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Biology Project---. The Experiments of comparing the concentration of catalase that break down hydrogen peroxide in different pig’s organ and the effect of different pH on the rate of reaction. Our investigation falls into two parts. 1) Investigation on the amount

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Biology project

Biology Project---

The Experiments of comparing the concentration of catalase that break down hydrogen peroxide in different pig’s organ and the effect of different pH on the rate of reaction


Biology project

Our investigation falls into two parts.

1) Investigation on the amount

of catalase present in different

organs of a pig

2) Investigation on the the effect

of different pH on the catalase


Biology project

Apparatus and materials

Low pressure sensor , 6% hydrogen peroxide solution,

buffer solution (pH 4, 7, 10), different organ tissues( lung, kidney, muscle)

Preparation before experiment

Put the organ in the mixer and start turning them into semi

liquid form by stirring

Pour the semi liquid and water in the to mixer. Stir it thoroughly.

Prepare the hydrogen peroxide (6%) by diluting it to 3%.


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Investigation on the amount of catalase present in different organs of a pig


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Hypothesis


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All cells use molecular oxygen in metabolism which will produce small amounts of hydrogen peroxide. Hydrogen peroxide is extremely reactive and can cause cellular damage. It is critical that any hydrogen peroxide molecules should be quickly removed before they can damage the cell. The organ with higher metabolic rate should have a higher concentration of catalase that break down hydrogen peroxide into oxygen and water. We think kidney is the site where many metabolic reactions occur should have the highest concentration of catalase when compared to muscles and lung.


Biology project

Add 1cm3 of organ liquid into the test tube by using a

syringe

Add the organ liquid into test tube which is with

5 cm3 hydrogen peroxide.

Start recording the pressure by using the data logger,

once the organ liquid is added.

Stopper the test tube so that gases will not release

to the outside.


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Stop recording after the pressure reaches the relative maximum of the pressure sensor which is 10 Pa.

Calculate the time taken to reach the maximum pressure.

Repeat the experiment by using different organs.


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Analysis


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Results:

Sample 1: Lung


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For the blue curve:

time taken to reach the relative maximum pressure= 15 s

For the red curve:

time taken to reach the relative maximum pressure= 14s

For the purple curve:

time taken to reach the relative maximum pressure = 12.5s

The average time taken = 13.8 s


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Sample 2: Kidney


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For the red curve:

time taken to reach the relative maximum pressure= 0.4s

For the pale blue curve:

time taken to reach the relative maximum pressure= 0.8 s

For the pale pink curve:

time taken to reach the relative maximum pressure= 0.6 s

The average time taken = 0.6 s


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Sample 3: Muscle


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For the blue curve:

time taken to reach the relative maximum pressure= 250 s

For the orange curve:

time taken to reach the relative maximum pressure= 220 s

For the red curve:

time taken to reach the relative maximum pressure= 250 s

The average time taken = 240s


Biology project

For the lung: The average time taken = 13.8 s

For the kidney: The average time taken = 0.6 s

For the muscle: The average time taken = 240s

The fastest is the kidney, that means it produced the largest amount of oxygen at the shortest time. And we can concluded that it contained the most amount of catalase.


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Investigation on the the effect of different pH on the catalase


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Hypothesis


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We think that the rate of dissolved oxygen produced at a faster rate in neutral pH value, as the enzyme is denatured in high pH and low pH


Biology project

Add 1cm3 of buffer of pH 4 into the test tube

Fill the 1cm3 syringe with kidney tissue

Add the kidney tissue into test tube

Once the tissue is added, stopper it and record the result using low pressure sensor

Repeat the experiment by using buffer solution of pH 7

and pH 10.


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Results:

Sample 1: in pH 7


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Sample 2: in pH 4


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Sample 3: in pH 10


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By comparing the three graphs, we can see that they have similar slopes. Slopes show the rate of reaction. This implies that the rate of reaction of enzyme on substrate in pH4, pH7 and pH10 are more or less the same.

In all three graphs, there’s a general increase in pressure, showing that the enzyme works in all the pH used.


Biology project

As the rate of reaction are similar in all three cases, it seems that pH have little effect on enzymes.

Besides, as the enzyme works from pH4 to pH10, it seems that it has a large suitablepH range for reaction to occur.

However, from our biological knowledge, pH has a great effect on enzyme. A change in the pH value alters the shape of the active site and thus affect the activity of enzymes. Great changes of pH cause denaturation.

Also, enzymes usually work in a narrow range of pH. Their activities change greatly with small changes in the pH of the medium.


Biology project

Strange results are obtained from our experiment. This may be due to the tissue which is in too dilute form. The amount of enzyme is so small when compare to water content. Thus, the effect of pH on enzyme is not so prominent. It is better to perform the experiment with more concentrated tissue.

Conclusion:

No conclusion can be made and our hypothesis can’t be proved.


Biology project

Sources of error:

1. We can't stopper the test tube immediately after we

insert the organ sample, therefore some oxygen

may leak out.

2. The concentration of the “organ liquid" was not the

same in each experiment, that is we use different

amount of water to mix with different amount of

organs, the results may not be compared accurately.


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Improvement:

  • 1. Cut the residual organ into smaller size in organ solution (after the organ has been stirred in he stirring machine) to increase the surface area so that the rate of reaction is faster.

2. Use the same amount of water and organ tissue to make the “organ liquid”, so as to get a same concentration for the three samples.


Biology project

  • 3. Remove the fat of organ before making the organ solution (putting into stirring machine) as some fat may present in the organ solution ,when with drawn the solution for testing ,fat may retain in the syringe so the amount of solution of kidney is not up to 1 dm3,thus amount of enzyme in kidney working on peroxide reduce.


Biology project

Group Members:

6AS Donna Chan (3)

6AS Priscillia Chiu (7)

6AS Mandy Choy (10)

6AS Agnes Wong (26)

2001 - 2002


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