Understanding Enzyme Function & Experimental Methodology

Categories: Chemistry Concentration Enzyme

Essay, Pages 4 (905 words)

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If the temperature is too high then the enzyme will denature. This means that the active site will be damaged, and will no longer fit with the substrate. This means that no reaction will occur.

pH Independent - If the pH is very different to an enzymes optimum pH then the enzyme can be denatured as the hydrogen ions (of which pH is a measure) can interact with the amino acid R groups and affect the way they bond with each other.

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Enzyme Concentration Independent - Enzyme concentration causes there to be a fast initial rate of reaction as there are lots of free active sites for the substrate to collide with.

It is unlikely, with a higher concentration of enzyme than substrate, that the substrate will be queuing, and this means that the reaction will happen faster. If the concentration of the enzyme is lower than that of the substrate then the reaction will be slower as the enzyme will be working at Vmax and the substrate will be queuing.

Inhibitors Independent - Inhibitors slow down or stop a reaction from happening. Competitive inhibitors compete with the substrate for the enzyme's active site. These slow reactions down.

If it is reversible it means that if the substrate concentration is increased then there will be less inhibition, speeding the reaction up. If the inhibition is non-competitive irreversible then the inhibitor will bind to the enzyme's active site and remain there, even if substrate concentration is increased. This will prevent a reaction from occurring.

Sometimes the inhibitor will bind to the enzyme but not with the active site. This is seen as non-competitive inhibition and while bonded no reaction can occur.

Initial Rate of Reaction Dependant - - Below are the results from my pre-test.

O2 Collected (cm3) Amount of H2O2 (ml) Amount of Water (ml) 1These results show that as the concentration of H2O2 increased, the amount of O2 collected increased. This means that my prediction is most likely to be correct although there is a chance that the results above are anomalous as the results were only taken once and not three times like they will be in the actual test.

A prediction is important as it provides a chance to see what will happen in the experiment and gives the opportunity for any errors, with the way the experiment is carried out or with the materials used, to be changed before the proper experiment is carried out.

Equipment/Material

Amount of material

Yeast 0.1g each time (1.5g altogether)
Catalase, the enzyme for the reaction
Hydrogen peroxide 45ml altogether (variable) Needed because it is the variable in the investigation.
Boiling tubes 15 Where the reaction will take place. Need 15 as each experiment will be carried out 3 times
Water bath 2 One to keep a constant temperature in the boiling tubes and one to help trap O2 given off
Measuring Cylinder(s) 50ml and 100ml To trap the O2 given off. During the pre-test it was found that the O2 given off was more than 50ml for some of the experiments so a larger cylinder was required.
Syringe To add the substrate to the yeast
Stopwatch To time the reaction
Bung To stop O2 escaping
Tubing Goes from boiling tube into water bath where it releases the O2 into the measuring cylinder. For the experiment a measuring cylinder in a water bath will collect the O2 given off.

In the boiling tube will be a piece of tubing that the O2 will pass through and then it will collect in the measuring cylinder. Every 10 seconds for 2 minutes the O2 collected will be recorded so that the rate of reaction can be worked out. To alter the substrate concentration, the H2O2 will be mixed with water. The first experiment will contain 1ml of H2O2 and 4ml of water, and then the second will have 2mls of H2O2 and 3ml of water. Using 5ml of solution means that it is easy to change concentration, decreasing one by a fifth and increasing the other by a fifth.

Throughout the experiment a water bath will keep the temperature at a constant of 37i?? C. This ensures that the experiment is fair as each one will be carried out at the same temperature, necessary because temperature affects the rate of an enzyme reaction. Each experiment will be carried out three times so that any anomalous results will be obvious. The data that is collected will be put into results tables and then a graph will be produced with Time in seconds on the x-axis and O2 collected on the y-axis. When using Hydrogen Peroxide it is important that many aspects of safety are observed.

H2O2 is corrosive and can cause burns in concentrations of 5.9M and irritation to skin and eyes in concentrations stronger or equal to 1. 5M. Therefore it is important to wear goggles to protect the eyes, and a lab coat to protect skin. If the H2O2 does get onto the skin or clothes then, if in large quantities, remove the clothing and wash the area of skin with lots of water. If H2O2 gets into the eyes then the eyes must be rinsed for 10-15 minutes and then medical attention should be sought. With any chemical it should not be swallowed. However, if it is swallowed then the mouth should be washed out and 2-3 glasses of water should be drunk.