General ---------Biology ------------------Online------------------------- Ch. 3 Water and the fitness of the environment

1. Polarity of water molecules results in hydrogen bonding

• acts as a solvent for water soluble chemicals (e.g. amino acids, sugars)
• resists rapid temperature change, i.e. has a high "specific heat"
• coheres to itself (e.g. surface tension)
• adheres to hydrophilic chemicals like cellulose
• pours like a liquid
• cools you as it evaporates from your skin
• liberates heat on condensation (the energy driving a thunderstorm)
• forms a spherical drop
• floats when it freezes
• dissociates into hydrogen ions and hydroxide ions

WARNING:  "HYDROGEN BOND" IS A MISLEADING TERM.  IT IS NOT A COVALENT BOND BETWEEN A HYDROGEN AND A CARBON.

HYDROGEN BONDS ARE WEAK MAGNETIC ATTRACTIONS BETWEEN POLAR COVALENT BONDS IN MOLECULES LIKE WATER, SUGAR, PROTEINS AND DNA,  AND ARE SHOWN AS DOTTED LINES IN YOUR TEXT.  To see an example view the figure above.  For another image click here.

Summary:  write summary statements as bullet points below.
 
 

Test your knowledge:  Practice Quiz # 13.  Be able to label this figure.