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Chapter 3 Water and the Fitness of the Environment

Chapter 3 Water and the Fitness of the Environment. Why is water special? Unique Properties of Water Acidic/Basic conditions. Abundance of water is the main reason the Earth is habitable. Earth’s surface – 75% submerged in water. Why is water special?. Molecule that supports all life

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Chapter 3 Water and the Fitness of the Environment

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  1. Chapter 3 Water and the Fitness of the Environment Why is water special? Unique Properties of Water Acidic/Basic conditions

  2. Abundance of water is the main reason the Earth is habitable • Earth’s surface – 75% submerged in water

  3. Why is water special? • Molecule that supports all life • Biological Medium • Metabolic Reactions • Required for survival of all living organisms • Exists in nature in all 3 states

  4. Water Structure • Polar molecule • Dipole • H bonds • Contributes to unique properties

  5. What’s wrong with this picture?

  6. Unique Properties of Water • Ice floats a. Less dense than liquid water b. H bonds more ordered and stable in solid water

  7. Since Ice floats in water • Life can exist under the frozen surfaces of lakes and polar seas

  8. Unique Properties of Water • Water has high specific heat • Moderates air temp 1. When air is warmer 2. When air is cooler

  9. Review terms 1. Kinetic energy 2. Heat 3. Temperature

  10. Review terms 4. specific heat of a substance

  11. Unique Properties of Water • Water’s high specific heat a. Resists change b. Large bodies of water can absorb heat w/o large temp change c. Heat absorbed when H bonds break Heat released when H bonds form

  12. d. Bio sig • Water keeps temp fluctuations to within limits that permit life • Due to H bonding, water molecules hold tightly to each other • Aids in homeostasis

  13. Unique Properties of Water • High heat of vaporization a. Vaporization (evaporation) b. Heat of vaporization

  14. Bio sig Evaporative Cooling • Due to high heat of vaporization • Allows water to cool a surface ex.

  15. Unique Properties of Water • Cohesion • As a liquid, water forms FRAGILE H bonds • H bonds are constantly breaking and reforming • Definition of cohesion

  16. Bio sig Transport of water and dissolved nutrients against gravity

  17. Pond Walkers • Bio sig 1. Surface Tension 2. Skin of tightly H bonded water molecules, forms @air/water interface

  18. Unique Properties of Life • The Solvent of Life a. Terms 1. Solution 2. Solvent 3. Solute 4. Aqueous Solution

  19. Water is versatile solvent • Hydrophilic • Hydrophobic • Why? Polarity Two impt features 1. shape 2. H bonds

  20. Water has ability to dissolve macromolecules • Can form sphere of hydration ex. Fig 3-7 Lysozyme molecule

  21. Hydration shell Polar water can interact with ionic compounds called solutes and dissolve them

  22. Most biochem rxns occur in water To calculate concentration of solutes in aqueous solutions: 1. Mole 2. Molarity

  23. Unique Properties of Water • Water and pH a. Dissociation of water molecules affect living organisms

  24. Acid/Base 1. Acid 2. Base

  25. pH 1. determined by relative conc of H+ ions 2. Definition pH =

  26. pH scale 1. acidic 2. basic

  27. Bio sig 1. Homeostasis all living orgs have a vary narrow pH range over which they can survive. 2. Organisms maintain pH by using

  28. Buffers a. Substances that minimize changes in the concentrations of H+ and OH- ions in a solution b. Buffer systems are reversible – depends of H+ concentration

  29. Buffers consist of: Weak acid and its anionic salt • Weak acid dissociates in aq. Solution • Anionic salt is the negative ion

  30. Buffer example - Carbonic Acid CO2 + H20

  31. Clarification

  32. Acid Precipitation Rain, snow, or fog with a pH lower than 5.6 Caused by pollutants mixing with water in the air

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