Chemical Reactions Chemical Reactions Chemical Reaction process that

Chemical Reactions

Chemical Reactions • Chemical Reaction: process that changes one set of chemicals into another set of chemicals • Reactants - elements or compounds entering the reaction • Products - elements or compound formed by the reaction – Break bonds in reactions and form new bonds in products • CO 2 + H 2 O H 2 CO 3 • H 2 CO 3 CO 2 + H 2 O

Energy in Reactions • Chemical reactions can release energy or absorb energy when chemical bonds are formed or broken. • Reactions that release energy occur spontaneously. • Heat, light, or sound • Reactions that absorb energy need a source of energy to begin. • 2 H 2 + O 2 –> 2 H 2 O

Activation Energy • Activation Energy: energy need to start a reaction – Cellulose, in paper, burns in the presence of oxygen and release heat and light, but requires the energy of match to start the reaction. • Catalysts: a substance that speed up the rate of chemical reactions; – Lowers activation energy – Use catalysts when activation energy is too great or reaction is too slow

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Enzymes • Enzymes: protein catalyst that speed up reaction inside cells • Specific: each enzyme only catalyzes only one reaction • Each enzyme has a specific, complex shape • names end in -ase

Enzyme Action • Enzymes provide a site where reactant can come together to react reduces energy need • substrates: reactants of enzymecatalyzed reaction • substrate binds to the active site

Enzyme Action • lock & key: which have complementary shapes • once the substrate binds to the enzyme, it becomes Enzyme-Substrate Complex – they remain bound until the reaction occurs – after which, the products are released – the enzyme can start anew • Regulation of Enzyme Activity – affected by temperature & p. H

Enzyme Animation • http: //www. lpscience. fatcow. com/jwan amaker/animations/Enzyme%20 activit y. html