Preliminary Results
The results I took showed how affective using the data-harvesting program can be.
Other preliminary work I have, which I can use to support this experiment is my enzyme investigation, which looked at how enzymes were affected with the change of temperatures. From this l learnt that as temperature increases then so did the rate of reaction, however once the enzymes passed the optimum temperature of between 30oC and40oC then the enzymes would begin to denature, which would then decrease the rate of reaction. This will help me as I intend to take a much larger range of results than the ones displayed above. Now if I needed to extend this experiment, then I could work out the respiratory quotient. If I wanted to do this using the respiorometer then I would have to calculate the oxygen consumption at a specific temperature. Then I would maintain the temperature for the respirometer and the organisms and conduct the experiment as before. However I would not use sodium hydroxide to absorb the carbon dioxide. Then I would be able to determine if the volume of oxygen consumption is the same as the produce of carbon dioxide. We will know by assuming that the RQ=1 when the level of the fluid is constant on the manometer scale. This is yet another reason for us to choose data harvesting equipment.
Variables involved (constant and changing)
In this experiments there are a number of points in which I need to make sure do not alter the investigation. If I was to use the respirometer I would need to make sure that temperature and pressure in the experiment doesn’t alter as otherwise the volume of the air in the apparatus is affected which leads to inaccurate results. To solve this I shall use for both experiments a thermostatically controlled water bath however to drop the temperature I may have to use ice. The presence of the second test tube (control tube) helps to compensate for changes in atmospheric pressure. I have also decided that I will use 20 fresh maggots for each experiment. This does bring up the problem of weather to use the same maggots on the repeats and throughout the temperatures. However I feel that maggots are similar enough organisms for the change in maggots not to affect the experiment much at all. So I will use a fresh back of maggots for each repeat and temperature. Also if I do use the respirometer I need to make sure I have something to counteract th4e production of carbon dioxide. So I would use sodium hydroxide, which would absorb all of the carbon dioxide and would allow the respirometer to measure the consumption of oxygen. Finally I have decided that the temperatures 40oC, 45oC, 50oC 60oC and room temperature (22oC). At each of these temperatures I would repeat three times to ensure that no anomaly results happen. However using the data-harvesting equipment should mean that my results will be correct first time round, unless we have set the experiment up wrong.
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Method
As you can see on the previous page I have two different diagrams. This shows I have two different ways of attaining my results.
The temperatures I will inflict on the invertebrates will be 3oC, 30oC, 40oC, 45oC, 50oC 60oC and room temperature (22oC). I must ensure if I was to use the respirometer that temperature and pressure don’t alter as otherwise the volume of the air in the apparatus is affected which leads to inaccurate results. To solve this I shall use a thermostatically controlled water bath however to drop the temperature I may have to use ice. The presence of the second test tube (control tube) helps to compensate for changes in atmospheric pressure.
The other diagram (which I intend to do) involves using a computer and the data-harvesting program, which will enable me to use just one test tube containing the invertebrates. I will then put that test tube at what temperature I desire, and insert a rod linked to the computer, which will tell me how much oxygen has been consumed. Due to it all being linked up I will be able to plot a graph of oxygen consumption against time.
Finally when I have completed all temperatures I will plot a graph of oxygen consumption against temperature. I can do that with either method.
Detailed plan 4a .
Logical sequence 6c .
Prediction
My prediction for this investigation is that as the temperature’s increase, the rate of respiration will increase. This is until it reaches about 50oC or 60oC in which case the rate of respiration will begin to slow again. I should expect that the optimum temperature for the rate of respiration would be between 30oC and 40oC.
The reason I believe this is because I know that respiration is an enzyme controlled reaction. The glucose (major respiratory substrate) is a relatively large molecule containing six carbon atoms all in a reduced state. When respiration occurs then glucose undergoes a series of enzyme catalysed oxidation reactions. There are three major reactions, which are Krebs cycle, glycolysis and the electron transfer system.
Glycolsis occurs in the cytosol and is the series of reactions in which the six carbons are broken down into two molecules containing three carbons, known as Pyruvate ions. Glycolysis is very common in both aerobic and anaerobic respiration. They have a production (net synthesis) of two ATP for each glucose split. The diagram below helps explain the process of glycolysis.
The Krebs cycle, as shown below, always happens in the mitochondrion. Pyruvate that was produced by glycolysis enters the mitochondrion, where it is decarboxylated (due to the use of decarboxylase enzyme) by the removal of carbon dioxide. The other two carbons then react with sulphydryl group of co enzyme A. This forms acetylcoenzyme A simultaneously the hydrogen atoms are transferred to the hydrogen acceptor (NAD goes to NADH2). Acetylco-A reacts with oxaloacetate (an ion with four carbons, as a organic acid) in the presence of an enzyme. The acetyl group pulls off and citrate is produced and co enzyme A is released for re-use. Then eventually citrate is converted back to oxaloacetate ion to be used again. During the cycle two molecules of carbons dioxide are given off, a pair of hydrogen atoms is removed and a molecule of ATP is formed. the hydrogen atoms are taken up by NAD, but one pair that is attached straight to flavine adenine dinucleotide.
The pairs of hydrogen’s taken from taken from the respiratory intermediates during the oxidation of glucose are accepted by a hydrogen acceptor (NAD). The hydrogen atoms in NAD2are finally oxidised to water by oxygen. This is known as the Electron Transfer System. At three points in the chain, energy is released and is used in the synthesis of ATP from ADP and a phosphate in the presence of an ATP-synthesis enzyme.
As you can see from all of these three steps enzymes are a major factor in respiration. So as the temperature increases then we know that enzymes begin to denature and do not work as efficiently. So therefore the rate will slowly begin to decrease. If you look at our preliminary work then you can see I have already investigated into the effect of temperature.
Safety conditions.
Finally we have to take into account some safety issues. Now because I am using the data-harvesting program, there are much fewer safety precautions. The main hazard we need to consider is when using maggots. I need to ensure that I wash my hands so no food poisoning may occur after the experiment.
