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2-4 Chemical reactions and enzymes
Objectives: Explain how chemical reactions affect chemical bonds in compounds. Explain why enzymes are important to living things.
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Warm Up Chemical reaction demo
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Introduction Everything that happens in an organism is based on chemical reactions
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Chemical reactions Chemical reaction: a process that changes one set of chemicals into another set of chemicals Reactants: the elements or compounds that enter into a chemical reaction Products: the elements or compounds produced by a chemical reaction Chemical reactions always involve the breaking of bonds in reactants and the formation of new bonds in products
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Energy in reactions Elephant’s toothpaste demo
Energy is released or absorbed whenever chemical bonds form or are broken Involve changes in energy
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Energy changes Energy changes are one of the most important factors in determining whether a chemical reaction will occur Chemical reactions that release energy often occur spontaneously Absorb energy will not occur without a source of energy Borax and glue demo
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Energy changes Energy can be released in the form of heat, light, or sound Organisms need to carry out reactions that require energy Every organism must have a source of energy to carry out chemical reactions Plantssunlight Animalseating food and drink
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Activation energy Activation energy: the energy that is needed to get a reaction started do.edu/en/simulat ion/reversible- reactions
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enzymes Catalyst: a substance that speeds up the rate of a chemical reaction Work by lowering a reaction’s activation energy Enzymes: proteins that act as biological catalysts Speed up chemical reactions that take place in cells
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Enzymes Cont’d Enzymes are very specific
Generally catalyzing only one chemical reaction Part of an enzyme’s name is usually derived from the reaction it catalyzes
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Enzyme action Reactants must collide with enough energy so that existing bonds will be formed If there’s not enough energy, they will be unchanged after the collision
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The enzyme-substrate complex
Substrates: the reactants of enzyme-catalyzed reactions Active site: the substrates bind to a site on the enzyme The substrates and active site have complementary shapes (like puzzle pieces)
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The enzyme-substrate complex Cont’d
Forms the enzyme- substrate complex Remain together until reaction is finished Then the products are released The enzyme moves to start the process again
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Regulation of enzyme activity
Enzymes can be affected by any variable that influences a chemical reaction pH values Temperature
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Regulation of enzyme activity Cont’d
Cells regulate activities of enzymes Cell proteins turn enzymes “on” and “off” Enzymes are essential in Regulating chemical pathways Making materials that cells need Releasing energy Transferring information
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2-4 Exit ticket Answer the following questions.
Use complete sentences. You may NOT use your book. You MAY use your notes. This is a quiz grade. Explain how chemical reactions affect chemical bonds in compounds. Explain why enzymes are important to living things.
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