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(a) Liquid-^ ordered state Lo
Mr &¥n=EÉB%÷E←← É%¥ § Ema physical properties^ §⑨ʳMg[BOM} Dynamic +^ flexible^ structures • EEɣɧÉEEˢ¥E?E¥¥? Exist In various (^) phases +^ undergo phase transitions 11
Heat produces thermal
motion of^ side^ chains
Not permeable -10 large - polar solutes -110ns^ (Lo^ →^ Ld^ transition^ )^.
(b) Liquid -^ disordered^ state Ld
Permeable -10^ small polar solutes^ +^ nonpolar compounds Phases §¥ ¥EñEÉEEE* ←¥r%^ goq Depends on^ composition +^ temp q%O•CB@B⑨B →•→¥B EE ¥s%EBM^ a§} lipid (^) bilayer can be^ lngel / fluid^ w-cr-T.DK#mf-&----
liquid ordered^ state^ →^ Individual^ molecules^ do^ not^ move^ around
liquid disordered^ state^ →^ Individual^ molecules^ can^ move^ around
Heating →^ phase^ transition^ from^ get^ -10^ fluid
Organisms can^ adjust^ Membrane^ Composition
Under physiological conditions →^ more fluid like
Membrane (^) fluidity →^ Mainly fatty acid (^) composition -1^ melting point must be^ fluid^ for (^) proper function^ More fluid membranes (^) require shorter + (^) more unsaturated (^) fatty acids Fatty Acid^ Composition^ of^ E-^ Coli^ Cells Melting temp Las double bonds are added cultured at Different^ Temperatures Melting temp^ >^ with^ length of^ saturated^ fatty acids percentage oftotalfattyacidsa Higher temp^ →^ cells^ need^ more^ long saturated^ fatty acids
104 20°C 30 ' C 404
Lower (^) temp →^ cells need^ more unsat Myristicaold^4 4 4 Palmitic acid^18 25 29 48 Dynamics : Lateral^ Diffusion
Palm / 1-oleic^ acid 26 24 23 9
Individual lipids undergo fast lateral diffusion within the leaflet
Oleic acid 38 34 30 12 Hydroxymyrlstlcacld 13 10 10 8 Uncatalyzed saturation Ratio 2.9 2.0 1.6 0.38 ⑨⑨⑨@@⑥②@@^ • •@⑨@@a@@@ " """"""""" sterols +^ Hopanols Increase Membrane (^) Rigidity and^ ↑Hi↑Ñii↑iHv÷^ •%::! Permeability (^) • ••@@•@•• 11mm^ /s) Eukaryotes →^ sterols "^ €E5_É~ Cholesterol (^) • Cholesterol in animals '" (^) " (^) • (^) phytosterolsln plants μ ,^ ,T-^ led fa • ergosterol in (^) fungi
ergosterol
,=] OH Prokaryotes^ →^ hopanois ◦ H 1-10 OH OH One (^) particular hopanol
Dynamics:^ FRAP tlhcatalyzedtransb/ (^) layer (^ " flip-flop " ) (^) diffusion 7 Fluorescence (^) recovery after (^) photobleaching GG@@@@⑥⑥⑥ GGG@GO.GG@ //μ
Monitor lateral lipid diffusion by monitoring rate of
fluorescence return MINIHAN 1411111111111111 Rate^ off^ return^ of^ lipids , the^ diffusion^ coefficient^ of^ a ⑧@@@@⑨⑥@@ HIM In^ days) @⑨②⑨⑥⑨⑨⑥⑥ hpidintheleafietcanbe^ determined
Rates of lateral diffusion are high /up -101 Hm / Sec)
Transverse Diffusion
Spontaneous flips from^ one^ leaflet^ -10^ another^ lipids^ can^ circumnavigate^ an^ E.^ Coli^ cell^ in^ 1sec
; rare charged head^ group must^ transverse^ hydrophobic §IÑʰ←[
§_g§ffh§BTÑf
tall region of the membrane
Flippases 1%8%
Special Enzymes catalyze transverse^ diffusion
%¥f¥☒q
.in#M
!÷i¥ *¥iÉ;¥¥¥f:¥¥i¥÷÷i¥¥¥¥¥É¥¥÷¥÷÷¥
É÷¥¥÷¥¥*÷→
" fhppase " → unique unidirectional + bidirectional
enzymes to^ catalyze^ lipid^ movement some (^) use start energy of^ ATP^ -10^ move^ lipids^ against the (^) concentration (^) gradient ¥m Catalyzed trans^ bilayer translocations Outside Rafts
%i%q••↑↑↑↑μ^ §•••%%f^ ↑☒¥EqÑ%↑i
Lipid distribution^ lnaslngle leaflet^ →^ not^ random^ /^ uniform
- contain clusters of (^) glycosphlngohpldswth longer """
aqA¥¥%"¥ñh•%m
"""^ !%% "
•h⑤M
- • • •• tnanusuaitans
- more ordered
Inside - contain specific doubly /triply acylated proteins
ATP (^) ADPTP; ATP ADPTP; - (^) allow (^) segregation of (^) proteins in the membrane
Flippase Floppase scramblase
IP- type ATPase) (ABCtransporter) moves lipids in Raft
moves PE and PS moves phospholipids either direction, ,^ enriched^ in
from outer -10 from spningolipids,^ cholesterol
cytosolic-10^ toward^ equilibrium
cytosolic leaflet^ outer^ leaflet^ I
⑨rÉ
{ Cholesterol
§GP
- linked {
Outside (^) ✗ protein MMMMM'Mñ .MN#HMMMfpkM %:$:#1%1%1%
.EE#-EEi-MoEFgHH.*H
.IM
•;;:::::::÷.;÷÷.
" Inside
prenylated
'Palm"°Y "
acylated protein MY'^ "-1091) protein
