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The aim of this experiment is the effect of temperature on the rate of photosynthesis in Elodea canadensis.

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Biology coursework Investigating the rate of photosynthesis in Elodea canadensis INTRODUCTION AIM: The aim of this experiment is the effect of temperature on the rate of photosynthesis in Elodea canadensis. BACKGROUND KNOWLEDGE: As level: From Biology 1 (2000) JONES, FOSBERY + TAYLOR From AS level we learnt about enzyme structure and how products are formed. When carbon dioxide comes into contact with Rubisco it is converted to 2 X Glycerol-3-Phosphate. The yellow object is an enzyme. Enzyme's act as a catalyst to speed up the reaction and remains unchanged at the end of the process. With an enzyme present it increases the likelihood of a collision of the substrates to form a product. Enzymes are globular proteins and are coiled into three-dimensional shape, which have hydrophilic side chains on the outside to make sure they are soluble. In picture 1, we have a carbon dioxide molecule and a Rubisco molecule. These are called the substrate molecules. In picture 2, we have carbon dioxide and a Rubisco molecule combined with an enzyme. The enzyme is there to combine both molecules together. It is now called an enzyme-substrate complex. It is held together by temporary bonds between the substrate and side chains of the enzyme. In picture 3, the two molecules are combined and have now formed our product, Glycerate-3-phosphate. Picture 4 just demonstrates the products out of the enzyme. When an enzyme is present, the likelihood of a collision between the two substrates increases. The enzyme increases the rate that chemical reactions take place. When a substrate is converted to a product, (In our case when carbon dioxide and Rubisco is converted to glycerol-3-phosphate (GP)) energy is required, this is called the activation energy. An enzyme reduces the activation energy, when the substrates come in contact with the enzyme its shape changes briefly to encourage the two substrates to combine to form our product, Glycerol-3-phosphate. ...read more.


Length in bubble (mm) 0.0 8 0.5 10 1.0 8.5 1.5 11.5 2..0 12 2.5 12 The temperature for this experiment was 24OC, the plant weighed 2.63g, it was also measured in a 2 litre beaker, light was in excess at 240 watts and the length of each bubble was recorded at 3 min intervals. From this experiment unlimited CO2 looks like it would be in excess when at least 2 grams of NaHCO3 is present. Water Plants can use NaHCO3 ions as a substrate instead of CO2 concentration. I think a good estimate for NaHCO3 ions to be used is 1 gram per 1 litre of water. * Volume of water to remain constant at 2 litres. * The water used will be distilled water and will come from the same tank. * When doing the experiment the environment is to stay the same. * I think it could be an idea to use oxygenated water to help with the synthesis of CO2. MEASURING TECHNIQUES The measuring technique I will use will be collecting the bubbles and measuring the volume of the bubbles collected per minute, this will be more accurate then counting the bubbles because it is much harder and less accurate then the first method. If you decide you want to count the bubbles, you will find it extremely hard as a lot of bubbles will be leaving the plant and you will have to be very quick not to miss any. The apparatus I will use to measure the volume of the bubbles collected will be a gas burette designed to trap bubbles of oxygen. PRELIMANARY WORK PRELIMANARY WORK When doing an experiment like this many things are to be carried out before. For example collecting secondary data to see how and why an experiment maybe carried out and what the results maybe like in different circumstances. For my preliminary work, I used a few sources, examples of these would be: the light in excess experiment, the CO2 in excess ...read more.


The way to calculate this is by using the volume calculation, which is: Volume = ? r2 X l r = 0.5mm, ? = 3.14, l = length of bubble As we are measuring it in 3 minute intervals, we divide the answer by 3. Also the weight of the plant, we want to work it so it is measured as: per gram/per min of rate of photosynthesis against temperature. So say for example the weight of the plant is 1.45g at 3 minute intervals, we divide the answer by 3 and then by 1.45 to calculate per gram/per min. EQUIPMENT NEEDED * 2 litre beaker. * A plant of Elodea canadensis from a source where it has been well illuminated and photosynthesising actively. * A thermometer. * Ice cubes. * Hot water from a kettle for the higher temperatures. * A gas burette. * A syringe for the gas burette. * Scales for measuring the weight of the Elodea canadensis. * A ruler to measure its length. * A razor blade. * A stopwatch. * A heat shield. * 14 litres of distilled water, 2 litres for each experiment. * 2 litre beaker. * A syringe for the gas burette. * 3 lamps of 60 watts each. * 14 grams of Sodium Hydrogen Carbonate (NaHCO3), 2g's for each experiment. SAFETY The safety aspects to this experiment are: * Using a plug socket: Always make sure you have dry hands when using electrics as there is a chance of electric shock. * Using a razor blade: A razor blade is sharp, use with caution and do not leave it somewhere where someone may hurt themselves. * Beaker size: As the size of the beaker we are using is a 2 litre one, be careful not to knock it off the edge of a table. * Using an irritant (NaHCO3): From the Haz Card, Sodium Hydrogen Carbonate is an irritant, so take care with handling it, for example wear eye protection and use a spatula when handling it. Natasha Jarvis 1 Sunday 9th March 2003 ...read more.

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