BIOL 203 Module 1: Chapter 2

Chemical Basis of Life

How to atoms interact to form bonds and make molecules?

Share or transfer electrons to give atoms full valence shells

Polar covalent Bond

e- not shared equally; partial charge

Nonpolar Covalent Bond

e- equally shared; no charge

Ionic Bond

e- transferred from one atom to another; gives both atoms a full valence shell; full charge

Hydrogen Bond

between water molecules; H+ atom w/ O or N **

Hydrophobic Interactions

NP molecules cluster away from the water molecules —> strength

Van der waals forces

weak electrical attractions due to temporary and minute partial charges

Bonds and interactions in order of strength (highest to lowest)

Polar Covalent, Nonpolar covalent, Ionic, H bonds, hydrophobic interactions, and van der waals forces

NLO - Atoms are made of

Protons, Neutrons, and Electrons

Properties of Water?

1. Polar

2. Hydrogen bonds between water molecules

3. Water molecules dissociate into an H+ ion and OH- ion

Why is water necessary for life?

1. Effective Solvent for charged and polar solutes

1. -Transports nutrients

2. Water is denser as a liquid than as a solid

   -Insulation

3. High capacity for absorbing energy

   -Homeostasis

4. Cohesive and Adhesive

   -Photosynthesis

Multiple water molecules, e-, charged, and bonds

How do charged and polar molecules interact w/ water

Dissolve easily in water due to hydrogen bonding (hydrophilic)

How do nonpolar solutes interact w/ water?

NP doesn’t dissolve (hydrophobic)

Difference in proton concentration when given pH

Acidic: H+ > OH-

Neutral: H+ = OH-

Basic: H+ < OH-

NLO - Acid

Give up P and increases the concentration of the hydronium ion in water

NLO - Base

Acquire P and decrease the concentration of the hydronium ion in water

Functional Groups? Hydrophobic or Hydrophillic?

1. Amino - depends

2. Carboxyl - Hydrophilic

3. Carbonyl - Hydrophilic

4. Hydroxyl - Hydrophilic

5. Phosphate - Hydrophilic

6. Sulfhydryl -Hydrophobic

separately interact to build the large molecule

Types of interactions/bonds by functional groups

• Amino: hydrogen and ionic bonds

• Carboxyl: hydrogen and ionic bonds

• Carbonyl: hydrogen bonds

• hydroxyl: hydrogen bonds

• Phosphate: n/a

• Sulfhydrl: di-sulfide bonds

How water is involved w/ the assembly of macromolecules

Condensation/Dehydration Rxn: remove H20 (create)

-water is the product

Hydrolysis: add H20 (destroy)

-water is the reactant

How is water involved w/ the disassembly of macromolecules?

Hydrolysis Rxn: adding H20