• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11
  12. 12
    12

How Does the pH of a Solution Affect the Rate of Starch Digestion By Diastase

Extracts from this document...

Introduction

How Does the pH of a Solution Affect the Rate of Starch Digestion by Diastase Abstract: This investigation was designed to show the effect of pH on the activity of enzymes. I did this by making buffered 1% starch solutions and 2.5% diastase enzyme solutions and mixing 25 cm3 of both solution to each other and testing if the starch was broken down into maltose every 30 seconds. The experimental procedures were repeated 3 times for a range of 5 pH's of pH 3.45, pH 4.35, pH 6.27, pH 7.17 and pH 9.22. This plan worked and was very easy to prepare and implement. The enzyme used showed positive results and gave some unexpected results in respect to the research that I have done about the diastase group of enzymes. Aim: I am going to perform experiments to determine the optimum pH for the digestion of starch by the enzyme diastase and I will be measuring the time it takes the enzyme to digest the starch solution. Preliminary Work: I tested a wide range of pH's in my preliminary work. I started by testing buffered solutions at pH 1, pH 3, Ph 5, pH 7, pH9 and pH 12. This gave me a rough idea of where my enzyme was going to be active. After analysing my data I decided that pH's 3 and 9 were going to set the extremes to my range or different pH's. I decided to add pH 6 to my solutions to give a more rounded result and replace pH 5 by pH 4. ...read more.

Middle

The different diastases are Alpha-Amylase, Beta-Amylase, Fungal Amylase, Glucoamylase and Malt Diastase. [2] What is pH? The pH scale measures the concentration of aqueous H+ ions (protons). This controls the acidity of solutions. Thomas Lowry and Johannes Br�nsted independently came up with a definition for acids and bases in 1923. The Lowry-Br�nsted definition for acids and bases is: "An acid is a substance that can donate a proton (an H+ ion) and a base is a substance that can accept a proton". [10] There is a conventional accepted definition for pH and that is "-log10 [H+ (aq)]". The square brackets in this definition are there to show the concentration of H+ ions in mol dm-3. The pH scale depicts the concentration of ions present, as the number gets smaller, the concentration of H+ ions increases. A jump of 1, like from pH5 to pH4 for example, represents a tenfold increase in the concentration of H+ ions. [11] What is a Buffer Solution? A buffer solution is one that can resist changes to the concentration of the OH- ions and the H+ ions within the buffered solution. Buffer solutions usually withstand changes in pH when moderate amounts of acid or base are mixed within them. [11] The pH in a buffer solution can be calculated using the Henderson Equation. The Henderson Equation is: Ka = [H+ (aq)] eqm [A- (aq)] [HA (aq)] eqm [11] Apparatus and Glassware List ==> 10 x Spotting Tile ==> 2 x Spatulas ==> 2 x Glass Rod ==> Weighing scale accurate to 2 d.p. ==> 4 x 200ml Beakers ==> 2 x Funnel ==> 5 x 250ml Volumetric Flask ==> 1 x 500ml Volumetric Flask ==> ...read more.

Conclusion

I found that the enzyme that I used was inactive in pHs that are pH 7 and above. This tells me that the enzyme was denatured by neutral or basic conditions. My results have thus shown me that the enzyme that I have been supplied with would have a range from pH 3 to pH 6, the specific enzyme can then be determined as Glucoamylase and that the range of this enzyme is pH 3 to pH 6. The optimum pH is somewhere in the boundary of pH 4.0 to pH 4.9. Limitations to my experiments mean that I cannot guaranty this result although I can be certain which enzyme this is if I were to increase the number of trials that I did and if I use more accurate equipment and methods of measurement. I could also increase my experimental margin to the effect of pH on diastase in different temperatures. Another thing that could have affected my results was the accuracy of my equipment. Values that I am aware of will always be different from the actual result. The 250ml and 500ml volumetric flasks I used to make my stock solutions had an error margin of �0.05ml and the 25ml pipettes that I used to measure the solutions to mix has an error margin of �0.06ml. One other error in measurement came from the weighing scale as I could only measure accurately to 2 decimal places. After concluding my experimental procedures and analysing my results, I have decided that a more accurate range of pH's is needed for better accuracy for my result. Decreasing the sample time from 30 seconds to 15 seconds will also help me achieve more accurate results. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Here's what a teacher thought of this essay

3 star(s)

***
The background theory and account of the preliminary experiment are mostly very good quality. However, there is little discussion of variables and data presentation could be improved.

Marked by teacher Adam Roberts 17/09/2013

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Molecules & Cells essays

  1. Marked by a teacher

    Effect of temperature on the enzyme pectinase in fruit juice production.

    3 star(s)

    This enzyme would behave in a more predictable manner. 6. The experiment should be repeated more than twice to obtain more results and a better average. It should be repeated at least 3 times to obtain more reliable results, minimise errors and obtain more accurate average.

  2. Marked by a teacher

    The Effect of pH on Pectinase

    3 star(s)

    If this is not controlled then the variable of enzyme concentration will not have been controlled. If there were an increased number of enzymes then the reaction would take place faster than the other reactions and I would have made the test unfair as I could not tell if it

  1. The Effect of Concentration on Pectinase Using Apple

    However the volume added was kept constant at 2.5ml and therefore the differences in volumes are due to the concentration of pectinase alone. The graphs for 5.00%, 2.50% and 1.00% show most clearly that the volume obtained rises in a linear fashion with time.

  2. Investigating The Activity Of The Enzyme Lipase On Milk

    50 50 50 0.020000 2.000 50 61 64 67 64 0.015625 1.562 60 136 130 131 132 0.007575 0.757 Analysis of results From the graph, I am able to back up my theory. I can see when the enzyme is most active and when it starts to denature.

  1. Investigating the effect of temperature on the activity of free and immobilised enzymes.

    they are unable to move, so higher temperatures are needed to allow the substrate molecules to move enough. After 40�C the rate will fall for the free lactase because the enzymes will denature. This is due to the attractions between amino acid molecules in the enzyme breaking and the enzyme will lose its shape.

  2. Investigating Whether Temperature Affects The Bromelain Enzymes Inside Pineapples By Changing The Rate Of ...

    The tubes will then be removed and placed in a bath of ice until the temperature of the juice lowers to 20 degrees Celsius.

  1. Acid Hydrolysis of Polysaccharides.

    When the test tubes are cool pour each solution into a separate cuvette and read the extinction at 540nm against the blank. Repeat this process for each tube at appropriate time intervals. Results TIME IN BATH (MINUTES) SPECTROPHOTOMETER READING OF GLYCOGEN 10 0.46 20 0.659 30 0.856 40 1.075 50

  2. DETERMINING THE WATER POTENTIAL OF A POTATO TUBER CELLS USING THE WEIGHING METHOD.

    The stronger the concentration the slower the movement of water molecules present due to more bonds between the solutes and the water molecules, therefore the more negative the water potential. The unit for water potential is kPa because it's the measurement of the pressure acting on the water molecules.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work