Boc membranes L1 Flashcards

1
Q

What percent of membrane is lipid by weight

A

30-50

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2
Q

polysaccharides less than…

A

10%

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3
Q

Draw phosphoglyceride

A

see notes

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4
Q

What kind of bonds are there

A

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

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5
Q

How named?

A

phosphatidyl + charged group eg. phosphatidylserine

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6
Q

What is sphingophospholipid

A

see notes

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7
Q

Major fatty acids how many carbons long

A

14-24

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8
Q

in eukaryotes how many usually saturated

A

1

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9
Q

glycolipid describe and draw

A

see notes

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10
Q

sterol describe and draw

A

see notes

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11
Q

at physiological pH…

A

most phospholipids zwitterions ie no net charge repulsion allows close packing

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12
Q

Thylakoid membrane enriched in?

A

glycolipids to allow sharp bends in stacks

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13
Q

how can you look at membrane fluidity?

A

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)

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14
Q

when T low state is…

A

gel

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15
Q

what is phase transition temp and what is state here

A

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

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16
Q

at high T state is….

A

disordered liquid

17
Q

v saturated lipid phase transition temp?

A

40-50 degrees

18
Q

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

A

lower phase transition temp bc weaker VdW

19
Q

what do sterols do below and above transition temp?

A

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

20
Q

sterols make up what max percent of lipid bilayer?

A

50

21
Q

what is homeoviscous adaptation?

A

when plants change proportion of unsaturated fatty acids depending on temp

22
Q

what is time scale of jump?

A

10^-7 s

23
Q

flex time?

A

10^-9 s

24
Q

flip time?

A

10^5 s

25
Q

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

A

see notes

26
Q

what side of membrane are new phospholipids added at

A

cytoplasmic side hence need to flip-flop

27
Q

what do flipases do?

A

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

28
Q

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

A

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

29
Q

what are 3 methods of membrane protein attachment?

A

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

30
Q

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

A

see notes