Biology Cells Unit: Enzymes Worksheet 1. What is a catalyst?: a substance that increases the rate of a chemical reaction by reducing the amount of energy needed to start the reaction 2. What is an enzyme?: an organic catalyst that catalyzes (helps) reactions in living organisms 3. What is the active site and what is it's job?: specially-shaped area of the enzyme that fits around the substrate. It is where the enzyme grabs onto the substrate. 4. What is a substrate?: the biological molecule that the enzyme will work on. The enzyme grabs onto the substrate in the active site. 5. What is a product?: when the enzyme lets go of the substrate, it returns to normal and is able to do another reaction. The substrate is now different and is now called the product. 6. Explain how an enzyme works using the terms from 1-5.: The enzyme grabs onto the substrate in a special area called the active site. The active site is an area of the enzyme that fits around the substrate. A catalysis happens. Catalysis is when the substrate is changed. It could be broken down or combined with another molecule to make something new. The enzyme lets go, returns to normal and is ready to do another reaction. The substrate is no longer the same, it is now called the product. 7. What is denaturing and what causes it to occur?: Enzymes sometime need to be controlled when done with their function. Other times they are controlled because of poisons. Denaturing occurs when the control changes the enzyme's shape. 8. What 4 things can affect the way enzymes work?: 1. Temperature: proteins change shape as temperatures change. Temperature changes can make enzymes stop working. 2. Activators make enzymes work harder and faster. They can help the enzyme bind to the substrate. 3. pH levels can change the shape of proteins. Proteins denature if they are too acidic or too basic. 4. Inhibitors slow down or stop the activity of an enzyme. A competitive inhibitor blocks the active site; an allosteric inhibitor bonds to another spot, causing the shape to change When the shape changes, the enzyme will not work the same way. 9. How can a lock and key be used to describe an enzyme?: A door that is locked needs a key that is just the right shape to fit in that lock. Enzymes work in a similar way. Enzymes complete very specific roles and do nothing else. Enzymes are very specific locks and the compounds they work with are the special keys. 10. Why do enzymes generally only bind to one type of substrate?: because they do very specific jobs and nothing else. 11. Label the following terms in the following picture: enzyme, 1/2 products, substrate, active site: 12. Using graph 1, explain how enzymes work. Include the term activation energy and compare the two curves , explaining which is with the enzyme.: Enzymes are biological catalysts. Catalysts lower the activation energy for reactions. The lower the activation energy for a reaction, the faster the rate. Enzymes speed up reactions by lowering activation energy. 13. Using graph 2, explain how temperature affects enzyme activity. Use the word denature.: Raising temperature generally speeds up a reaction. Lowering temperature slows down a reaction. Extreme high temperatures can cause an enzymes to lose its shape (denature) and stop working. 14. Using graph 3, explain how pH affects activity. Relate to temperature effects.: Each enzyme has an optimum pH range. Changing the pH of this range will slow enzyme activity. 2/2