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Water. Ch. 3. Water is essential to life. Biological Importance of Water. Water is abundant on Earth Life evolved in water All cells contain water Biochemical reactions occur in water. +. +. -. Polar Covalent Bond. H2O doesn’t share e- evenly Oxygen atom is electronegative
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Water Ch. 3
Biological Importance of Water • Water is abundant on Earth • Life evolved in water • All cells contain water • Biochemical reactions occur in water
+ + - Polar Covalent Bond • H2O doesn’t share e- evenly • Oxygen atom is electronegative • Hydrogen atoms are slightly positive
Hydrogen Bonding • Occurs when two water molecules interact • This bonding type allows water to have unique properties vital for living things
Liquid Awesome • https://www.youtube.com/watch?v=HVT3Y3_gHGg
1. Cohesion & Adhesion • Water molecules stick together & other molecules • Important for: • Surface tension • Capillary action
2. Good solvent • Water dissolves other polar molecules • Salt, glucose, and enzymes • Water does not dissolve nonpolar molecules • Lipids
3. Moderation of Temperature • Water has a high specific heat • a lot of energy is required to change its temperature. • Water creates stable environment
4. Heat of vaporization & fusion • Water evaporates if provided with energy • Sweating removes heat from living organism • Water freezes if provided with energy • Cells resist freezing
5. Floating ice insulates water • Less dense as solid than liquid
6. Water Disassociates • H shifts from one H2O molecule to another • Result: • a hydronium ion (+) & a hydroxide ion (-) • Buffers protect life from extreme pH solutions