Substrate Concentration Coursework

Introduction: An enzyme is a biological catalyst made of protein. Enzymes are protein molecules found in living organisms and in this case I will use a yeast catalase. Catalase is an enzyme that catalyzes the reduction of hydrogen peroxide. Hydrogen peroxide is a poisonous by-product of metabolism, so it is very important that it is broken down quickly, otherwise it would cause damage to cells. Catalase causes the reaction of the catalyst to break down hydrogen peroxide (2H2O2) into oxygen and water. 2H2O2 + Catalase -> 2H2O + O2 These enzymes are needed to control the speed of a reaction.

If not, reactions would be too slow to maintain life or too fast which would denature the cell, damaging it and not being able to function properly. The more hydrogen peroxide you add with the yeast catalase, the faster the reaction of breaking down the hydrogen peroxide into water and oxygen will be. This is so, because the shape of the catalase active site matches the shape of the hydrogen peroxide molecules. The higher the concentration of substrate added with the catalase enzymes, causes an anabolic reaction where more and more molecules are broken down into smaller pieces.

Thus, more oxygen and water will be produced and therefore causing the gas syringe to take in more pressure and have a higher reading. Method: (See “Substrate concentration and yeast catalase” exercise document) Timeframe of experiment: 20-second intervals for each reaction Apparatus: Gas syringe Metal stand Yeast Catalase Hydrogen Peroxide – Concentrates (%) at (2. 5, 5. 0, 7. 5, 12. 5 and 15. 0) Boiling tube Connecter tube Beaker Small needle syringe (1cm3) Stop watch Medium syringe for yeast (10cm3) Test tube rack Tap water Variables Independent:

Concentration of hydrogen peroxide Dependent: Reaction to reach it maximum level within 20 seconds Control: Enzyme / hydrogen peroxide Concentration Volume of hydrogen peroxide and catalase solution Size of boiling tube and gas syringe Temperature Qualitative Reading: 2. 5 % Concentration: Little bubbling, slow movement along the gas syringe 5. 0 % Concentration: Little more bubbling/ foaming, increase movement on syringe 7. 5 % Concentration: Faster reaction, More bubbling and foam is higher, faster movement along gas syringe indicating faster reaction to oxygen and water 12.

5 % Concentration: High amounts of foaming and bubbling forming, fast movement along gas syringe and starting to make quiet noise 15. 0 % Concentration: Same as 12. 5 % reaction, a lot of foaming and bubbling and fast movement along gas syringe. Data Table 1: Effect of Substrate Concentration on the Activity of yeast Catalase using a gas syringe Concentration of hydrogen peroxide solution ( % )Measurement of built up gas in syringe at a time of 20 seconds (± 0. 5 mL3)AverageSD 12345 2. 50. 51. 51. 01. 01. 01. 00. 35 5. 03. 03. 03. 53. 53. 03. 20. 27 7. 55. 05. 05. 04. 54. 04. 70. 45 10. 06. 06. 05. 56. 06. 05. 90. 22 12.

57. 09. 06. 07. 07. 07. 21. 10 15. 08. 07. 07. 08. 07. 57. 50. 50 Data Processing Data table 1 shows the final results of the experiment. As one can see, the average increases by over a factor of 1. 0 every time the concentration of hydrogen peroxide increases. Each measurement on the gas syringe was (±0. 5mL3) giving us an unreliable measurement because it is not specific enough to which decimal place the gas actually fell into. Uncertainties: Yeast solution added: 10cm3 (± 0. 25 mL3) Hydrogen Peroxide added: 1cm3 (± 0. 005 mL3) Concentration of hydrogen peroxide: 0. 02 % Stopwatch being stopped at 20. 00 seconds: 0.

01 seconds + human reaction Uncertainty of exact measurement of gas syringe: (±0. 5 mL 3) The error bars represent the range of the data Conclusion and Evaluation It is clear to see from the graph above that as more hydrogen peroxide substrate is added to yeast catalase, the faster the reaction will occur. Thus, causing a positive correlation on the graph because more pressure is being made from the oxygen and water that is being produced. As more hydrogen peroxide is added, the faster the reaction happens up until 12. 5% concentration, where the reaction rate starts to slow down. This is shown by the gradient on the graph.

This is happening because at this point the solution’s active sites have become saturated, meaning that all active sites of the catalase are occupied with the hydrogen peroxide. All active sites are being used, meaning the reaction rate will slow down and the extra hydrogen peroxide molecules will have to wait for the active sites to become available again. Showing that more hydrogen peroxide added after 15. 0% concentration will have no real affect on the rate of reaction. However, there is never a theoretical maximum rate of reaction, which means all active sites are occupied at the same time.

There will always be time for the substrate molecules to attach to the enzyme and leave it so the maximum rate of reaction is never to be reached, but slightly under it. The error bars are not very wide on the graph because the gas syringe was only measured to 0. 5 mL3 and therefore not being able to leave specific and significant differences between each trial. However, on 12. 5% concentration one can see a larger error bar than the others. This could be due to human errors of added too much or too little hydrogen peroxide or catalase into the trial and thereby affecting the experiments results.

This experiment contained some important errors that could have affected the final results. I tried to keep each variable the same throughout the experiment except for the concentration of hydrogen peroxide, however some variables are almost impossible to keep the same without special equipment. The major errors, limitations and improvements for this experiment are as follows: When inserting the hydrogen peroxide into the yeast catalase solution, due to the thin needle through the cork barrier there was a delay of hydrogen peroxide being added.

For the human recording the time with the stopwatch this was an error for the starting time of the stopwatch affecting actual time of 20 seconds and reaction rate. This is not a significant error that would truly affect the outcome of the experiment because I did the same procedure for each trial. There is no way to fix this error without using highly expensive equipment that would insert all of the hydrogen peroxide at the same time as the timer started. Next was the error of the measurement of each solution using different size syringes.

The gas syringe was an error in measuring the exact volume of the gas after 20 seconds because it is measured at 0. 5 mL3. Because of this, the gas was simply rounded to the nearest marker by observing. Luckily for this experiment it does not matter what it’s exact value is because we are just discovering the basic correlation of hydrogen peroxide on yeast catalase and not it’s exact values. Even though the experiments results still proved the point being made of an increased rate, it is still a minor error and could be improved by a digital gas reader or another gas syringe measured with smaller intervals.

Same with the other syringes as well, however the small syringe measuring the hydrogen peroxide was pretty reliable because it is measured at 0. 005 mL3, which shows an almost exact reading. One of the biggest errors was the stopwatch. Starting and stopping the time at exactly 20. 00 seconds and obtaining an exact measurement on the gas syringe is an unrealistic accomplishment by a human and can only be done using computers. Our reaction time was too slow along with the uncertainty of the stopwatch time; therefore saying the timing of the experiment was unreliable and could affect the final results.

Only improvements would be to use a more reliable time reader such as a computer, which is expensive. Another error that occurred was the excess water at the bottom of the test tube after rinsing it out from the previous trials. While doing this experiment quickly and with only 2 test tubes, there was no time to completely dry the insides of the test tubes and therefore creating a large volume for the yeast that was to be put into them. This could affect the rate of reaction and solution when conducting the experiment.

This was a human error and I don’t believe it had a huge affect on the overall results because comparing results with other experiments showed to be very similar. For next time as an improvement, better drying of the test tubes and making sure there is no water mixed with the solution should help the final results to be more accurate and more reliable. Finally, only five trials were conducted. I believe a further 3 (at least) trials would help obtain a better and specific average, improving the reliability of the experiment. I would have liked to add another concentration level to the experiment as well.

If the levels went out to 20. 0% concentration, it would better explain and prove if the enzymes become saturated and to see if the graph would slow down and level off. Despite the improvements that I have suggested, human errors and more trials would make this data more reliable but are proven to be very time consuming. The current trends of the data show that no further improvements are needed to reach the desired conclusion. I think it is safe to safe that the final results are somewhat reliable because it shows that as more hydrogen peroxide substrate is added to catalase enzymes, the faster the rate of reaction will occur.

Bibliography “Effect Of Substrate Concentration On The Activity Of Catalase. ” 123HelpMe. com. 16 Dec 2013 [online] Available at: . HubPages. 2012. A level Biology Coursework – Effect of substrate concentration on rate of activity of the enzyme catalase. [online] Available at: http://luno2012. hubpages. com/hub/A-level-Biology-Coursework-enzyme-catalase [Accessed: 16 Dec 2013]. Oshino, A. 2013. The cellular production of hydrogen peroxide. [Biochem J. 1972] – PubMed – NCBI. [online] Available at: http://www. ncbi. nlm. nih. gov/pubmed/4404507 [Accessed: 16 Dec 2013].





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Describe the relationship between substrate concentration and the initial reaction rate of an enzyme-catalyzed reaction. Is this a linear relationship? What happens to the initial reaction rate as substrate concentration increases? Yes, the relationship is linear. The initial reaction rate increases as the substrate concentration increases. With more substrates, there will be a more of the reaction ocuring, as there is more to be used up. As the initial reaction rate increases it goes faster. What is the maximum initial reaction rate for the lactase enzyme at pH 7? 350 Explain why the maximum initial reaction rate cannot be reached at low lactose concentrations. There is not enough substrate for it to reach the maximun initial rate. What does your data indicate about the optimum pH level for this lactase-catalyzed reaction? The date indicates that the lactase at pH of 7 is where the highest enzyme activity is. Enzymes function most efficiently at the temperature of a typical cell, which is 37 degrees

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