Bio 185 Lab today: Bio185 K Lab1: 1:00 2:30 PM Bio 185 K Lab2: 2:30 4:00 PM SCC 211. Lab manual available in the bookstore. Elemental Composition of living material: Chapter 2 The nature of molecules. Elemental and molecular composition of living matter: 1. Elemental composition 2. Structure of an atom 3. Chemical bonds. Lecture outline. 1. E LEMENTAL COMPOSITION OF THE LIVING MATTER. Major elements: N, O, C, H. Minor elements: Trace elements. 2. S TRUCTURE OF AN ATOM. Elements and atoms (SBM p27-31) 3. C HEMICAL BONDS. C HEMICAL BONDS (SMB P 32-36) ionic bonds and salts covalent bonds Frequency of elements in the Earths crust Elements Common in Living Things EARTHS CRUSTHUMANPUMPKIN Oxygen47 Oxygen65 Oxygen85 Silicon28 Carbon18 Hydrogen11 Aluminum8 Hydrogen10 Carbon3 Iron5 Nitrogen3 Potassium0 Calcium4 2 Nitrogen0 Sodium3 Phosphorus1 0 Potassium3 0 Calcium0 Magnesium2 Sulfur0 Magnesium0 Sodium0 Iron0 Chlorine0 Sodium0 Elemental composition of living material: Chemical composition of living material: 1. Major elements (95%) O, H, C, N 2. Minor elements (5 %) Na, K, P, Ca, Mg, Cl, S, 3. Trace elements Simple structure of an Atom. electron proton neutron nucleus Atom number = # electrons = # protons Atom mass = # protons + # neutrons Atom number determines chemical reactivity Structure of the noble gas NEON Both the K (2 e-) and L (8 e-) are completely filled: the atom is unreactive. Molecules: atoms are held together by chemical bonds. Covalent bonds: Ionic interactions: The octet rule : atoms tend to establish completely full (8 electrons) outer energy levels. Chapter 2 The nature of molecules. Non-polar covalent bonds. Water is a dipole. pH and buffers. Re-visit Covalent Bonds. A pair of electrons is shared equally in a covalent bond. Single covalent bondDouble covalent bond The force with which an atom pulls on a shared electron pair is given by its electronegativity. Non-polar covalent bond. Polar covalent bond Structure of a water molecule; water is a dipole. Water is a DIPOLE Hydrogen bonds: Water molecules Butanol and water Water is COHESIVE Waters high specific heat helps maintain temperature. Waters high heat of vaporization facilitates cooling. Cooling of a surface by transition from liquid to gas. Water has a high heat of vaporization. Hydroxyl-group Carbonyl-group Hydrogen bond Spheres of Hydration Around Two Charged Ions Salt (NaCl) dissolves in water and separates into Na + and Cl - Hydration shell or water mantle Water ionizes: Buffer: maintains [H + ] free despite addition or removal of H +. The End.