3. State Standard SB1B - Explain how enzymes act as catalysts.

4. Physical vs. Chemical  A physical change alters the substance’s appearance but not its composition.  There is no formation of a new substance. 6.2 Chemical Reactions Chemistry in Biology Physical reaction Chapter 6

5. Physical vs. Chemical Cont’d  A chemical reaction is the process by which atoms or groups of atoms in substances are reorganized into different substances. 6.2 Chemical Reactions  Clues that a chemical reaction has taken place include the production of heat or light, and formation of a gas, liquid, or solid.  Not reversible! Chemistry in Biology Chemical reaction Chapter 6

6. Chemical Equations Chemistry in Biology  Chemical formulas describe the substances in the reaction and arrows indicate the process of change.  Chemical equations have 2 sides:  Reactants are the starting substances, on the left side of the arrow.  Products are the substances formed during the reaction, on the right side of the arrow. 6.2 Chemical Reactions Chapter 6

7.  Example of a chemical equation: During cellular respiration, Glucose and oxygen react to form carbon dioxide and water. Chemistry in Biology 6.2 Chemical Reactions Chapter 6 Chemical Equations Cont’d Practice your knowledge by labeling the parts of the equation above.

8. Chemistry in Biology  The activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction. Energy of Reactions 6.2 Chemical Reactions Chapter 6

9. Chemistry in Biology  A catalyst is a substance that lowers the activation energy needed to start a chemical reaction.  Enzymes are proteins that act as biological catalysts.  It does not increase how much product is made – only how quickly it is made. Enzymes 6.2 Chemical Reactions Chapter 6

10. Chemistry in Biology  All living things are driven by constant internal chemical reactions (metabolism).  Enzymes help these reactions happen quickly enough for an organism to stay alive.  Enzymes increase the rate (speed) of a reaction by lowering activation energy. 6.2 Chemical Reactions Chapter 6 Enzymes Cont’d

11. Chemistry in Biology  The reactants that bind to the enzyme are called substrates.  The specific location where a substrate binds on an enzyme is called the active site. 6.2 Chemical Reactions Chapter 6 Enzymes Cont’d

12. Chemistry in Biology 6.2 Chemical Reactions Chapter 6  The active site changes shape and forms the enzyme-substrate complex, which helps chemical bonds in the reactants to be broken and new bonds to form. This is called induced fit. Enzymes Cont’d

13. Chemistry in Biology  Enzyme activity is affected by factors such as pH, temperature, & other substances.  Extreme pH & temperature can change the shape of the enzyme and render it useless. This is called denaturing. 6.2 Chemical Reactions Chapter 6 Enzymes Cont’d

14. Chemistry in Biology  Enzymes are named for the substrates that they react with…  Enzyme names end with the suffix “-ase”.  Examples:  Sucrase breakes down the sugar sucrose  Lactase breaks down the sugar lactose  Protease breaks down protein molecules 6.2 Chemical Reactions Chapter 6 Enzymes Cont’d

15. Chemistry in Biology  Enzyme action is often compared to the action of locks & keys… 6.2 Chemical Reactions Chapter 6 Enzymes Cont’d …because each enzyme is shaped to fit together with a specific substrate and they are reusable.

16. Chemistry in Biology Chapter 6

17. A. substrates B. enzymes C. ions D. reactants Identify the proteins that speed up the rate of chemical reactions. Chemistry in Biology Chapter Diagnostic Questions Chapter 6

18. A. a match burning B. salt dissolving C. water boiling D. gasoline evaporating Which is a chemical reaction? Chemistry in Biology 6.2 Formative Questions Chapter 6

19. A. It acts as a reactant. B. It reduces the amount of heat produced. C. It increases the amount of product. D. It lowers the activation energy. How does an enzyme increase the rate of a chemical reaction? Chemistry in Biology 6.2 Formative Questions Chapter 6

20. What occurs at the active site in the enzyme substrate complex? Chemistry in Biology 6.2 Formative Questions Chapter 6

21. Chemistry in Biology 6.2 Formative Questions Chapter 6 A. An exothermic chemical reaction takes place. B. Chemical bonds are broken and new bonds are formed. C. The enzyme gets used up in the reaction. D. The substrates provide energy for the enzyme.

22. A. hormone B. nucleic acid C. protein D. steroid What type of biological molecule is an enzyme? Chemistry in Biology 6.4 Formative Questions Chapter 6

23. A. activation energy B. reactants C. products D. enzymes Look at the following figure. Determine what the upward curve represents. Chemistry in Biology Chapter Assessment Questions Chapter 6 ?