3-Lecture_3

3-Lecture_3 - BCHM 561 Chapter 1 REVIEW OF CHEMICAL...

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Unformatted text preview: BCHM 561 Chapter 1 REVIEW OF CHEMICAL CONCEPTS Friday, August 29, 2008 1 Unity in Biochemistry Genetic Information: DNA or RNA Catalysts: Proteins / 20 Amino acids Energy Production: Oxidative Pathways / ATP formation Biosynthesis: Synthetic Pathways Small Biomolecules: metabolites, hormones, etc Friday, August 29, 2008 2 Model Organisms Escherichia coli Saccharomyces cerevisiae Schizosaccharomyces pombe Dictyostelium discoideum (slime mold) Caenorhabditis elegans Drosophila melanogaster Zebrafish (Danio rerio) Xenopus laevis Mouse (Mus musculus) Arabidopsis thaliana Friday, August 29, 2008 3 DNA - double helix To discuss forces that hold macromolecules together Friday, August 29, 2008 4 DNA is comprised of 4 bases Friday, August 29, 2008 5 Sugar-Phosphate Backbone Friday, August 29, 2008 6 Hydrogen-bonded base pairs Friday, August 29, 2008 7 DNA - double helix Friday, August 29, 2008 8 DNA Replication Friday, August 29, 2008 9 Covalent and Noncovalent Bonds are Crucial in Stabilizing the Structure of Biological Molecules Friday, August 29, 2008 10 covalent bonds Friday, August 29, 2008 11 Covalent Bond Energies (kcal/mol) (kcal/mol) (112) (170) (120) (195) (222) (51) Friday, August 29, 2008 12 Ethane Friday, August 29, 2008 13 Resonance Structures bond length C–C 1.54 Å C=C 1.34 Å C4–C5 1.40 Å neither canonical structure exists hybrid structure exists, electrons delocalized over carbons involved 14 Friday, August 29, 2008 Weak Noncovalent Bonds in Aqueous Systems are Crucial for Stabilizing Macromolecules Friday, August 29, 2008 15 Electrostatic Interactions kq1q2 F= 2 Dr q1 and q2 - charges D - dielectric constant r - distance between charges Friday, August 29, 2008 16 Energy is equivalent to force X distance (r) kq1q2 E= Dr q expressed in units of electron charge (+1e, -1e) k = 332 kcal mol-1·Å D = 1 vacuum = 80 water = 24.3 ethanol = 1.9 hexane r = 3Å D = 80 E = – 1.4 kcal -1 mol Friday, August 29, 2008 17 Hydrogen Bonds Water forms hydrogen bonds δ+ dipole δ– δ+ longer than covalent bonds 1-5 kcal mol-1 Friday, August 29, 2008 18 Hydrogen Bonds in Biology Friday, August 29, 2008 19 Hydrogen Bonds have preferential geometries Friday, August 29, 2008 20 van der Waals Interactions when in close contact, two uncharged atoms influence one another transient asymmetry in electron distribution creates a transient dipole the transient dipole can induce a dipole in a neighboring atom the dipoles generate an electrostatic interaction Friday, August 29, 2008 21 van der Waals Interactions E = 0.5 – 1.0 kcal mol-1 Friday, August 29, 2008 22 Properties of Water δ+ – δ δ+ Friday, August 29, 2008 23 The Hydrophobic Ef fect decreased entropy Friday, August 29, 2008 24 hydrophobic interaction Friday, August 29, 2008 25 ...
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