Chapter_2_Outline_Part_II_-2

Chapter_2_Outline_Part_II_-2 - Chapter 2 (Part II) Atoms,...

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Chapter 2 (Part II) Atoms, Molecules & Life
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Importance of Water n Makes up  60-90% of most organisms body  weight n Water molecules  attract one another n  hydrogen bonds form between water molecules n Cohesion   of water molecules produces surface  tension  n Tendency for water surface to  resists being broken n  supports living organisms n n Ex: plants   pull water from the roots up to leaves n Adhesion  =  tendency of water to stick to surfaces
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Fig. 2-8 Basilisk Lizard
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n Interacts with many other molecules n Water serves as  an excellent solvent for molecules n  solvent=substances that dissolves other substances n ions n  solution= solvent containing one or more dissolved  substances n Molecules in solutions move around more freely to react  with one another n  directly involved in many chemical reactions n Ex:  water aids in the breakdown of fats and proteins Importance of Water (cont)
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Water as a Solvent n Ex: Table salt solution (NaCl + H2O) n When salt is added to H2O: n Positive H poles of H2O congregate around negative Cl ions n Negative O poles of H2O attract the positive   Na ions n Result:  salt dissolves n H2O molecules  block the Na and Cl ions from interacting Fig. 2-9 Salt crystal
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n Hydrophilic molecules n “water-loving”- dissolve readily in water n    polar molecules that electrically attract water  molecules n Water acts  as a solvent n Ex:   Salt (NaCl) n Hydrophobic molecules n  “water-fearing”- do not dissolve in water n  large, non-polar molecules that clump together and 
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This note was uploaded on 02/24/2012 for the course BIOL 1001 taught by Professor Minor during the Spring '08 term at LSU.

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Chapter_2_Outline_Part_II_-2 - Chapter 2 (Part II) Atoms,...

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