End Show Slide 1 of 34 Copyright Pearson Prentice Hall Biology

End Show Slide 2 of 34 Do Now: Collect the papers at the front. Why do we consider monomers building blocks of proteins? Copyright Pearson Prentice Hall

End Show Slide 3 of 34 Announcements Test next week! Study! Look at your notes! Ask questions! Copyright Pearson Prentice Hall

End Show Slide 4 of 34 Copyright Pearson Prentice Hall 2–4 Chemical Reactions and Enzymes Part I

End Show 2–4 Chemical Reactions and Enzymes Slide 5 of 34 Copyright Pearson Prentice Hall Chemical Reactions A chemical reaction is a process that changes one set of chemicals into another set of chemicals.

End Show 2–4 Chemical Reactions and Enzymes Slide 6 of 34 Copyright Pearson Prentice Hall Chemical Reactions The elements or compounds that enter into a chemical reaction are known as reactants. The elements or compounds produced by a chemical reaction are known as products.

End Show 2–4 Chemical Reactions and Enzymes Slide 7 of 34 Copyright Pearson Prentice Hall Energy in Reactions Energy Changes Chemical reactions that release energy often occur spontaneously. Chemical reactions that absorb energy will not occur without a source of energy.

End Show 2–4 Chemical Reactions and Enzymes Slide 8 of 34 Copyright Pearson Prentice Hall Energy in Reactions When hydrogen gas reacts with oxygen to produce water vapor, it is an energy-releasing reaction in which energy is given off as heat. 2H 2 + O 2 2H 2 O What are the reactants? 2H 2 + O 2 What is the product? 2 H 2 O

End Show 2–4 Chemical Reactions and Enzymes Slide 9 of 34 Copyright Pearson Prentice Hall

End Show 2–4 Chemical Reactions and Enzymes Slide 10 of 34 Copyright Pearson Prentice Hall Energy in Reactions Activation Energy Chemists call the energy that is needed to get a reaction started the activation energy.

End Show 2–4 Chemical Reactions and Enzymes Slide 11 of 34 Copyright Pearson Prentice Hall Enzymes Catalysts Catalysts are chemicals that increase the rate of reaction and reduce the amount of energy needed. Some chemical reactions that make life possible are too slow or require a significant amount of energy. Enzymes are biological catalysts.

End Show 2–4 Chemical Reactions and Enzymes Slide 12 of 34 Copyright Pearson Prentice Hall Enzymes Enzymes speed up chemical reactions that take place in cells.

End Show 2–4 Chemical Reactions and Enzymes Slide 13 of 34 Copyright Pearson Prentice Hall Enzymes Function of the Enzyme –Speed up chemical reactions that take place in cells –Reduce the amount of energy needed for reaction to take place The Enzyme-Substrate complex is the structure where the reaction will occur.

End Show 2–4 Chemical Reactions and Enzymes Slide 14 of 34 Copyright Pearson Prentice Hall Enzyme Action What is the Enzyme- Substrate Complex? Enzymes provide a site where reactants can be brought together to react Match substrate/reactant exactly Substrate Reactants of enzyme- catalyzed reactions are known as substrates.

End Show 2–4 Chemical Reactions and Enzymes Slide 15 of 34 Copyright Pearson Prentice Hall Enzyme Action An Enzyme-Catalyzed Reaction

End Show 2–4 Chemical Reactions and Enzymes Slide 16 of 34 Enzymes Names Enzymes are named for the reactant they are associated with –Most enzymes end in “ase” –For example, lactose (milk sugar) is broken down by lactase Sucrose (table sugar) is broken down by sucrase –Don’t always break down, also build up DNA polymerase – builds DNA polymers Copyright Pearson Prentice Hall

End Show 2–4 Chemical Reactions and Enzymes Slide 17 of 34 Copyright Pearson Prentice Hall Enzyme Action Part II Regulation of Enzyme Activity Enzymes can be affected by any variable that influences a chemical reaction. pH values Changes in temperature Enzyme or substrate concentrations

End Show 2–4 Chemical Reactions and Enzymes Slide 18 of 34 Denaturation At high or low temperatures and at high or low pH, proteins unfolds and are no longer functional. _protein-denaturation_fun Copyright Pearson Prentice Hall

End Show 2–4 Chemical Reactions and Enzymes Slide 19 of 34 The pH Scale Measures the acidity or alkalinity of a substance pH is a measure of the amount of H ions in the substance. Alkaline substances (also called “basic”) have high pH –Bleach –Milk –Soap Acidic substances have very low pH –Lemon juice –Vinegar –Hydrochloric acid Copyright Pearson Prentice Hall

End Show 2–4 Chemical Reactions and Enzymes Slide 20 of 34 Enzyme Activity Effect of pH on enzyme activity –What is the optimum pH for this enzyme? 8 –What happens to enzymes at low or high pH? Enzymes denature Copyright Pearson Prentice Hall

End Show 2–4 Chemical Reactions and Enzymes Slide 21 of 34 Enzyme Activity Effect of temperature on enzyme activity What is the optimum temperature for this enzyme? –38C –What happens at low or high temperatures? Enzyme is denatures or breaks apart Copyright Pearson Prentice Hall

End Show 2–4 Chemical Reactions and Enzymes Slide 22 of 34 What is the effect of concentration on enzyme activity? As the enzyme concentration increases, The rate of the reaction increases Copyright Pearson Prentice Hall

End Show 2–4 Chemical Reactions and Enzymes Slide 23 of 34 As the amount of substrate increases, The rate of the reaction increases Until all enzymes are attached to a substrate Then the rate of the reaction remains the same Copyright Pearson Prentice Hall

End Show 2–4 Chemical Reactions and Enzymes Slide 24 of 34 Copyright Pearson Prentice Hall

End Show 2–4 Chemical Reactions and Enzymes Slide 25 of 34 Exit Slip Remember my cat Toby? The vet has recommended that my cat be on a high protein, low fat, low carbohydrate diet. Why would he encourage this diet, for my lazy fat cat? Copyright Pearson Prentice Hall

End Show - or - Continue to: Click to Launch: Slide 26 of 34 Copyright Pearson Prentice Hall 2–4

End Show Slide 27 of 34 Copyright Pearson Prentice Hall 2–4 The elements or compounds produced by a chemical reaction are known as a.reactants. b.enzymes. c.products. d.waste.

End Show Slide 28 of 34 Copyright Pearson Prentice Hall 2–4 Chemical reactions always involve a.changes in energy. b.enzymes. c.catalysts. d.changes in the atomic number of the reactants.

End Show Slide 29 of 34 Copyright Pearson Prentice Hall 2–4 The factor that prevents many energy-releasing reactions from occurring at relatively low temperatures is called a.catalytic energy. b.chemical bond energy. c.enzyme energy. d.activation energy.

End Show Slide 30 of 34 Copyright Pearson Prentice Hall 2–4 Which of the following statements is true? a.All proteins are enzymes. b.All catalysts are enzymes. c.All enzymes are catalysts. d.All catalysts are proteins.

End Show Slide 31 of 34 Copyright Pearson Prentice Hall 2–4 What happens to an enzyme after the reaction it catalyzes has taken place? a.The enzyme is destroyed, and the cell must make another. b.The enzyme holds on to the product until another enzyme removes it. c.The enzyme is unchanged and ready to accept substrate molecules. d.The enzyme changes shape so it can accept a different kind of substrate.

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