lec 5 memb pt 1

what are membranes, what bonds are they held tgt by, and what are they mostly composed of and why

MEMBRANES are lipid-protein assemblies held by NONCOVALENT bonds

-mostly made of lipids because their dissolving power corresponded to that of oil

-also has proteins

whats the most energetically favorable oritentation for lipid bilayer

polar head facing OUTER aqueous components

what is lipid bilayer stabilized by? what bonds between polar head groups and water

lipid bilayer stabilized by Van der Waals interactions (in fatty acyl chains)

-ionic + H bonds between polar/water

why are membranes called DYNAMIC?

due to lipid bilayer FLUIDITY

define lipid bilayer

structural BACKBONE and BARRIER to PREVENT RANDOM MOVEMENTS of materials in/out cell

lipid to protein ratio linked to function, for example why does mitochondria vs myelin sheath have their ratios

mitochondria more protein for electron transport

myelin sheath more lipids for electrical insulation

list 5 functions of biomembranes

1. Compartmentalization (surround cell/organelles)

2. Scaffold (platform) for biochem activities

3. Selective permeability barrier

4. Respond to external signals

5. Crucial to Production of Energy

3 types of lipids that make up membranes. which most abundant

Phosphoglycerides (most abundant), Sphingolipids, Sterols

why is phosphoglyceride amiphipathic? think abt structure

-fatty acid chain one side (nonpolar)

-polar head group other side

which type of phosphoglyceride has important role in signal transduction

Phosphatidy - inositol (PI)

what is sphingolipid derived from

CERAMIDE (sphingosine + fatty acid)