Temperature See Attatched Document A Certain Point example essay topic

Harry Fox 11 ST Biology Science 1 - Strand 1: Planning Aim In my experiment, my aim is to find out any correlation between rate of respiration of glucose by yeast and the mixtures temperature. I shall do this by conducting an experiment which will involve the timing of the yeast, water and glucose which has been mixed with a little methylene blue. I shall time how long it takes to revert to the original colour using a control. This shall be done at various temperatures. To obtain the best range of values to use in my final experiment, I shall conduct a preliminary experiment. This will also aid accuracy of the final experiment by uncovering potential flaws in the method.

Hypothesis and Theory There are many ideas to suggest that the change in temperature will cause an increase of respiration in yeast. Yeast is a single celled fungus made up mostly of protein which has been used for its applications in fermentation. Yeast, after activation creates the ferments carbon dioxide and ethyl alcohol by secreting the enzyme zymase (a complex of 12 enzymes) in the yeast which acts on simple sugars such as glucose. The alcohol produced has been used in making wines and beers and the carbon dioxide produced has been used in baking as it gets trapped in the dough and causes it to rise. Enzymes are catalysts which speed up reactions, they are made from protein and are specific as to which substrate they work on.

Enzymes basically work due to the lock and key theory, where the substrate substance (the key) fits into the active site on the enzyme and they bind together, the reaction takes place and the substrate unlocks to form one or more new substances leaving the enzyme ready to perform the binding again. An enzyme ca only bind with a substrate that fits the shape of the active site unique to that kind of enzyme. A zymase-complex enzyme will only bind with a glucose molecule to produce the ferments carbon dioxide and alcohol which brings about the fermentation in my experiment. This ties in with the Induced Fit theory which states that the substrate cannot bring about catalysis and the reaction itself, but the active site, when it comes in to contact with the substrate slightly changes its shape to form an effective fit and arrangement of catalytic groups on its surface which brings about the catalysis reaction. To display this, think of a hand in a glove where the hand acts as the key and substrate, inducing a change in the shape of the glove which acts as the enzyme. When some substrate substances induce a fit with the enzyme, the enzyme may not be able to accept some other substrate (s).

These ideas tie in with my experiment to explain the formation of the products of respiration of yeast. Yeast have to make energy, stored as ATP to carry out all cellular functions. To do this they can respire both aerobically when there is plenty of oxygen, but where oxygen is short, they respire anaerobically; by this, they are called partial anaerobes. This produces less energy, but keeps the yeast alive. Pyr uvic acid has to be broken down in respiration when formed by breaking down of glucose molecules, this cant be done in the same way as it is aerobically when respiring anaerobically which is how the carbon dioxide and ethanol is formed through the zymase.

Here is the equation for anaerobic respiration: enzymes in cytoplasm (zymase complex) glucose ethanol + carbon dioxide +energy C 6 H 12 O 6 2 C 2 H 5 OH CO 2 210 Kj / mole 210 Kj / mole in anaerobic respiration as a posed to 2890 Kj / mole in aerobic respiration There is 2 ATP from each respired glucose molecule - in aerobic there is 38 ATP. Kinetic theory states that, with an increase in temperature, the rate of reactions will increase. This is due to the increase of speed of the particles, brought about by the extra energy given to them by heat. Faster particles will bring about more particle collisions and so the reaction will take lace faster. Enzymes are sensitive to temperature changes up until a certain temperature and will increase in their activity also.

The reactions that take place in the enzymes will be quicker and so will create more of their products. As a general rule of thumb, it has been said that there is a doubling of the rate of reaction for every 10 C rise this is called the Q 10 = 2 theory. This should be evident when the concentration of the enzyme and substrate are kept the same also. Enzymes are sensitive to temperature up untill a certain temperature where the shape of the active site is altered drastically, so much so that binding hardly ever takes place. This is called denaturisation. Prediction With reference to my theory, I predict that the rate and speed of respiration of glucose by yeast will increase with temperature rise up until a certain point where the enzyme used and secreted by the yeast will become denatured and cease to function, reducing the rate significantly.

This is explained through Kinetic theory, yeast respiration and the nature of enzymes. Initial Investigation In my initial investigation, I simply counted the number of bubbles released by the yeast in a 2 minute period. I did his because I only wanted to uncover the general trend and temperatures where there was or wasnt notable activity so I could use this information when conducting my final experiment. I used 1 g of glucose and 1 g of yeast, creating a 50: 50 split, I also used 10 cm 3 of distilled water. I mixed the three in a boiling tube, warmed it a little and shook it to activate the yeast. I then left it for one minute to let the mixture acclimatise to the temperature and then assembled the apparatus as shown and counted how many bubbles were formed during 2 minutes.

My independent variable was the temperature; the dependant being the number of bubbles. I increased the temperature by 10 C each time. I took three readings at each temp took their mean. I timed from the first bubble.

Initial Investigation Diagram See Attatched Document Initial Investigation Results See Attatched Document See Attatched Document 0 0 0 0 0 See Attatched Document 10 0 0 0 0 See Attatched Document 20 4 6 4 4.7 30 11 9 10 10 40 18 16 14 16 50 22 20 19 20.3 See Attatched Document 60 4 10 6 5 See Attatched Document At this last temperature, I think the 10 bubbles at 60 C was an anomalous result. This may be due to improper heating and will be discussed in my evaluation. It was not included in my mean number of bubbles. See Attatched Document Graph Variables In my main experiment, I shall use the time taken for methylene blue test tube with yeast and glucose solution to turn the colour of the control as my dependant variable and the temperature as my independent variable.

Here is a list of variables that can have an affect on my experiment and also how I will control them if possible. Temperature Amount of methylene blue Amount of yeast Amount of glucose Volume of water Amount of shaking and acclimatization Light and atmospheric conditions TEMPERATURE Temperature of the experiment will have a great affect on the results as explained by kinetic theory. Temperature will affect the rate of yeast respiration. I shall keep the temperature of he mixture and water bath under control by using a thermometer and checking it constantly. I shall also keep swirling the thermometer to keep the heat distributed. Also, as it will take longer for the temperature inside the test tube the same as the water bath, I shall leave the apparatus for two minutes, keeping the temperature constant.

AMOUNT OF METHYLENE BLUE Methylene blue is sensitive to oxygen and will go blue with contact with oxygen and colourless with the production of NADH during glycolysis as the glucose is broken down. The amount of this would affect the accuracy of the readings as the rate of NADH production affects the methylene blue and a differing amount of methylene blue would not give fair and reliable results. I shall keep the amount of drops of methylene blue the same at each timing. AMOUNT OF YEAST The amount of yeast is crucial, more yeast means more glucose will be respired and more products created. An imbalance will upset the results. The amount of yeast will be weighed out on an accurate top-pan balance each time.

AMOUNT OF GLUCOSE The amount of glucose will affect the results also, as more glucose means that there are potentially more products, which would make the results accurate or the experiment fair. The glucose will be weighed out each time using an accurate top-pan balance. VOL. OF WATER The volume of water may have a slight affect to the results as it may cause less accuracy when distributing the heat in the test tube. The volume of water will be kept constant by using a measuring cylinder at each preparation.

ACLIMATISATION AND SHAKING Acclimitisation and shaking will help to activate the yeast and prepare the solution for timing. If it is improperly mixed, acclimatised to temperature or activated, the results would not be fair and inaccurate. I will shake the test tube thoroughly each time until I can see bubbles being created well and I shall do this while it is warm to aid activation. I shall also leave this in the water bath at the required heat for two minutes, regulating the temperature with the Bunsen. LIGHT + ATMOSPHERIC CONDITIONS These would not have a great deal of affect on my experiment and are beyond my control. Some of the substances may be sensitive to these, but I doubt they are sensitive enough to affect the results.

Diagram of final experiment Apparatus Bunsen Burner Stopwatch Yeast Glucose Stand and Gauze Methylene-blue Syringe Pipette Boiling tubes (x 2) Beaker Bungs Method In my final experiment, I shall use methylene blue in the solution. I shall time how long it takes for methylene blue to go colourless in the solution, constantly checking against a control which contains a little methylene blue for continuity. To avoid unfair contact to Oxygen in the air, I will put a layer of oil over the mixture. I shall weigh out 2 g of glucose and 2 g of yeast this time and 25 cm 3 of water to aid accuracy. My independent variable is the temperature and the dependant is the time taken to change colour of control. I shall take readings from 20 C to 60 C at 10 C intervals.

I will start from 20 C as I found out from my initial investigation that there was no respiration activity below this temperature. I shall proceed in this sequence as it is the easiest way of collecting results and will help to find out other flaws at a lower temp. Also to aid accuracy, I shall take three readings at each interval and take the mean. Results headings Time (s) t 1 t 2 t 3 T (mean) Rate (S-1) Temp (C) Safety See Attatched Document HAZARD DANGER (0-3) LIKELIHOOD (0-3) SCORE ACTION See Attatched Document Burn (Bunsen, 1 2 2 Goggles, care hot water) when heating and handling, orange flame when not used. See Attatched Document Broken glass 2 2 4 Goggles, care when hot and handling, clean up all fragments Broken 3 1 3 Care when using thermometer dont hit hard, or leave to roll off desk. Biology Science 1 - Strand 2: Obtaining Revised Method I have made only slight alterations to my proposed method in the planning.

I have kept everything the same, except that I shall take multiple readings of smaller intervals around the plateau of my results so as to gain a more accurate understanding of what is happening and where the peak in activity happens. This will also help me to analyse my hypothesis. Variables Time taken for solution to decolourise: Dependant Variable Temperature of solution: Independent Variable Range: 20 C - 60 C in 10 C intervals mapping out plateau in 2 C intervals from 42 C - 56 C. Measurements for both variables have been taken and I have calculated the mean after taking three readings at each interval. Results See Attatched Document Time (s) t 1 t 2 t 3 T (mean) Rate (S-1) x 103 See Attatched Document At 60 C the solution started to decolourise but with the last two, it didnt fully decolourise showing eventual denaturisation of the yeasts enzymes. Converting and manipulating data usually proves useful and aids analysis and I have been able to calculate the rates for my results with my dependant variable using 1/t. As this is inverse, and rates should always be in seconds, the unit I shall use is S-1.

I have made my rate results positive by multiplying them by 103 so making it easier for me to plot and use. To aid the final analysis and to certify precise and reliable results, I decided to map out the top plateau of results at 2 C intervals. The values used cover the rise, peak and fall of the plateau. The results for this are shown below. This will allow me to form an accurate optimum temperature for the respiration of yeast. had taken all the precautions that I had done previously and used the same method. I will talk about the validity of all my results in my Evaluating.

See Attatched Document Temp (C) t 1 (s) t 2 t 3 Time (mean) Rate (S-1) x 103 See Attatched Document 42 125 109 116 117 0.00855 8.55 See Attatched Document 44 96 107 105 102 0.00980 9.80 See Attatched Document 46 100 92 95 96 0.0104 10.4 See Attatched Document I have ensured that my results are accurate by controlling all the variables stated in my Planning. I also took care when using the equipment so as to retain continuity throughout the experiment. For this, I checked everything was set up correctly at each reading and prepared my solution in the same way. I did not prepare a batch of solutions as this would have given some more time to acclimatise and more time to react and respire, changing the conditions. When weighing out glucose and yeast on the top pan balance, I checked that the air bubble was always centered and adjusted it accordingly, if left un centered, this could cause biased results. When measuring out distilled water, I carefully checked that the bottom of the waters meniscus sat horizontal with the required gradient on the measuring cylinder when looked at from 90 at the side.

I also kept the same water in the water bath so as to keep fair the distribution of heat to the test tubes, I mixed this as well. To further manipulate my results I shall record logs of my results so I can plot this in my analysis. This will also display my results in such a way that will allow me to easily find an optimum temperature for anaerobic respiration in yeast. It will also allow me to calculate the Q 10 mean value for my experiment. This would go some way to see the accuracy of my results, but mostly to see whether the reaction is in line with the Q 10 theory and regularity of the rate of reaction. I will plot log temp against log rate to generate my log graph.

This is one of many data manipulation methods I shall use in my analysis to find out as much as I can from my data. I also found that the rate of respiration dropped of completely after a certain point, highlighting the denaturisation of the yeasts enzymes. See Attatched Document This shows that the temperature See Attatched Document a certain point where respiration stops. Temp (C) To calculate the Q 10 gradient of my results so I can gain information about the nature of the reaction, I shall create a graph of my logs given in my Obtaining.

From my log graph I can give the optimum temperature for yeast respiration and calculate the Q 10 reading for my experiment. I can calculate my Q 10 value as shown: See Attatched Document See Attatched Document See Attatched Document Conclusion I have found that as I increased the temperature of the yeast solution, the rate of respiration of the yeast increased to a certain point where, as the temperature rose to a certain level, (in my case about 58 C) the rate of respiration eventually cut off. I have also found that my Q 10 value is 1.43. Seeing as the most accurate value for a Q 10 reaction is 2 (the rate of reaction doubling for every 10 C rise) this makes my reaction look a bit inaccurate yet with positive signs of correlation. A Q 10 reading as low as 1.43 suggests there were either faults with the method or apparatus or that the reaction was not a true Q 10 = 2 reaction; this reaction should be a typical Q 10 = 2 reaction, so my method or apparatus probably give the inaccuracies. I will talk further about this in strand iv to suggest reasons.

My hypothesis and prediction can be backed up with the findings; from looking at my results and graphs you can see the rise and fall of respiration, further displayed by the reactions Q 10 reading which, although quite a lot less than 2, it still gives the presence of the reactions sensitivity (through zymase) to temperature. Thus my hypothesis and prediction are shown to be present and displayed to a large extent. They are explained due to the theories of enzyme-substrate with lock and key and kinetics. Where these meet is when kinetic theory states that an increase in temperature means more particle collisions between reactants and so a faster rate of reaction; and in enzyme-substrate where the enzyme is sensitive to heat, and about a certain temperature, the active site will begin denaturing, so slowing and eventually stopping the reaction. This will give an area where the rate of respiration drops off and goes to nothing instead of a precise cut-off point. These both apply to my experiment and were described in my planning.

Biology Science 1 - Strand 4: Evaluation My Method The experiment went quite well as I was able to obtain sets of recordings and calculate means, rates and logs, and my Q 10 value from them. I did not find any results to be anomalous when looking at the results table. This could be explained by the small spread of results at each interval and that the reaction could not be totally accurately controlled with the apparatus used. I think that the method I used, whilst giving results, was also quite sensitive to changes and didnt allow to tap the full potential of the experiment. I would suggest using equipment which would not allow any biased results or ignore anything that is happening in the solution. I would want to spread out the solution in something like a pert dish to give maximum surface area to help conduct heat and to evenly spread the methyl blue.

I would consider either not using the methyl blue colour change technique at all or use a substance which is more precise as I felt that the method did not allow accurate use of methyl blue because of how it was used and what it acted on. This added to the slight unpredictability of the experiment. My Results To make sure that the results were as reliable as I could make them, I calculated the mean of three results at each interval when dealing with the rate and also used these to produce my log values. I took all precautions to make the apparatus used to be reliable and give good values so I think the slight unreliability was caused by the preparation of the solution and the unpredictability of how the reaction went that came with it. To obtain more reliable results I would want complete continuity with preparations, maybe arranging sets of substances to create multiple solutions beforehand or preparing them but not actually activating the yeast so as to prevent any getting a head start over the others. This would ensure that all the preparations are the same and would give continuity.

I would want to be more strict and thorough with preparing solutions and mixing them up. I would want each one to be thoroughly acclimatised to the surroundings and had the same amount of methyl blue and same activating and mixing time. This would help give more reliable results throughout. If I were to further investigate this experiment and my results, I would probably want to calculate the point where the enzymes begin to denature for respiration in yeast. I could also examine the change in rate between the intervals to determine validity and continuity, also running them through maybe more intricate calculations involving log. At this stage, I shouldnt think there is to be much more I could do.

I wouldnt want to investigate any other variables or reactions at this time..