Introduction:
Plant leaves contain many enzymes, and the rate of enzyme reaction differs with the concentration of the substrate present. One of the enzymes present in any plant’s leave is catalase. Catalase is an extremely reactive enzymes that do not need cellular reductants, as they usually catalyse a dismutase reaction (Mhamdi, Queval, Chaouch, Vanderauwera, Breusegem & Noctor 2010) One may find out the rate of catalase reaction through placing different plant leaves of the same species in different concentrations of hydrogen peroxide, and measuring the time taken for the leaf to flip over or counting the amount of oxygen bubbles produced in a set time. In this experiment, the rate of enzyme reaction was measured by measuring the time
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This is because when catalase reacts with hydrogen peroxide, water and oxygen is formed (Mhamdi, Queval, Chaouch, Vanderauwera, Breusegem & Noctor 2010). Hence, as the concentration is not high, there will be less hydrogen peroxide for the catalase to catalyse, hence less oxygen will be produced and thus the leaf in the lowest hydrogen peroxide concentration solution will take the longest time to rise. Therefore, it was predicted that the leaf that would take the longest time to rise to the surface was the leaf in the 1% hydrogen peroxide concentration solution, and the leaf that would take the shortest time to rise would be the leaf in the 5% hydrogen peroxide …show more content…
In the experiment, the same volume of hydrogen peroxide was used for each set up. We used 20cm3 of hydrogen peroxide so that the only factor affecting the rate of enzyme reaction would be the concentration of hydrogen peroxide and not any external factor.
The second control variable was the size of the leaf used as the size of the leaf affects rate of enzyme reaction.
Another one of the control variables was the size of the leaf. This was because the bigger the size of the leaf, the more catalase is present. Hence, each leaf was cut to the dimensions 2 by 3cm so as to ensure that the only factor affecting the rate of enzyme reaction was the concentration of hydrogen peroxide and not the amount of enzymes present.
The third control variable was the species of brassica rapa leaves only as the species of leaf used affects rate of enzyme reaction.
This is because different species of leaves have different amounts of catalase. Hence, if the species of the leaf is different, the results will be inaccurate and unreliable as the rate of enzyme reaction will not be purely based on the concentration of hydrogen peroxide, but will also be dependant on the amount of substrates in the different leaves.
Method:
Equipment
Amount
Forceps
6