An investigation into the effect of temperature on the rate of reaction, on the enzyme Amylase.

Properties of enzymes:

• They are all proteins
• They are all catalysts
• They all have active sites
• Enzymes are denatured by high temperature. (40°c)
• Enzymes work best at 37°c, (normally body temperature)
• Enzyme work best at pH7. Except stomach enzymes. (pH2)
• Enzymes are specific and only produce certain things.

The specificity of enzymes.

        Enzymes have a specific shape that fits with their substrate, known as the “lock and key theory”.

             

     

Substrate + enzyme                         enzyme/substrate                    enzyme + product

                                             Complex

Enzymes have optimum conditions where they perform best. The two most important factors are;

1. pH
2. Temperature

                                      

        Most enzymes have an optimum pH of about 7 but some, such as enzymes in the stomach have a different optimum.

        As with temperature sub optimum pHs cause the shape of the enzyme to change.

Temperature – a measure of the average kinetic energy of the particles of matter

• Kinetic energy is the energy an object possesses because of its motion.
• The SI unit for energy is the joule.
• The joule is a derived SI unit equal to (kilograms)(metres) / s2 (squared).
• KE = mv2 (squared) / 2
• The calorie is sometimes used to describe heat. This unit is defined as the amount of heat needed to raise the temperature of one gram of water one-degree Celsius. A “food calorie” is 1000 calories, or one kilocalorie.

PLANNING:

Method:

        We are doing an investigation in order to find out the effect that temperature has on the effect of enzymes. The equipment we will use to do this experiment will be;

• Water bath
• Test tube
• Dropping pipette
• Dimple tiles
• Iodine solution
• Glass rods
• Stop watches
• Amylase (the enzyme)
• Starch (the substrate)

Plan

        I will set up the apparatus to get the experiment ready. I will get the water bath to the correct temperature so I am ready to put the test tube in. I will put 2.5ml of starch into the test tube after I have put the amylase in so I can get a correct reading at the start to tell me if starch is present. I will put the test tube in the bath with the starch, then add the amylase and then take a sample. The dimple tray will have a drop of iodine in each dimple so I can begin to take samples to ensure starch is still present. I have to take a sample every 20 seconds so I will be close to when the starch goes, therefore, a sample every 20 seconds should give me a more accurate reading. I will mix the starch and amylase together to make sure the reaction takes place properly. I will carry out 3 tests at each temperature to ensure that my results are accurate, and then I will get an average of the time taken to put in my results. I will do the experiment at five different temperatures, 20°c, 30°c, 40°c, 50°c and 60°c, so that my results will be over a good temperature range, with results going both below and above the optimum temperature. The results will give an accurate idea of how the enzyme works at different temperatures.

Safety:

        In order to ensure that my experiment is as safe as it can possibly be I will;

1. Ensure that I am wearing goggles.
2. Make sure I have a clean and tidy environment to work in.
3. Ensure that if I get iodine on me I wash it off as soon as possible as it will stain the colour of my skin.

Fair test:

        To make sure that my test is a fair one I will;

1. Repeat all temperatures of the experiment three times and take an average.
2. Be as accurate as possible with my stop watch and measuring.

        Amylase + Starch                         Glucose.

Hypothesis:

        My hypothesis is that as the temperature increases, the rate of reaction increases up until 40°c when the enzymes are denatured and don’t work at all so they will take forever. (The reaction stops altogether).

        I think that with every 10°c rise, the rate of reaction will double. I think all reactions will stop at 40°c.

        

        My hypothesis is scientifically valid as most enzymes have an optimum temperature of around 37°c. Above the optimum temperature, the enzyme begins to lose its shape and eventually denatures. (They are permanently damaged). I have done a fair test. I have also used a decent range, repeated the experiment 3 times incase of a fluke, and an average. I was as accurate as I could possibly be with my stopwatch and measuring.

Results:

Analysis:

        After I collected my data I can see that starch disappears quickest at 40°c. Between 20° and 40° the time taken decreased, then after 40° the time takes longer. The longest time for it to disappear is at 60° where it reaches 11.5 minutes. At our first temperature, which is 20° the starch disappears after 4.5 minutes. The time taken between the first recorded temperature and the second is a very large gap of 7°. The shape of my graph goes down, and then curves at the bottom before rising up again.

        As in my hypothesis, I predicted that the starch would digest quickest at 40°c as the enzyme changes shape in order for the substrate to fit in the correct place and that when the temperature goes above 40°c the digestion process would take a lot longer and the reaction would take a lot longer. (The reaction would stop altogether), therefore my hypothesis was correct.

Evaluation:

        I think that my experiment went well, there were no problems and everything went to plan! The dropping pipettes were not accurate enough though and also, stirring the amylase and starch was not a good idea as this could contradict the fact that my experiment was a fair test as I may have stirred one experiment more than another causing it to digest faster and then not stirred another enough which would mean it taking longer to digest.