Chapter 5: membranes
Membrane structure: phospholipids arranged in bilayers
- Fluid mosaic model
1. Phospholipid bilayer
a. Flexible matrix, barrier to permeability
2. Transmembrane proteins
a. Integral membrane proteins
3. Interior protein network
a. Peripheral intracellular membrane proteins
4. Cell surface makers
a. Glycorprotiens and glycolipids
Phospolipids
- Glycerol- 3 carbon polalcohol
- 2 fatty acids attached to glycerol
- Nonpolar and hydrophobic
- Phosphate group
- Polar and hydrophilic
- Bilayers are fluid because of the lateral movement of phospholipid molecules.
- Hydrogen bonding of water to itself and to polar heads, holds the layers together
- Individual phospholipids and unanchored proteins can move through the membrane
- Influences on fluidity
- Saturated fatty acids make the membrane less fluid than unsaturated fatty
acids, saturated it more solid therefore less fluid
- Cholesterol
- Warm temp makes it more fluid
Membrane proteins
- Transporters
- Enzymes
- Cell surface receptors
- Cell surface identity markes
- Cell-to-cell adhesion proteins
- Attachments to cytoskeleton
- Intergrean membrane
- Span the bilayer(transmembrane)
- Nonpolar regions in interior
- Polar regions of the protein protrude from both sides
- Transmembrane damian
- Spnas the lipid bilayer
- Hydrophobic amino acids arranged in alpha helices
Functions
- Peripheral proteins
- Anchoring molecules attached membrane proteins to surface
- Nonpolar regions that insert into the internal portion of the lipid bilayer
- Chemical bonding domains that think directy to proteins
Transmembrane domains
- Proteins only need a single transmembrane domain to be anchored to the
membrade, btu they often have more than one such domain
Membrane structure: phospholipids arranged in bilayers
- Fluid mosaic model
1. Phospholipid bilayer
a. Flexible matrix, barrier to permeability
2. Transmembrane proteins
a. Integral membrane proteins
3. Interior protein network
a. Peripheral intracellular membrane proteins
4. Cell surface makers
a. Glycorprotiens and glycolipids
Phospolipids
- Glycerol- 3 carbon polalcohol
- 2 fatty acids attached to glycerol
- Nonpolar and hydrophobic
- Phosphate group
- Polar and hydrophilic
- Bilayers are fluid because of the lateral movement of phospholipid molecules.
- Hydrogen bonding of water to itself and to polar heads, holds the layers together
- Individual phospholipids and unanchored proteins can move through the membrane
- Influences on fluidity
- Saturated fatty acids make the membrane less fluid than unsaturated fatty
acids, saturated it more solid therefore less fluid
- Cholesterol
- Warm temp makes it more fluid
Membrane proteins
- Transporters
- Enzymes
- Cell surface receptors
- Cell surface identity markes
- Cell-to-cell adhesion proteins
- Attachments to cytoskeleton
- Intergrean membrane
- Span the bilayer(transmembrane)
- Nonpolar regions in interior
- Polar regions of the protein protrude from both sides
- Transmembrane damian
- Spnas the lipid bilayer
- Hydrophobic amino acids arranged in alpha helices
Functions
- Peripheral proteins
- Anchoring molecules attached membrane proteins to surface
- Nonpolar regions that insert into the internal portion of the lipid bilayer
- Chemical bonding domains that think directy to proteins
Transmembrane domains
- Proteins only need a single transmembrane domain to be anchored to the
membrade, btu they often have more than one such domain
