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Plan for an experiment - How does temperature affect the rate of photosynthesis?

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´╗┐An investigation into the effects Temperature has on the Rate of Photosynthesis Aim: The aim of this experiment is to investigate the effect of various temperatures on the rate of photosynthesis by measuring the volume of oxygen produced by elodea. Introduction: Temperature is one of the main factors that can speed up as well as limit the rate of photosynthesis in plants because it has a direct effect on plant enzymes, which are essential to photosynthesis. Enzymes are globular proteins which act like ?biological catalysts?, as they?re able to increase the rate of reactions within living organisms by lowering the activation energy needed for a reaction without actually being used up themselves. Enzymes have an active site, which is a region on the surface of the enzyme that substrates bind to and catalyses a chemical reaction. The active sites are specific to certain substrates, as only a few substrates can fit the active site, this is called enzyme-substrate specificity. Enzymes have a small range of temperatures within which they?re able to work. When there?s an increase in temperature, enzyme activity generally tends to double with every increase of 10 degrees, as both the enzymes and substrates have more kinetic energy and are therefore moving faster and having more collisions, which would speed up the rate of photosynthesis. All enzymes have an ?optimum temperature?, where they?re able to work at their best by having more kinetic energy and collisions, however after the optimum temperature, the temperature tends to be too high for the enzymes to function properly, as their active sites began to denature. ...read more.


I will only measure the volume of oxygen produced within a three minute interval. Concentration of CO2 CO2 is essential for photosynthesis to take place, so it can?t be a limiting factor. I will put the elodea in a solution of 0.2% NaHCO3 so that CO2 will be produced in excess Concentration of the enzyme Concentration of enzymes and substrates are one of the limiting factors of enzyme activity, a low concentration of enzymes or a saturation of substrates could decrease the rate of photosynthesis. RuBisCO is the most abundant enzyme on the planet, so it?s likely to assume the concentration of enzymes would not be a limiting factor in this experiment. Length/Size of Plant Having different sizes of plants would make the experiment an unfair test. I will use elodea that?s 15cm long for each condition. Equipment For this experiment, I will be measuring the amount of oxygen that?s produced whilst the elodea is submerged in water of different temperatures, therefore I will be setting up a photosynthometer, which is shown in figure 1. (figure 1) Diagram of a photosynthometer [http://www.studyblue.com/notes/note/n/photosynthesis/deck/4525820] Equipment Quantity Use Units and Uncertainties Lamp 1 Photosynthesis needs light in order to take place. The purpose of the lamp is to make sure the elodea gets plenty of light for photosynthesis and light intensity doesn?t become a limiting factor. - Beaker 11 10 beakers are used to contain the test tube, heated water and the elodea for the experiment. ...read more.


Do this for each condition of the experiment to make sure the light intensity stays consistent. 8. Set the test tube with the elodea inside the first water bath. Start the stop watch and allow the elodea to sit in the water for one minute. This is to allow the elodea to acclimatise to the water. 9. After one minute, restart the stop watch. 10. Start the stop watch again and wait for 3 minutes. If you have more time to do the experiment, you may choose to wait for 5 minutes instead. 11. As soon as the time is up, SLOWLY pull the oxygen bubbles that have been produced through the capillary tube with the syringe. Pull them along until they line up with the scale (see fig 1). 12. Record the length of the oxygen bubbles and use this to work out the VOLUME of oxygen produced. You can work out the volume with this formula, where ?r? is half the diameter of the capillary tube and ?h? is the length of the oxygen bubbles. V = ?r2h 13. Repeat steps 7 ? 12 for each temperature condition at least five times. This is to make sure your results are more reliable. Always make sure the light intensity and distance of the lamp from the equipment is consistent to keep the experiment fair. Risk Assessment As with all lab experiments, a lab coat and goggles should be worn at all times, particularly when handling NaHCO3 as this can irritate the eyes. ...read more.

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