Anaerobic Respiration In Yeast.pdf

Anaerobic respiration in yeast Background information Yeast, any of about 1,500 species of single-celled fungi, most of which are in the phylum Ascomycota, only a few being Basidiomycota. Yeasts are found worldwide in soils and on plant surfaces and are especially abundant in sugary mediums such as flower nectar and fruits 1There are different kinds of economically important ascomycete yeasts used in bread, bear and wine production. But some yeast can be dangerous pathogens of humans and other animals such as histoplasma and blastomyces. Because yeasts are part of fungi they are eukaryotic organisms. Their diameter is usually about 0.075 mm. Most yeast reproduces by process called buddingsmall bump separates from a parent cell, enlarges, matures and detaches. But some of them produce by fission-parent cell dividing into two equal cells. In food manufacture, yeast is used to cause fermentation and leavening. Cell respiration is a process through which our cells get energy to perform everyday functions. It’s essentially breaking down glucose and other respiratory substrates to make molecules called ATP. There are 2 types of cell respiration: aerobic and anaerobic. Aerobic respiration uses oxygen and produces higher yield of ATP while anaerobic doesn’t need oxygen to preform cell respiration and end product is smaller yield of ATP. Both anaerobic and aerobic pathways begin with the anaerobic breakdown of glucose which is called glycolysis. Glycolysis breaks down glucose(6-C) into 2 molecules of pyruvate(3C) and also produces: hydrogen carriers(NADH) from an oxidized precursor(NAD +) and a small yield of ATP(net gain of 2 molecules).In animals the pyruvate is converted into lactic acid(lactate) and in plants and yeast the pyruvate is converted to carbon dioxide and ethanol. Purpose of anaerobic respiration is to restore stocks of NAD +-as this molecule is needed for glycolysis. By restoring stocks of NAD+ via anaerobic pathways, organism can continue to produce ATP via glycolysis. The conversion of pyruvate into lactic acid (animals) or ethanol and CO2 (plants / yeasts) is reversible. So pyruvate levels can be restored once oxygen is present and greater yield of ATP may be produced aerobically. Muscle contractions require high amounts of energy and thus require high levels of ATP.Therefore body will begin breaking down glucose anaerobically to maximize ATP. This will result in an increase in production of lactic acid, which leads to muscle fatigue. When the individual stop doing exercises, oxygen levels will increase and lactate is converted back to pyruvate. Although carbohydrates, lipids and proteins can all be used as energy sources, only carbohydrates will typically undergo anaerobic respiration. Term anaerobic respiration is also known as fermentation. Fermentation results in the production of ethanol and carbon dioxide – which can be used in food processing (in yeasts).Bread-CO2 causes dough to rise ( leavening),ethanol evaporates during baking. Alcoholethanol is intoxicating agent in alcoholic beverages (concentration above 14% percent can damage yeast).In yeasts the reaction rate will increase if sugar with a higher concentration is used, which means that more CO2 will be producd.

Research question: How does concentration of sugar glucose affects amount of CO2 produced(rate of reaction)? Hypothesis: If concentration of glucose rises, level of CO2 produced will also increase ,which means that rate of reaction is also increasing. Variables:

Dependent variables Independent variables Controlled variables

Instruments used and units

unit ml /

CO2 produced Glucose concentration Glucose, room temperature, Temperature of solution

Measuring cylinder ,ml

Uncontrolled variables

range 3-14 5-25

Possible effects on results Measuring substance can be imprecise ,repeat measuring process(have more trials) in order to be more precise and accurate

/ Figure 1: table of variables

Materials glassware

Measuring instruments Measuring Graduated cylinder,(±0.25ml) pipette Beaker,(±0.5ml) (±0.25 ml)

Apparatus

Chemicals

Disposable gloves Water bath Flask Rubber stopper

Glucose (5%,10%,15%,20%,25%) 50 ml Yeast 50 ml

Figure 1: table of materials Method: 1.Prepare a water bath-35 °C and put yeast solution in it 2.Than make a mixture of yeast and glucose(1:1) and mix it with glass stirring rod 3.Than remove rubber stopper from flask and place the mixture in it attach a tube to rubber stopper 4.Close it and place it water bath 5.Take another measuring cylinder and fill it water and turn it upside down 6.Make sure any liquid doesn’t spill and then slowly put a tube inside it 7.Now measure the CO2 produced every 2 min(by looking at how much liquid is left) 8.Repeat this procedure for each of glucose concentration. Safety and ethical considerations: Because working with toxic chemicals or any things that could be potentially dangerous is not present no special equipment is required for this set up but I would highly suggest to wear the standard equipment that is always required (latex gloves , apron and goggles).Because pipettes are used it is preferred to use the reusable ones in order not to produce waste There aren’t any ethical considerations involved. Data collection: Quantitative data: Raw data: Concentration of glucose 5%

10% 15% 20% 25%

Amount of CO2 produced(±0.25ml)

Trial 1 (after 2 minutes) 3ml 6ml 7ml 10.5ml 11ml

Trial 2(after 4 minutes) 5.5ml 7ml 11ml 11ml 11.5ml Figure 3: raw data

Trial 3(after 6 minutes) 6ml 7.5ml 11ml 11.5ml 14ml

Processed data: Sample calculations: Mean(glucose concentration 5%)= sum of total amount of CO2 produced /number of trials =(3+5.5+6)ml/3 =4.83 Range (glucose concentration 5%)=Subtract maximum value from minimum value =6-3 =3 Rate of reaction=amount of substance produces/amount of time needed =4.83/360(6×60) =0.013

concentration 5% 10% 15% 20% 25%

Mean 4.83 6.83 9.67 11.00 12.17

STDV 1.31 0.62 1.89 0.41 1.31

Range 3 1.5 4 1 3

Rate of reaction 0.013 0.019 0.027 0.031 0.034

*rate of reaction wasn’t showcased with 2 significant figures in order for difference to be seen Figure 4: processed data

Uncertainty for measuring cylinder (measuring amount of yeast and glucose) = uncertainty/measurement×100 =0.25/20ml(10 ml of glucose and 10 ml of yeasr)×100 =1.25% Uncertainty for measuring cylinder (measuring amount of CO2 produced) = uncertainty/mean of CO2 produced×100( for 5 % glucose)

=0.25/4.83×100 =5.18% Concentration of glucose 5% 10% 15% 20% 25%

Uncertainty of C02 produced 5.18% 3.67% 2.59% 2.28% 2.05%

Graph:

amount of CO2 produced(±0.25ml) 14 12 10 8 amount of CO2 produced(±0.25ml)

6 4 2 0 5%

10%

15% 20% concentration of glucose

25%

rate of reaction 0,04 0,035 0,03 0,025 0,02 rate of reaction

0,015 0,01 0,005 0 5%

10%

15%

20%

25%

concentration of glucose

Analysis: As we can see from the graph it is increasing constantly (it’s almost linear).So for concentration of 5% glucose average value is 4.83 ml of CO2 produced in 6 minutes ,and then there is a slightly higher increase when concentration reaches 15%(which of course isn’t very obvious) while for the highest concentration average amount of CO2 is 12.17 ml(again time is the same).Error bars are also included as shown on the graph but the uncertainty error is small so they are almost invisible. The graph showing the rate of reaction is also included (the trend is very similar to amount of C02 produced) for a comparison between them. The lowest rate of reaction(for 5% is 0.013) and there is a constant increase once again and highest value is 0,034(for 25% of glucose) so the range is 0.021 which is considered small.

Conclusion: So if we are talking about reaction of yeast with certain sugar(in this case glucose) amount of CO2 produced is very different(and so is the rate of reaction).It’s very much higher around 500ppm(parts per million, this number is considered as theoretical value)if it’s measured with

proper equipment but values that were collected in this experiment are notably smaller because equipment used wasn’t precise. But still the trend was noted and was in line with hypothesis that was set up on begginig. The concentration of substance (in this case CO2)does effect the rate of reaction in that way that there is correlation between them (as concentration of sugar increases the amount of CO2 also increases which means that rate of reaction is also higher)Lowest value that was collected was that average amount of CO2 produced was around 4.83 ml(this measuring was done by measuring cylinder with a uncertainty of ±0.25) while the highest value was around 12.17(same method of measuring was used) and range of the average CO2 produced was around 7.34 which is low considered theoretical value mentioned in beginning but reason of that was mentioned earlier.First in the mean that is showcased there is a general trend of increase which means hypothesis that was stated it’s true and this isn’t the only indicator of course because other calculations were done. So standard deviation (STDVhow much values differ from mean) gotten was also calculated and overall it’s concluded that valuation of standard deviation doesn’t go over 2,which is considered low which means the equipment used was precise. Therefore , further calculation was done and range of values also was included. It of course differed and general trend wasn’t found but it didn’t go over value of 4 which once again showed precision in experiment conducted. Equipment that was used was precise but the reason of this variation from theoretical value was in method used to conduct this experiment(this will be discussed in evaluation of the overall process). Evaluation: The method used of collecting data was demanding and difficult, it definitely took more than one person for this experiment to be conducted(one to make the measuring and the other to collect data).Set up of it as seen from the part were method was given wasn’t the easiest so there was a couple of trials were it was just necessary to get used to set up before collecting the data. While the measuring cylinder and pipette used had a small uncertainty,method was the main source of error.If it was done by a electric device that measures the CO2 produces results were a lot more accurate even graph could be made if it was connected to laptop in order for a rate of reaction to be calculated by programs such as Logger Pro. And because water bath was also needed for this experiment the temperature of water wasn’t constant so it would be better if Bunsen’s burner was used to keep it same throughout the experiment. Yeast was held in water bath so that’s the reason of this as a potential source of error. So overall experiment set up was precise but inaccurate so next time different method could be used(as there are few of them).But also if sugar is too concentrated the rate of reaction would be significantly slower and there is a possibility it couldn’t occur at all (1) Yeast | Definition & Uses | Britannica.com https://www.britannica.com/science/yeastfungus (accessed Feb 24, 2019).