State where each reaction works in the digestive system. The salivary glands in the mouth secrete saliva, which helps to moisten the food. Look at Figure 1.
Average final volumes of oxygen for each concentration of hydrogen peroxide. Evaluation Overall, I believe my experiment went well and that I gained sufficient results because I repeated each concentration three times and investigated eight concentrations in total.
I believe that my results were also relatively reliable because as the concentration decreased the volume of oxygen produced also decreased. Also, most of the points were on or close to the curve of best fit for each concentration.
However, there are some factors that I must take into consideration. Apparatus Limitations Firstly, there were limitations on the apparatus that I used. Each piece of apparatus has an apparatus error with an upper and lower limit.
This obviously affects the amount of catalase present, which means that there could be more or fewer collisions and resulting successful collisions between enzyme and substrate molecules depending on the greater or lower mass of yeast.
For example, if there were more molecules of yeast, the rate of reaction would increase because there would be more collisions between enzyme and substrate molecules. This would result in a greater probability of successful collisions, and therefore more enzyme-substrate complexes being produced.
This means that in my results, the volume of gas produced in the first 5 seconds may have been higher than it should have been if I had used exactly 0. The same idea applies to the substrate concentration in that the pipettes also had an apparatus error.
This means the amount of substrate could have been different for each repeat, even though I used the same concentration. So in cm3, the actual volume could have been either If there were fewer molecules of hydrogen peroxide, there would have been fewer collisions between molecules of enzyme and substrate, resulting in fewer enzyme-substrate complexes being made.
However, I do not believe the substrate concentrations were significantly different because my repeats were mostly concordant, so a similar amount of oxygen was produced which must mean that there was a similar number of substrate molecules in each concentration.
Choice of Method I tried to select the method I considered would be most accurate. I decided on the gas syringe method because, as I explained in my section on preliminary work, it measured the volume of gas directly and minimised the volume of oxygen which could potentially dissolve in water.
However, some oxygen was displaced in the gas syringe and I had to solve this by subtracting this small amount from the volumes produced in each of the reactions. Also, I noticed if the barrel was wet, the syringe often got stuck for a short time before it recorded the volumes of gas.
To prevent this I had to dry out the barrel and syringe before commencing the procedure. It was very hard to insert the small 5cm3 beaker into the conical flask, and when it came to tipping it over, some of the substrate was still trapped inside the beaker.
I solved this by swirling the conical flask constantly throughout the reactions, which seemed to solve the problem, although this meant that the amount of swirling had to be the same in order to ensure a fair test.
I tried to keep this constant by making sure I swirled the conical flask evenly. The accuracy of the results showed that this factor did not distort the results too much, and so a similar amount of substrate molecules were present in each reaction.
Another factor which was hard to measure was the volume of gas produced, because some of the higher concentration reactions were very fast, so it was hard to read the correct values every time.
I tried to make this as accurate as possible by keeping my eyes level with the gas syringe. Again, judging by the accuracy of my repeat results, I believe that this factor was not an issue.
Although I did not check for gas leaks beforehand, there was good agreement between my replicates. If my replicates had not been so close I would have had to change the tube. Surface Area of Yeast Molecules I ground up the yeast to try to make the surface area as similar as possible because surface area is a major factor in my experiment.
A larger surface area means there are more molecules being exposed to collisions with other molecules, with sufficient energy to cause a reaction.
This means that having the same surface area of yeast in each reaction is very important in ensuring a fair test because the number of molecules exposed to collisions must be the same. Consistent Temperature Temperature is a major factor which affects the rate of reaction.
This is because at higher temperatures, molecules of both enzyme and substrate have more kinetic energy and collide more often. This results in a bigger proportion of molecules having a kinetic energy greater than that of the activation energy. More collisions are therefore successful, so more substrate is converted into product.In this investigation, you will test this hypothesis: Catalase works best at a pH of 7 (neutral).
1 Label five 50 cm3 beakers pH , , , , 2 Measure 5 cm3 of 3% hydrogen peroxide. GCSE AQA Biology Organisation and The Digestive System B3 Third Edition If you have any query or doubt about the notes or questions answers, you can comment in the comment box.
5 Comments on “ GCSE AQA Biology Organisation and The Digestive System Questions B3 Third Edition ”. - Investigating Oxygen Produced From a Reaction The objective of this coursework is to investigate how the surface area of the potato affects the amount of oxygen produced from the reaction: Hydrogen peroxide [IMAGE] water + oxygen Potato (Catalyst) Catalase Introduction: Enzymes are found in .
Class practical or demonstration. Hydrogen peroxide (H 2 O 2) is a by-product of respiration and is made in all living cells. Hydrogen peroxide is harmful and must be removed as soon as it is produced in the cell. Cells make the enzyme catalase to remove hydrogen peroxide.. This investigation looks at the rate of oxygen production by the .
Testing for enzymes Class practical Hydrogen peroxide is used to detect the presence of enzymes in liver, potato and celery, which catalyse the decomposition of hydrogen peroxide, by detecting the presence of the oxygen gas formed. Search the history of over billion web pages on the Internet.