Boc membranes L1 Flashcards
What percent of membrane is lipid by weight
30-50
polysaccharides less than…
10%
Draw phosphoglyceride
see notes
What kind of bonds are there
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
How named?
phosphatidyl + charged group eg. phosphatidylserine
What is sphingophospholipid
see notes
Major fatty acids how many carbons long
14-24
in eukaryotes how many usually saturated
1
glycolipid describe and draw
see notes
sterol describe and draw
see notes
at physiological pH…
most phospholipids zwitterions ie no net charge repulsion allows close packing
Thylakoid membrane enriched in?
glycolipids to allow sharp bends in stacks
how can you look at membrane fluidity?
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)
when T low state is…
gel
what is phase transition temp and what is state here
at this temp bilayer interior becomes more fluid but head groups still closely associated, bilayer in liquid crystal state
at high T state is….
disordered liquid
v saturated lipid phase transition temp?
40-50 degrees
what happens when more cis kinks introduced in lipid fatty acid tails?
lower phase transition temp bc weaker VdW
what do sterols do below and above transition temp?
below: prevent close packing and maintain fluidity
above: sterol restricts hydrocarbon chain movement and prevents chains coming apart
sterols make up what max percent of lipid bilayer?
50
what is homeoviscous adaptation?
when plants change proportion of unsaturated fatty acids depending on temp
what is time scale of jump?
10^-7 s
flex time?
10^-9 s
flip time?
10^5 s
Describe the experimental evidence for flip-flop in the lipid bilayer
see notes
what side of membrane are new phospholipids added at
cytoplasmic side hence need to flip-flop
what do flipases do?
overcome this energy and allow this 10^4/10^5 x faster than is spontaneously possible
for each of the following is membrane symmetry absolute: i) lipid ii) protein iii) carbs
i) no, no species found on just one side of bilayer
ii) yes
iii) yes, carbohydrate portions localised only on non-cytosolic side
what are 3 methods of membrane protein attachment?
transverse bilayer, attach via covalent attachment to lipid, attach by non-covalent interactions (NB peripheral membrane proteins can be dettached by cold shock)
What is an experiment to find out if PM proteins span the membrane?
see notes
