Photosynthesis in pondweed Elodea sp.
...l cause a change in the rate of photosynthesis • Amount of sodium bicarbonate This is because changing the amount of sodium bicarbonate will cause a change in the rate of photosynthesis • Length of pond weed This is because changing the length of pond weed will change the amount of chlorophyll and cause a change in the rate of photosynthesis Apparatus • Heat proof mat • Thermometer • Pondweed • 100cm3 water • Wire gause • Bunsen burner • Lamp • 5g sodium hydrogen bicarbonate this is because this was the best amount during the pre-test Plan 1. Set up apparatus as in the diagram (have the light 0cm away from the beaker, this was the most effective distance in our pre-test) 2. Heat the beaker to 30°c 3. Wait 5 minutes to allow the pond weed to acclimatise 4. Count the amount of bubbles that rise to the surface from the pondweed per minute 5. Recount it three times, if there are any anomalous results, recount until you have three non- anomalous results 6. Take the average of the three to reduce the effect of anomalous results 7. Increase the temperature by 5°c and repeat until you have readings up to 50°c 8. Plot the results into a graph. Analysing evidence (results) and drawing conclusions Bubbles/min Temp (°c) Reading 1 Reading 2 Reading 3 Average 30 58 60 62 60 35 110 118 120 116 40 114 115 115 114 45 31 32 20 30 50 29 30 31 30 Conclusion I found that as predicted, the rate of photosynthesis increased with the temperature, but once the temperature got to 40°c the rate of photosynthesis started to go down. This is because when the temperature was increasing, the amount of collisions between the CO2 and the enzyme’s active site increased, causing more reactions and therefore more oxygen to be produced. However, once the temperature increased to 40°c, the enzymes denatured, causing the active site to change shape. This meant that no matter how many times the CO2 and the active site collided, there would not be a reaction. Evaluating There were some errors in my method. There were a lot of bubbles coming off at one time, making it very difficult to count them all at the same time, so my calculations could have been inac...