The Effects of Temperature on the Rate of Photosynthesis in Canadian Pond Weed

The Effects of Temperature on the Rate of Photosynthesis in Canadian Pond Weed
The purpose of the experiment is to find out how the effect of temperature will alter the rate of photosynthesis. What will happen with an increase of carbon dioxide, upon the rate of photosynthesis, when a certain amount of sodium hydro carbonate is added? Predicted Outcome ===== During the experiment I predict that, as the temperature gradually rises, the rate of photosynthesis will also rise which will result in more oxygen being given off. As the temperature reaches 50oC ? 60oC, I think the enzymes will start to breakdown and denature. This will result in photosynthesis decreasing, so therefore there will be a reduction in oxygen given off. Oxygen will be released until photosynthesis has completely finished. Hence between the temperatures of 100C and 600C there will be definite signs of an increase in oxygen given off but also definite signs of recreation in photosynthesis. If the lamp is placed nearer to the apparatus There will more oxygen given off. The sodium hydro carbonate will also speed up the process of photosynthesis. With the experiment that we are doing, we are giving the Canadian pondweed an artificial environment, so therefore we will not receive accurate results. Scientific Explanation of Predictions
The process by which plants make food is called photosynthesis. For this chemical reaction to take place the plant must use inorganic materials, mainly carbon dioxide, which is obtained from the atmosphere and water from the soil and in the presence of chlorophyll and energy (from the sun) will manufacture carbohydrates. If the lamp is placed nearer to the pond weed, (the lamp acting as the sun), the rays of light will get trapped in the chlorophyll, the water molecules split up into oxygen and hydrogen, and therefore giving off more oxygen. The hydrogen that is given off during this process combines with the carbon dioxide, from the atmosphere, and starts the manufacture of carbohydrates, proteins, fats and most vitamins. This again provides the plant with more oxygen. In my prediction, I said that the enzymes (proteins that have been manufactured) would start to breakdown. Enzymes are very important, because they are chemicals that are produced by the living cells, which have the power to alter the rate of chemical reactions occurring in the plant. Being that all enzymes are proteins, many enzymes can be produced from the process described above. All enzymes need water before they are able to function properly, due to the fact we are dealing with photosynthesis; we will not have to add excess water for the enzyme to work. Another property that an enzyme has is its narrow range of temperature. A rise in temperature would speed up any reaction but also a decrease in temperature will slow down the reaction. Maybe just as little as 100C could increase the rate of reaction by double the rate. As they are proteins, high temperatures will denature them. This is because the enzymes control the chemical reactions, which keep the cell alive. When a protein is heated to such a temperature of say 500C, the cross-linkage in its molecules break down; the bonds will start to vibrate or even brake. The molecules will lose their shape and will never again be able to regain their shape. This is the point when the cell denatures. Controls ==== 1. I will keep the light from the lamp at a constant distant away from the pondweed. I will do this so I will be able to get fair results and it will help reduce the number of anomalies. If the lamp is moved about during the practical it could alter the rate of photosynthesis. 2. Throughout the practical the water level inside the test tube should be keep at a constant level to ensure good results and so that photosynthesis isn?t altered. If more water is added it is likely that the enzymes will speed up giving us an unfair test. 3. The sodium hydro carbonate will be added at the beginning of the practical and only then. If it is added once more it could affect the rate of photosynthesis. This can happen because the hydrogen, that is given off when the water molecules are split up, combines with the carbon dioxide (from the extra sodium hydro carbonate that is added), which manufactures more proteins (enzymes). Which will speed up the chemical reaction because there is know more enzymes present. 4. Keeping the pondweed the same size throughout the practical is essential because you may have more/less leaves exposed to the light or the water, which could increase/decrease photosynthesis. Variables ===== 1. The temperature surrounding the pondweed in the test tube will change temperature throughout the practical. Also, the water bath will be changing temperature. We are changing the temperature because are trying to find out the rate of photosynthesis under different temperatures. The Plan ==== Apparatus: ? Tripod ? Bunsen Burner ? Thermometer ? Beaker ? Sodium Hydro Carbonate ? Gauze ? Boiling Tube ? Lamp ? Clamp ? Paper Clip ? Pond weed Plan: 1. Gather and set up the apparatus (as drawn above) make sure that you have plenty of room and that your workspace is safe and tidy. 2. Before the start of the experiment I will need to make a table of results so I can record how many bubbles of oxygen is given of. The results table will consist of six columns. The first being the temperature at which I would like the water to be at. The next three are for counting how many bubbles are being released. The next column is for any anomalies that may occur. The last column is for the mean number of bubbles given off at that temperature. 3. I will mark on the test tube a level that I want the water to be at, I will then add 0.6g of sodium hydro carbonate. 4. Once all the apparatus are set up, as shown above, I will cool the water bath and the test tube water down to 100C. 5. While the water is cooling I will cut the pondweed to 8cm. And at the top of the pondweed I will cut it at an angle so that there is a larder surface area for the oxygen to be released. Then a paper clip will be attached to the bottom of the pond weed, so the pond weed doesn?t float to the top because if it did float to the top we are unable to the oxygen bubbles released and therefore cannot count them. 6. When the thermometer reads 100C, I will leave the weed to acclimatise for 1-2 minutes. 7. Now the weed has acclimatised I will now start to count the bubbles being released from the pondweed and record them down in my table of results. 8. I am going to count the bubbles of oxygen being released three times so I can gather an average. 9. Now, I will raise the temperature by another 100C and repeat the procedure again. 10.I will increase the temperature by 100C each time until I get to 600C. 11.Once I have gathered all the results onto my table, I will then transfer that information onto a graph. The information that I will put onto the graph will be the averages of the counts by the temperature. 12.After that I will examine those results and see what has happened and include that in my conclusion. Analysing Evidence and Drawing Conclusions ========== Number of Bubbles Given off per min Temperature oC 1st 2nd 3rd Anomaly -?? Mean -- 10 10 12 11 11 20 27 24 26 26 30 56 56 52 29 55 40 86 85 89 73 87 50 42 40 43 42 60 1 3 1 8 2 All the evidence shown above was recorded during the practical and all the evidence below was recorded in the practise practical. Temperature oC 1st 2nd 3rd Anomaly Mean 10 15 17 16 16 20 33 33 31 32 30 60 59 62 66 60 40 98 99 97 98 50 55 50 51 34 52 60 1 4 2 10 2 With the results shown on the page before, I have placed them on a graph. I have done this so I can roughly find out, when the weed is starting to denature and when the weed is giving of the most oxygen. On the graph I have plotted six points, each of those points is the mean of the three readings that were taken, during the experiment. I have chosen to use the mean, so it would give me a more accurate graph. In the results table there is a anomalies column, this was put there because when the experiment was taking place, there was one or two results which looked out of place, so I then took the reading again. I took another reading and generally find that it followed the trend. As you can see from the graph the plant started to denature after 400C, you can see that it also denatured very quickly. The rate of oxygen also went up quickly. So therefore the enzymes started to break down after 400C. Conclusion From the practical, I learnt that the rate of reaction would increase with an increase of temperature. This is because of the enzymes in the pondweed. Enzymes are chemicals produced by living cells, which have the power of altering the rate of chemical reactions occurring in the cell. One reason why, enzymes are present in plant cells is because of photolysis. Photolysis is when, energy from the sun, is trapped by the green pigment, chlorophyll, and splits water molecules into oxygen and hydrogen. Sunlight 4H2O -?????- 4OH + 4H Chlorophyll The hydrogen that is given off combines with the carbon dioxide in a series of reduction reactions. The product acts as a starting point for the manufacture of all carbohydrates and proteins. The proteins from this manufacture produce the enzymes in the plant. I supplied the plant with a constant amount of water so that the enzymes wouldn?t break down at an early stage, because all enzymes need water before they are able to function. Enzymes only work in a narrow range of temperature because, when it is heated to over 500C, the cross-linkages in the molecules beak down. They will then lose their shape and will not regain their shape even when it has been cooled. It is to be said that the enzyme has been denatured. This is because the protein will have lost its original properties and the molecule structure has been changed. With an increase in carbon dioxide will increase and then stay at a constant. The rate of photosynthesis will stay constant when a certain concentration of carbon dioxide is reached. If the lamp was placed closer to the pondweed I think that the rate of photosynthesis would increase by even more than it did. In conclusion I think that increased light, carbon dioxide and temperature will increase the rate of photosynthesis. But if they are all or even one is exceeded the rate of photosynthesis will plummet. The results show the point at which the rate of photosynthesis starts to increase and when the weed starts to denature. It can also show at what temperature the pondweed needs to be at for the best results. Evaluating the Evidence The experiment that we carried out gave us a good set of results. It was suitable because showed us what we wanted to find out. It helped us to understand how enzymes handle being put under pressure. The evidence we obtained gave us sufficient knowledge of how the pondweed would react to added carbon dioxide and added sunlight. With the experiment we carried out, we gave the pondweed an artificial environment. This is so because when a plant is photosynthesising it relies on the water and nutrients from the soil, the light from the sun and the carbon dioxide from the atmosphere. Because none of this was included in the experiment we wouldn?t get an accurate set of results. The procedure of the experiment was adequate but could have been improved. For instance we could have used electric water bath. This would improve the experiment because it is more accurate and more efficient. During the practical I felt rushed and could of easily made many silly mistakes, so having more time for the experiment would be good and would make the practical more successful. The evidence obtained supported my conclusion. In my conclusion I mentioned that when the temperature exceeded 400C the pondweed would start to denature and at 500C. The graph showed that the rate was decreasing so therefore the enzymes were breaking down rapidly. This meant that the pondweed was coagulating. In a further practical you could investigate how carbon dioxide or sunlight improves the rate of photosynthesis. The experiment would be efficient because you would be on the same theme and you would also be using the same variable.

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