Name: _____________________________________________ Date: __________________ Period: _________ BIO | Enzymes Directions: Read the following summary of enzymes and answer the questions. What are Enzymes? Enzymes are proteins that reduce the amount of energy needed to start biochemical reactions within living cells, i.e. catalysts. For example: Each time a cell repairs DNA, breaks down sugar molecules to release energy, or builds proteins, enzymes are involved. Enzymes are proteins made by cells that act as catalysts in biochemical reactions. Biochemical reactions can build, split, or transform molecules, such as the examples listed above, and they always involve changes in energy. Enzymes speed up chemical reactions by reducing the required activation energy, which is the amount of energy needed to start the reaction. Although enzymes participate in chemical reactions, they are not consumed (broken down) in the process; they remain intact (whole) after the reaction is complete. Just like the key used to unlock the front door of your home; you don’t have to get a new key made every time you unlock/lock the door, nor do the grooves of the key change after it is used. The key can be used over and over again, and because of this you store it on your key chain, just like you’re your body stores enzymes in its cells. Enzymes also do not affect the reaction equilibrium, which means they do not change the direction of the reaction or change the product being made. Function Enzymes have specific structures that help align certain reactants (substance changed during a chemical reaction) for a reaction to take place. The lock and key model illustrated above will further show this idea. Just as a key fits into a lock, a reactant (e.g., glucose, lactose, fructose) fits into an enzyme. The three‐
dimensional structure of an enzyme is crucial to its function (remember that structure and function theme from the previous unit). If the enzyme’s structure changes, the reactants will not be able to fit, and the enzyme will not be able to speed up the chemical reaction. Different environmental conditions can alter an enzyme’s structure, and thus its ability to work. These conditions include: • Temperature: Enzymes usually work within a small range of temperatures, near the organism’s normal body temperature (e.g., Humans = ~95 degrees F to ~99 degrees F). • Ionic Conditions: Enzymes can stop functioning if they are exposed to inappropriate concentrations or type of salts. • pH: Many enzymes function best at a nearly neutral pH. Some, however, such as digestive enzymes in the stomach, work best under acidic conditions (e.g., Human blood has a pH range of 7.35 to 7.45). Questions 1. Proteins that reduce the amount of energy needed to start a chemical reactions are called A. reactants. C. sugars. E. products. B. ions. D. enzymes. 2. Enzymes depend on their structure to function properly. Which of the following does not alter an enzyme’s structure? A. Temperature C. Concentration of reactants B. pH D. Ionic conditions 3. In an experiment you find that high temperatures reduce enzyme activity. This result is most likely due to the effect of high temperature on the A. structure of the enzyme. C. function of the reactants. B. pH of the environment. D. amount of activation energy required 4. In the graph (top right), which reaction is catalyzed by an enzyme? A. A B. B C. Both A and B D. Neither A nor B 5. After the enzyme amylase breaks down a starch molecule, it can A. not be reused. B. break down more starch molecules. C. change its shape to a different reactant. D. alter equilibrium conditions. 6. The enzyme depicted in the graph (below right), functions best at which temperature? A. 0° C E. 40° C B. 10° C F. 50° C C. 20° C G. 60° C D. 30° C Enzyme Concept Map Directions: Using the terms in the word bank, fill in the bubbles. Hint: It helps to read each bubble like a fill in the blank sentence (e.g., Enzymes are __________ . Lower __________ needed to start __________.) Activation Energy Amylase Catalysts Chemical Reactions Fats Lipase Living Things Lock & Key Structure pH Proteins Specific Starch Temperature