BIOL 1090 Lecture Notes - Lecture 3: Lipid Raft, Lipid Bilayer, Membrane Fluidity
23 Mar 2017
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March 6th, 2017
Lecture 3 – Membrane
Proteins that penetrate the lipid bilayer are also called lipid – anchored proteins.
Structure of biological membranes:
- 6 nm thick (with associated water)
- Stable and flexible
How will the transition temperature of a membrane be affected if the amount of
unsaturated lipids in it increase?
- It will become lower
Transition temperature:
Membrane fluidity:
Biological membranes are dynamic
- Lipids move easily, laterally, within the leaflet
- Lipid movement to other leaflet is slow (specific flippases are involved)
- Membrane proteins diffuse within the bilayer
o Movement of proteins is restricted
o Some proteins do not move
o Rapid movement is spatially limited
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March 6th, 2017
o Long range diffusion is slow
o Biochemical modification can dramatically alter protein mobility in
the membrane (part of signal transduction)
- Different membranes contain different types of lipids and proteins
Lipid rafts: Membrane Micro-domains
- Lipid rafts are small areas of the
plasma membrane that are enriched
in certain types of lipids (ex:
cholesterol)
- Rafts are relatively rigid
- Some membrane proteins accumulate
in rafts
- May for futioal opartet
(nature/function of rafts is
controversial)
Movement of substances across cell membranes: net flux, influx, efflux
- Lipid bilayers do not allow many compounds to pass through them freely
- Small, uncharged molecules cross membranes relatively easily (O2, CO2,
NO, H2O)
- Large/polar/charged compounds cannot easily cross lipid bilayers
- Specific mechanisms exist for the controlled transport of many substances
across membranes
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Proteins that penetrate the lipid bilayer are also called lipid anchored proteins. Lipids move easily, laterally, within the leaflet. Lipid movement to other leaflet is slow (specific flippases are involved) Membrane proteins diffuse within the bilayer: movement of proteins is restricted, some proteins do not move, rapid movement is spatially limited. March 6th, 2017: long range diffusion is slow, biochemical modification can dramatically alter protein mobility in the membrane (part of signal transduction) Different membranes contain different types of lipids and proteins. Lipid rafts are small areas of the plasma membrane that are enriched in certain types of lipids (ex: cholesterol) May for(cid:373) (cid:862)fu(cid:374)(cid:272)tio(cid:374)al (cid:272)o(cid:373)part(cid:373)e(cid:374)t(cid:863) (nature/function of rafts is controversial) Movement of substances across cell membranes: net flux, influx, efflux. Lipid bilayers do not allow many compounds to pass through them freely. Small, uncharged molecules cross membranes relatively easily (o2, co2, Large/polar/charged compounds cannot easily cross lipid bilayers. Specific mechanisms exist for the controlled transport of many substances across membranes.
