1. Copyright © 2009 Pearson Education, Inc. PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey Chapter 2 The Chemical Basis of Life Lecture by Richard L. Myers

2. Introduction: Who Tends This Garden?  Chemicals are the stuff that make up our bodies and those of other organisms –They make up the physical environment as well  The ordering of atoms into molecules represents the lowest level of biological organization –Therefore, to understand life, it is important to understand the basic concepts of chemistry Copyright © 2009 Pearson Education, Inc.

3. 2.1 Living organisms are composed of about 25 chemical elements  Matter - anything that occupies space and has mass (weight) –Matter is composed of chemical elements –Element—a substance that cannot be broken down to other substances Copyright © 2009 Pearson Education, Inc.

5. Sodium ChlorideChlorineSodium + Compound — a substance consisting of two or more different elements combined in a fixed ratio

6. 2.4 Atoms consist of protons, neutrons, and electrons  Atom - smallest unit of matter that still retains the properties of a element –Proton - positive electrical charge –Electron - negative electrical charge –Neutron - electrically neutral Copyright © 2009 Pearson Education, Inc.

7. Electron cloud Protons 2e – Nucleus Electrons Mass number = 4 Neutrons 2 2 2

8. Electron cloud Protons Nucleus Electrons Neutrons Electron arrangement determines the chemical properties of an atom

9. Na Sodium atom Transfer of electron Cl Chlorine atom Na + Sodium ion Cl – Chloride ion Sodium chloride (NaCl) + – Ion - atom or molecule with an electrical charge resulting from gain or loss of electrons –Ionic bond - attraction holds ions together

10. Covalent bond - atoms share electrons Molecule - atoms are held together by covalent bonds Electronegativity Polar and nonpolar covalent bonds

11. (–) O HH (+) Hydrogen bonds are weak bonds important in the chemistry of life http://www.youtube.com/watch?v=CT4pURpXkbY

12. Hydrogen bond

13. Hydrogen bonding causes molecules to stick together - cohesion Cohesion is related to surface tension - a measure of how difficult it is to break the surface of a liquid Hydrogen bonds make liquid water cohesive

14. Water-conducting cells Adhesion Cohesion 150 µm Direction of water movement

15. Water can resist temperature change better than other liquids Heat is absorbed when bonds break; heat is released when bonds form Evaporative cooling - water molecules with the greatest energy leave. Ex. Perspiration Water’s hydrogen bonds moderate temperature

16. Liquid water Hydrogen bonds constantly break and re-form Ice Hydrogen bonds are stable Hydrogen bond Ice is less dense than liquid water

17. Food for thought?!??!?!?!?!? 1. Would the ocean levels change if ice did not float? 2. How does this affect our ideas about global warming? 3. Is the formation of a layer of ice on the surface of a lake good or bad? Why? 4. How does water affect sidewalks, roadways, and parking lots?

18. Ion in solution Salt crystal Water is the solvent of life solution = solvent (dissolving agent) + solute Universal solvent http://www.youtube.com/watch?v=QH1yphfgfFI

19. Acidic solution pH scale Battery acid 0 1 2 3 4 5 Lemon juice, gastric juice Grapefruit juice, soft drink, vinegar, beer Tomato juice Rain water Human urine Saliva Pure water 6 7 Human blood, tears Seawater 8 9 10 11 12 13 Milk of magnesia Household ammonia Household bleach Oven cleaner Neutral solution Basic solution NEUTRAL [H + ]=OH – ] Increasingly ACIDIC (Higher concentration of H + ) 14 Increasingly BASIC (Lower concentration of H + ) The chemistry of life is sensitive to acidic and basic conditions

20. Acidic solution Neutral solution Basic solution

21. Interpreting Data  These are the results of a laboratory experiment to test the effect of trace nutrients on the productivity of Pacific Ocean water. After 6 days which nutrient had the greatest effect on productivity?  Iron.  Manganese.  Copper.  Zinc. Adapted from Coale, Kenneth H. 1991. Effects of Iron, Manganese, Copper and Zinc Enrichments on Productivity and Biomass in the Subarctic Pacific. Limnology and Oceanography. 36: 1851-1864

22. Answer  These are the results of a laboratory experiment to test the effect of trace nutrients on the productivity of Pacific Ocean water. After 6 days which nutrient had the greatest effect on productivity?  Iron. Adapted from Coale, Kenneth H. 1991. Effects of Iron, Manganese, Copper and Zinc Enrichments on Productivity and Biomass in the Subarctic Pacific. Limnology and Oceanography. 36: 1851-1864

23. Biology and Society  One of the authors of your text once overheard the following:  “It’s paranoid and ignorant to worry about industry or agriculture contaminating the environment with their chemical wastes. After all, this stuff is just made of the same atoms that were already present in our environment anyway.”  What do you think of this statement? Why? Disagree Agree Strongly A B C D E Strongly

24. Biology and Society  Too little iodine in the diet can lead to goiter—the condition afflicting this person. Goiter is not common in developing countries because iodine is added to salt and other foods.  Do you think that adding trace elements to food items is good public policy? Why? Disagree Agree Strongly A B C D E Strongly