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A investigation into the effect of inhibitor concentration on the enzyme catalase.

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A Investigation into the Effect of Inhibitor Concentration on the Enzyme Catalase Aim: To investigate how the concentration of inhibitor (lead nitrate) affects the rate of reaction of the enzyme Catalase. Hypothesis: In my hypothesis I state that Hydrogen Peroxide (H O ) will breakdown to oxygen and water in the presence of catalase from the potato. The rate of reaction will decrease with increasing inhibitor (lead nitrate) concentration when molecules of Hydrogen Peroxide are freely available. However, when molecules of the inhibitor are in short supply, the increase in the rate of reaction is limited and therefore will have little affect. Predicted Graph: Background Knowledge: Enzymes- Enzymes are complex 3-D globular proteins, some of which have other associated molecules. Enzymes are catalysts which alters the rate of chemical reaction without itself undergoing a permanent change, and therefore can be used over and over again. Enzymes help reactions speed up which would otherwise take place very slowly. While the enzyme molecule is relatively larger than the larger than the substrate molecule it acts upon, only a small part of the enzyme molecule actually comes into contact. This region is called the ACTIVE SITE. The active site of an enzyme is the region that binds the substrate and contributes the amino acid residues that directly participate in the making and breaking of chemical bonds. However, all enzymes operate only on a specific shape and therefore fits only complementary locks, so only substrates of a particular shape will fit the active site of an enzyme. Substrate Concentration- For a given amount of enzyme, the rate of an enzyme controlled reaction increases with increasing substrate concentration-up to a point. At low substrate concentrations, the active sites of the enzyme molecules are not all used- there simply are not enough substrate molecules to occupy them all. As the substrate concentration increases, more and more sites come into use. ...read more.


We do this to provide us with the enzyme catalase for the experiment. 2. Once this is done separate 4ml of the crushed potato into burette 1, (leaving the rest if the potato for the other burettes) using a syringe. We use a syringe to do this as it is easy to measure with and is accurate. 3. Next add 20cm of pH7 buffer solution with a different syringe. This is added to keep conditions constant during the experiment. 4. Then add the pre-made lead nitrate solution and add the amount required into burette 1 as shown on the table above (i.e. burette 1 would have 10cm distilled water and 0 lead nitrate solution). 5. Finally put your safety goggles on, and add 2cm of hydrogen peroxide (H O ). 6. To ensure everything is mixed in properly for the experiment to occur successfully remove the burette from the wooden clamp stand, place your thumb at the top end so the contents don't spill out and tip upside down two or three times so the contents are shuffled properly. 7. After the burette is safely placed back in to the wooden clamp start the stop clock and take readings of the increase in froth level every 30 seconds for 10 minutes. 8. Repeat steps 2-7 for burettes 2-6. Concentration of lead nitrate will differ for each burette, check on table to see what proportion of distilled water to add to each lead nitrate concentration in each burette. Results: 10cm Distilled Water 0cm Lead Nitrate Solution TIME FROTH LEVEL VOLUME OF FROTH LEVEL 0 20.3 24.36 30 +1.2 +1.44 60 +1.8 +2.16 90 +2.4 +2.88 120 +3.4 +4.08 150 +4.5 +5.4 180 +5.6 +6.72 210 +6.7 +8.04 240 +7.7 +9.24 270 +8.8 +10.56 300 +9.3 +11.16 330 +9.9 +11.88 360 +10.5 +12.6 390 +11.1 +13.32 420 +11.5 +13.8 450 +12.0 +14.4 480 +12.3 +14.64 510 +12.6 +15.12 540 +12.9 +15.48 570 +13.1 +15.72 600 +13.2 +15.84 Total Increase =+13.2 Total Increase =+15.84 8cm of Distilled ...read more.


This was used to maintain the pH level in the experiment. However if I had varied the pH level, it may have resulted in an increase or decrease in rate of reaction. This is because pH is a measure of hydrogen ion concentration. By breaking the hydrogen bonds which give enzyme molecules their shape, any change in pH can effectively denature enzymes. Each enzyme works best at a particular pH- (7 being a neutral point), and deviations from this optimum may result in denaturation. Another precaution was taken with safety equipment. As I was handling hydrogen peroxide, the safety precaution I had to take was to wear safety goggles, especially when pouring it into the burette. To further my investigation, certain experiments could be carried out into the effect of inhibitor on rate of reaction. The major one being to carry out repeats at each inhibitor change, this will enable me to get more reliable and more accurate results, as I will be able to work out he average of this and be able to draw a graph of error bars, which may portray my present obtained results in a different but precise way. I could also test at even more narrower inhibitor changes, to give me more accurate results. Perhaps I could use also try and use a different source to provide me with the enzyme catalase, this is because the desired amount of catalase from the potato may be less or more than what I want it to be. I t was quite hard to measure and there wasn't really a quick way of knowing- making my results negotiable. Consequently, maybe using catalase from yeast would've been easier to use and handle. Specific amounts could be measured much more precisely, and may give more precise results. Another way could also be to use a gas syringe instead of a burette, as this would increase time availability and be easier to record the froth level, because it saves time calculating the froth level increase and gives exact readings. Answers won't need to be rounded by the calculator. 14 1 ...read more.

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