1. Human Anatomy and Physiology I Chapter 2 The Chemical Basis of Life Instructor: Mary Holman

2. Matter Elements –Can’t be broken down into simpler substances –97 natural elements, >100 known –Organized into a Periodic Table

4. Major Elements in the Human Body Oxygen Carbon Hydrogen Nitrogen Calcium Phosphorus O C H N Ca P % body wt 65.0 18.5 9.5 3.3 1.5 1.0

5. Other Important Elements In the Human Body Potassium K Sulphur S Sodium Na Chlorine Cl Magnesium Mg

6. Trace Elements Iodine IMolybdenum Mo Fluorine F Chromium Cr Iron Fe Selenium Se Copper Cu Aluminum Al Silicone Si Boron B Vanadium V Tin Sn Zinc Zn Cobalt Co Manganese Mn

7. Atomic Structure Atom smallest portion of an element that retains all the properties of the element composed of subatomic particles: Proton – carries a single positive charge found in the nucleus Neutron – carries no electrical charge found in the nucleus Electron – very small particle that carries a single negative charge found moving in varying energy levels around the nucleus

8. Particle Charge Location Electron Proton Neutron -- + none In nucleus Outside nucleus Major Subatomic Particles

9. Fig. 2.3a Hydrogen (H) + - Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10. Fig. 2.3b Helium (He) - - 00 + + Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11. Fig. 2.3c Lithium (Li) - - - 0 0 + + 0 0 + Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

12. Atomic number - equal to the number of protons or electrons in an atom Atomic mass - equal to the average total number of neutrons plus protons Isotopes - atoms with differing numbers of neutrons in atoms of the same element 12 C 13 C 14 C

13. Periodic Table of the Elements 7 Nitrogen N 14.0067 Periodic Table Appendix D - Pg 931

14. Bonding of Atoms Bonds form when atoms combine with other atoms through interactions between their electrons Electrons of an atom occupy regions of space called electron shells which circle the nucleus For atoms with atomic numbers of 18 or less, the following rules apply: The first shell can hold up to 2 electrons The second shell can hold up to 8 electrons The third shell can hold up to 8 electrons

16. Valence Number Number of electrons in outer shell or energy orbital of an element These electrons participate in bonding with atoms of other elements Shifting of valence electrons occurs in bonding with other atoms

17. There are two types of bonds that hold atoms together in a molecule: Ionic bond Covalent bond Valence # determines which kind of bond an atom is likely to make

18. Bonding of Atoms: Ions Ion An atom that gains or loses electrons to become stable An electrically charged atom Cation Positively charged ion Formed when an atom loses electrons Anion Negatively charged ion Formed when an atom gains electrons

19. Ionic Bonds An attraction between a cation and an anion Formed when one atom gives up one or more electrons to another atom

20. Fig. 2.4a 11p + 12n 0 Sodium atom (Na)Chlorine atom (Cl) (a) Separate atoms If a sodium atom loses an electron to a chlorine atom, the sodium atom becomes a sodium ion (Na + ), and the chlorine atom becomes a chloride ion (Cl – ). 17p + 18n 0 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 2.4a Two Atoms Forming An Ionic Bond

21. Fig. 2.4b +- 11p + 12n 0 Chloride ion (Cl - ) Sodium ion (Na + ) (b) Bonded ions These oppositely charged particles attract electrically and join by an ionic bond. Sodium chloride 17p + 18n 0 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 2.4b Bonded Ions

22. Important Ions in the Body Na + K + Ca 2+ Mg 2+ Cl - PO 4 3- NH 4 + HCO 3 -

23. Covalent Bonds Formed when atoms share electrons Organic compounds contain many covalent bonds

24. Hydrogen atom + H Hydrogen molecule H2H2 Hydrogen atom H ++ ++ -- - - Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 2.5 = A Covalent Bond creating a Molecule of Hydrogen

25. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H C O N Fig. 2.6 Atomic # - 1 Atomic # - 8 Atomic # - 7Atomic # - 6

26. Fig. 2.6a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. HH H2H2 Structural Formulas versus Molecular Formulas

27. Fig. 2.6b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. OO O2O2 The Double Covalent Bond O : : O......

28. Fig. 2.6d Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. COO CO 2 Carbon Dioxide

29. Fig. 2.6c Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O HH H2OH2O Water - A Polar Molecule (+) (-) (+)

30. Bonding of Atoms: Polar Molecules Polar Molecules Molecule with a slightly negative end and a slightly positive end Results when electrons are not shared equally in covalent bonds Water is an important polar molecule Slightly negative end Slightly positive ends Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 2.8a O H H

31. Hydrogen Bonds A weak attraction between the positive end of one polar molecule and the negative end of another polar molecule Formed between water molecules Important for protein and nucleic acid structure H H H H H H H H H H O O O O O Hydrogen bonds (b) Fig. 2.8b

32. Molecular Formulas Depict the elements present and the number of each atom present in the molecule H 2 H 2 O C 6 H 12 O 6

33. Acids, Bases, and Salts Electrolytes – substances that release ions in water Acids – electrolytes that dissociate to release hydrogen ions in water HCl  H + + Cl - Bases – substances that release ions that can combine with hydrogen ions NaOH Na + + OH - Salts – electrolytes formed by the reaction between an acid and a base NaCl  Na + + Cl - HCl + NaOH H 2 O + NaCl

34. Acid and Base Concentration pH scale - indicates the concentration of hydrogen ions in solution Neutral pH 7; indicates equal concentrations of H + and OH - Acidic pH less than 7; indicates a greater concentration of H + Basic or alkaline pH greater than 7; indicates a greater concentration of OH - OH – concentration increasesH + Acidic H + Relative Amounts of H + (red) and OH – (blue) Basic OH – 2.0 gastric juice 6.0 corn 7.0 Distilled water 8.0 Egg white 10.5 milk of magnesia 11.5 Household ammonia pH 01234567891011121314 Basic (alkaline)Neutral Acidic 3.0 apple juice 4.2 tomato juice 5.3 cabbage 6.6 cow’s milk 7.4 Human blood 8.4 Sodium biocarbonate Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pg. 68

35. Buffers A buffer solution is one that maintains a constant pH upon the addition of either acid or base. It consists of a weak acid and a weak base. It can “sponge up” excess H + if added to a solution, or it can release H+ if the H+ concentration drops.

36. Inorganic Compounds Generally do not contain C* Usually smaller than organic molecules Usually dissociate in water, forming ions Water, oxygen, carbon dioxide, and inorganic salts * exceptions: CO, CO 2, HCO 3

37. Important Inorganic Compounds Water (H 2 O) Most abundant compound in living material Two-thirds of the weight of an adult human Major component of all body fluids Medium for most metabolic reactions Important role in transporting chemicals in the body Absorbs and transports heat Oxygen (O 2 ) Used by organelles to release energy from nutrients in order to drive cell’s metabolic activities Necessary for survival

38. Important Inorganic Compounds Carbon dioxide (CO 2 ) Waste product released during metabolic reactions Must be removed from the body Inorganic salts Abundant in body fluids Sources of necessary ions (Na +, Cl -, K +, Ca 2+, etc.) Play important roles in metabolism

39. Organic Compounds Contain C and H Usually larger than inorganic molecules Dissolve in water or organic liquids Carbohydrates, lipids, proteins, nucleic acids, and adenosine triphosphate