Catalase Lab

Objective:

In this lab activity, we studied the factors that effect the activity of enzymes. Catalase is a type of enzyme that is found in most cells that speeds up the break down of hydrogen peroxide. Ridding the body of hydrogen peroxide is crucial because hydrogen peroxide is very lethal and kills nearby cells.

Materials:

• 50 mL beaker
• 10 mL and 50 mL graduated cylinder
• Catalase solution
• Filter paper punches
• Hole stopper
• Stop Watch (iPad)
• Reaction chamber
• Tweezers
• Tub of water

To begin, we took the vial of catalase solution and carefully dipped a filter paper punch in it using tweezers. We then stuck the soaked paper to the top, inside wall of the chamber. Next, we added 10 mL of 3% hydrogen peroxide into the chamber, making sure it didn't touch the filter paper. If it had touched the filter paper, it would start to react, and ruin the experiment.

                           
                           

We then put in the stopper and placed the entire contraption into the water. Next, we filled the cylinder with water by laying it horizontally and letting the air bubbles out and carefully tilted it into a vertical position, making sure the water stayed in it. Then for a whopping ten minutes, we held the graduated cylinder above the chamber to catch the released oxygen, making sure to switch places when our arms began to cramp. Now for the science behind it! Hydrogen Peroxide naturally decomposes when exposed to light in this reaction: 2 H202 -> 2 H20 + 02. The rate of this decomposition changes due to factors such as temperature,  concentration, and pH. Sadly, we only were able to experiment with concentration. Hydrogen Peroxide begins to decompose when exposed to sunlight because the light provides enough energy to exceed the required activation energy and begin the reaction. This is why Hydrogen Peroxide is kept in dark, opaque containers to prevent the decomposition from commencing. Catalase speeds up the decomposition by finding a way to orientate the hydrogen peroxide molecule in a way that the oxygen can be freed more easily. Back to our experiment. Using the scale on the side of the graduated cylinder, we measured the amount of oxygen produced every 30 seconds. The results were nearly linear! We repeated the same steps with 2 and 4 paper punches. Our results are below:

Sadly, we were short on time, so we weren't able to do 3 paper punches and could only do 5 minutes of the 4 paper punches. Looking back at our data, we concluded that each paper punch of catalase sped the reaction time up by about 3 times. This was a little surprising because one would assume having two instead of one would only be twice as fast if the rate is related to the surface area of the paper punch or the total volume of the Catalase.  Therefore, there must be another factor that we don't yet understand. 

Diffusion through Dialysis Blog

For this lab, we did a simulation of diffusion inside cells using dialysis tubing. First, we tied the end of two dialysis tubes. These dialysis tubes are non-living material that have small pores which separate larger molecules from smaller ones.

We then poured soluble starch within 4 cm of the top of one tube, tied the remaining end, and put it into a beaker of water mixed with a few drops of iodine. We repeated the same steps with the second tube, using glucose instead of starch. We then set up a time-lapse and waited patiently for 20 minutes. After a while, the iodine diffused into the tube and reacted with the starch, creating a blue color. The beaker and dialysis tube with glucose didn't show any changes. We then dipped glucose test strips into the beaker. The glucose strip turned green.

Finally, just for fun, we cut the tube, releasing all the contents into the beaker. The entire beaker turned dark blue instantly.

After some more research, I found that the starch and iodine turned blue because the starch contains a polysaccharide known as Amylose. When it reacts with the iodine, the blue color results from changes in electron orbitals. 

Analysis:

1. The Iodine molecules diffused through the membrane, and reacted with the starch. Since the beaker didn't turn blue, that means the starch molecules were too big to diffuse out of the tube. This was validated when we cut the tube open and the whole beaker turned blue.
2. The glucose test strip showed that some glucose diffused through the membrane. 
3. We didn't wait overnight, but if we did, I would imagine that the tubes, because of osmosis, would start to swell due to the concentration of water being lower on the inside.
4. The starch molecules didn't pass through the membrane because they were too large.
5. My hypothesis is that iodine passes through the membrane, reacting with starch. The glucose could pass through the membrane, which is why the glucose test showed a concentration of glucose.
6. I assumed that the two dialysis tubes had the same number and sizes of pores, and that the pores were just big enough to let the glucose through, but not the starch.