BI 118 – Unit 1 Review

BI 118 – Unit 1 Review - BI118Unit1Review...

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BI 118 – Unit 1 Review 04:00 CHEMICAL BONDING Covalent bonds:  sharing of electrons (B.E ~ 50-100 kcal/mol) Non-covalent interactions:  do not involve formal sharing of electrons Van-der walls : weak interactions between e- clouds (B.E ~ 1 kcal/mol) H-bonds : involve partial e- sharing (B.E ~ 3-7 kcal/mol) Ionic : change in charge (each species has formal charge) (B.E ~ 3-7 kcal/mol) Dipolar : any molecule that has non-uniform charge in/around molecule (B.E ~ 2  kcal/mol) Electronegativity : attraction of a nucleus to an e-   nonpolar  = 2 atoms close in electronegativity   polar  = e- are drawn to 1 nucleus more than the other Bond Energy:  amt. of energy needed to put into system to break a bond Hydrophobic Interactions:  tendency of non-polar molecules to aggregate in water  solutions WATER SOLUTIONS Solvation    polar molecules can dissolve in water Water is liquid at physiological temps. because   H-bonds and dipolar interactions with  itself  4 H-bonds available per molecule  Solid > dense than liquid because solid lattice structure prevents closer  interactions
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Acids:  release H+ (strong = fully ionize in water) Bases:  accept H+  Buffers:  solution of weak acid + corresponding base  minimizes the effect of an added acid or base has on pH GIBB’S FREE ENERGY G =  H - T G = Free Energy ( G > 0 = unfavorable/endergonic) H = Enthalpy (“heat”) S = Entropy (disorder in a system) HYDROPHOBIC EFFECT  H 2 O organizes itself around hydrophobic molecule so molecules aggregate to  minimize surface area   minimize contact with water  entropy of H 2 O increases  MACROMOLECULES Proteins:  composed of amino acids   enzymes, structure Nucleic Acids: Polysaccharides:  composed of multiple monosaccharides  Lipids:  energy, storage, membranes
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AMINO ACIDS Charged Side Chains   Arginine =  positive Lysine = positive Histidine = positive Aspartic Acid = negative
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This note was uploaded on 11/27/2011 for the course BI 118 taught by Professor Multiple during the Spring '10 term at BU.

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BI 118 – Unit 1 Review - BI118Unit1Review...

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