For the preliminary experiment I took two results. One at the lowest temperature that I would record: 10°c, and the other at the highest: 60°c. For my actual experiment I will increase the temperature by 5°c each time going from 10°c - 60°c. The results for the preliminary experiment were:
10°c - 2.57 Seconds 60°c - 3.56 Seconds the time was measured in minutes and seconds. When I plot the points on the graph I will use only seconds. For example 2.57 would be written as 177 seconds
Variables:
The four variables that could influence my results are
• The amount of the potato used (surface area of potato)
• The temperature
• The pH level
• The amount of hydrogen peroxide
The constant variables will be the size of the potato, the pH, and the amount of hydrogen peroxide. The variable that will be changed is the temperature.
Apparatus:
Potato;
Stopwatch;
Hydrogen Peroxide;
Measuring Tube (small);
Measuring Tube (large);
Tub of Water;
Delivery Tube;
Water Bath;
Test Tube with bung;
Beaker;
Thermometer;
Knife
Method:
- Cut 10 pieces of potato into 7mm wide and 2mm thick slices
- Fill water bath with water.
- Fill beaker with 200ml of water.
- Measure 10ml of hydrogen peroxide and pour it into a boiling tube
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Place boiling tube with hydrogen peroxide into the beaker and then a piece of potato into the beaker with water in of required temperature for 5 minutes this is to get to the same temperature. Fill measuring cylinder with water and upturn it in the water bath. Secure it in position using a clamp and stand.
- After 5 minutes put the potato into the hydrogen peroxide and immediately place the bung on top of the boiling tube and delivery tube under measuring cylinder.
-
When bubbles begin to rise in the measuring cylinder, start the stopwatch. When water level has dropped to 2cm3 stop the timer.
- Record the results
- Repeat experiment using different temperatures each time.
I will take 10 results, with the temperature starting at 10°C and increasing at approximately 5°C each time, eventually stopping at 60°C.
I will measure how fast the reaction is going by looking at the time it takes to drop 2cm3 of water. The longer it takes the longer it takes to react so the quickest time will be the optimum temperature.
Safety:
To keep my experiment a safe one I will wear safety goggles at all time and make sure I will try not spilling any Hydrogen Peroxide, but if I do I will wipe it up immediately
Research:
The enzyme may catalyse a reaction in which the substrate is split into two or more molecules. Alternatively, it may catalyse the joining together of two molecules. When the reaction is complete the product or products leave the active site. The enzyme is unchanged by this process, so now is able to receive another substrate molecule. The rate of reaction can be very quick. For example, the enzyme catalyse can bind with hydrogen peroxide, split them into water and oxygen and release their products at 107 molecules per second. As catalysts, enzymes increase the rate at which chemical reactions happen. Most of the reactions would occur so slowly without enzymes that they would practically not happen at all. In many reactions, the substrate will not be converted to a product unless it is temporarily given some extra energy. This energy is called activation energy. These graphs show the activation energy with and without enzymes:
To change into a product the energy of the substrate must be briefly raised by an amount known as the activation energy. This could be done by heating the substance.
When a substance binds to the active site of an enzyme the shape of its molecule is slightly changed. This makes it easier to change into a product: the activation energy is lower
The graph opposite shows how the rate of a typical enzyme catalysed reaction varies with temperature. At low temperatures, the reaction takes place very slowly (A). This is because the molecules are moving slowly. When they are moving slowly, there is less chance that the molecules will collide with the enzyme. As temperature rises, the enzyme and substrate molecules move faster so collisions happen more frequently, which means substrate molecules, enter the site more often. What's more, when they do collide, they collide with more energy making it easier for bonds to be broken so that the reaction can occur. As temperature continues to increase, the speed of movement of the substrates and enzymes continue to increase. However, above a certain temperature the enzymes start to become denatured (C). They denature because the enzyme vibrates so quickly that some of the bonds holding the enzyme in its shape begin to break. At first the substrate fits less well into the active site of the enzyme, so the rate of reaction begins to slow down. Eventually the substrate won’t fit at all. The temperature at which an enzyme catalyses a reaction at the maximum rate is called the optimum temperature (B). Most human enzymes have an optimum temperature of around body temperature (400C).
Results
I did not repeat my results because it is near impossible to do things identical with enzymes
Analysis
My results show that the optimum temperature for these enzymes to work is about 30°. This is because heat energy causes more collisions between the particles in the enzyme and particles in the substrate. But at low temperatures the enzymes de-nature changing the shape of the enzymes making it harder for the substrate to fit within the enzyme molecule at very low temperatures the product is rarely completed. Also with out the lack of heat energy it takes a lot longer for the reaction to happen. The same type of thing happens when enzymes are at high temperatures although chemically we are increasing the chances of breakdown, but also increasing the chances of break down of the enzymes. As heat makes the enzymes molecules vibrate this put a strain on the enzymes.
