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Lecture 1Chemistry Is the Logic that Underlies BiologicalPhenomenaOutline• Distinctive Properties of Living Systems• Biomolecules: Molecules of Life• Biomolecular Hierarchy• Properties of Biomolecules• Organization and Structure of Cells• Viruses as Cell ParasitesDistinctive Properties of Living Systems• Organisms are complicated and highly organized• Biological structures serve functional purposes• Living systems are actively engaged in energy transformations• Living systems have a remarkable capacity for self-replicationBiomolecules: The Molecules of LifeH, O, C and N make up 99+% of atoms in the human bodyELEMENT PERCENTAGEOxygen 63.0Hydrogen 25.2Carbon 9.5Nitrogen 1.4which adds up to 99.1%…what is the rest?C, H, O and N form Strong Bonds with Each Other• Some biolmolecules need to be aroundfor a long time• The molecules in human oocytes (eggcells) have to last from before birth tomenopause– at least 50 years!• Covalent bonds made by sharingelectrons are necessaryTypical Covalent Bond EnergiesBond Energy kJ/mol H-H 436 C-H 414 C-C 343 C-O 351Covalent Bonds Give a Wealth of Shapes in 3-DAnd a Wealth of Functionality• ATP• Energy is stored in phosphoric anhydridebonds• Hydrolysis gives 3x as much energy asacetic anhydride!• NADPH• Stereoselective reducing agent• H- is transferred to only one face of thesubstrate molecule• What do you know about hydrides inorganic chemistry?• DNA• C=O and N-H functionalities– H-bond acceptors and donors• Covalent bonds make the backbone and the bases (A,C,G,T)• H-bonds dictate the register and direction– A:T– G:C– antiparallelA Biomolecular HierarchySimple Molecules are the Units forBuilding Complex Structures• Metabolites and Macromolecules• Organelles• Membranes• The Unit of Life is the CellProperties of Biomolecules Reflect their Fitness for Life• Macromolecules and their building blocks have a “sense” or directionality• Macromolecules are informational• Biomolecules have characteristic 3-dimensional architecture• Weak forces maintain biological structure and determine biomolecularinteractionsChiral Monomers make Complex BiopolymersWhere’s the chirality?Higher Order Structures are Maintained by Weaker H-bondsKnow the H-bond donors and acceptors!Weak Bonds and Weaker Bonds…Important numbers!• Van der Waals: 0.4-4.0 kJ/mole• Hydrogen bonds: 12-30 kJ/mole• Ionic bonds: 20 kJ/mole• Hydrophobic interactions: <40 kJ/moleTwo Important Points About Weak ForcesWeak Chemical Forces MediateBiomolecular Recognition……and Restrict Organisms to a Narrow Range of EnvironmentalConditionsOrganization and Structure of Cells• Prokaryotic cells– A single (plasma) membrane– no nucleus or organelles• Eukaryotic cells– much larger in size than prokaryotes– 103-104 times larger!– Nucleus plus many organelles– ER, Golgi, mitochondria,


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UVM CHEM 205 - Lecture Notes

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