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To investigate whether the concentration of substrate (starch) affects the time taken for color change.

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Strategy- Enzyme Concentration Investigate what Factors affect enzyme activity Enzymes are biological catalyst; they are responsible for chemical reactions in living organisms. Furthermore enzymes are proteins made of large molecules made up of long chains of amino acids, which speed up the chemical reaction in every living organism. The common model used to explain how food is broken down is called the lock and key model. The model consists of an active site, enzyme, and the product. An active site has a specific shape that whereby only another complimentary substrate can fit in. When the substrate has the matching shape it then fits into the active site. Then the enzyme speeds up the reaction, breaking down the substrate into 2 products. Now that the activation energy has been reduced to its minimum, the rate of reaction will escalate drastically. Sourced from Google images Factors that affect the rate of enzymes * Temperature- Enzymes have an optimum temperature of 37 degrees, the higher the temperature the faster the rate of reaction, but enzymes are proteins, and proteins at too high temperatures start to denature and therefore become inactive. * pH- Enzymes have an optimum pH (pH7), and if the pH is too high or too low the active site changes shape (denatures) ...read more.


My results were also affected by human error, as when adding iodine we were only meant to add 5 drops, but we added more. This was because the solution had not turned dark blue. Second Preliminary Hydrogen peroxide and Catalase On my second preliminary experiment, I decided to investigate whether the concentration of hydrogen peroxide changes the volume of gas created. The substrate is hydrogen peroxide and the enzyme is catalase. We first diluted the hydrogen peroxide with water, with concentrations of 25%, 50%, 75%; this gave us a wide range of results. Then we measured 5ml of catalase and 10ml of hydrogen peroxide. During the experiment I added 5ml of catalase and hydrogen peroxide with water consequently. Then I put the bung on and started the timer, and for every 10 seconds I recorded the amount of gas produced; I did this until 50 seconds. Amount of catalase(ml) Amount of Hydrogen peroxide +(water)(ml) Concentration of hydrogen peroxide Volume of gas 10sec 20sec 30sec 40sec 50sec 5 4+ 6 25% 0 3 5 5 6 5 5+ 5 50% 3 3 4 10 10 5 6+ 4 75% 2 2 2 2 2 My results show that using a concentration of hydrogen peroxide at 50% made the most gas, but the 75% concentration barley produced any gas and this told me that there barely was a reaction. ...read more.


* Boiling tubes- to hold our solution and allows us to have a more focused concentration of our enzyme. * Boiling tube rack- to hold our boiling tubes. * Stopwatch- to measure our measurements. * Measuring cylinders (10ml) - We chose to use the 10ml measuring cylinders because they have more intervals; allowing us to have more accurate results. * White paper- From our preliminary experiments we have learnt that if you keep a white paper behind the boiling tube rack then you can see when the solution has turned fully transparent. Method 1. Measure out 5ml of amylase in a boiling tube. 2. Using a pipette measure out 5ml of starch and 5ml of water (50%) in a separate boiling tube. 3. Add 7 drops of iodine to the starch using a buffer. 4. Then add the amylase to the blue starch solution. 5. Start timing on the stopwatch until the solution is transparent then stop. 6. Record your results of how long it took. 7. Carry on doing this with 5ml, 10ml, 15ml and 20ml of starch with 5ml of amylase each. I have worked out these concentrations because it gives me a good range of data. Risk Assessment Iodine- Harmful by inhaling and when in contact with skin. (Avoid contact with eyes, secure the lid firmly on the iodine, clean up ant spillages). By Mustafa Subhe ...read more.

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