Enzyme Catalysis Lab

Purpose

The purpose of this experiment is to observe the change of hydrogen peroxide to water and oxygen gas by an enzyme catalase as well as to measure how much oxygen was made and calculate the rate of the enzyme-catalyzed reaction.

Introduction

Enzymes are proteins made from living cells that acts as a catalyst which affects the rate of a chemical reaction. In an enzyme-catalyzed reaction, the substrate binds  the active site of the enzyme. Each enzyme is specific for a certain reaction because each into acid sequence is unique and enzyme can be affected by the salt concentration, pH, temperature and activations and inhibitors.

Methods

We first created a base line in order to determine the hydrogen peroxide that is initially in the solution and use that base line to see the uncatalzyed rate of decomposition versus the catalyzed rate of decomposition. Sulfuric acid is added to inhibit the enzymes because of the acidic environment and cause it to stop reacting. After adding sulfuric acid, a 5-mL sample is taken in order to be titrated to see the catalyzed rate or change over time. potassium permanganate is added drop by drop from a burette until the solution is turned a pink or brown color.

Cups to be mixed fit various amounts of time.

When testing the baseline sample, there is initially a brown/pink color, but with some stirring, that hue disappears (pictures 1 & 2).  Once some potassium permanganate is in the solution and the color doesn't dissolve, the reaction has reached the end (picture 3).

Adding catalase extract (yeast) to begin reaction.

Adding Sulfuric Acid to stop reaction.

Taking a 5mL sample to test with potassium permanganate.

Test with potassium permanganate until there is a consistent pink or brown color.


Data

Discussion

The overall objective of the experiment was to observe the relationship between Hydrogen Peroxide and the catalase extract.  More specifically, observing the transformation of Hydrogen Peroxide to water and oxygen gas due to an enzyme catalase (in this case, the enzyme catalase was yeast).  Each time another aspect of the experiment was conducted, aka the catalase was left in the Hydrogen Peroxide for a longer period of time, the results varied.  From ten seconds to thirty seconds to sixty seconds, the amount of Potassium Permanganate consumed was sporadic, going from 3.2mL to 2.8mL, then back up to 3mL.  While these results were all very close, no true patterns were apparent.  In general, the amount of Potassium Permanganate consumed decreased between ten seconds and 360 seconds of the Hydrogen Peroxide solutions being mixed with the yeast.  The same applies to the amount of Hydrogen Peroxide used throughout the reaction: there was a general trend of decreasing of the usage of the solution as the length of time increased--although there were multiple instances in which the data did not follow the trend exactly.  For example, from ten seconds to thirty seconds to sixty seconds, the amount of Hydrogen Peroxide used initially decreased, but then increased right after.  The interval of time from 0-10 seconds had the highest rate because that is when there were the most enzymes and substrates present.  It is clear that the interval of 180-360 seconds had the lowest rate, which is because by the time the solution had been being mixed for so long, most of the enzymes and substrates were essentially used up, causing the reaction to plateau.  Since there was a relatively sure and consistent amount of the Hydrogen Peroxide, enzyme catalase, and Sulfuric Acid being used in each sample, and each time a titration took place, it was always with 5mL of the entire solution, the inconsistencies most likely come from the titration part of the experiment.  It is very easy to let a little too much Potassium Permanganate through the titration at once.  If too much is released when the pink or brown color was already sticking around, the results could easily be impacted.  To improve this experiment in the future, it would be important to make sure all measurements are accurate--from the amount of each solution used, to the amount of time each solution is mixed for.

Conclusion

Through this lab we observe how the catalase increases rate of decomposing of hydrogen peroxide. We see how hydrogen peroxide and enzyme catalase are able to work together. With the different time trials we are able to see how the enzyme breaks down hydrogen peroxide over a period of time. Uncatalzyed decomposition is slower than catalyzed decomposition of hydrogen peroxide. The catabolic process helps to speed up decomposition and break down, an example of our liver's ability to break down toxins.

Diffusion and Osmosis Lab

1A - Diffusion

Purpose

The purpose of the lab was to evaluate the diffusion of both large and small molecules through a semipermiable membrane.  We were testing to see if glucose would diffuse through the dialysis tubing.  The independent variable was 

Introduction

Diffusion is the random movement of molecules from a higher concentration to a lower one.  Osmosis is a specific type of diffusion, which involves water.  The movement of ions and molecules is not completely due to diffusion and osmosis, but also because of active transport.  Active transport moves a substance from a lower concentration to a higher one.

Methods

By taking dialysis tubing, which is semipermeable, filled with a glucose and starch mixture, we looked to see which substances would pass through the tubing from the water and iodine mixture it was submerged in.

Dark purple liquid within dialysis tubing, sitting in iodine solution. (After reaction)

Indicators for the presence of glucose throughout experiment.

Data

Discussion

Our results from this lab helped to further prove the laws of diffusion, osmosis, and the ability of membrane pore sizes to allow molecules to either pass or not pass through. From our data we can conclude that molecules in areas of high concentration will always move (diffuse) to areas of low concentration unless the molecules are too large to pass through the membrane or the membrane pores are too small. We know this to be true due to the fact that the contents inside the dialysis tubing and in the beaker had changed color by the end of the lab. Before the lab had begun, the beaker solution was a red/orange color and the dialysis tubing solution was clear. At the end of the experiment, the beaker was still a red/orange color but thr dialysis tubing solution had turned a purple color. This change in color was a result of the diffusion of iodine into the tubing. Iodine entered the tubing and glucose left the tubing. If we were to change or improve anything about this lab we would want specific amounts of solution (water, glucose, starch, etc.) so we could know how much to add to get even more accurate results. To conclude, our results were seemingly accurate and met the criteria of the laws of diffusion.

Conclusion

We found that glucose travelled from inside the cell to the solution. This means, in respect to the glucose, this was a hypertonic solution. Overall, this indicates iodine and starch cannot pass through the membrane as easily as glucose can.  The dark purple a appearance of the bag's contents indicates a change in the solution and solute. 

References

http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect09.htm

1B - Osmosis

Purpose

Determine the water potential within a potato cell (plant cell), the different molar concentrations of sucrose that the potato cores are placed into determine this.  The independent variable is the molar concentrations of sucrose and the dependent variable are the potato cores. The change in sucrose helps to see the change in water potential. 

Introduction

Water always moves from area of high water potential to an area of low water potiential, meaning that water moves from an area with a lot of water to an area with little to no water. the water potential itself is affected by solute and pressure being added to or taken away from an area.  

Methods

Data

Discussion 

Our results from this lab helped to prove the laws of osmosis, the diffusion of water. Just like diffusion, osmosis strives for equilibrium. When a solution is hypotonic this means that it has a low level solution and a high level of water. When a solution is hypertonic this means that is has a high level of solution and a low level water. In order to reach equilibrium, more water is required in hypertonic solutions and less water is needed in hypotonic solutions. Water always diffuses from an area of high concentration to an area of low concentration. This is proved in our lab because after soaking different solutions of sucrose in dialysis tubing that was submerged in water, the masses of the tubing changed. Osmosis had occurred. If we were to repeat this lab and improve it, we would have measured the solutions more precisely in order to get more uniform answers and would have also been more careful when drying and weighing the solutions in the dialysis tubing. The results of our lab further prove the laws of osmosis. 

Conclusion

References

1C - Water Potential 

Purpose

Introduction

Methods

Coring the potatoes.

Data

Discussion

Our results from this lab helped us determine the water potential of each potato cell and what water potential really is. Our data proves that areas of high water potential will always move to areas of low water potential. Water potential is affected by two things; pressure potential and solute potential. Our data also proved that water potential and solute potential are inversely related. If solute potential is high then water potential will be low and vice versa. Our data is seemingly accurate due to the fact the fact that these points were proven. If we were to improve any aspects of this lab we would Improve the measurements. Not all potato cells/solutions/etc. we're exactly the same. This means that not all data corresponded to each other. This means that the results were a bit more difficult to compare and contrast. Overall, this experiment went well and got accurate and favorable results. 

1E

Disscusion

Plasmolysis is movement of water out of the plant cell and shrinking of the of the plant cell due to the loss. The water that is diffused out of the cell goes into a hypertonic solutionthat is surrounding the cell.  The space between the cytoplasm and the cell wall is filled with the exertonic solution. Because an oninon cell is a plant cell and the area around the onion has a lower water potential so the  water would move out of the cell. If plant cells are exposed to a hypertonic solution such as salt water, the water in the plant cell is drained  from the cell and into the hypertonic salt water around it.

Refrence

http://biologymadesimple.com/topics/absorption-by-roots/absorption-by-roots-page-4/

Milk Lab

Purpose 

In this lab, we were trying to determine the actual percentage of protein on skim milk. We were testing protein properties (such as protein denaturation). In this scenario, the dependent variable would be the molecular structure and the the independent variable would be the acetic acid added to the milk.

Introduction 

Proteins are macro-molecules composed of chains of amino acids. The sequences of amino acids usually result in the different structures (primary, secondary, tertiary and quaternary) which then determines it's function. When a chain of amino acids come together, they form polypeptide bonds.  

Methods 

In this lab, we started off by weighing an empty beaker so we could later subtract this mass from the mass of the liquid and the beaker combined. We then measured out 15-mL of non-fat milk into the beaker. Next we added acetic acid to the beaker filled with milk and stirred it. We then recorded the mass do the solution and the beaker together. Next we poured the solution through a filter paper and into a beaker. The filter paper caught the curds. We then let the filter paper and curds dry out over night and massed it the next day. 

Data

Discussion

The overall objective of the experiment was to determine the percentage of protein that is in nonfat milk, according to the label there is supposedly 8 grams of protein per serving. We calculated a -31.152% error meaning that we had approximately 30% less protein found in our milk then our expected value. The reasons behind this error could be as follows: incorrect measurements and the filter paper used to filter out the protein. In order to revise and improve the experiment for another test, there must be a more efficient way for filtering the milk solution and separating out the proteins. More precise measurements and calculations would help to determine a more accurate account for the protein. 

The results of the experiment support our hypothesis on the outcome of the experiment because protein was shown to be present when the milk and its proteins were in the process of separating. When Biuret reagent was added, the remaining coagulated milk turns a purple color meaning that protein leaked through the funnel into the liquid and separated from the rest of the protein. 

. 

(Amount of Protein Per Serving: 8g)

Sample from Non-fat milk

Adding concentrated acetic acid to milk

Acid denatures milk protein

Milk begins to form curds

Solution poured into funnel to separate protein

Using water as negative control.

Adding Biuret to milk solution.

Purple color shows presence of protein in solution. 

Separating protein from funnel.

Setting filter paper to dry overnight.

Conclusion 

To conclude our experiment, the actual percentage of protein found in skim milk (due to our findings) was much less than what we expected it to be. The carton said there was supposedly 8 grams. We found a lot less than this. We are basing our information off of the data we found in this lab. There might have been skewed data from incorrect measurements at times but generally our findings were accurate.

References

http://en.m.wikipedia.org/wiki/Whey

http://chemistry.about.com/od/foodscienceprojects/a/Yogurt-Chemistry.htm