Diverse forms of respiration happen in yeast cells. The first is endogenous respiration as it uses the substrates already stored in yeast cell and the second is exogenous respiration which is the rate of reaction to any additional substrate that you add. But these can take on two different types of respiration such as either aerobic or anaerobic respiration.
Apparatus
Method
- Set up water bath to appropriate temperature to 20º C
- Aliquot 200 ml sucrose solution into 250 ml conical flasks
- Weigh out 1 g of yeast.
- Re-suspend yeast in 20 ml distilled water by continuous stirring.
- Set up water trough with appropriate measuring apparatus. Connect delivery tubes to rubber bung.
- Add yeast suspension to sucrose solution and seal flask with rubber bung.
- Leave it for 10 minutes to allow respiration to occur.
- Measure the volume of gas produced.
- Repeat above steps each time for different temperatures.
Method for immobilised yeast cells.
There are many benefits to immobilising an enzyme and they are: -
- be reused once immobilised.
-are stabilized through the process unlike without it.
-the enzyme can be easily separated from the product, which makes it easier to handle.
- Mix .8g of sodium alginate in 20cm³ of distilled water and stir until smooth.
- Leave to soak for 5minutes so to allow the mixture to set.
- Stir a gram of yeast into 20cm³ and leave to soak for 5minutes.
- Add the yeast mixture to the alginate solution and mix well with a glass rod.
- Put 10cm of the mixture into a syringe and drop the mixture at a constant pressure.
- Measure out 100cm³ of 1.4% calcium chloride solution into a beaker.
- Then place this beaker underneath the syringe.
- Allow beads to stand for 20minutes in the calcium chloride solution.
- Set up water bath to temperature of 20ºC.
- Once beads are well formed then strain with a tea strainer to separate the beads from the Calcium Chloride solution.
- Measure 200cm³ of 3% sucrose solution into a 250cm³ conical flask.
- Set up the water trough with correct apparatus.
- Place the conical flask into the water bath.
- Measure the amount of gas produced.
- Repeat steps 11-14 for different temperatures.
Result table
Conclusion
In conclusion, it appears that the immobilised yeast cells were most effective for this particular experiment because they appear to respire the most within the given time.
Also it would appear that the optimum temperature for the immobilised yeast cell was 50ºC as the gas collected at it was highest at 11.6cm³. While non-immobilised yeast cell had an optimum temperature of also 50ºC but the amount of gas collected was higher with 14.6cm³.
It would seem that I have neither found evidence to support nor reject my earlier predictions. I found thus to be the case as my prediction stated that the optimum rate for the immobilised yeast cells would be of a greater volume than that of the non-immobilised yeast cells. It would seem that I collected a greater volume of gas with the non-immobilised yeast cells at the same temperature than with the non-immobilised yeast cells. Though the optimum temperature for yeast is 37ºC, it would appear that instead of the cells of the yeast becoming denatured they have instead kept on respiring. Due to this I believe that the tough cellulose and protein outer shell of the yeast cell has enabled it to be able to withstand such a high temperature.
Analysis
Evaluation
I found that in my experiment that there may have been errors involved in it that have influenced my results. Human error can occur when tools or instruments are used or read incorrectly, they can be random because the power of concentration of the experimenter is fading. It is possible that I may have misread the temperature on the thermometer and so ended up with an incorrect temperature reading.
The degree of precision will influence the instrument that you choose to make a measurement. It is also possible that I may have not been total precise in the weight measurements and so end up with some temperature mixture having more yeast cell than the other does. As I used an electronic water bath I had to constantly check the thermometer in the water bath to make sure that it also read the same temperature. If they do not agree then there will be an error at any other temperature being used. The instruments were properly calibrated and regularly so to reduce the risk of systematic error.
Safety analysis:
A risk assessment is nothing more than a careful examination of what, I believe in my experiment, could cause harm to people, so that I may weigh up whether the steps that I have taken is enough as a precaution or if more should be done to prevent harm. The aim is to make sure that no one gets hurt or becomes ill. I found while conducting my experiment that it would be essential for me to follow certain precautions, so to avoid getting hurt.
I had a spillage on the floor due to dropping a conical flask on the floor containing sucrose solution. I alerted others so that they may avoid the spill when possible.
. To avoid slips, trips and it was dealt with as soon as possible.
I also had to be careful whilst handling the apparatus in the experiment as previously I’d ended up with a broken burette due to improper handling of it.
I had to use an electrical apparatus (i.e. the water bath) and this carries the potential hazard of giving an electric shock which may be fatal following contact with live components. I had to put into consideration not to tamper with electrical equipment to attempt repairs and to previously check that it was unsafe in any manner. I also checked the re-test dates on it, kept water away from mains electrical sockets.
The shards of the broken conical flask were disposed of immediately as they could have caused severe physical injuries. Broken glassware is never cleaned up by hand. Instead dustpans and brushes were used to collect the broken glass and it is disposed of appropriately.
I also made sure not to use any damaged glassware.
The sucrose solution is considered to be toxic to the central nervous system can induce confusion, fatigue, irritability, and other behavioural changes.
I organised my work around my work top to reduce exposure to hazards.
Non-latex gloves would be worn during the experiment were I to have any broken skin or rashes on my hands were present during the experiment.
Hands were washed after viable materials are handled and before leaving the laboratory and at the conclusion of the experiment. Hands are washed following removal of gloves.
No eating, drinking, applying cosmetics, or handling of contact lenses is permitted in the work area.
References
22-03-06 11.09am
