Enzyme Lab Post-Lab

1. Define catalyst A chemical that speeds up the rate of a reaction without being used up or destroyed

2. How are enzymes & catalysts similar? Different? They both speed up reaction rates without being destroyed (same function) Enzymes are proteins produced by living cells whereas catalysts can be any chemical that speeds up reaction rates (a catalyst does not have to be a protein)

3. What substance used in Part 1 is a catalyst? Manganese dioxide

4. What source of enzyme gave a better reaction -- liver or potato? Why? The liver Liver contains more heme, which is attached to the protein part of catalase

5a. In Part 3, what are you really adding when you add more liver? More enzyme (catalase)

5b. Why does the reaction turn out as it did when more liver is added? Nothing happened when fresh liver was added to the test tube because the peroxide was already broken down - there was nothing for the enzyme to act upon

5c. What happens when more peroxide is added to the old liver + liquid? A reaction occurred - the enzymes in the old liver broke down the fresh peroxide

5d. What do the results of this part of the experiment tell you about enzymes & how they react? An enzyme is not used up or destroyed during a reaction - it can be used over and over again

6a. How does the reaction rate in Part 4 differ with that in Part 2 for potato? For liver? The reaction rate is faster in Part 4 for both the potato & the liver

6b. Explain why. This is because the smaller (crushed) pieces have a greater surface area of enzyme exposed to the peroxide = faster reaction rates

7a. What general statement can you make about reaction rates & temperature? For this reaction, the warmer the temperature, the faster the reaction rate (up to a point)

7b. What does kinetic energy have to do with this? Kinetic energy is the energy of motion- the increased temperature causes the molecules to move faster & interact with each other more quickly

7c. What was your predicted reaction rate for 100 degrees Celsius varies

7d. Did you results support your prediction? Explain. Varies Varies; too much heat will denature (change the shape) of an enzyme, making it useless

8a. What is pH a measure of? How acidic (lots of H+ ions) or basic (lots of OH- ions) a substance is

8b. Which pH conditions reacted poorly? NaOH (basic) and HCl (acidic)

8c. Under what conditions did the enzyme work well? Neutral (water)

8d. Would you say that enzymes are specific or nonspecific about the pH of the environment in which they must function? Specific - catalase only worked well under neutral conditions

9a. What temperature change occurs in the tube for Part 7? The temperature increases

9b. What caused this change? The chemical reaction gave off heat

9c. Would you say that the reaction of catalase and hydrogen peroxide is an endothermic or exothermic reaction? Exothermic

10a. Which gas is given off during this reaction? oxygen

10b. Why do you think so? The glowing splint flared up (burned brighter)

10c. What substance is left in the test tube after the breakdown of hydrogen peroxide? Water (H2O)

10d. Write a balanced equation for this reaction. (catalase) 2H202 ----------------> 2H20 + O2