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Investigating how the Concentration of a Substrate affects the Rate of Activity of immobilised Catalase

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Introduction

GCSE Biology Coursework: Investigating how the Concentration of a Substrate affects the Rate of Activity of immobilised Catalase Planning: "Catalase" Catalase is an enzyme; enzymes are protein based biological catalysts (substances which increase the rate of reaction but don't take part in it themselves). Catalase is found within many living cells, and is used to break down hydrogen peroxide (highly toxic) into water and oxygen (more useful substances). One molecule of it can deal with six million molecules of hydrogen peroxide in 1 minute. Formula: Hydrogen Peroxide Water + Oxygen 2H2O2 2H2O + O2 Enzymes are also found speeding up reactions in our bodies as well as in industrial processes. There are 2 primary types of enzyme: * Intracellular enzymes, which control reactions that occur within cells. * Extra-cellular enzymes, which control reactions that occur outside cells (for example, digestive enzymes work outside cells in the gut). Such examples are: * Amylase which turns starch into maltose. * Lipase, turn fats into fatty acids and glycerol. * Proteases, such as pepsin, turn proteins into amino acids. To do this, Enzymes help to break down the substrate, the substrate being a molecule of the substance that the enzyme is designed to break down, and turn it into the product. To achieve this, each enzyme has an active site, which has a unique shape into thus only a substrate of the exact same unique shape can fit. When this substrate fits into the active site it forms an enzyme-substrate complex. The substrate binds into this site, is held by a particular charge pattern, reacts and then leaves as the product. This process is called the "lock and key theory" Diagram: Factors to consider when using enzymes: * pH level: Each enzyme has an optimum pH level; this level can vary between the enzymes however. Some enzymes prefer a more acidic ph environment such as within the stomach as it has hydrochloric acid residing within it. Therefore the optimum pH level for these enzymes is 2. ...read more.

Middle

Variation either side of pH results in the enzyme denaturing and a slower rate of reaction. Action: I will use the litmus paper to indicate the pH is the same every so often. Preliminary Experiment Safety: Hydrogen Peroxide is an irritant and could blister or redden the skin. * Therefore safety goggles must be worn during the investigation to prevent chemicals from damaging eyes. * Care should also be taken whilst handling the chemicals. * Wash area that has been in contact with any chemicals after the experiment. Method: I sucked up-using a syringe, 1ml of catalase and 9ml of sodium alginate and shook it to mix the two. I then made up a beaker of 200ml of CaCl2 and then I gently released the contents of the syringe drop by drop into the beaker; making sure that the drops were of even consistency and size. I then filtered out the contents of the beaker using a sieve, making sure no beads escaped. After washing the beads with distilled water, I took 3 measuring cylinders and measured 10ml of each H2O2 concentration (1, 5, and 10 VOL) into each cylinder. To actually create this concentration, we had to pour the correct ratio of the hydrogen peroxide to distilled water for example, 1ml Hydrogen Peroxide, 9ml distilled water, for the 1 VOL reading. I then took a single bead using the forceps and dropped it into the measuring cylinder with the concentration I was testing. When the bead hit the H2O2 I had to start the stopwatch, and then stop it when the bead re-surfaced. Results: Time taken for bead to reach Concentration of H2O2 (VOL) surface of H2O2 (sec) 18.3 1 11.5 5 06.2 10 Conclusion: As I predicted, the concentration of hydrogen peroxide increases the time taken for the bead to rise decreases. Modifications: I will test a larger number of concentrations as to ascertain more accurate results and I will also test each concentration 5 times so I can be more accurate again and to get the average rate-this will help to eliminate any anomalous results. ...read more.

Conclusion

* The H2O2 becomes less and less concentrated as you test each bead so the beads may rise and fall at different rates. Improvement: Re-fill the measuring column with the H2O2 after each bead is dropped into it. * The beads may be released at differing heights from the surface of the H2O2 solution. (so some beads may have a higher/lower speed when hitting the surface, meaning that they may be faster/slower). Improvement: Use a form of delicate clamp that is set at a certain height as to keep the height constant. Whilst these improvements would cause the experiment to be rather more accurate, the majority would also be expensive and in effect a waste of money. You need to look at the experiment in context of what you are trying to achieve and it what environment: in this case to prove a point not a specific result and in a school rather than a research lab, so they do not really need to be made. I could increase the number of concentrations I do, so that I do every 1VOL rather than 2. But I would probably not go past 12 VOL as I can see that the best fit line will eventually turn into a horizontal straight line. This is because, even though there are still plenty of particles left, all of the active sites have been filled so there are no free ones left. You could also increase the number of readings you take for each concentration, but to make it even better, you could try out how different enzymes respond to this experiment (with their respective substrates). And find out whether the results to this experiment are shared throughout, plus you could add other factors to find the rate of reaction with differing concentrations and temperature and pH levels. Gary Grewal Candidate No 2052 5J Centre No 20468 Biology Coursework Mr Wood ...read more.

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