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An Investigation into the Effect of Temperature on the Rate of Photosynthesis.

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Introduction

An Investigation into the Effect of Temperature on the Rate of Photosynthesis Theory The aim of my experiment is to determine how temperature affects the rate of photosynthesis of the aquatic plant Elodea. Photosynthesis is a chemical reaction that takes place in the leaves of green plants building up food compounds from carbon dioxide and water, and using the energy from sunlight, which is absorbed by chlorophyll. The chemical equation for the reaction of photosynthesis is: - chlorophyll 6C02 + 6H20 --> C6H1206 + 602 Carbon water light glucose oxygen Dioxide energy produced released This reaction will take place in my experiment and the oxygen released will be measured using the technique of counting the number of oxygen bubbles released from the aquatic plant. Catalysts speed up many chemical reactions without being used up or changed. Inside living organisms, chemical reactions take place all the time with a specific enzyme controlling every reaction. Enzymes are biological catalysts as they effect metabolic reactions. In all chemical reactions one thing is changed into another thing. The substance at the start of the reaction is called the substrate and the substance produced by the reaction is called the product. As enzymes are unchanged in reactions, a small amount of enzyme can catalyse the conversion of a lot of substrate into a lot of product. In the case of this experiment the enzyme is chlorophyll, the substrate is the carbon dioxide dissolved in water. ...read more.

Middle

Here is a results table of the small number of results I took in preliminary work. Bubbles released per minute Temp ( C) 1st reading 2nd reading 3rd reading Average 10 0 0 0 0 20 54 58 61 58 40 167 171 170 187 60 42 37 29 36 80 0 0 0 0 Apparatus * Safety glasses * 500ml of water * Bunsen burner * Tripod * Heat mat * Wire gauze * Thermometer * Clamp stand * Boss clamp * Stop-watch * Lamp * Ice cubes * Beaker * Glass rod * Paper clip * Aquatic plant Plan * Set up apparatus as shown. Cut a slanted slit through the top of the aquatic plant's stem. This allows bubbles to be released, and the slanted slit ensures a larger surface area for the bubbles to be released through. Attach the paper clip to the other end of the aquatic plant, holding it vertically underneath 500ml of a water solution containing 1g of HCL. Position the lamp 10cm from the beaker, being sure to maintain this for the duration of the experiment. Clamp the thermometer into place in a suitable position. * Cause the water temperature to settle at 20 C, the first temperature at which a reading will be taken. Do this by heating the beaker with the Bunsen burner or by adding ice to the water. ...read more.

Conclusion

Evaluation To a large extent my experiment went to plan, although looking back I have become aware of some drawbacks in the method. Firstly, accuracy of measuring bubbles was very hard to achieve. I encountered difficulty counting oxygen bubbles, as they were released so fast from the plant and they were so small. The size of bubbles could also have changed during the experiment, which made me question the reliability and accuracy of the experiment. If performing the experiment again, I would employ another method for measuring the amount of oxygen released, for instance, collecting the volume of oxygen. I performed the observation 3 times at each temperature, in order to over come this problem and I think this was a suitable amount of times to repeat each test. However, I did obtain one anomalous result in my third reading at 50 C, which suggests that the enzymes in the chlorophyll were denaturing after the second observation at this temperature. It would have been better to perform the experiment three separate times, instead of taking three observations at each temperature. To obtain a smoother graph it would be desirable to take readings at shorter intervals of temperature change. The light intensity could vary if the experiment was repeated on 3 separate occasions to gain refined reliability. One relevant variable that was not accounted for was pH. This should be kept constant as it affects the shape of enzymes altering the rate at which they convert substrate to product. ...read more.

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