85 + 86 + 84 = 255, 255 ÷ 3 = 85
Another fair test could’ve been that you could keep the temperature constant, by doing this it will allow the yeast cells to grow steadily, if the temperature is high then the yeast cells will die and if the temperature is low this will just prolong the process.
You could also keep constantly stirring the solution as a fair test, this will agitate the solution and the process will quicken, you could also keep providing the yeast population will oxygen because the oxygen acts as an catalyst and speeds up the process.
The Factors that will affect the growth of the yeast cells are as followed:
- Temperature: - Temperature affects the growth of the yeast cells because in low temperatures the process and chemical reactions in the solution are slowed down and in how temperatures the yeast cells are killed, they’re a lot like human, they can only handle certain temperatures.
- Ph Level: - The Ph level affects the growth of my yeast cells due to the fact that if the Ph becomes too low or high it would kill the yeast cells, acids and alkalises don’t help yeast cells in any way so the Ph level needs to keep to 7.
- Nutrients/Food: - This is one of the most important things needed in this experiment and it is very essential, the nutrients is basically the food for the yeast population to help them grow, obviously without the nutrients the yeast cells would die, but also with too much nutrients the yeast cells will also die, feeding the yeast population with a lot of nutrients will also increase the amount of toxins in the solution and the more toxins the quicker the deaths of the yeast cells, so basically putting it, the more nutrients the more toxins, and the more toxins the quicker the death of the yeast population.
- Gases (Oxygen): - Oxygen is also an important part of this experiment, the oxygen is provided for the yeast cells to respire and they will let off carbon dioxide as a waste product, the oxygen just acts as a catalyst, if you was to decrease the amount of oxygen the yeast is receiving then the process would take longer.
- Agitation (Impeller): - Agitation is there to keep the yeast cells moving and active, I don’t know much about agitation or agitators but an agitator is required to achieve a number of mixing objectives, e.g. bulk fluid and gas phase mixing, air dispersing, oxygen transfer, suspension of solid particles and maintaining a uniform environment.
- Space: - As the space in the beaker decreases there is a lot more competition between the yeast cells in the beaker and they begin to fight for their space, and oxygen and there is more of a chance for a diseases to spread, so space is an important factor.
- Toxic Waste: - Toxic waste is something that you should definitely remember when doing this experiment because you could easily become carried away and forget about the fact that the waste from the yeast population may kill them, As the population increases more toxic waste is produced resulting from metabolism. In humans toxic waste is excreted by the kidneys (Urea) however waste products from microbes build up in the environment and can kill them e.g. more than 15% alcohol is capable of killing the yeast cells making the alcohol.
Procedure/ Method:
- To begin the experiment you must firstly collect a 250cm³ beaker and place it down where you are going to do your experiment, you must then start off by using a measuring cylinder and measure out exactly 10cm³ of yeast suspension, make sure you don’t spill any yeast because yeast has a bad smell.
- You must then pour the yeast from the measuring cylinder into the beaker and then rinse out the measuring cylinder and then measure out 200cm³ of glucose solution and then pour it into a clean unused beaker; you must then stir very very gently.
- Now you must rinse out the measuring cylinder and all the other equipment that have already been used and then place them onto the trolley.
- At this point of the experiment the beaker must have a very small population of yeast cells which will grow within a few days times. You must now take a clean cuvette and fill it with a sample of your yeast population using a pipette, after that you must then collect your colorimeter and put it on, at this period of time it will begin to warm up.
- Now you should place your cuvette into the slot on the colorimeter and a beam of light should now be passing through the cuvette. At this point you should then set the colorimeter to read 100% transmission and then leave the colorimeter settings for the next lesson.
- Now empty the cuvette and rinse it out clean so that it is ready for your next lesson and replace it on the trolley, then take a sticky label, write your name on it, and then stick it onto the beaker and then place the beaker onto the trolley for next lesson.
Questions:
- Why are you growing yeast cells in a glucose solution?
Answer: I am growing yeast cells in a glucose solution because glucose is a simple respiratory substrate.
- Where would it be best to store the suspension?
Answer: It would be best to store the beaker of yeast cells and glucose in a warm and damp atmosphere, warm and damp conditions help the yeast to populate faster, it acts as a catalyst.
- What do you expect to happen to the transmission % as the population grows?
Answer: The transmission % will decrease slowly because it becomes more difficult for the light to pass through the beaker full of yeast cells.
- How could I present the results?
Answer: I could present the results in tables one table will have the transmission and another table will have 1/transmission, there will be a column for days, a column for transmission and a column for 1/transmission, I could also present the table in scatter graphs and other kind of graphs.
Results:
When I first begun my experiment the population of my yeast was very small, and also the colorimeter was at 100%, but as the days went by changes took place such as:
- The liquid within the beaker gradually became more
cloudier as the days progressed.
- The population of the yeast cells rapidly increased.
- And the smell of the liquid became more and more bad.
My Results Table:
The table below is the table for 1/transmission of light through yeast population over time:
And this table is just for the yeast population:
Conclusion to Results:
When looking over my results table and the graph that I drew up, I noticed that the curve was a little different than it should’ve looked, as the yeast cells were growing the population was increasing and on my graph this would’ve been the point where the curve was going upwards, and then eventually the yeast cells would’ve died due to the toxins from yeast cells, and this would’ve been the part on the growth curve that goes downwards, but on my growth curve the curve didn’t go downwards this was because I wasn’t given enough time to do the experiment therefore I only had time for the yeast cells to grow and the curve to go upwards this is because I stopped doing the experiment before the yeast cells all died. Apart from the fact I had no time, my curve was correct and the experiment was done smoothly. There could be a chance that the curve also went slightly incorrect because I didn’t provide it with enough oxygen and also because I didn’t agitate the solution much, if I was to do this, this would’ve speeded up the chemical reaction in the beaker and the quicker the process the quicker the death of the yeast cells.
Improvements:
A very good idea would be to do the experiment in a very large beaker with a lot of nutrients/food and a fair amount of yeast population, this way it would give the yeast cells good time to grow and when they do grow they would have plenty of food and plenty of space but I must also take toxic into account, this will still kill the yeast even though space is important for the yeast population to grow in but the toxins can be dealt with if we were to have some sort of equipment that is able to drain out the toxins or we could have some sort of chemical that destroys toxins, more research needs to be done to see if this is possible or not. Another improvement we could have if we was to use additional equipments in our experiment such as a Ph sensor, temperature control, exit gas and exit liquid flow, antifoam and so on. The Ph sensor would be helpful because we will be able to identify the Ph level and we could be able to adjust it using certain methods, the temperature control could be helpful because we wouldn’t want to kill the yeast population so therefore having control over the temperature would be helpful, the exit gas and exit liquid flow would be helpful in the experiment because we will then be able to remove the waste products.
Final Conclusion:
Overall, from doing this experiment I think that it was successful and I came out with the results that I was expecting at the beginning of the experiment, improvements can be made to the experiment such as changing the method of the experiment and this may result in having more accurate results.
From doing the experiment and this coursework I managed to prove that as the yeast population increases it will become more difficult for the light rays to pass through the yeast population filled cuvette and this will decrease the transmission percentage.