Elodea experiment

Prediction

I predict that the elodea will photosynthesise greatest at around 30 c because this is the optimum temperature for enzymes and I think this will be reflected in the enzymes that do photosynthesis. However I think that at about 50 c the elodea will no long photosynthesise because the heat will denature the enzymes, there for the graphs to show my results will have an "n" shaped curve. I think this will happen because at lower temperatures than 30 c the enzymes will not work as well and so photosynthesise slower, but do not denature. The only limiting factor is temperature because we have constant light supply from the lamp and plenty of carbon dioxide from the sodium hydrogen carbonate. At about 60 c I think the enzymes will be denatured and so will no longer photosynthesise. The shape of the enzymes will be permanently changed and so even if you cool the elodea down it will no longer photosynthesis as efficiently. Photosynthesis works by the enzymes bumping into the particles of water and carbon dioxide and breaking them down into energy, glucose and oxygen. As the heat increases in the plant, the amount of kinetic energy held by the enzyme increases so they bump into the particles more and so can break them up more rapidly. This is why I think the higher the temperature the greater the rate of photosynthesis. However, when the enzymes reach a certain temperature, then shape will change and so they will no longer be able to break down the particles, this is denaturing.

Starting

Temperature ( c)

Temperature

Reached ( c)

Number of

bubbles in 5 minutes

Number of bubbles per minute.

23

-

0

0

23

33

4

3

36

46

21

4

48

58

95

9

57

66

92

8

65

75

200

20

75

85

0

0

Diagram

Method

I followed my plan except I decided to go up in tens instead of fives. So I measured the temperature as 10 c above the starting temperature, then 20 30 40 and 50 c above the starting temperature.

Conclusion

The optimum temperature for photosynthesis in elodea is about 75 c. The enzymes denatured somewhere between 75 and 85 c. The optimum temperature for photosynthesis enzymes is a lot higher than the enzymes used for digestion in the human body. I think this is because the enzymes can cope with higher temperatures before they denature. My results are quite reliable but when it got to temperatures such as 66 and 75 c there were a lot of bubbles so it is possible that I may have miss-counted. Also the heat may not have been evenly distributed throughout the water so some parts of the elodea may have been hotter than other areas. Also the temperature fluctuated while I was counting the number of bubbles, sometimes being higher than the temperature I was aiming for, and sometimes being lower. When I was counting the bubbles, they were different sizes that meant that if a large bubble were produced it would contain more carbon dioxide, and would mean more photosynthesis would have been done. I only counted large bubbles as one bubble, and small bubbles also as one bubble, which meant that the actual rate of photosynthesis was not accurately recorded. This would mean that the results are inaccurate and are therefore only be an estimate. The graph reflects the "n" shape that I predicted in my prediction. In my prediction I thought that the optimum temperature would be around 30 c but in fact it was twice as much. If I were to repeat this experiment I would like to be able to heat the water more accurately to ensure that the heat was distributed evenly. I would also try and find a more effective method of counting the bubbles, because at high temperatures it was difficult to count all the bubbles.