Chemical reactions and enzymes

1. Chemical reactions and enzymes Section 2

2. Section 2 Vocabulary: ( 6 words) • chemical reaction (reactants, products), • activation energy, • catalyst, • enzyme, • substrate, • active site.

3. SC.912.L.18.11 • Explain the role of enzymes as catalysts that lower the activation energy of biochemical reactions. • Identify factors, such as pH and temperature, and their effect on enzyme activity.

4. Energy is the ability to cause change

5. Mechanical Energy • Thermal Energy • Chemical Energy • Light Energy • Sound Energy • Electrical Energy

6. Thermodynamics: the study of energy transformation

7. First Law of Thermodynamics: Energy cannot be created or destroyed; it can only be converted from one form to another • Using food for movement • Using food for maintaining body temperature • *Usable energy decreases as some is transferred to heat.

8. Energy can be stored or released by chemical reactions.

9. Chemical Equations • Reactants: substances that are combined or broken apart • Products: new substances that are formed • REACTANTS  PRODUCTS

10. Some reactions give off energy ( heat) Exergonic. The amount of energy is less at the end due to heat being released. and some take it in Endergonic! The amount of energy is greater at the end! Heat is taken in! These reactions require energy to occur!

11. Energy storing Energy releasing

13. The number before each chemical formula represents the number of molecules. The subscripts indicate the number of atoms of each element.A chemical equation is balanced when the numbers of atoms of each element are equal on each side of the arrow.2H2 + O2 2H2O

14. Respiration The chemical reaction that living things use to take glucose And oxygen and release the energy Stored in the chemical bonds And form ATP molecules while producing Water and carbon dioxide as products!

15. 1. Write the chemical reaction for respiration 2. Circle the reactants and box the products in the above reaction

16. . 3. In a balanced equation, How many molecules of glucose are used in this reaction? ONE How many molecules of oxygen are used? six

17. Activation Energy: energy needed to start a chemical reaction • Gasoline doesn’t burn on its own…it needs a spark

18. 4. What is activation energy? energy needed to start a chemical reaction

19. Enzymes Lower the activation energy!

20. Enzymes provide activation energy for the biochemical reactions in cells. • Enzymes are catalysts—they increase the rate of reactions at lower temperatures by lowering the activation energy needed. • Words that end in –ASE are enzymes.

23. enzymes

24. Substrate: molecule to which an enzyme binds • Active site: place on enzyme where substrate binds.

27. Example: Amylase catalyzes the breakdown of starch into glucose. • Enzymes attach only to certain molecules.

28. pH and temperature affect the shape of an enzyme.

29. 5. Factors that might affect the rate of an enzyme catalyzed reaction include what? • Temperature, pH, concentrations of the enzyme and substrate • Anything that alters the shape of the enzyme so that the substrate can’t fit into the active site or the availability of the enzyme.

30. 6. What does changing the pH do to an enzyme? It can break bonds between the chains of amino acids and the shape of the protein can be changed so that the active site is no longer open for bonding the substrate! This denatures the enzyme! • 7. Changing the temperature? Can do the same as pH it can break the hydrogen bonds that hole a protein in the proper shape and denature the enzyme!

31. 8. The major role of an enzyme in biochemical reactions is what? • They lower the energy of activation! This allows chemical reactions to take place at greater rates and lower temperatures.

32. 9. What is the active site of an enzyme? • The place on the enzyme where the substrate binds! an enzyme: protein that lowers the activation energy! Catalyst!

33. 10. Draw a graph of an enzyme catalyzed reaction and a reaction without

34. BIOLOGY LAB: • Title: The Enzyme CATALASE

35. INTRODUCTION: • What would happen to your cells if they made a poisonous chemical? • You might think that they would die. • In fact, your cells are always making poisonous chemicals. They do not die because your cells use enzymes to break down these poisonous chemicals into harmless substances.

36. Enzymes are proteins that speed up the rate of reactions that would otherwise happen more slowly. • The enzyme is not altered by the reaction. • You have hundreds of different enzymes in each of your cells. Each of these enzymes is responsible for one particular reaction that occurs in the cell.

37. In this lab, you will study an enzyme that is found in the cells of many living tissues. • The name of the enzyme is catalase (KAT-uh-LAYSS); • it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless substances--water and oxygen. • The reaction is as follows: • 2H2O2 ----> 2H2O + O2

38. This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of many normal cellular reactions. • If the cells did not break down the hydrogen peroxide, they would be poisoned and die.

39. In this lab, you will study the catalase found in liver cells. • You will be using chicken or beef liver. It might seem strange to use dead cells to study the function of enzymes. • This is possible because when a cell dies, the enzymes remain intact and active for several weeks, as long as the tissue is kept refrigerated.

40. Problems:write these down • What living materials contain catalase? • Is catalase used up in the reaction? • What happens to the rate of the catalase reaction when the temperature and pH levels are raised/lowered? • How does crushing/cutting up the material affect the rate of the reaction?

41. PRELAB REVIEW: • Before you begin this lab, review pH. Recall that pH is the measure of the acidity or alkalinity of a solution. • An acidic solution has many hydrogen ions (H+) and a pH below 7. • An alkaline, or basic, solution has very few hydrogen ions and a pH above 7. • A neutral solution has a pH of 7.

42. Recall that the substrate is the molecule that the enzyme acts on, and the products are the molecules produced by the reaction. Review that enzymes are reusable because they are not part of the reaction!

43. denatured • Under certain conditions enzymes are denatured. • An enzyme is denatured when the protein molecule loses its proper shape and cannot function. • Some things that can denature an enzyme are high temperatures, extremes of pH, heavy metals, and alcohol.

44. MATERIALS: 1 acetic acid (vinegar) (in dropper bottle)1 sodium bi carbonate base (baking soda solution) (in dropper bottle)6 Test tubes and rackTest tube holder10-ml Graduated cylinder40 ml 3% Hydrogen peroxide solutionScalpel 3 beakers for water bathsScissors and Forceps (tweezers)ThermometerStirring rodpH paperFresh liver, chicken meat, Apple, and Potato

45. Hypotheses:write these down! • Make your own hypothesis for each of the problems for this lab! Write them in the same order as the original problems! • Example; Problem number 2: This researcher believes the catalase will not be used in the reaction. • There will be a hypothesis for each of the 4 problems!

46. 1. It is hypothesized that liver, chicken, apple and potato will or will not contain catalase? Make a hypothesis for each substance!! And then in your conclusion, did you accept or reject each one?

47. 2. It is hypothesized that catalase will or will not be used up in the reaction. • 3. • When the temperature is raised above room temperature the rate of the reaction will… • When the temperature of the reaction is lowered below room temperature the rate will… • When the pH is 7 the rate will … • When the pH is below 7 the rate will be… • When the pH is above 7 the rate will be … 4. Crushing the samples will __________ the rate of the reaction.

48. Throughout this investigation you will estimate the rate of the reaction (how rapidly the solution bubbles) on a scale of 0-5 (0=no reaction, 1=slow, 5= very fast). • Use the height on the test tube to help estimate the rate of the reaction. 5 4 2 1

49. PROCEDURE: • Part I Normal Catalase ActivityNOTE: Be sure to clean your stirring rod (and test tubes) between steps. Wash all test tubes before using!!

50. 1. Place 2 ml of the 3% hydrogen peroxide solution into a clean test tube. • 2. Using forceps and scissors cut a small piece of liver and add it to the test tube. • NEW!!! Measure the mass of the piece of liver so you can cut pieces approximately the same size each time!!! Push it into the hydrogen peroxide with a stirring rod. Assume that the reaction in step 2 proceeded at a rate of "4" and record the speed in DATA TABLE 1, and DATA TABLE 2 as the rate at room temperature.