2.1 Weak interactions Aqueous Systems

The most abundant substance in living systems

Water 70% of organisms

Four points about water

1. The solvent properties of water shaped the evolution of living things

2. The ionization behavior of water and of weak acids and bases dissolved in water can be represented by one or more equilibrium constants

3. An aqueous solution of a weka acid and its slat makes. A buffer that resists changes in pH in response to added acid or base

4. Enzymes, which catalyze all of the processes inside a cell, have evolved to function optimally at near neutral pH

Water has a higher ?

Np, Bp, and heat of vaporization than most other common solvents

The H-O-H bond angle is

104.5

Define hydrogen bond

A weak electrostatic attraction between one electronegative atom (oxygen or nitrogen) and a hydrogen atom covalently linked to a second electronegative atom

Define bond dissociation energy

Energy required to break a bond

Define hydrophilic

Polar or charges; describes molecules or groups that associate with water

Define hydrophobic

Nonpolar; describes molecules or groups that are insoluble in water

Define amphipathic

Containing both polar and nonpolar domains

Define hydrophobic effect

The aggregation of nonpolar molecules in aqueous solution, excluding water molecules; caused largely by an entropic effect related to the hydrogen bonding structure of the surrounding water

Define Michelle’s

An aggregate of amphipathic molecules in water, with the non polar portions int he interior I and the polar portions at the exterior surface, exposed to water

Define Vanderbilt walls interactions

Weak inter-molecular forces between molecules as a result of each inducing polarization in the other

Define colligative properties

The properties of a solution that depend on the number of solute particles per unit volume; for example freezing point depression

Define osmosis

Water movement across a semi permeable membrane driven by difference in osmotic pressure