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Apparatus.
The following pieces of equipment will be used to carry out my experiment:.
A potato – this is the source of the enzyme catalase.
Hydrogen peroxide – this is compound that is to be decomposed during the experiment. .
A cork borer - this is to extract the potato.
A ruler and a knife– this will be used to measure and cut consistent quantities of potato.
Two boiling tubes - this will be used to carry out the experiment which breaks down the hydrogen peroxide.
A Measuring cylinder - to collect the oxygen which forms once the hydrogen peroxide has decomposed. .
Water bath – this is a thermostatically controlled bath which enables the experiment to be carried out at precise temperatures. .
A bung with plastic tubing – this is used to connect the first boiling tube to the collecting bath. .
A stopwatch – this is to enable the experiment to be accurately timed .
The collision theory is based on the principle that for a reaction to occur the reacting molecules must collide with each other with enough energy to react. The higher the temperature the more energy the molecules will have and the faster they will move, increasing the number of collisions and the chance that the collisions will lead to a reaction.
In terms of enzymes, we are trying to get the substrate to collide with the enzyme and for the catalyzed reaction to take place. Again, the higher the temperature the more likely there will be effective collisions. .
Using the lock and key theory, enzymes have a part of their surface called an active site which has a specific shape so it can join only with specific substrates (like a key in a lock). In extremes of temperature the shape of the active site changes and we say the enzyme is denatured. If the shape of the active site has changed then the substrate molecule won't fit and the reaction won't take place. So as the temperature increases above the optimum more enzymes become denatured slowing the rate of reaction until all of the enzymes are denatured and the reaction cannot take place.