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Effect of different size beads on the activity of immobilised catalyse

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Introduction

Effect of different size beads on the activity of immobilised catalyse Aim: To find out how varying the size of beads containing yeast varies the rate of activity of catalase in a fermentation reaction of hydrogen peroxide with immobilised enzymes. A catalyst is a substance that speeds up the rate of a chemical reaction, without itself being used up in the process however it maybe affected physically i.e. degradation of the surface of the catalyst. Catalysts work by reducing the activation energy needed for a particular reaction by offering a different path for the reaction to take place. Activation energy is the energy, which needs to be supplied before a reaction can occur, basically the amount of energy needed to overcome the bonds between the molecules and atoms. Catalysts are usually specific to one reaction, that is, different reactions need different catalysts. This is the lock and key theory however there is another theory as well called the induced fit theory. Since a catalyst is not used up during a chemical reaction, it can be used over and over again to convert reactants to products. In this experiment I will be using the immobilised enzyme yeast. When an enzyme is immobilised in this case it is encapsulated in a sodium alginate gel. When an enzyme is immobilised it is in a more stable state, they are better able to resist alteration to shape and activity. In particular they are less likely to be inactive or denatured by changes in pH, presence of other chemicals, or high temperatures. Immobilised enzymes can also be used for longer periods before their activity reduces which is useful in the experiment as the rate must stay the same otherwise after a certain amount of the time the results would become invalid as some enzymes rates would decrease at a slower rate then others. Lock and Key theory Enzymes are specific to a particular substrate molecule or a restricted group of substrate molecules. ...read more.

Middle

Solutions stronger or equal to 1.5 moles i.e. 5% or 18 volume but less than 5.9 moles are irritants to the eyes and skin. Wear gloves and eye protection. It's a dangerous substance if swallowed, as it causes serious internal damage due to the releases of oxygen. Yeast is only classed as a multi celled fungal organism, so there are not really any ethical issues. For safe disposal of the microorganism the equipment will be autoclaved which is a process where they are washed at 100 �c where all organisms are killed off, and the sink will be treated with bleach. Method 1. Collect 20 cm3 of 2 % sodium alginate solution. 2. Stir it with a glass rod to ensure an even consistency. 3. Fill the water bath to near full and switch on, turn temperature to 40�c, and allow water to heat up. 4. Dissolve 1.4 grams calcium chloride in 100ml of deionised water. 5. Weigh out 5 grams of yeast and pour it into another beaker of 100 ml of deionised water, stir the mixture. 6. Add 2 cm3 of yeast solution to the alginate gel, and stir to mix. 7. Draw some of the alginate mixture into a syringe. Expel it drop by drop into the calcium chloride solution, from a height of about 10 cm this will allow it to form beads. 8. Leave the beads to stand in the calcium chloride solution for 10 minutes, to allow the beads to set completely. 9. Drain the beads through a piece of muslin necklace gauze, rinse with tap water. 10. Attach a glass syringe to a side arm flask via airtight tubing, and place the side arm flask in the water bath. 11. Measure out 50 ml of hydrogen peroxide and pour into side arm flask. 12. Measure out a volume of 8 cm3 of beads. 13. Empty the beads into the side arm flask put the stopper and simultaneously start the stopwatch. ...read more.

Conclusion

Other experimental errors, which lead to, the anomalous set of results in the first experiment is also due to the difficulty in measuring the volumes of beads, as I was using a simple method of pouring the beads into a measuring tube however this could of lead to miss calculations into the total volume of beads due to the air spaces in between the beads. Another factor to consider would be whether in the larger sized beads actually allowed for the hydrogen peroxide molecules to diffuse through and into the bead itself, thus the surface area enzymes with a high surface area to volume ratio which have a larger amount of enzymes around the surface of the bead. However this becomes a less prominent effect if the hydrogen peroxide molecules can diffuse through the membrane of the bead because they can react with the enzymes inside the bead itself. To further investigate this experiment I could vary the temperature of the reaction, this would show the how stable the immobilised enzymes are and whether the size contributes to their stability. Another factor to consider would be whether to when measuring out the volume of beads or the number of beads, in my experiment I measured the volume this meant that the surface area to volume would definitely work. If I took the number of beads though the result might be different because a small bead might have a larger surface area to volume ratio however the bead might be so big that there might be more enzymes on the outer surface. Percentage errors I can work out the percentage errors for my measurements, by using this formula. Mass of calcium chloride (0.005 x 100)/1.4 = 0.7% Mass of sodium alginate (0.005 x 100)/0.4 = 0.2% Pipette (0.05cm3 x 100)/10=5% (0.05cm3 x 100)/5=2.5% (0.05cm3 x 100)/15=7.55% (0.05cm3 x 100)/2=1% (0.05cm3 x 100)/50=25% Measuring beaker (0.2 cm3 x 100)/250 =0.08% Measuring tube (0.1 cm3 x 100)/10 =1% Measuring tube containing hydrogen peroxide (0.1cm3 x 100)/50 =0.2% Measuring tube containing water (0.1cm3 x 100)/100 =0.1% Measuring tube to calculate volume of beads (1cm3 x 100)/8 =12.5% ...read more.

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