Enzyme Lab

Variables:

  • Independent- pH
  • Dependent- Time
  • Control- H202

Data:

Object

Mass (In grams)**

Color

Beef Liver #1

3.78g

Reddish Brown

Beef Liver #2

3.83g

Reddish Brown

Beef Liver #3

3.81g

Reddish Brown

Beef Liver #4

3.83g

Reddish Brown

Beef Liver #5

3.81g

Reddish Brown

**Note that this is after the mass of the petri dish was deducted.

 

Object

Solution

pH

Length of Reaction

1

H2O2 (10 mL)

4

9 mins. 30 secs

2

H2O2 + 5 drops of Vinegar

3

2 mins. 39 secs

3

H2O2 + 10 drops of Vinegar

3

2 mins. 39 secs.

4

H2O2 + 5 drops of Sodium Chloride

7

4 mins. 25 secs.

5

H2O2 + 10 drops of Sodium Chloride

9

2 mins. 21 secs.

 

Class Data

Groups

pH

Temperature

1

9

-1.1 C

2

9

****

3

6

65 C

4

7

71 C

5

2

15 C

Class Average

6.8

99.45 F

****Group 2 didn’t perform the second part of the lab, which contained temperature.

Analysis:

                  Although the second part of the lab was not completed, there were some very interesting results. In order for the experiment to be manipulated, we used solutions such as vinegar and sodium chloride to change the pH of the overall solution. The more vinegar you add, the more acidic the solution will be; the more sodium chloride you add, the more basic the solution will be. So when 5 drops of vinegar were added to our control (hydrogen peroxide, which had a pH of 4), the pH didn’t became a bit more acidic; however, when 10 drops of vinegar was added to the control, the pH didn’t change. Even though our solution became neutral once 5 drops of sodium chloride was added, the solution did become more basic than before.  Lastly, when 10 drops of sodium chloride was added to the controlled solution, the new solution had a pH of 9.  The length of the reaction includes from the time the solution starts to bubble to the time that it stops bubbling. The test tube that only contained hydrogen peroxide had the longest reaction, almost 10 minutes long.  Next was the solution that had a neutral pH at a little over 4 minutes, and then the rest of the solutions stopped reacting at around the same time. Another thing that I noticed was the color of the beef liver changed from reddish brown to a brown color.  Lastly, the shorter reactions tended to have a more violent response, and as the reaction became more violent, the beef liver actually moved up to the top of the test tube along with the bubbles.

 Discussion:

                       Interestingly enough, everyone in the class received different results when conducting this experiment; pH levels ranged from 2 to 9 and temperature ranged from -1.1 C to 71 C. The class average for pH was 6.8 which was slightly lower than the results my lab produced, but it turns out that class suggested that the optimum pH of an enzyme is neutral, while my lab proved to be basic.  For temperature, the class average was 99.45 F or about 37.5 C, which is about regular body temperature. Some things that could have affected the outcome of the experiment were it was hard to differentiate the colors of the pH strips and that could be due to how long ago the strips were purchased. Also, I would have thought that the pH level would change when a significant amount of vinegar was added to the hydrogen peroxide, but that can also be a factor of how old the substance was. Lastly, the location of the piece of liver could have affected the length of the reaction because most of the time the liver moved up the test tube and I’d have to push the liver back in, which also caused a delay in when the reaction would stop (a bigger test tube may have solved this problem).

Conclusion:

           Even though all enzymes, depending on location, have various pHs suitable to each of them, my lab proved that the optimum pH of an enzyme should be more basic, ideally around 9. All enzymes are proteins; factors that affect enzyme activity are enzyme concentration, substrate concentration, coenzyme concentration, pH, and temperature. It came to my attention that the reason that a pH of 9 was more suitable for an enzyme was because of the length of the reaction, only 2 minutes and 21 seconds. Since enzymes are supposed to speed up chemical reactions, a shorter reaction would indicate that the enzyme is placed in better conditions. When there is an excess of H+ or OH-, pH changes the shape of the active site so that an enzyme can’t catalyze reactions. Chemical reactions speed up as temperature is increased, so, in general, catalysis will increase at higher temperatures. So according to the class data, a temperature of about 99 F doesn’t cause too much damage, but if the liver were to be placed in a solution that reached boiling point, then the liver may fry. Another general conclusion that can be drawn is that if the temperature of the catalase is significantly below or above its optimal temperature it will make the enzyme less effective. This is because heat usually damages proteins by denaturing them and causing the enzyme to lose its effectiveness.

 

           

 

 

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s