Chapter 1-Biophysical Principles Flashcards
London dispersion (van der Waals)
- motion of electrons at any instantaneous moment is synchronised so that each atom has a distorted electron distribution giving a momentary dipole moment
- dipoles directed to give attractive force between particles
Clathrate cage structure
A cage of associated water molecules surround a hydrocarbon dissolved in water—> contributes to lowering of water entropy
- hence requires hydrocarbons to self-associate so less water molecules r involved in clathrate formation
List aggregates formed with decreasing water content
Micelle, hexagonal cylindrical, lamellar
Why do phospholipids prefer to form lamellar liquid crystalline aggregates?
More rod-like (cylindrical) in shape and prefer to form lamellar structures
Why do most amphipathic molecules prefer to form micelles in water? (At low molecule concentration)
More cone-like in shape, easily pack to form spheres for steric reasons
What interactions stabilise proteins?
- Tendency to maximise H bonding with secondary structure
- Hydrophobic effect
- Existence of sulphur bridges and salt bridges
Describe 2ndary structure in proteins
- maximise formation of h bonded secondary structure elements by forming alpha helices and beta sheets
Describe hydrophobic effect in proteins
- drives non-polar side chains to be buries inside globular protein, stabilised by van der Waals forces between them
- drives polar side chains to be exposed to exterior aqueous solvent stabilised by ion-dipole or dipole-dipole interactions
Dipole moment formula
u=qx
q is charge, x is distance between the charges