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Unformatted text preview: e bond in them, they are not going to pack together as thightly as saturatd
fatty acids, which are a simple long chain. When u have sturated fatty acids, they
pack together thightly, and tend to give u a less fluid membrane. This is one of the
reasons why most membrane phospholipids/phosphoglyceroid have one saturated
and one unsaturated fatty acid, to give that right degree of fluidity. The length of the
hydrocarbon chains in the fatty acids also helps to deterime fluidity. Long chains all
pack together nicely. If u have a mix of long and short chains, they dont pack together
nicely. They are therefore more fluid. You can increase membrane fluidity by going for
a mix of long and short fatty acid chains. You can increase membrane fluidity by
desaturating the fatty acid chains, by adding double bonds.
3) Polarity of Head Group: Phophotidlecholine b/c of the structure of choline, it tends
to adpot a very cylinderical structure, that packs together very nicely, and gives u rigid
membrane/less fluid membrane. Phosphotidleytholamine, this head group its structure
is more like a cone, it does not pack together as tightly, it is associated with more fluid
4) Presence of Sterols: Sterols have a four-ring framework, and that framework is
realitively stiff, incomparison to fatty acid chains. When u insert a four-ringed structure
into a membrane, at cold temps the siffness of the structure prevents the fatty acids
from packing thightly, it tends to make the membrane more fluid. At a higher temp,
when the memrane is fluid the four-ringed structure adds some stability, therfore
makes it a bit more rigid. Overall sterols buffer the effects of temp. > Homeoviscous adaptation, normally temp changes will affect Properties: membrane fluidity Homeoviscous adaptation
Alterations in lipid composition to maintain
membrane fluidity at different
environmental temperatures Responses within an individual organism Evolutionary responses Fig. 13.12 Moyes & Schulte 2008
PC/PE fluidity PC/PE fluidity Fig. 15-8, Sherwood et al. 2005 BIO 1140 –...
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This note was uploaded on 02/19/2014 for the course BIO 1140 taught by Professor Fenwick during the Winter '07 term at University of Ottawa.
- Winter '07