1. Chemical Reactions

2. Law of Conservation of energy Kinetic energy=energy of motion Potential energy=stored energy – Chemical energy= found in food Law of Conservation of energy=energy is transferred between kinetic and potential Activity

6. Chemical reactions of life Metabolism – forming bonds between molecules dehydration synthesis _____________ reactions – breaking bonds between molecules hydrolysis _____________ reactions anabolic catabolic

7. Examples  dehydration synthesis  hydrolysis

8. Chemical reactions & energy Some chemical reactions _________________ – digesting polymers – hydrolysis = catabolism Some chemical reactions require ______________________ – building polymers – dehydration synthesis = anabolism digesting molecules= less organization= lower energy state building molecules= more organization= higher energy state Release energy energy

9. Energy & life Organisms require energy to live – where does that energy come from? coupling exergonic reactions (___________ energy) with endergonic reactions (___________ energy) ++ energy + + Activity release require

10. Practice The sum total of all the chemical reactions in a living structure is called its 1. energetics. 2. entropy. 3. metabolism. 4. digestive power. 5. activity. Water held back by a dam represents what kind of energy? 1. Kinetic 2. At times, all of these 3. Hydroelectric 4. Irrigation 5. Potential

11. Spontaneous reactions? If reactions are “downhill”, why don’t they just happen spontaneously? – because ___________ bonds are ____________ Why don’t polymers (carbohydrates, proteins & fats) just spontaneously digest into their monomers covalent stable

12. Activation energy Breaking down large molecules requires an initial input of energy – large biomolecules are stable – must __________ energy to break bonds energy cellulose CO 2 + H 2 O + heat Activity add

13. Activation energy the amount of energy needed to _______________ the bonds of a molecule – moves the reaction over an “energy hill” Got a match? No, that’s too much energy to get the work of life done! break

14. Reducing Activation energy Catalysts – _____________ the amount of energy to start a reaction Pheew… that takes a lot less energy! reduces Call in the... ENZYMES!

16. Enzymes Biological _______________ – proteins (& RNA) – facilitate chemical reactions ____________ rate of reaction without being consumed ___________ activation energy – required for most biological reactions – highly specific thousands of different enzymes in cells – control reactions catalyst increase reduce

17. Practice Without enzymes, the chemical reactions in your body would 1. require a different pH. 2. occur at much the same rate as they do now. 3. give off too much heat. 4. occur too slow to support life processes. 5. happen too fast.

18. Enzymes & substrates ____________ reactant which binds to enzyme enzyme-substrate complex: temporary association ______________ end result of reaction substrate product

19. Fig. 5-09-1 Active site Enzyme (sucrase) Sucrase can accept a molecule of its substrate. H2OH2O

20. Fig. 5-09-2 Active site Enzyme (sucrase) Sucrase can accept a molecule of its substrate. Substrate (sucrose) Substrate binds to the enzyme.

21. Fig. 5-09-3 Active site Enzyme (sucrase) Sucrase can accept a molecule of its substrate. Substrate (sucrose) Substrate binds to the enzyme. The enzyme catalyzes the chemical reaction. H2OH2O

22. Fig. 5-09-4 Active site Enzyme (sucrase) Sucrase can accept a molecule of its substrate. Substrate (sucrose) Substrate binds to the enzyme. The enzyme catalyzes the chemical reaction. H2OH2O Fructose Glucose The products are released.

23. Enzymes & substrates Enzyme + substrates  products – sucrase enzyme breaks down sucrose binds to sucrose & breaks disaccharide into fructose & glucose – DNA polymerase enzyme builds DNA adds nucleotides to a growing DNA strand

24. Lock and Key model Simplistic model of enzyme action – 3-D structure of enzyme fits substrate Active site – enzyme’s catalytic center – pocket or groove on surface of globular protein

25. Induced fit model More accurate model of enzyme action – 3-D structure of enzyme fits substrate – as substrate binds, enzyme changes shape leading to a tighter fit “conformational change” bring chemical groups in position to catalyze reaction

26. How does it work? Variety of mechanisms to lower activation energy & speed up reaction – active site orients substrates in correct position for reaction enzyme brings substrate closer together – active site binds substrate & puts stress on bonds that must be broken, making it easier to separate molecules

27. Practice An enzymatic reaction can bring about only synthesis, i.e., two smaller molecules joined to form a larger molecule. A) True B) False The reactants in an enzymatic reaction are called the substrates for that enzyme. A) True B) False The ______ is a place where the substrates fit onto the enzyme in such a way that they are oriented to react. When the substrate binds to the enzyme, the active site undergoes a slight alteration to achieve the best fit. A)True B)False

28. Practice An active site is 1. the part of the substrate that binds with an enzyme. 2. the site where enzymes are found in cells. 3. the site where energy is added to an enzyme catalyst. 4. None of these 5. the part of the enzyme that binds with a substrate. The molecules that are acted on by an enzyme are called 1. effectors. 2. products. 3. carriers. 4. substrates. 5. prosthetics.

29. Practice What occurs when an enzyme and a substrate interact at an active site? 1. The enzyme is changed by the reaction. 2. Activation energy is unchanged. 3. Activation energy is reduced. 4. The products are bound irreversibly.

30. Properties of Enzymes

31. Specificity of enzymes Reaction specific – each enzyme is ______________ due to fit between active site & substrate – substrates held in active site by weak interactions » H bonds » ionic bonds – enzymes named for reaction they catalyze sucrase breaks down sucrose proteases break down proteins lipases break down lipids DNA polymerase builds DNA pepsin breaks down proteins (polypeptides) Substrate specific

32. Reusable ________________ in reaction – single enzyme molecule can catalyze thousands or more reactions per second – enzymes unaffected by the reaction Not consumed

33. Practice Every reaction in a cell requires a specific enzyme. A) True B) False A cell must produce large quantities of each enzyme in order to survive. A) True B) False Each enzyme can speed up only one particular reaction. This specificity is due to the ______. A) shape of both the enzyme and the substrate B) lowering of the energy of activation C) pH of the surrounding medium D) temperature of the surrounding medium E) permanent binding of the enzyme-substrate complex

34. Practice Which of the following statements about enzymes is true? 1. Enzymes lower the energy barrier. 2. Enzymes have a specific amino acid sequence. 3. Enzymes are proteins. 4. All of these 5. Enzymes are highly specific.

35. Factors that Affect Enzymes

36. Factors Affecting Enzymes Enzyme concentration Substrate concentration Temperature pH Salinity Activators Inhibitors catalase

37. 37° Temperature temperature reaction rate What’s happening here?!

38. Temperature Effect on rates of enzyme activity – Optimum T° greatest number of molecular collisions human enzymes = 35°- 40°C (body temp = 37°C) – Increase beyond optimum T° increased agitation of molecules disrupts bonds – H, ionic = weak bonds denaturation = lose 3D shape (3° structure) – Decrease T° molecules move slower decrease collisions

39. 7 pH reaction rate 20134568910 pepsintrypsin What’s happening here?!

40. pH Effect on rates of enzyme activity – protein shape (conformation) attraction of charged amino acids – pH changes changes charges (add or remove H + ) disrupt bonds, disrupt 3D shape – affect 3° structure – most human enzymes = pH 6-8 depends on localized conditions pepsin (stomach) = pH 3 trypsin (small intestines) = pH 8

41. Practice Enzymes speed up the reaction by a.Increasing the energy of activation b.Decreasing the energy of activation c.Increasing the temperature of the reaction d.Increasing the substarte concentration e.Decreasign the kinetic energy of the reaction

42. Practice Which of the following will change the rate of reaction of an enzyme Energy of motion is referred to as _______ energy The sum of all chemical reactions occurring inside a living cell is called ______. The sum of all chemical reactions occurring inside a living cell is called ______.

43. Practice Which molecule is considered to be the energy currency of cells? A) glucose B) lipids C) proteins D) ATP E) oxygen Until reaching a point where the enzyme is denatured, an increase in temperature will cause molecules to move faster, thereby decreasing the chance of the reactants colliding. A) True B) False

44. Practice Which of the following statements is NOT correct about enzymes? A) Most enzymes are protein molecules. B) Every reaction in a cell requires a specific enzyme. C) Enzymes speed up a chemical reaction. D) Enzymes are often named for the products formed. E) Enzymes are absolutely necessary to the continued existence of a cell.

45. Practice Too high or low a pH disrupts the hydrogen bonding and interactions between ______ of a protein and cause the enzyme to become denatured. A) amino acids B) R group side chains C) nucleic acids D) monosaccharides E) fatty acids (An) ______ is any organic, nonprotein molecule that binds with an enzyme other than its substrate. A) reactant B) product C) inhibitor D) coenzyme

46. Challenge Question For each group of experiments, explain how the differences in experimental conditions could affect the reaction. a. You compare two side-by-side experiments. In experiment 1, you use X amount of the enzyme. In experiment 2, you use 2X amount of the same enzyme. b. You compare two side-by-side experiments. In both you use equal amounts of the enzyme. In experiment 3, you allow the products to accumulate over time. In experiment 4, you remove the products from the system as they are produced. c. In the next two experiments, you use equal amounts of the enzyme. You run experiment 5 at 20ºC and experiment 6 at 25ºC. d. In two final experiments, you use equal amounts of the enzyme. You run experiment 7 at pH 6 and experiment 8 at pH 8.