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Chapter 12

BCM 475 Chapter Notes - Chapter 12: Methylene Group, Choline, Phospholipid


Department
Biochemistry
Course Code
BCM 475
Professor
Welch
Chapter
12

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LIPIDS AND CELL MEMBRANES
Functions
- Prevent leaking/entering of unwanted molecules
o Lipid components form barrier of permeability and protein components form
pumps/channels
- Fuel molecules, energy stores, signal molecules/messengers, components of membranes
Common Features of Biological Membranes
1.
Sheetlike structures
only 2 molecules thick (form
closed boundaries)
between diff. compartments
2. Consist of
lipids
and
proteins
and
carbs
3. Lipids are small molecules with both hydrophilic/hydrophobic molecules (lipid bilayers)
o Form closed bimolecular sheets in aqueous media
4.
Specific proteins mediate different functions
o Pumps, channels, receptors, energy transducers, enzyme
5. Membranes consist of noncovalent interactions
6.
Asymmetric
7.
Fluid structures
lipid/proteins diffuse rapidly in membrane (unless anchored by proteins)
o Membranes are 2D solutions of proteins/lipids
8. Most cell membranes are
electrically polarized
(inside is negative)
o Lipid/proteins do not readily rotate
FATTY ACIDS
Hydrophobic lipids are essential to their ability to form membranes (thanks to fatty acids)
Fatty acids long hydrocarbon chains of various lengths and degrees of unsaturation terminated with
carboxylic acid groups
Naming Fatty Acids
- 18:0 denotes C18 fatty acid with NO double bonds; 18:2 would have 2 double bonds
- Begin numbering at carboxyl end
o Carbon 2 = | carbon 3 = | last carbon at end =
Position of double bond =
o Ex. Cis-9 means there is cis double bond between carbon atoms 9 and 10
o Trans-2 means a trans double bond between carbon 2 and 3
Count from distal end (-carbon is number 1)
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