Transcript Cell Membrane - Informatics: Indiana University

Cell Membrane
Haixu Tang
School of Informatics
Membrane Lipids Are Amphipathic
Molecules
hydrophilic and hydrophobic molecules
interact differently with water
Packing arrangements of lipid
molecules
The spontaneous closure of a
phospholipid bilayer
Phospholipid mobility
The other composition of membrane
Cholesterol and glycolipids
It inhibits possible phase transitions: (1) decreases the
permeability of the bilayer to small water-soluble molecules;
(2) prevents the hydrocarbon chains from coming together
and crystallizing.
Cholesterol
Glycolipid
Four major phospholipids in
mammalian plasma membranes
Cell wall
Lipid raft
The asymmetrical distribution of
phospholipids and glycolipids
Functions of phospholipids in cell
signaling
Membrane proteins
Membrane attachment of Water
soluble proteins
Transmembrane polypeptide chain
crossing the lipid bilayer
Using hydropathy plots to localize potential ahelical membrane-spanning segments
b-barrels (occasionally)
Solubilizing membrane proteins
with a mild detergent
Two detergent
Reconstituting
functional
membrane
protein
system
Red cell membrane
Preparing red cell ghosts
SDS polyacrylamide-gel electrophoresis
pattern of the proteins in the human red
blood cell membrane
Three major ways of proteins
association with membranes
• Noncovalently Associated with the
Cytosolic Side: Spectrin
• Extends Through the Red Blood Cell Lipid
Bilayer as a Single a Helix: Glycophorin
• Multipass Membrane Protein: Band 3
protein
Spectrin: cytoskeleton protein
Spectrin-based cytoskeleton
Glycophorin: single pass
membrane proteins
Band 3: Anion Transporter
The polypeptide chain (about 930 amino acids long) is
thought to extend across the bilayer 12 times.
Photosynthetic reaction center
The Cell Surface Is Coated with
Sugar Residues
Carrier proteins and channel
proteins
A typical ion channel
The gating of ion channels
Potassium ion gate
Passive and active transport
Three ways of driving active
transport