1. C H A P T E R © 2013 Pearson Education, Inc.© Annie Leibovitz/Contact Press Images Chemistry Comes 2

2. Chemical Reactions Occur when chemical bonds are formed, rearranged, or broken Represented as chemical equations using molecular formulas –Subscript indicates atoms joined by bonds –Prefix denotes number of unjoined atoms or molecules Chemical equations contain –Reactants Number and kind of reacting substances –Chemical composition of the product(s) –Relative proportion of each reactant and product in balanced equations 6/13/20122MDufilho

3. Chemical Reactions Reactants – End Products - Catalysts - 6/13/20123MDufilho

4. Note: CH 4 is a molecular formula Examples of Chemical Equations Reactants H + H  4H + C  Product H 2 (Hydrogen gas) CH 4 (Methane) 6/13/20124MDufilho

5. Patterns of Chemical Reactions Synthesis (combination) reactions Decomposition reactions –Oxidation-Reduction (Redox) Exchange reactions 6/13/20125MDufilho

6. Synthesis Reactions A + B  AB –Always involve bond formation – Anabolic 6/13/20126MDufilho

7. Decomposition Reactions AB  A + B –Reverse synthesis reactions –Involve breaking of bonds –Catabolic 6/13/20127MDufilho

8. Exchange Reactions AB + C  AC + B –Also called displacement reactions –Bonds are both made and broken 6/13/20128MDufilho

9. Oxidation-Reduction (Redox) Reactions Are decomposition reactions –Reactions in which food fuels are broken down for energy Are also exchange reactions because electrons are exchanged between reactants –Electron donors lose electrons and are oxidized –Electron acceptors receive electrons and become reduced C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP Glucose is oxidized; oxygen molecule is reduced 6/13/20129MDufilho

10. Energy Flow in Chemical Reactions All chemical reactions are either exergonic or endergonic –Exergonic reactions—net release of energy Products have less potential energy than reactants Catabolic and oxidative reactions –Endergonic reactions—net absorption of energy Products have more potential energy than reactants Anabolic reactions 6/13/201210MDufilho

11. Reversibility of Chemical Reactions All chemical reactions are theoretically reversible –A + B  AB –AB  A + B Chemical equilibrium occurs if neither a forward nor reverse reaction is dominant Many biological reactions are essentially irreversible – Due to energy requirements – Due to removal of products 6/13/201211MDufilho

12. Rate of Chemical Reactions Affected by –  Temperature   Rate –  Concentration of reactant   Rate –  Particle size   Rate –Catalysts:  Rate without being chemically changed or part of product Enzymes are biological catalysts 6/13/201212MDufilho

13. Biochemistry Study of chemical composition and reactions of living matter All chemicals either organic or inorganic 6/13/201213MDufilho

14. Classes of Compounds Inorganic compounds Water, salts, and many acids and bases Do not contain carbon Organic compounds Carbohydrates, fats, proteins, and nucleic acids Contain carbon, usually large, and are covalently bonded Both equally essential for life OYO – Learn the basics from handout 6/13/201214MDufilho