becomes amino acids)
Temperature and pH levels will effect greatly, if the pH and/ or temperatures are at extreme highs/ lows compared to the enzymes’ optimum temperature/ pH the enzyme will denature. This graph shows what happens when temperature or pH is to far away from the optimum of the enzyme.
This is also explained more by the collision theory take an enzyme and put it at 20oc
There are very few collisions so not much activity
But at around 35oc
There is much more kinetic energy which means more collisions and more reactions.
Denaturation: - this is when the heat is too high or too low and the proteins (therefore the enzymes as they are made of proteins) change shape and don’t function properly therefore being the wrong shape to fit the “loch” according to the “lock and key” theory.
Activation energy is the energy needed to start a reaction. Having a catalyst lowers the energy needed making it easier to start the reaction.
Preliminary results:
Evaluation of preliminary results:
These results show that as the temperature rises to 35oc more reactions take place but they also show that if the temperature rises too high (past 35oc) the enzymes cannot function and begin to denature at 40oc. This is shown by my background information which shows that either the “lock” has become misshapen which means the “key” won’t fit. Or that there is too much kinetic energy meaning that the particles are moving around so fast they don’t connect properly meaning there is no reaction at the active site.
Apparatus:
Liquid syringe (10 cm3)
Gas syringe (100 ml)
Rubber tubing
100 ml conical flask
Calf liver
10% hydrogen peroxide solution
Beaker (250 cm3)
Bunsen burner
Gauze
Tripod
Clamp
Boss
Stand
Diagram:
Syringe containing
Hydrogen peroxide (10cm3)
Gas syringe (100 ml)
Bung
Beaker and water
Conical flask
(Containing liver) gauze
Clamp and stand Tripod
HEAT
Method:
At first I will have to get the liver, I will then cut it into cm3 pieces using a knife.
I will then heat a water bath using a beaker, 250cm3 of water a Bunsen burner and a thermometer to the temperature that is being tested.
The liver will be placed in a conical flask (and weighed) with a bung that has a syringe connected that contains the 10 % hydrogen peroxide solution (10 cm3). The bung is also linked to a pipe and then to a gas syringe which is held up by a clamp, boss and stand.
Once it is all ready and the bath is at the right temperature (20 -50oc) I will remove the Bunsen (because it shouldn’t cool too much in 1 minute to affect the results) and the time will start as soon as I start to inject the 10 % hydrogen peroxide solution.
Then once 1 minute has passed the amount of gas produced will be read and recorded also the weight of the liver.
This will be repeated for each temperature and then again and again to make a total of 3 tests for each temperature.
Prediction:
My prediction is backed by the collision theory because I believe that the more heat there is the more kinetic energy and the more collisions which should mean more reactions. Although I also believe that the proteins will denature due to the temperature being too high and the enzymes cannot function properly, thus slowing down the rate of reaction. Because this is what happened in my preliminary results that I carried out on a laptop.
I think the optimum conditions will be about 35 – 40oc because this is the kind of temperature that the living body operates at. I think the graph will look a bit like this:
This will show my optimum temperature and the temperatures that the proteins (enzymes) denature on either side of the optimum as you can see.
Fair test:
All tests will only last one minute.
All pieces of liver will be the same size (or as close as possible).
Concentration of hydrogen peroxide will be as it comes from the bottle.
The temperature will be the only variable changed.
The same top pan balance will be used for all tests.
The range of temperature will be 20, 25, 30, 35, 40, 45, 50and each test for each temperature will be repeated 3 times.
Safety issues:
Bunsen burner when not being used but being kept on should be left on safety flame.
Safety glasses and lab coat must be worn in case of any hydrogen peroxide spitting or being spilt.
Results:
Table of averages and rate of reaction:
I calculated the rate of reaction by using this equation: Rate 1/x=O2 produced
-----------------
Time in seconds
=___ cm3/sec
Analysis:
After carrying out this experiment I have observed that the amount of O2 produced becomes more as the temperature rises but gets to a certain point where it begins to drop again because the enzymes have reached an optimum temperature I know they reach an optimum temperature because I have found that out when researching my background knowledge.
The rate of reaction also reaches it optimum between 35oc according to my graph of results (or 37oc) as this is the temperature the body works at.
The relation between oxygen and temperature are shown by my graph for example when the temperature is at 20 degrees Celsius the oxygen given off is 3.20cm3 and when it goes up 10 degrees to 30 degrees Celsius it reaches 27 cm3 of oxygen given off which is almost 10 times bigger than it was at 20 degrees.
My graph shows that the temperature affects the enzymes this can be linked to the lock and key theory because if the enzyme is at a high or a low temperature it denatures and this could be explained by saying that the “lock” is actually re-shaped which means the “key” does not fit and therefore a reaction cannot take place. it can also be explained by the collision theory because if there is not enough heat/kinetic energy the reaction takes longer because particles take longer to meet and if it is to hot so there are mass amounts of kinetic energy which can mean the particles rush past each other and don’t meet. This corresponds to my hypothesis except I have described how they have too much energy. Also this is exactly what happened in my preliminary results the optimum temperature and rate of reaction are the same.
My graph that shows rate of reaction against temperature has the same proportional relationship as oxygen given off against temperature.
In real life animals that live in hot environments have to produce sweat and blood capillaries have to dilate. Also animals in cold environments blood capillaries must constrict and sweat is highly reduced and more energy is used to keep the optimum body temperature for their enzymes and bacteria to function properly.
Evaluation:
My investigation compared to my original intention was fairly good because the collision theory I used to predict my results also explained my final results without being too tentative.
My points mainly fit the line of best fit but there are a few anomalous results as you can see by my graph these maybe due to that the solutions weren’t the right temperature to start off with, or the pieces of liver of these anomalous results were slightly bigger than the others; however there is a clear trend.
I could have improved the procedure by using a water bath that was set to the exact temperature so I would have had no temperature that were a few degrees celcius out which may have cause anomalies. Also I should have left the liver in the bath for longer without adding the hydrogen peroxide so the catalase had time to reach the temperature aimed and this would allow any enzymes to reach the right temperature.
I could have improved this experiment by using an electric water bath that is set to one specific temperature which is a lot more precise and a lot easier.
I could extend this experiment by perhaps looking at the temperature closer and having the range of temperature based immediately around the optimum temperature I found on this experiment. Or I could investigate into another variable such as pH or surface are of liver.
Even though I could have improved my experiment the results compared to my preliminary results fairly evenly.
