How temperature affects respiration
An increase in temperature causes an increase in the rate of respiration. This is because respiration is controlled by enzymes, and enzymes work better at high temperature because there is more energy in the reactants (causing them to vibrate) so they react quicker with an enzyme as the collision frequency between enzyme and reactant will increase. However, most organic molecules will move too violently at about 45ºC causing them to denature. So, if you raise the temperature to increase the rate of respiration this will only be affective up to 45ºC; this is because the enzymes controlling respiration will denature after this temperature has been reached, and the organism will probably die.
The Quotient 10 law
The Quotient 10 (Q10) law states that the rate of respiration will approximately double with every rise in 10ºC between 4ºC and 40ºC.
This can be seen most obviously in reptiles that live in desert climates as there body reaches different temperatures at different points in the day and their respiration rate changes dramatically during this time.
The formula for the Q10 law is (where t is the chosen temperature):
Rate of respiration at t + 10ºC
Rate of respiration at t
References
Mike Boyle and Kathryn Semor, Biology
Glenn and Susan Toole, Understanding Biology for Advanced Level
William F. Lyon, Rearing Wax Worms, Ohio State University
Hypothesis
Due to respiration being controlled by enzymes; I predict that as I increase the temperature of the environment of the wax worms their rate of respiration will also increase. According to the Q10 law, as the temperature is raised by 10ºC the rate of respiration will double. Therefore, I predict that as I change the temperature by 10ºC the rate of respiration in the wax worm will double.
Plan
To test my hypothesis I must measure the rate at which wax worms respire over different temperatures. To measure their respiration I will use a respirometer as it is a fairly accurate piece of equipment to measure respiration. To change the temperature of the environment of the wax worms I will use a water bath and boiling tubes, in which I will place the wax worms. I will use soda lime the absorb the carbon dioxide the wax worms give off, so that the change in the respirometer will be due to a change in oxygen levels only. The water bath that I will use will consist of a large beaker full of water that I will change the temperature of by adding boiling water or ice cubes to because it would be very difficult to set up a respirometer and boiling tubes in a thermostatically controlled water bath.
Before I carry out my study I will conduct a pilot study in order to get used to using a respirometer and maintaining a temperature in the water bath as these will be the most difficult tasks. I will carry out the experiment by placing three wax worms in a boiling tube that is attached to a respirometer and placing the boiling tube into the water bath at the temperature that I am testing. Then I can repeat this process over different temperatures to test all the temperatures that I am interested in testing the rate of respiration for. I will also repeat the whole process a second time to get an average for my results.
For my results to be significant in any form I must make this a fair test. To make a test fair all the variables must be kept constant apart from the variable that is being investigated. To make this a fair test I will have a control boiling tube hooked up to a respirometer to make sure that the change in the respirometer is due to the wax worms and nothing else. Time is also a varying factor so I will time the boiling tubes, five minutes should be a sufficient amount of time to notice a change in oxygen levels.
I have already decided to use a time limit of five minutes per temperature. The temperatures that I will test the rate of respiration for will be 10º, 20º, 30º, 40º. I chose these temperatures because, according to the Q10 law, I will notice an increase of approximately 10ºC when testing from 10 to 40ºC. If I tested any higher or lower temperatures I may damage the wax worms and the rate or respiration would not be accurate.
Risk assessment
Some of the equipment I will be using will be made of glass; this leaves the risk of the glass breaking and causing injury. To try and prevent possible injury from glass equipment I will be careful when using and carrying glass equipment, and keep all glass equipment away from the edge of a work surface. When using thermometers there is always the chance of the thermometer breaking and the corrosive mercury leaking out. To prevent this health risk I will be using an alcohol thermometer so if it breaks it will not be as dangerous. Soda lime is highly corrosive also. When I use soda lime I will wear gloves and use a spatula to take the soda lime out of its container and be careful not to spill any soda lime or leave it in anywhere where it may cause harm. I will also be using a kettle; the boiling water I use I will be careful with and will be quickly lowering the temperature of to fit my experiment. Finally, there is ethical concern about using wax worms, as they are living organisms. When I use wax worms I will take care not to harm them and the temperatures that I will test them at should not damage them.
Apparatus and materials
-
Respirometer, consisting of: ○ Two boiling Tubes
- Respirometer (see diagram below)
- Rubber tubing
- Stoppers
- Gauzes
- Syringe and hypodermic needle
- 500 ml Beaker
- Thermometer
- Two stands (with an extra arm for boiling tubes)
- Stop clock
- Kettle
- 100 ml manometer fluid
- Soda Lime
- Ice cubes
- Wax worms (24 is about the maximum amount I will need)
Equipment set-up Diagram
Method
- Set up the equipment as in the diagram above.
- Add boiling water or ice cubes to the water bath to get it to the temperature that you are testing (10º, 20º, 30º, 40º).
- Add three wax worms to one of the boiling tubes, seal the boiling tube and start the timer; leave the other (control) boiling tube empty.
- While the wax worms are in the boiling tube maintain the temperature of the water bath to that of what you are testing.
- When five minutes have passed record the change in the respirometer, remove the wax worms from the boiling tubes and rest the respirometer to its ‘rest’ position (indicating no change).
- Repeat steps one to five over the three other temperatures.
- Repeat steps one to six again to get an average.
Results
A table and graph of my results are shown below:
Conclusions and discussion
On the whole I have good results as I proved both of my hypotheses correct. Every time I increased the temperature in my investigation the rate of respiration increased also. Every interval of 10ºC raised saw a double in the rate of respiration. This shows that my work is correct and accurate because my finds fit in with the theoretical work that I carried out in the theory section. My results do not fit in exactly with the Q10 law, however this is an approximate pattern and my results approximately double with every 10ºC raised. This proves that the respiration of the wax worms was controlled by enzymes in their body and that raising the temperature made the enzymes work efficiently.
Evaluation
The data and results I collected were precise. Although the respirometer had a few small bubbles in it I don’t think was enough to affect the results dramatically. The piece of equipment that I used to measure the time with was accurate as it measured time up to a hundredth of a second. This investigation was a fair test; no other factors affected my results other than the factor that I was investigating, so the results must be precise. Also, no anomalies were present in my results, supporting the idea that they were accurate. I am aware that if I had one ‘off’ experiment my results could be completely different from what they are supposed to be. This is why I carried out the experiment twice, to get an average so my results were more accurate and so that the results could not have been the result of an ‘off’ experiment. My two sets of data are very similar and it is very unlikely that I had two ‘off’ experiments. The majority of the equipment that I used was accurate. One exception was the water bath. I chose to use a beaker and thermometer water bath for convenience reasons; if I had used a thermostatically controlled water bath the temperature would have been more constant and my results may have been more accurate. There were some bubbles present in the manometer fluid when I carried out the experiment, this may have made my results slightly inaccurate. Also there are probably more sophisticated respirometers that I could have used (a digital one, for example), to get more accurate results, however I do not think this would make such a significant difference. To improve this investigation I could use the equipment above, maybe different time (longer times), although different temperatures would not be a good idea as the wax worms looked uncomfortable at 40ºC.
