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Unformatted text preview: 09/05/2007 Lecture 3: Water and its Properties A. Essential to life 1. Humans are mostly water (70%-75%)- Cucumber or watermelon (90%-95% water) 2. Source oxygen- Water is a source of oxygen, breathing in oxygen, breathing out CO 2- In photosynthesis, water’s (oxygen’s) function is to accept the electrons- In respiration, the terminal electron acceptor is oxygen a. Photosynthesis: oxygen- light will come and break it apart, oxygen is releases (water produces oxygen by way of photosynthesis) b. Respiration: the oxygen is used to accept the electrons when we breathe it in 3. Solvent- Water is a solvent, a lot of substances are attracted to water (hydrogen bonding)- Processing organic compounds: • Break down proteins, build them up into our own proteins • Hydrolysis - water is used to BREAK DOWN molecule • Condensation – BUILDING molecules back up (water forming) B. Cohesion- Surface Tension (fig. 2-15) • Hydrogen has a slight positive charge and causes hydrogen bonds • When water sticks to water, it is called cohesion • Water striders press on the surface of the water, surface tension can support a small amount of weight because of hydrogen bonds C. Adhesion- Water binds to something other than water 1. Capillary Action (fig. 2-14)- Water rises because it is attraction to negative charge on sides of capillary- Cohesion holds water molecules together- Percolation (water filtering down through soil • Water drains through clay, capillary action holds it in place- Trees • water can travel from roots to branches through the tree’s cellulose tubes that act as capillary tubes • Adhesion...
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This note was uploaded on 05/30/2008 for the course BS 130 taught by Professor Smith during the Fall '07 term at University of the Sciences in Philadelphia.
- Fall '07