The hypothesis of the experiment was 'raising the temperature of the hydrogen peroxide solution will increase the rate of reaction until it reaches its optimum temperature at which point the rate of reaction will begin to decrease.' This theory was tested by changing the temperature of hydrogen peroxide and recording the time it took for a yeast-covered filter-paper disc to reach the top. It was concluded that the hypothesis was partially supported
An enzyme is a type of protein that speeds up the rate of reaction in living organisms; they act as a catalyst for particular chemical reactions. Enzymes convert the reactants (substrates) into certain, needed, product. They do this using the induced-fit model. Each enzyme has an active-site which has a shape complementary to a substrate or a pair of substrates. The substrate(s) then enters the active-site. The enzyme’s shape puts pressure on the bonds inside the substrate, causing them to break so that the one substrate can be split into 2 products or the 2 substrates will be merged into one product.
Hydrogen peroxide is created as a by-product of cell metabolism. The enzyme catalase (found in yeast) is needed, to stop the build-up of hydrogen peroxide, which is toxic to the cell. Catalase accelerates the conversion of hydrogen peroxide into 2 products: water and oxygen non-toxic in the cell.
The following experiment tests the effect of different temperatures on the enzyme catalase's activity. Small paper discs are dipped into yeast and then dropped into a solution of hydrogen peroxide, varying in temperature. The reaction that occurs will produce bubbles of oxygen which will cause the discs to float to the surface. Lower times taken to reach the top mean an increased rate of reaction has occurred.
Raising the temperature of the hydrogen peroxide solution will increase the rate of reaction until it reaches its optimum temperature at which point the rate of reaction will begin to decrease.
The independent variable being investigated in this experiment is the temperature of the hydrogen peroxide. The dependent variable is the rate of reaction.
The variables being kept constant are: the yeast that the discs are dipped in, the amount of hydrogen peroxide solution in the beaker and the concentration of hydrogen peroxide.
Hole punch - Forceps
Yeast suspension - Distilled water
50mL measuring cylinder - 0.1% hydrogen peroxide solution
Filter paper - Kettle
Ice - Bowl
1. A suspension of yeast was made by adding 10g of dry yeast to 100mL of water (~30°C) and left to stand for around 10 minutes.
2. 30 discs were then cut out of the filter paper using the hole-punch. Potential contamination was avoided by allowing the discs to fall onto a paper towel and contact with human skin was avoided as best as possible by using forceps to handle the discs.
3. 40mL of 0.1% hydrogen peroxide was poured into a small beaker. An ice-bath was created to lower the temperature of the hydrogen solution or if the temperature needed to be raised water was boiled in the kettle and set-up in a similar way to the ice bath.
4. When the thermometer showed that the temperature needed had been reached one of the discs was dipped into the yeast solution, shaken to remove the excess yeast, and then dropped into the hydrogen peroxide solution.
5. As soon as the disc hit the bottom of the beaker the stopwatch was started. The time it took for the discs to reach the surface of the hydrogen peroxide solution was measured and then recorded onto a table.
6. This technique was repeated 5 times for every variation in temperature, to obtain consistency in the data.
7. The average time taken to reach the surface was calculated for each temperature. The reciprocal of the average time taken was calculated next, and then converted into scientific notation.