Enzymes are folded up in such a way so that they have an indentation or a pocket on their surface. This pocket is called the active site. The Lock and Key Model postulates that the shapes of the reacting molecules (the substrates) and the enzyme's active site are such that they fit together much like a key fits into a specific lock. So the lactose molecule fits perfectly into the active site of the lactase enzyme, meaning that the lactase enzyme can only catalyze the breakdown of lactose.
Enzymes are important!
Enzymes carry out hundreds of chemical reactions that are essential for our survival. They carry out the reactions necessary for our digestion of foods, for the build-up and break down of DNA and RNA, as well as many other vital processes. A deficiency in the lactase enzyme, for example (which is rather common in humans) results in an inability to break down lactose, and a condition called lactose intolerance. Lactose intolerance can be overcome by swallowing tablets containing lactase enzymes before eating dairy products.
Collision Theory:
The energy of the collision
Activation Energy
Activation energy is the minimum energy required before a reaction can occur. You can show this on an energy profile for the reaction. For a simple over-all exothermic reaction, the energy profile looks like this:
If the particles collide with less energy than the activation energy, nothing important happens. They bounce apart. You can think of the activation energy as a barrier to the reaction. Only those collisions which have energies equal to or greater than the activation energy result in a reaction.
I plan to repeat the whole experiment to double check my results. If time permits and I don’t have enough time to double check my work I plan to just repeat any results that look anomalous so they can be corrected.
Method:
- Assemble apparatus
- Measure out 10ml of Hydrogen Peroxide
- Bore five cores of potato (must me same length and size or experiment is unfair)
- Place one whole core into Hydrogen Peroxide
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Place one whole core of potato into hydrogen Peroxide which is in the boiling tube. Place bung over the top of the boiling tube securely so no gas (oxygen) will escape resulting in a fair text and anomalous results.
- We then started the timer and timed how much oxygen was produced recording every minute for five minutes.
- We then repeated the above cutting the second cylinder into two equal pieces. The Third cylinder into 3 equal pieces, the fourth into 4 equal pieces and the 5 into 5 equal pieces.
- We then recorded the results onto a results table and noted any anomalous results.
Diagram:
Fair test:
To keep the experiment a fair test I had to keep a number of things the same. I had to keep the potato’s weight, size, and length the same because if a potato is bigger and weights more than the other potato’s then I will get anomalous results. I will also need to keep the bung over the top of the flask where the hydrogen peroxide and the potato are reacting. When they react oxygen is produced so it is important to place a bung over the top of the flask so that no oxygen escapes during the experiment leaving anomalous results.
The word equation for Hydrogen reacting with potato is:
Hydrogen peroxide Water + Oxygen Catalase
2H2O2 2H2O + O2
I will also need to keep the concentration and the volume of Hydrogen Peroxide constant in order to make a fair test, as both would increase the number of molecules present so the number present so the number of collisions would be greater.
Safety:
The safety aspects of this experiment was important because we are using Hydrogen peroxide which is irritant to skin and the eyes so eye protection and apron should be worn.
Prediction:
I predict that the smaller I cut the cylinder into the surface are increased so there are more surfaces for the hydrogen peroxide to react with. So more reactions can take place so more gas will be produced. If the Hydrogen Peroxide was a different concentration it would affect the rate of reaction.
Results Table:
Conclusion
From the results it can be seen that the greater the surface area presented to the Hydrogen Peroxide more reactions took place and so much more gas was produced i.e. less gas is given off by single cylinder. From the graphs I can see that a pattern does emerge. All the graphs over a period of time rise steadily. So as the surface area increases the amount of Gas produced in a given time increases.
Evaluation
I found if difficult to cut equal lengths of potato with the borer. The potato kept splitting also it wasn’t always possible to use the equipment, because the lessons were only 50 minutes long and because the periods were only 50 minutes long I kept on having to stop and continue next lesson. The syringe also was quite stiff so it was difficult for the gas to move the plunger. Look at my line of best fit and my results it can be seen that a couple of them don’t quite fit. Perhaps inaccuracy occurred where the bung was not placed on top tightly enough so some of the Gas was lost. I found that the problem with the plunger in the syringe awkward. So I’m not sure that how accurate my results are using the plunger. Also because I had to stop and change my equipment each lesson I might have had a different plunger that was not as stiff as the one I had before last lesson, so anomalous results could occur here. Another bad point about using the syringe is that when the plunger was quite stiff or was stuck gas would escape through the bung. This would also give anomalous results.
I would like to have repeated the whole experiment again to double check my results. I certainly would like to have repeated my anomalous results to how anomalous they were. Also I might have been interesting to use an upturned cylinder to compare with a syringe. I could compare what produces more anomalous results and if one produces more oxygen gas more than the other.
