• 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

    How does the pH affect the activity of amylase

    3 star(s)

    test to see if there is starch present Thermometer- this would be used to make sure the temp of the water bath is correct 5ml syringes (3) 3 syringes would be needed to take out some of the starch, amylase and buffer solution into the boiling tubes.

  2. Marked by a teacher

    Effect of temperature and inhibition on the rate of pepsin digestion.

    The third beaker, or control, contained only egg whites. After being thoroughly mixed, the beakers were placed on a hot plate to solidify the egg white enough to put into capillary tubes which would then be placed in an HCl-pepsin solution.

  1. Marked by a teacher

    Investigating the effect of temperature on the breakdown of starch by amylase.

    However, this effect was lessened with most of the temperatures as the mixture was cooling down to room temperature in the pipette. The method by which we tested to see if there was starch remaining did not work entirely satisfactorily.

  2. Investigation of the effect of adding different concentrations of NaCl to an enzyme-substrate (amylase-starch) ...

    Cofactors - some enzymes can only function efficiently in the presence of other substances. Cofactors Cofactors must be further investigated in the background information, as sodium chloride is a possible cofactor for the reaction between starch and amylase. Some enzymes only work in the presence of another chemical which serves as a 'helper,' such enzymes are called cofactors.

  1. An experiment to investigate the effect of chloride ion concentration on the activity of ...

    Seek medical attention if irritation develops or persists Sodium Chloride solution 2% Causes Eye Irritation Precautions: Avoid contact with eyes. Wash thoroughly after handling. First Aid: In case of eye contact, immediately flush eyes with plenty of water for at least 15 minutes.

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

    After the 24 hours of the pineapple juice being in the boiling tube with the gelatin, the liquid will be poured out of the boiling tube into a measuring cylinder and the amount of liquid obtained will be measured. This measurement will then be used to minus 5cm cubed from.

  1. An Investigation Into The Digestion Of Milk By Trypsin.

    range from several thousand to several million. The substrates on which enzymes act usually have molecular weights of several hundred. Because of the difference in size between the two, only a fraction of the enzyme is in contact with the substrate; the region of contact is called the active site.

  2. Explain transcription and translation in protein synthesis.

    moves onto and binds to a protein on the latest tRNA molecule, allowing previous tRNA, 'to detach themselves from the mRNA and return to the pool of tRNA in the cytoplasm from which they can be drawn upon again when required.'

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