CH 12 Lipids and Cell Membranes P1 Flashcards
Membrane Structure
sheet-like
2 molecules thick
form closed boundaries
most are electrically polarized
Membranes are composed of?
lipids and proteins
Lipids and proteins can be decorated w/?
carbs
Membrane Lipids
amphipathic molecules
form closed bimolecular sheets
prevent movement of polar / charged molecules
Membrane Proteins
mitigate impermeability of membranes
allow movement of info across cell membrane
Membranes are what type of assemblies?
noncovalent
Membranes are asymmetric, meaning?
outer surface always diff from inner surface
Membranes are what types of structures?
fluid
What are the key constituents of Lipids?
FAs
Fatty Acids (FAs)
chains of H-bearing C atoms w/ carboxylic acid at one end, methyl group at other.
What can be saturated or unsaturated?
FAs
FA C atoms are normally numbered beginning w/ the?
carboxyl terminal C atom
How do you label the C atoms in FAs?
C2 - alpha
C3 - beta
FAs can also be numbered from this group:
methyl C - omega C
FA names are based on their?
parent hydrocarbons
FAs vary in what properties?
chain length
degree of unsaturation
What normally have an even number of C atoms.
FAs
What are the most common numbered chains of FAs?
16C and 18C
What are the most common db’s in FAs?
cis configuration
In polyunsaturated FAs the db’s are sep’d by?
at least one methylene group
What enhances the fluidity of FAs?
short chain length
presence of cis db’s
Common Membrane Lipid Types
phospholipids
glycolipids
cholesterol
Phospholipid Structure
four components:
- 1-2 FA tails
- platform
- phosphate
- alcohol
Common Phospholipid Platforms
glycerol
sphingosine
Phosphoglycerides / Phosphoglycerols
phospholipids w/ a glycerol platform
How are Phosphoglycerides / Phosphoglycerols formed?
when an alcohol is added to a phosphatide
diacylglycerol 3-phosphate
Phosphoglycerides are derived from ____ by ____.
phosphatidate
formation of ester bond btw phosphate and an alcohol
Sphingomyelin
common membrane lipid
primary OH of sphingosine esterified to phosphorylcholine
Glycolipids
carb-containing lipids derived from sphingosine
carb linked to primary alcohol of sphingosine
Cerebrosides
simplest glycolipids single sugar (glucose / galactose)
Gangliosides
branched chain
as many as 7 sugar molecules
The carbohydrate components of glycolipids are on the ____ where they ____?
extracellular surface of cell membrane
play role in cell-cell recognition
Cholesterol
lipid based on a steroid nucleus
modified steroid, FA chain attached to one one, OH on other end
In membranes the OH group of cholesterol interacts w/?
phospholipid head groups
Membrane lipids contain which two moieties (properties)?
hydrophilic
hydrophobic
(aka amphipathic)
FA tail components provide?
hydrophobic properties
FA alcohol and phosphate components provide?
hydrophilic properties
Phospholipids and Glycolipids readily form?
bimolecular sheets in aqueous media
Membrane Bimolecular Sheet Formation
amphipathic nature of constituent lipid molecules.
phospholipids and glycolipids spontaneously form lipid bilayers in aq soln.
Membrane formation is driven by?
the hydrophobic effect.
These stabilize membranes:
van der Waals interactions btw hydrophobic tails.
These attractions exist in membranes:
electrostatic and H-bonding
btw polar heads groups and water molecules.
Micelles are readily formed by?
ionized FAs
Liposomes / Lipid Vesicles
aq compartments enclosed by lipid membrane (bilayer)
Protein-Liposome Complexes
investigate membrane protein functions
Liposomes
formed via sonicating a mixture of phospholipids in aq soln.
drug delivery systems.
Planar Bilayer Membranes
examine membrane properties like ion permeability in presence of voltage diff across membrane.
Glycine-Containing Liposomes
formed via sonication of phospholipids in presence of glycine, free glycine removed by gel filtration
Lipid Bilayers
highly impermeable to ions / most polar molecules
Small molecules can cross lipid bilayers bc
hydrophobicity (lack of polarity)
Lipid Bilayers have low permeability for?
ions
polar molecules
Membrane Proteins
allow transport of molecules and info across membrane
The % of variation in membranes is from?
< 20 to 75
Membrane Proteins can by visualized by?
SDS-PAGE
SDS-polyacrylamide gel electrophoresis
Membrane Protein types reflect:
biochemistry occurring in cell