Biological molecules are assembled from only a small subset of the atoms present in the periodic table Lecture 2 Periodic table Chemical bonds and interactions Covalent bond sharing of electron pairs very strong Iconic bond attraction of opposite charges Hydrogen bond sharing of H atom Hydrogen bonds between biological molecules and water determine solubility Solubility in water related to hydrophilic Hydrophobic interaction interaction of nonpolar substances in the presence of polars substances especially water van der Waal s interaction interactions of nonpolar substances Fluorine the most electronegative element is assigned a value of 4 0 and values range down to Caesium and francium which are the least electronegative at 0 7 A chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself Sheds protons example acetic acid which gives vinegar its sour taste has acidic properties because it is so polar In the case of two methyl groups neither of which can ionize they are not attracted to water Con icting associations with water Palmitic acid Linoleic acid The structure of amphipathic molecules gives us a clue as to how biological membranes are assembled Condensation reaction is sometimes referred to as dehydration Also referred to as a lipid bilayer Comprised of hydrophobic fatty acid tails sandwiched between hydrophilic heads Proteins can thread their way through the lipid bilayer Tetravalent molecules such as carbon one can creat asymmetric molecules with mirror symmetries denoted with the suf x ose examples triose pentose etc The asymmetry of the carbons determines its function Enzymes denoted with the suf x ase example lactase Electronegativities Carboxyl Amino sucks up protons example Hyrdophobic Amphipathic Membrane Asymmetric carbons Carbohydrates
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