The Extracellular Matrices Part l 2. Elastin fibers 3. Proteoglycans(PG)and glycosaminoglycans (GAG) 4. Cell-adhesion molecules(CAM)
The Extracellular Matrices Part II. 2. Elastin fibers. 3. Proteoglycans (PG) and glycosaminoglycans (GAG). 4. Cell-adhesion molecules (CAM). 1
Elastin fibers A network of randomly coiled macromolecules No periodicity. Highly extensible chains. Rubber-like elasticity is complicated by ydrophobic bonding effects Interaction of hy drophobic(nonpolar)aa with water leads to hydrophobic bonding. Primarily entropic, not energetic, bonding between molecules. It forces nonpolar macromolecules, such as elastin, to adopt a compact, rather then extended shape in hydrated tissue Stretching of elastin fibers leads to large entropy loss due to reduction in chain configurations and increased"ordering"of water molecules against nonpolar AA. spontaneous retraction Elastic ligament of neck, blood vessel wall
Elastin fibers • A network of randomly coiled macromolecules. No periodicity. Highly extensible chains. • Rubber-like elasticity is complicated by hydrophobic bonding effects. • Interaction of hydrophobic (nonpolar) AA with water leads to hydrophobic bonding. Primarily entropic, not energetic, bonding between molecules. It forces nonpolar macromolecules, such as elastin, to adopt a compact, rather then extended, shape in hydrated tissue. • Stretching of elastin fibers leads to large entropy loss due to reduction in chain configurations and increased “ordering” of water molecules against nonpolar AA. Spontaneous retraction. • Elastic ligament of neck. Blood vessel wall. 2
The Hydrophobic bond △G=△H-T△S Equilibrium when AG =0. G is Gibbs' free energy, the enthalpy is H=E+ pv, t is absolute temperature and s is the entropy. The process goes spontaneously from left to right when AG <0. Find the position of thermodynamic equilibrium for a well-known example of insolubility CH in benzene>Ch in Ho The experimental data show (all units in calories per mo):△G=△H-T△s +2600=-2800-298(-18 +2600=-2800+5400 Conclusion: Insolubility of paraffin in water due to entropy loss, not to enthalpy change!( Kauzmann)
The Hydrophobic bond 3 ∆ G = ∆ H − T ∆ S Equilibrium when ∆ G = 0. G is Gibbs’ free energy, the enthalpy is H = E + PV, T is absolute temperature and S is the entropy. The process goes spontaneously from left to right when ∆ G < 0. Find the position of thermodynamic equilibrium for a well-known example of insolubility: CH 4 in benzene → CH 4 in H 2 O The experimental data show (all units in calories per mol): ∆G = ∆ H − T ∆ S +2600 = −2800 − 298 ( −18 ) +2600 = −2800 + 5400 Conclusion: Insolubility of paraffin in water due to entropy loss, not to enthalpy change! (Kauzmann)
Historical models of cell membrane structure Image removed due to copyright considerations
Historical models of cell membrane structure Image removed due to c Image removed due to copyri opyright consi ght considderati eratioons ns 4
Cell membrane showing Extracellular bilayer Oligosaccharide Glycoprotein Peripheral Glycolipid rotein structure Integral c Hydrope Intracellular
Cell membrane showing bilayer structure 5