My aim is to investigate the breakdown of starch molecules (polysaccharides) into maltose molecules (disaccharides) catalysed by the digestive enzyme amylase. I am trying to find out if the rate of reaction is affected by pH.
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AS Biology T1 Individual Project Kevin Isaacs 12B1 22/10/02 Amylase Investigation Aim: My aim is to investigate the breakdown of starch molecules (polysaccharides) into maltose molecules (disaccharides) catalysed by the digestive enzyme amylase. I am trying to find out if the rate of reaction is affected by pH. Hypothesis: I predict that the amylase will be most effective at breaking down starch at a pH of around 7 to 8. As the pH moves further away from this level, either increasing (becoming more alkaline) or decreasing (becoming more acidic) I expect that the rate of reaction will slow down. Eventually, at very low or very high pHs I expect that the enzyme will not catalyse the reaction at all. Amylase is a biological catalyst. It is found in the mouth in saliva produced by the salivary glands and in the duodenum produced by the pancreas. It speeds up the chemical reaction of breaking down starch into sugar (maltose). A catalyst is a substance that speeds up the rate of a chemical reaction. The catalyst changes the mechanism of the reaction lowering its activation energy. This means that the reaction will take place more quickly as less energy is needed to make the substrate(s)
* Water bath - This will be needed to keep the temperature constant so as to make the experiment more accurate. * Iodine - This is a Universal Indicator to see how much starch is broken down. If there is starch present it will turn a blue-black colour, if not it will remain a light brown colour. 0.05% iodine will be needed. * Starch Solution - This will be broken down by the amylase. 5cm3 of 1% starch solution will be needed. * Pipettes -These will be needed to measure solutions and enzyme accurately.1cm3 and 5cm3 pipettes will be required. * Amylase - An enzyme, which catalyses in the breakdown of starch. 1cm3 of 0.625 % will be needed. * Range of Buffer solutions (pH of 3.0, 5.0, 7.0, 8.0). - These will be needed to change the pH of the starch solution for the investigation. 5cm3 will be needed. * Stopwatch -This will be required to keep track of the time whilst doing the investigation. * Spotting tile -This will be needed to see the colour of the iodine/solution mixture. Method: Firstly, drops of iodine will be spaced out on the cavity tile. Three test tubes containing 5 cm3 of starch solution, 5cm3 of buffer solution of pH 3.0 and 1cm3 of amylase respectively will be placed in a water bath of temperature 37o C and left for 2 minutes.
and Sodium Hydrogen Phosphate (0.2 mol dm -3 ). They are mixed together in different proportions to produce the levels of pH that I am going to use. I have shown how much will be needed of each substance in the table below. pH Na2HPO4 Citric Acid 3.0 20.55 cm3 79.45 cm3 5.0 51.50 48.50 7.0 82.35 17.65 8.0 97.25 2.75 When handling the acid take care as it may cause burns if it comes into contact with the skin. Gloves and protective clothing including gloves should also be worn. If it is swallowed, wash out mouth and give victim a glass of water. Seek medical attention as soon as possible. If the vapour is inhaled move the victim to fresh air to rest. If any of the liquid gets in eyes, flood the eye with gently running tap water for 10 minutes and seek medical attention. If any acid is spilt on the skin or clothes flood the affected area with water and remove contaminated clothing. Should any acid be spilt in the laboratory, wear eye protection and gloves and ventilate area of spill. Cover with mineral absorbent and clear up. Should any of the alkali be spilt in the laboratory, eye protection and gloves should be worn. Lay down mineral absorbent and scoop into a bucket. Treat the absorbent with water and citric acid and then pour down the drain.
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