Chapter 1-Biophysical Principles

Question 1

London dispersion (van der Waals)

Answer 1

• 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

Question 2

Clathrate cage structure

Answer 2

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

Question 3

List aggregates formed with decreasing water content

Answer 3

Micelle, hexagonal cylindrical, lamellar

Question 4

Why do phospholipids prefer to form lamellar liquid crystalline aggregates?

Answer 4

More rod-like (cylindrical) in shape and prefer to form lamellar structures

Question 5

Why do most amphipathic molecules prefer to form micelles in water? (At low molecule concentration)

Answer 5

More cone-like in shape, easily pack to form spheres for steric reasons

Question 6

What interactions stabilise proteins?

Answer 6

1. Tendency to maximise H bonding with secondary structure
2. Hydrophobic effect
3. Existence of sulphur bridges and salt bridges

Question 7

Describe 2ndary structure in proteins

Answer 7

• maximise formation of h bonded secondary structure elements by forming alpha helices and beta sheets

Question 8

Describe hydrophobic effect in proteins

Answer 8

• 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

Question 9

Dipole moment formula

Answer 9

u=qx

q is charge, x is distance between the charges