on temp

Question 22

what is time scale of jump?

Answer 22

10^-7 s

Question 23

flex time?

Answer 23

10^-9 s

Question 24

flip time?

Answer 24

10^5 s

Question 25

Describe the experimental evidence for flip-flop in the lipid bilayer

Answer 25

see notes

Question 26

what side of membrane are new phospholipids added at

Answer 26

cytoplasmic side hence need to flip-flop

Question 27

what do flipases do?

Answer 27

overcome this energy and allow this 10^4/10^5 x faster than is spontaneously possible

Question 28

for each of the following is membrane symmetry absolute: i) lipid ii) protein iii) carbs

Answer 28

i) no, no species found on just one side of bilayer
ii) yes
iii) yes, carbohydrate portions localised only on non-cytosolic side

Question 29

what are 3 methods of membrane protein attachment?

Answer 29

transverse bilayer, attach via covalent attachment to lipid, attach by non-covalent interactions (NB peripheral membrane proteins can be dettached by cold shock)

Question 30

What is an experiment to find out if PM proteins span the membrane?

Answer 30

see notes