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Immobilized Enzymes (Yeast)

Extracts from this document...

Introduction

Immobilized Enzymes (Yeast) By Candidate Name: Poon Shun Yan Candidate Number: 1556 T2 Investigation submitted for Advanced Level Biology to EDEXCEL GCE, June 2005 Woldingham School, Centre Number 64030, Marden Park, Woldingham, Surrey, CR3 7YA Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 2 - 3 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 4 - 7 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 8 - 10 Discussion and Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 11 - 13 Abstract Catalase is an enzyme found in living cells and is used to break down peroxides. Yeast cells, which contain catalase, are used to catalyse the decomposition of hydrogen peroxide solution into water and oxygen gas. ...read more.

Middle

50cm3 burette will be chosen to collect oxygen bubbles because it has a narrow bore, and small graduations from which readings can be read off accurately. Predictions Increasing the number of alginate beads, i.e. yeast concentration with excess substrate molecules, the volume of oxygen collected should increases in direct proportion. The rate of reaction will also be directly proportional to the enzyme concentration. The reasons of both predictions are because there are more active sites available for the substrate to fit in which will be able to form more products: - Modification While investigating the rate of reaction on hydrogen peroxide solution, 5 alginate beads were first used. However no gas bubbles were produced in 5 minutes. Ten more beads were the added to start the experiment with 15 beads. Gas bubbles were produced very slowly. Thus the minimum number of beads for the investigation was set to be 15 and the experiment was repeated using the following number of beads: 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 and 80. Risk Assessment Hazardous chemical or micro-organism being used or made, or hazardous procedure or equipment Nature of the hazard(s) Source(s) of information Control measures to reduce the risks Calcium chloride (a) Irritant to the skin and the membranes of eyes when contacted, and may cause asthma when inhaled (b) Dangerous with water under anhydrous salt can cause CLEAPSS hazcards Raising dust is avoided when making solution Hydrogen peroxide (a) Corrosive and causes burns if equal to or stronger than 5.9M (i.e. 20% or 71'vol') (b) Irritant if stronger or equal to 1.5M (i.e. 5% or 18 'vol.'), less than 5.9M and irritant to the eyes and skin (c) Explosive when contact with organic compounds such as propanone, ethanol, glycerol and many others. (d) Violent decomposition when contact with metals and metal oxides (especially if finely divided) and tin(II) chloride. (e) Dangerous if swallowed, may cause serious internal damage due to release of oxygen CLEAPSS hazcards The 20 vol. ...read more.

Conclusion

Percentage uncertainty Uncertainty value of the 50cm3 Grade B burette = 0.05cm3 Average volume Largest percentage uncertainty in volume of oxygen gas collected = 0.05/21 = 0.00238% (3 s.f.) The value is small enough to be ignored, which means the data obtained are precise enough. Improvements 1. A control experiment should be done when investigating the rate of reaction. The set-up should be the same but without adding any immobilized yeast. There might be a change of the burette reading after each time interval, since hydrogen peroxide decomposes easily into water and oxygen gas. The change of the reading should also be included in the table of result and should also be plotted on figures 4 and 5. 2. Under observation during the experiment was carried out, 1 bubble decreased about 0.2cm3 of the burette reading. This increased the time interval between each bubble. Thus some of the gas could not be collected at the time the reading was taken. A smaller internal diameter of delivery tube should be used to improve accuracy of the volume of oxygen gas produced. 3. New beads should be used each time as oxygen produced on the active sites of the enzymes did not fall off, which blocked the hydrogen peroxide substrate to fit in, and evidence was obtained from the purple line with 55 alginate beads which had proved the reliability of using new beads for each experiment. 4. Since the rate of reaction of catalase in the yeast cell is concerned in the experiment, only catalase should be immobilized instead of a whole yeast cell which will be more precise. NOTE: Chemistry investigation: change temperature, concentration of yeast is constant Gradient of rate against temperature, prove equation REF1: Central Team - BURTON G, HOLMAN J, LAZONBY J, PILING G, WADDINGTON D, (2000). Chemical Storylines. Heinemann Educational Publishers. [p.160 Fig.52] REF2: ADDS J, LARKCOM E, MILLER R, (2000). Molecules and Cells. Nelson Thornes Ltd. [p.45] REF3: SHEEHAN M, (1994). Biochemistry and Molecular Biology. Thomas Nelson and Sons Ltd. 1 Candidate Name: Poon Shun Yan Candidate Number: 1556 1 Candidate Name: Poon Shun Yan Candidate Number: 1556 ...read more.

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