The aim of this investigation is to produce data from which an accurate evaluation can be formed which shall show in quantitative terms how the anaerobic respiration of yeast occurs when the substrate concentration alters. Preliminary Research From my preliminary investigations I was able to deduct which of numerous methods stood the best chance of offering success in terms of giving quantitative data that was both accurate and reliable. In addition to this I was able to investigate which solutions offered the most activity and which range was most appropriate to the investigation.

From these, investigations I have concluded the following: 1. Methods 1 and 2 outlined in the planning section offered the best chance of accurate, reliable, safe and easily reproduced data. 2. The substrate to be used in terms of producing accurate data does not really matter in terms of whether orange Juice or Glucose is used. However, Orange Juice offers the best qualitative data, whereas, the absence of vitamins means that glucose substrate results offer better quantitative data. This, it seems appropriate that both substrates are used in this investigation. 3.

Although up to 2moldm-3 of glucose as a substrate gives good results. The optimum maximum concentration is 0. 2moldm-3. This is due to the higher concentrations drawing out more of the yeast’s water by osmosis to combat the high concentration gradient produced by the substrate compared to the cell interior. In severe cases of high concentration outside the yeast this can lead to the destruction of the yeast itself. For more detailed information of the method selection see A3 sheet enclosed. Method 1: Diagram Below is a diagram of the final experiment and procedure that was developed from my preliminary work:

Method To obtain accurate data from this investigation I must ensure that for every experiment that the following method is implemented. The science behind this is that if all the experiments have the same controls the data will only be affected by the one changing variable (substrate concentration), thus accurate data will be drawn from which so will be a conclusion. The method is as follows: 1. Set up equipment to diagram specifications. 2. Measure out required amounts of Yeast suspension and Substrate (add the required amount of distilled water to the substrate to obtain the desired concentration). 3.

Using distilled water obtain a mark for the maximum water volume of test tube and mark the limit with a Dry marker. 4. Empty the water and reduce the distilled water quantity by 2cm3 and repeat procedure to obtain the minimum level and dry mark. This is done so that we can accurately measure when the yeast has respired the amount of substrate that equates to 2cm3. Thus, when we stop timing in all our experiments the same amount of Carbon Dioxide would have been released. 5. Add the required concentration of substrate to the bath. 6. Add the yeast and immediately invert the test tube and place in a boiling tube.

7. At this instance start the timer. 8. NB all of the above should where possible occur in a temperature control bath and where not possible the apparatus must be only away from the bath as long as necessary. 9. As soon as the reaction has reached the second line stop the timer and record the result. 10. Dispose of all the liquid and wash the equipment thoroughly with distilled water. NB: For the experiment the 15ml test tube will be filled with 10ml of Yeast and 5ml of the required concentration of substrate- whether it be Orange Juice, nutrient supplemented yeast and glucose solution or glucose.

Apparatus For each experiment I shall require the following apparatus: 1. 2 X Test tubes 2. Stop watch (accurate to 2d. p. ) 3. Dry Marker pen 4. Distilled Water 5. Yeast suspension 6. Pre-determined concentrations of substrate 7. Test tube rack 8. Temperature control bath 9. Pipettes 10. 10ml measuring cylinder 11. 50ml measuring cylinder 12. Boiling tube Justification of method and apparatus I have decided to employ the following apparatus and method in this investigation for the following reasons: 1.

From the equipment available these pieces offer the best ability to measure accurately any gases and liquids required, i. e. the stop watch that is accurate to 1/100th of a second. 2. The method is easily repeatable and offers little chance of unexplained errors and differences in the next experiment. 3. Due to the time constraints the method allows a considerable number of experiments to be taken in a relatively small amount of time. Method 2: Diagram Below is a diagram of the final experiment and procedure that was developed from my preliminary work: Method.

To obtain accurate data from this investigation I must ensure that for every experiment that the following method is implemented. The science behind this is that if all the experiments have the same controls the data will only be affected by the one changing variable (substrate concentration), thus accurate data will be drawn from which so will be a conclusion. The method is as follows: 1. Set up equipment to diagram specifications. 2. Measure out required amounts of Yeast suspension and substrate (add the required amount of distilled water to the substrate to obtain the desired concentration).

3. Place Yeast and substrate together and immediately place bung connected to the delivery tube to the test tube with the Yeast and substrate. 4. At this instance start the timing. 5. Once 2cm3 of water has been displaced by the Carbon dioxide stop the watch and record the time. 6. Reset and safely dispose of all liquid or unnecessary apparatus. NB For accuracy each experiment shall be repeated three times. This will also improve the reliability. Apparatus: For each experiment I shall require the following apparatus: 1. Burette 2. Burette clamp 3. Stop watch (accurate to 2d.

p. ) 4. Yeast suspension 5. Distilled water 6. Substrate 7. Test tube rack 8. Temperature Control bath 9. Graduated pipettes 10. 10ml measuring cylinder 11. 50ml measuring cylinder 12. Delivery tube 13. Fine thin glass tubing Justification of method and apparatus I have decided to adopt this method and the apparatus to complete the investigation because of the following reasons: 1. From the equipment available these pieces offer the best ability to measure accurately any gases and liquids required, i. e. the stop watch that is accurate to 1/100th of a second. 2.

The method is easily repeatable and offers little chance of unexplained errors and differences in the next experiment. Also, in the event of errors being identified they can be easily traced and the fault countered. 3. The method is sophisticated and has the potential to produce reliable data. 4. It is extremely safe and easy to use. (NB: To gather the data required to draw a conclusion method 2 shall be used) Variables In this experiment to increase the accuracy and reliability of the data I must ensure that the method is capable of maintaining all the below variables precisely for each experiment.