Name:_________________________________ Enzymes A Catalyst is a substance that changes the rate of a chemical reaction without being consumed or changed. Enzymes are proteins that act as biological catalysts. Enzymes function as catalysts by weakening bonds, lowering the amount of activation energy necessary for a reaction to occur. Enzymatic reactions depend on a physical fit between the enzyme molecule and its substrate. Each enzyme has an active site with a shape that allows the substrate to fit. After the reaction, the enzyme releases the products. The enzyme is unchanged and can be used again. 1. Label the following parts with the correct letter (use figure at the top of page too help) Letter Part Enzyme Before Reaction Substrate EnzymeSubstrate Complex Products Enzyme after reaction Reactant Enzymes need specific conditions in order to properly function. Activity depends on: Temperature, pH (acidity or alkalinity), Ionic surroundings. Each of these may cause a change in the shape of the enzyme or substrate. 2. Experiments were designed to study the effect of pH on the rate of enzyme action for 2 different digestive enzymes: gastric protease and intestinal protease. *Use the graph to answer the following questions.* (Watch 2nd instructional video on reading the graph if you need help) a. At what pH is gastric protease working at its maximum rate? b. Gastric protease is produced in the stomach. What is the probable pH of the stomach? c. At what pH does gastric protease not work at all? d. At what pH is intestinal protease at its maximum rate? e. Intestinal protease is found in the intestine. What is the probable pH of the intestine? f. If gastric protease was put in the intestine, do you think it could still carry out its usual function of digestion? Why or why not? What letter is each of these labeled as in the above diagram (A, B, C, D, E)? letter term active site substrate enzyme glucose fructose Enzymatic Reactions Sucrose is a sweetener found in many candies (“-ose”=sugar!) It is a carbohydrate disaccharide made up of glucose and another sugar called fructose. When we eat sucrose, it must be digested or broken down into smaller substances, which our cells can absorb. An enzyme (protein) called sucrase speeds up this chemical reaction by breaking the chemical bond in sucrose, the substrate (“-ase”=enzyme). High heat and strong acids or bases destroy the enzyme and would stop the chemical reaction. The only way to make the reaction go faster is to add more enzymes. Scientists support the “lock and key” model below for how an enzyme speeds up chemical reactions. 3. What is a substrate? a. What is the name of the substrate in the picture above? b. What 3 letters in the substrate’s name tell that it is a sugar? 4. What is an enzyme? (define) a. What is the name of the enzyme in the picture above? b. What 3 letters in the enzyme’s name tells that it is an enzyme? 5. How can you tell from the diagram that sucrase is not used up during the chemical reaction? 6. What type of proteins speed up a chemical reaction? 7. How are enzymes destroyed? (3 things can affect enzyme a. b. activity…look under #1!) c.