Catalase Lab

Purpose: Use Catalase to see some characteristics of proteins and enzymes.

Background: (Read and write the answers to the following questions.)Proteins are a diverse family of molecules that perform many functions for living things. One of the most important functions is to cause chemical reactions. Proteins that cause chemical reactions to go faster are called Enzymes. Because of their shape, some enzymes can break molecules in two. (Other enzymes can cause two molecules to join.) Remarkably, enzymes themselves are not harmed or used up and can go on to break more molecules one after another. But enzymes must have the right shape to do their job.

Enzymes, like other proteins, work best in the right environment. If the environment is too hot or too cold or too acidic the enzyme loses its shape and won’t work properly. You’ve seen this: Ever wonder why an egg turns white when you fry it? It’s because egg “whites” are made of proteins. When they get too hot they change shape and turn white. Likewise, muscle proteins turn brown when meat is cooked. When this happens to a protein, we say the protein has “denatured”.

So why do proteins lose their shape? More heat causes atoms to vibrate more vigorously. When they get hot enough, the atoms in the protein will vibrate so violently that the bonds between them will break and the protein “unfolds” and loses shape. Changes in pH (more acidic or more basic) will also cause changes in chemical bonds.

In this lab you will observe the behavior of the enzyme catalase. Catalase is easy to detect in the laboratory with Hydrogen peroxide (H2O2) because it causes H2O2 to bubble and fiz. The fizzing means the H2O2 is being broken down into H2O & O2 gas (gas creates bubbles in liquids). If the catalase is denatured no fizzing will occur; it can’t break down H2O2 because it has the wrong shape.

All cells on Earth contain catalase because all cells need to protect themselves from Hydrogen peroxide (H2O2). H2O2 is a by-product of many chemical reactions in cells – for example when a high fat diet (fatty acids) is metabolized for energy in the mitochondria. If H2O2 were allowed to build up in cells, it would quickly kill them. Fortunately catalase breaks down H2O2 into non-toxic chemicals (H2O & O2 gas).

Background: (Answer in complete sentences.)1. What macromolecule category do enzymes come from? What are monomers and polymers of enzymes called?2. What is the job of an enzyme?3. What is the job of the enzyme catalase? (Make sure you understand the difference between “catalase” and a “catalyst”.) 4. We are taking catalase from potato cells. Human liver cells have lots of catalase; why does this make sense? Why is catalase important to cells?5. How can you tell if catalase is working? If catalase is working, what can you see happening? What kinds of conditions might make catalase slow down or stop working?

You can include more information than just answering the questions, but you must at least answer these questions in your background paragraph.

Question: (Copy into lab book) Which temperature will provide the best working condition for catalase? A) Ice water - 0◦C B) Cold tap water 20◦C C) Warm tap water 30◦C

D) Hot water 60◦C E) Boiling water 100◦C

Hypothesis: (if…then…because…)

Manipulated Variable:

Responding Variable:

Controlled Variables: (list 4 or more)

Materials: (copy into lab book) potato solution, 3% H2O2 (hydrogen peroxide), 3 test tubes, , ice water, room temp water, boiling water, dish soap, graduated cylinders

Methods: (copy into lab book)1. Teacher puts potatoes through a blender to get catalase enzyme out of the potato cells. 2. Label 5 clean test tubes with the 5 temperatures. 3. Pour 5 mL potato juice into each test tube.4. Place each test tube into the appropriate temperature bath for at least 10 min. 5. Write your hypothesis while you are waiting.6. After 10 minutes or more pour the 5 mL potato solution into the graduated cylinder. 7. Add 1 drop of dish soap into graduated cylinder. 8. Add 1 drop food coloring into graduated cylinder.9. Add 5 mL hydrogen peroxide into graduated cylinder.10. Wait 5 minutes for the foam to build.11. At 5 minutes record volume of soap bubbles produced in mL.12. Repeat steps 6-10 for the other 4 temperatures.

Results: Table 1. Group Data for Temperature (°C) on Potato Catalase Experiment.

Temp (◦C)Volume (mL)

Table 2. Class Data for Temperature (°C) on Potato Catalase Experiment.Temperature (°C)

Volume (mL)

12345678910

Averages:

Make a Line Graph of team and class data: Volume of foam produced by Catalase at different temperatures.

Analysis: a. Draw a diagram or story board of what you imagine it looks like when an enzyme is breaking down other

molecules. (it may help to re-read the first few paragraphs at the beginning.) Label the enzyme, the monomers and the polymers in your diagram. Color your diagram.

b. Explain your results; what do they actually mean? Discuss error analysis regarding your lab technique. c. Answer the following questions in your analysis:

1. What temperature does the enzyme seem to work best? How do you know?2. Was catalase making dehydration synthesis or hydrolysis happen? Explain how you know. 3. Think of the shape of the enzyme and its protein structure. What is each of the following solutions doing to

the structure of the enzyme?a. ice water temperatureb. warm water temperature c. boiling water temperature

4. What do protein levels of structure, enzyme active sites, and induced fit have to do with each other? Why is this so important? 5. Did the reaction slow at lower temperatures? If so why? Can you think of a reason it would slow if the enzyme were not damaged? 6. Some bacteria live in boiling water! The bacteria have enzymes that survive in hot temperatures. What do you think would happen if you took some of these enzymes and put them in ice water?

Conclusion: a. Restate hypothesisb. State whether hypothesis is “supported” or “not supported” by the data (report numbers)c. Explain why the results make sense (biological explanation) or explain why your results conflict with the

biological explanation (what went wrong), or explain how you could modify your experiment to clarify your understanding (new experiment).