The effect of heat on the rate of respiration

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Introduction:

All living things require energy in carrying out activities. The process by which energy is made available from nutrient of cells is called cellular respiration. Cellular respiration is the controlled release of energy, in the form of ATP from organic compounds in cells.

Respiration occur under two conditions which is with the presence of oxygen and without the presence of oxygen. If there is presence of oxygen, then the process is called aerobic respiration. However, if there is lack or absence of oxygen, then it will refer as anaerobic respiration.

Respiration involves enzyme that can be affected by the temperature. The rate of the respiration increase with the increase in temperature until it reaches the optimum temperature. This is where the rate of the respiration is the highest. Further increase in temperature only lowered the activity of the enzyme as it begins to denature.

Research Question:

How does the temperature affect the rate of respiration?

Objective:

Investigate the effect of heat towards the rate of respiration of Mung beans.

Hypothesis:

The rate of respiration increases with the increase in temperature. This will continue until it reaches 60oC where the rate of respiration is the highest.

Variables:

Variables

Range

Unit

Ways of controlling

Independent:

Temperature of the solution with the mung beans

300C,400C,500C and 600C

0C

The mung beans and the Bromcresol solution is put inside water bath with temperature 300C until it reaches they reach the temperature. Then, the mung beans are put inside the Bromcresol solution. The experiment is then repeated replacing the temperature to be 400C, 500C and 600C.

Dependent:

Time taken for Bromcresol solution to change from purple to yellowish colour.

-

Minutes and seconds (mins:s)

The time taken for the Bromcresol solution to change from purple to yellowish colour is measured using a digital stopwatch and recorded for every repeated experiment.

Controlled Variables

Unit

Ways of controlling

Possible effects on result

Mass of mung beans

g

100g of mung beans is measured using electronic balance and is used in every repeated experiment.

With the same number of mung beans, comparison between every repeated experiment can be made easily as the amount of the mung beans is the same by controlling its mass. If the mass is varied, the result will be hard to compare with the other.

Types of beans used

-

Mung beans is used for every repeated experiment.

The same type of beans will ensure the equality of each experiment and enable comparison of results obtained from the experiments. Different type of beans may respire with different rate and affect the result of the experiment.

Volume of Bromcresol

Drops

6 drops of Bromcresol is added using a dropper in the preparation of the indicator solution.

Bromcresol is used to detect the presence of carbon dioxide. With the increase of number of drops of bromcresol, the experiment will take more time for the reaction to occur. 6 drops of bromcresol ensures the experiment can be completed in the given time period.

Materials

Materials

Quantity

Bromcresol solution

6 drops

Mung beans

-

Apparatus

Apparatus

Quantity

Test tubes

6

10 ml measuring cylinder

1

100 ml measuring cylinder

1

250 ml beaker

1

Test tube stopper

6

Water bath

-

Dropper

1

Digital stopwatch

1

Straw

1

Thermometer

1

Procedure:

a) Prepare the indicator solution

1. 50ml of tap water was added into a beaker, and then 6 drops of Bromocresol purple solution was added.

2. The colour of the solution changed to purple.

b) Prepare the standard solution

1. 10 ml of the indicator solution was transferred from the beaker into a test tube.

2. Expiring gas is blown into the solution using a straw. The solution changes colour from purple to greenish.

3. This was used as standard solution.

c) Conducting the experiment

1) The outer skin mung beans were peeled and the mung beans are put in a beaker. 100g of the beans is measured and put in a test tube.

2) 10 ml of the indicator solution was added into the test tube. The test tube containing mung beans is then put inside a water bath of 300C.

3) The temperature of the test tube is recorded and maintained using a thermometer.

4) Once in a while, the test tube was shaken and the time taken for the solution to change colour from purple to yellow as the standard solution was recorded using a digital stopwatch.

5) The experiment was repeated by changing the temperature (400C, 500C and 600C) respectively. It was controlled that the temperature of the mung beans and the solution while in the water bath reaches the temperature needed before adding both together.

6) The time taken for the colour to change for all different temperature is recorded suing a digital stopwatch.

Data collection:

Quantitative data:

Temperature

oC ± 0.05oC

Time taken for solution indicator to change to yellowish colour, minutes and seconds ±0.001seconds

Trial 1

Trial 2

Trial 3

30

14:40

14:40

8:04

40

8:40

3:00

4:03

50

5:27

2:15

2:50

60

2:45

0:50

0:55

Table 1.1 - Shows time taken for solution to change to yellowish colour for every temperature.

Qualitative data:

Initial

When the indicator solution is added into the test tube containing the mung beans, the colour of the solution is purple.

Final

After a few minutes, the colour of the solution changes from purple to yellow. In the room temperature, 30 oC, the test tube feels warm.

Table 1.2 - Shows The Qualitative data obtained by observation at initial and final result.

Data processing and analysis

Changing the unit of minutes and seconds into seconds

For the ease of calculations, the unit of time is changed to seconds. To change the unit of minutes and seconds into seconds we can use the following formula:

As an example, in trial 1at 30oC, the time taken was 14:40 minutes. To change the unit into seconds, the calculation is:

(14x60) + 40 = 880 seconds.

The calculations for other temperature are tabulated in the table below:

Temperature

oC ± 0.05oC

Time taken for solution indicator to change to yellowish colour, seconds ±0.001seconds

Trial 1

Trial 2

Trial 3

30

880

880

484

40

520

180

243

50

327

135

170

60

165

50

55

Table 2.1 - Table shows the time taken for solution indicator to change to yellowish colour in unit seconds for every temperature.

Calculating the average time taken for each temperature.

Average time taken is calculated to find the mean of the time taken for the solution to change to yellow from purple. The average time taken for each temperature is calculated by using the following formula:

As example of the calculations, the average time taken for the purple colour of indicator solution to turn to light yellow colour at 30oC :

= 776 seconds

Therefore, the average time taken for the purple colour of indicator to turn to yellow at 30oC is 776 seconds.

Temperature

oC ± 0.05oC

Time taken for solution indicator to change to yellowish colour, seconds ±0.001seconds

Trial 1

Trial 2

Trial 3

Trial 4

30

880.00

880.00

484.00

860.00

40

520.00

180.00

243.00

250.00

50

327.00

135.00

170.00

155.00

60

165.00

50.00

55.00

65.00

Table 2.2 - Average time taken for the purple colour of indicator to turn to yellow for every temperature

The uncertainty of average time taken.

To calculate the uncertainty for the average time taken, we can use the formula of standard deviation:

sd= ;

Where,

sd= Standard Deviation

∆= uncertainty

mean= average time taken

x= time taken

n= number of trial

As an example, below is the calculation for the experiment at temperature of 30oC where the average time taken is 776.00:

Temperature oC

Trial

x

(x-mean)2

30

1

880.00

10816

168.78

2

880.00

10816

3

484.00

85264

4

860.00

7056

Table 2.3 - calculation for the experiment at temperature of 30oC

For the other value, the calculation is made and is tabulated in the following table:

Temperature

oC ± 0.05oC

Time taken for solution indicator to change to yellowish colour, seconds ±0.001seconds

Average time taken, seconds

±0.001seconds

Trial 1

Trial 2

Trial 3

Trial 4

30

880.00

880.00

484.00

860.00

776.00

40

520.00

180.00

243.00

250.00

298.25

50

327.00

135.00

170.00

155.00

196.75

60

165.00

50.00

55.00

65.00

83.75

Table 2.4 - the average time taken for the purple indicator solution to change to yellow colour with the uncertainty of average time.

Rate of respiration

After obtaining the average time taken, we can easily calculate the rate of respiration of the beans. Rate of respiration is calculated by using the formula of:

As an example, at 30oC, the rate or respiration is:

= 0.001289 s-1

Therefore, the rate of respiration at 30oC is 0.001289 s-1. Table below shows the calculation for the other values:

Temperature

oC ± 0.05oC

Average time taken, seconds

±0.001seconds

Uncertainty of average time taken, seconds.

Rate of respiration, s-1

30

776.00

±168.78

0.001289

40

298.25

±130.90

0.003353

50

196.75

±76.22

0.005083

60

83.75

±47.22

0.01194

Table 2.5 - Table below shows the rate of respiration for each temperature.

Uncertainty of rate of respiration

The uncertainty of the rate of respiration can be calculated after obtaining the rate of respiration itself. To calculate the uncertainty of rate of respiration, the formula is:

∆R = x R

Where,

R = Rate of time taken

t = time taken

∆ = uncertainty

At 30oC, the rate of respiration is 0.001289 s-1. The uncertainty of rate of respiration is calculated as example below:

∆R = x 0.001289

= 0.0002804 s-1

Therefore, the rate of respiration at 30oC is 0.001289 s-1 ±0.0002804 s-1 .

The following table shows the rate of respiration of the mung beans for every temperature:

Temperature

oC ± 0.05oC

Average time taken, seconds

Uncertainty of average time taken, seconds.

Rate of respiration, s-1

Uncertainty of rate of respiration, s-1

30

776.00

±168.78

0.001289

±0.0002804

40

298.25

±130.90

0.003353

±0.001472

50

196.75

±76.22

0.005083

±0.001970

60

83.75

±47.22

0.01194

±0.006732

Table 2.6 - The rate of respiration of mung beans for every temperature.

Based on table 2.6, the graph of rate of respiration against temperature can be plotted.

Discussions:

Theoretically, the rate of respiration increase when the temperature increase until it reaches optimum temperature. At the optimum temperature, the rate of respiration is at the highest. After that, the rate of respiration will drop due to the denatured of the enzyme that involve in respiration.

But after the experiment is done, the results obtained shows that the rate of respiration keeps increasing till 60oC. We can say based on our experiment, the optimum temperature for the respiration of mung beans is more than 60oC.

The error is too small to be shown on the graph. This is because less error is being put in doing the experiment and safety precaution is taken.

The rate of respiration increases as the temperature increases until it reaches optimum temperature. Enzyme works efficiently at higher temperature because high energy is required for the enzyme undergoes the effective collision with the substrate frequently.

The Bromcresol solution function is to determine the existence of carbon dioxide gas in the air. If there is carbon dioxide gas, it will change colour from dark brown to yellow. So, time taken for the solution to change colour can be used up to measure the rate of respiration.

Limitations and suggestions

Limitation

Suggestion

1. It is difficult to maintain the temperature of the test tube in 60oC as there is no electronic water bath is available.

The water for 60oC should be added so that it is easier for the students to maintain the experiment at 60oC rather than having their own water bath using Bunsen burner and beaker.

2. The exposure of the bromcresol solution to the surrounding may affect its reliability as an indicator. Some carbon dioxide gas from human respiration will affect the colour of the indicator.

The test tube that contains the bromcresol solution must be closed by using rubber stopper at all times.

3. The usage of distilled water in preparing the indicator solution is not suitable as the solution will be yellow when added with bromcresol.

Students should be aware of different situations of different solution and advised to use tap water in similar upcoming experiments

Conclusion

The rate of respiration increases with the increase in temperature. This will continue until it reaches 60oC where the rate of respiration is the highest. From this experiment, the optimum temperature of the respiration of the mung beans is 60oC. Hypothesis is accepted.

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