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- 1. BIOL 101 General Biology I Chapter 3 Water & the Fitness of the Environment Rob Swatski Associate Professor of Biology HACC – York Campus1
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- 3. Water: The Molecule That Supports All of Life • Water is the biological medium on Earth • All living organisms require water more than any other substance • Most cells are surrounded by water, and cells themselves are about 70–95% water • The abundance of water is the main reason the Earth is habitable 3
- 5. Surface of Mars Surface of Earth 5
- 6. Water = Polar molecule N S + - 6
- 8. Properties of Water How do they benefit living things? 8
- 9. Emergent Properties of Water Cohesion Moderates temperature Expands when frozen Versatile solvent 9
- 10. 10 Cohesion How?
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- 16. Moderation of Temperature by Water • Water absorbs heat from warmer air and releases stored heat to cooler air • Water can absorb or release a large amount of heat with only a slight change in its own temperature 16
- 18. Metric System Units - Energy Celsius calorie (cal) kilocalorie (kcal or Calorie) joule 1j = 0.239 cal 1 cal = 4.184 j 18
- 19. Specific Heat 1 cal/g/ºC So what…? HEAT +/- 1 g 1ºC 19
- 20. • Water’s high specific heat can be traced to hydrogen bonding – Heat is absorbed when hydrogen bonds break – Heat is released when hydrogen bonds form • The high specific heat of water minimizes temperature fluctuations to within limits that permit life 20
- 22. 22 Heat Heat What happens to the bond?
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- 24. 24 Heat Heat What happens to the bond?
- 25. Santa Barbara 73° Los Angeles (Airport) 75° Pacific Ocean 68° Santa Ana 84° Burbank 90° San Bernardino 100° Palm Springs 106° Riverside 96° San Diego 72° 40 miles 70s (°F) 80s 90s 100s 25
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- 30. Floating of Ice on Liquid Water • Ice floats in liquid water because hydrogen bonds in ice are more “ordered,” making ice less dense • Water reaches its greatest density at 4°C • If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth 30
- 37. Colloid 37
- 38. Solute Concentration in Aqueous Solutions • Most biochemical reactions occur in water • Chemical reactions depend on collisions of molecules and therefore on the concentration of solutes in an aqueous solution 38
- 39. • Molecular mass: the sum of all masses of all atoms in a molecule • Numbers of molecules are usually measured in moles, where 1 mole (mol) = 6.02 x 1023 molecules • Avogadro’s number and the unit dalton were defined such that 6.02 x 1023 daltons = 1 g • Molarity (M): the number of moles of solute per liter of solution 39
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- 43. Hydronium ion (H3O+) Hydroxide ion (OH–) 2H2O H H H H H H H H OOOO Hydrogen is Shifty gains H+ loses H, but keeps e- 43 Dynamic equilibrium: dissociation rate = reformation rate
- 45. 45 pH Scale
- 46. Acidic [H+] > [OH–] Neutral [H+] = [OH–] Basic [H+] < [OH–] 7 0 14 46
- 47. pH Scale Battery acid Gastric juice, lemon juice Vinegar, wine, cola Beer Tomato juice Black coffee Rainwater Urine Saliva Pure water Human blood, tears Seawater Inside of small intestine Milk of magnesia Household ammonia Household bleach Oven cleaner Basic solution Neutral solution Acidic solution 0 1 2 3 4 5 6 7 8 9 10 Neutral [H+] = [OH] IncreasinglyBasic [H+]<[OH] IncreasinglyAcidic [H+]>[OH] H+ H+ H+ H+ H+ H+ H+ H+ OH OH H+ OH H+ OH OH OH OH H+ H+ H+ H+ OHOH OH OH OH OH OH H+ 11 12 13 14 47
- 48. 48 pH Values
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- 50. Buffers • The internal pH of most living cells must remain close to pH 7 • Buffers are substances that minimize changes in concentrations of H+ and OH– in a solution • Most buffers consist of an acid-base pair that reversibly combines with H+ 50
- 53. How can your commute affect coral reef growth in the Caribbean Sea? 53
- 54. Acidification: A Threat to Water Quality • Human activities such as burning fossil fuels threaten water quality • CO2 is the main product of fossil fuel combustion • About 25% of human-generated CO2 is absorbed by the oceans • CO2 dissolved in sea water forms carbonic acid; this process is called ocean acidification 54
- 55. • As seawater acidifies, H+ ions combine with carbonate ions to produce bicarbonate • Carbonate is required for calcification (production of calcium carbonate) by many marine organisms, including reef-building corals 55
- 56. CO2 CO2 + H2O H2CO3 H+ + HCO3 H+ + CO3 2 HCO3 CaCO3CO3 2 + Ca2+ H2CO3 56
- 57. (a) (b) (c) 57
- 58. • The burning of fossil fuels is also a major source of sulfur oxides and nitrogen oxides • These compounds react with water in the air to form strong acids that fall in rain or snow • Acid precipitation is rain, fog, or snow with a pH lower than 5.2 • Acid precipitation damages life in lakes and streams and changes soil chemistry on land 58