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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.
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Elemental Composition of living material: 1. 2. 3.
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Chapter 2 The nature of molecules. Elemental and molecular composition of living matter: 1. Elemental composition 2. Structure of an atom 3. Chemical bonds.
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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
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Frequency of elements in the Earth’s crust
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Elements Common in Living Things
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EARTH’S 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
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Elemental composition of living material:
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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
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Simple structure of an Atom.
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electron proton neutron nucleus Atom number = # electrons = # protons Atom mass = # protons + # neutrons
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Atom number determines chemical reactivity
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Structure of the noble gas NEON Both the K (2 e-) and L (8 e-) are completely filled: the atom is unreactive.
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Molecules: atoms are held together by chemical bonds.
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Covalent bonds:
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Ionic interactions:
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The ‘octet’ rule : atoms tend to establish completely full (8 electrons) outer energy levels.
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Chapter 2 The nature of molecules. Non-polar covalent bonds. Water is a dipole. pH and buffers.
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Re-visit Covalent Bonds.
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A pair of electrons is shared equally in a covalent bond. Single covalent bondDouble covalent bond
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The force with which an atom pulls on a shared electron pair is given by its electronegativity. Non-polar covalent bond.
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Polar covalent bond
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Structure of a water molecule; water is a dipole.
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Water is a DIPOLE
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Hydrogen bonds:
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Water molecules Butanol and water
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Water is COHESIVE
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Water’s high specific heat helps maintain temperature. Water’s high heat of vaporization facilitates cooling.
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Cooling of a surface by transition from liquid to gas. Water has a high heat of vaporization.
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Hydroxyl-group Carbonyl-group Hydrogen bond
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Spheres of Hydration Around Two Charged Ions Salt (NaCl) dissolves in water and separates into Na + and Cl -
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Hydration shell or water mantle
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Water ionizes:
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Buffer: maintains [H + ] free despite addition or removal of H +.
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The End.
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