Catalysis In Enzymes And Biochemical Reactions Biology Essay

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An enzyme is a protein that participates in biochemical reactions. It takes part in these reactions by acting as a catalyst. A catalyst can cause or speed up a chemical reaction without being affected. One thing a catalyst does to affect chemical reactions is it lowers the activation energy. Activation energy is the least amount of energy needed for a reaction to occur. A substrate, the molecule the enzyme acts upon, binds to the enzyme on the active site. Once the substrate is bonded to the enzyme, the activation energy is lowered, and the products are formed. The enzyme is not changed during the reaction so it can act upon more than one substrate molecule. The activity of an enzyme can be changed in many ways:

Enzyme concentration: As the amount of an enzyme increases, the amount of the substrate that is broken down also increases.

Figure One¹: Affects of enzyme concentration on substrate breakdown

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Substrate Concentration: If the concentration of enzymes stays the same and the substrate level increases, then the speed at which the enzymes break the substrate down will increase until the enzyme reaches a maximum speed.

Figure Two²: Enzyme speed in relation to substrate concentration

Activators/Inhibitors: Enzyme inhibitors stop or slow down the rate of reaction, while activators speed up the rate of reaction. An inhibitor can block the enzyme's actual substrate from binding, unfold the enzyme, or alter its shape.

Figure Three³: Enzyme inhibition

Temperature: Chemical reactions speed up as temperature increases⁴. However, a temperature optimum can be reached. A temperature optimum occurs when the temperature is so great that the enzyme begins to denature, or come apart. When this happens, enzyme activity decreases

Figure Four⁵: Affect of temperature on enzyme activity

pH: Like temperature, there an optimum pH. Extremely high and extremely low temperatures can greatly decrease enzyme activity.

Figure Five⁶: Affect of pH on enzyme activity

One important enzyme reaction prevents the build-up of Hâ‚‚Oâ‚‚, which is toxic. It does this by converting it to water (Hâ‚‚O) and oxygen (Oâ‚‚). Once the experiments have been completed, an understanding of how temperature, pH, enzyme/substrate concentration, and environmental factors effect a reaction will be understood. The hypothesis was that the longer the enzymes were in the Hâ‚‚Oâ‚‚, the more Hâ‚‚Oâ‚‚ that will be broken down.

Materials and Methods:

Base Line:

2 beakers

1.5% Hâ‚‚Oâ‚‚

Hâ‚‚O

1.0M Hâ‚‚SOâ‚„ 10mL

Syringe

5mL pipette

Rubber Gloves

White sheet of paper

KMnOâ‚„

Put on the gloves

Take 10mL of Hâ‚‚Oâ‚‚ and put it in the beaker.

Add 1mL of Hâ‚‚O to the same beaker.

Add 10mL of Hâ‚‚SOâ‚„ to the beaker. Use extreme caution.

Mix the contents of the beaker.

Take a 5mL sample of the first beaker's contents and place it in a second beaker.

Put the beaker with the sample onto the sheet of paper.

Draw 5mL of KMnOâ‚„ into the pipette.

Use the pipette to add drops of KMnOâ‚„ to the sample one at a time, stirring after each drop. Keep doing this until the sample turns pink or brown. Use caution when using KMnOâ‚„.

Record the amount of KMnOâ‚„ leftover in the pipette in the pipette.

Uncatalyzed decomposition of Hâ‚‚Oâ‚‚:

15mL Hâ‚‚Oâ‚‚

2 beakers

1mL Hâ‚‚O

10mL of 1.0M Hâ‚‚SOâ‚„

Pipette

3 syringes

Put 15mL of Hâ‚‚Oâ‚‚ in a beaker.

Store it for 24 hours, uncovered.

Once 24 hours have elapsed, repeat steps 2-10 from the base line experiment.

Record your data.

Catalyzed decomposition of Hâ‚‚Oâ‚‚:

Stopwatch

1.5% Hâ‚‚Oâ‚‚

14 beakers

3 syringes

Hâ‚‚SOâ‚„

KMnOâ‚„

Rubber gloves

Enzyme catalase

7 5mL pipettes

Put 10mL of Hâ‚‚Oâ‚‚ in a beaker.

Add 1mL of the enzyme catalase to the beaker.

Swirl the mixture for 10 seconds. Use the stopwatch to time.

Add 10mL of Hâ‚‚SOâ‚„ once 10 seconds have elapsed.

Remove a 5mL sample and put it in a second beaker.

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Add drops of KMnOâ‚„ to the sample one at a time using a syringe. Keep doing this until the sample turns pink or brown. Record how much KMnOâ‚„ is left in the pipette.

Obtain 2 more clean beakers and another clean pipette

Repeat steps 1-7, but replace 10 seconds with 30, 60, 90, 120, 180 and 360 seconds

Results:

Base Line:

Final reading of syringe:_1.35_mL

Initial reading of syringe:__5__mL

Uncatalyzed decomposition of Hâ‚‚Oâ‚‚:

Final reading of syringe:_1.35_mL

Initial reading of syringe:__5__mL

Catalyzed decomposition of Hâ‚‚Oâ‚‚:

Final reading of pipette:_1.35_mL

Initial reading of pipette:__5__mL

Table One: Amount of KMnOâ‚„ in the syringe

Time (seconds)

10 30 60 90 120 180

KMnOâ‚„ (mL)

Base line

Final reading

2.2

3.2

3.4

3.7

2.8

2.4

Initial reading

5

5

5

5

5

5

Amount of KMnOâ‚„ consumed

Amount of Hâ‚‚Oâ‚‚ used

Discussion:

Base Line:

Final reading of pipette:_1.35_mL

Initial reading of pipette:__5__mL

Base line (Final-initial) _3.65_mL KMnOâ‚„

In the experiment, the base line was found by subtracting the final reading of the pipette from the initial reading of the pipette. The pipette started with 5mL of KMnOâ‚„ (initial reading) and ended with 1.35mL of KMnOâ‚„ (final reading) after the drops were added and the brown color was achieved. By subtracting the amounts of KMnOâ‚„ in the syringe, a base line of 3.65mL was established.

Uncatalyzed decomposition of Hâ‚‚Oâ‚‚:

Final reading of pipette:_1.35_mL

Initial reading of pipette:__5__mL

Amount of KMnOâ‚„ Titrant (final-initial):_3.65_mL

Hâ‚‚Oâ‚‚ spontaneously decomposes at such a slow rate, that it is undetectable. Therefore, the amount of Hâ‚‚Oâ‚‚ in the beaker after twenty-four hours was the same as the amount of Hâ‚‚Oâ‚‚ in the base line experiment.

Catalyzed decomposition of Hâ‚‚Oâ‚‚:

Final reading of pipette:_1.35_mL

Initial reading of pipette:__5__mL

Base line (Final-initial) _3.65_mL KMnOâ‚„

Table Two: Amount of KMnOâ‚„ used in proportion to time

Time (seconds)

10 30 60 90 120 180

KMnOâ‚„ (mL)

Base line

3.65

3.65

3.65

3.65

3.65

3.65

Final reading

2.2

3.2

3.4

3.7

2.8

2.4

Initial reading

5

5

5

5

5

5

Amount of KMnOâ‚„ consumed

2.8

1.8

1.6

1.3

2.2

2.6

Amount of Hâ‚‚Oâ‚‚ used

.85

1.85

2.05

2.35

1.45

1.05

Figure Six: Amount of KMnOâ‚„ used in proportion to time

During the 10, 30, 60, and 90 second time intervals, the KMnOâ‚„ titrant used decreased. This is because the amount of Hâ‚‚Oâ‚‚ in the beakers decreased due to the enzymes breaking it down. The longer the enzyme was in the beaker, the more Hâ‚‚Oâ‚‚ that was broken down. The 120 and 180 second time intervals were opposite. The amount of KMnOâ‚„ titrant used did not decrease, but increased. This is because the reaction reached equilibrium. The 360 second time interval used an amount of KMnOâ‚„ that suggests there was more Hâ‚‚Oâ‚‚ in the beaker than was initially there. This is impossible so disregard that data. The Hâ‚‚SOâ‚„ is an acid. It was added to the beakers to denature the enzymes. When enzymes become denatured, they cannot function properly (if they function at all).

Figure Seven: Amount of Hâ‚‚Oâ‚‚ Used

When the concentration of a substrate is greater than the concentration of an enzyme, then a decrease in the concentration of the substrate will not affect the interactions of the enzyme and substrate. This only applies to a short period of time at the beginning of the enzyme's activity. The initial rate is the slope of the graph of the enzyme's activity during the early portion of the reaction. As the reaction gets longer, the rate that the substrate and enzyme interact at decreases.

The hypothesis was partially right. During the 10, 30, 60, and 90 second time intervals, the KMnO₄ titrant used decreased. The decrease in the amount of KMnO₄ that was needed shows that there was less H₂O₂ in the beaker. The 120 and 180 second time intervals were opposite. The amount of KMnO₄ titrant used did not decrease, but increased. This is because the reaction reached equilibrium. Equilibrium is the point in the reaction where the concentration of a substrate is equal to the concentration of the products.⁷

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Citations:

Worthington, . Enzyme Concentration. Worthington Biochemical Corporation, 2010. Web. 7 Nov. 2010. <http://www.worthington-biochem.com/introbiochem/enzymeConc.html>.

Worthington, . Substrate Concentration. Worthington Biochemical Corporation, 2010. Web. 7 Nov. 2010. <http://www.worthington-biochem.com/introbiochem/substrateConc.html>.

Worthington, . Inhibitors. Worthington Biochemical Corporation, 2010. Web. 7 Nov. 2010. <http://www.worthington-biochem.com/introbiochem/inhibitors.html>.

College Board. AP Bio Lab Manual. USA: The College Board, 2001. Print.

Worthington, . Temperature Effects. Worthington Biochemical Corporation, 2010. Web. 7 Nov. 2010. <http://www.worthington-biochem.com/introbiochem/tempEffects.html>.

Worthington, . Effects of PH. Worthington Biochemical Corporation, 2010. Web. 7 Nov. 2010. <http://www.worthington-biochem.com/introbiochem/effectspH.html>.

Campbell, Neil A., and Jane B. Reece. "Chapter 8: An Introduction to Metabolism." AP EDITION BIOLOGY Seventh Edition. Eds. Beth Wilbur, Deborah Gale, and Pat Burner. San Francisco, CA: Pearson Education, Inc., 2005. 145. Print.