• 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
  13. 13
    13
  14. 14
    14

Activity of Diastase On Starch

Extracts from this document...

Introduction

ACTIVITY OF DIASTASE ON STARCH Brief Starch is a polymer where the individual units in the polymer are glucose molecules. The most important enzyme that degrades starch is called diastase. This enzyme catalyses a split in the starch polymer so that eventually what is left over are short chains consisting of just a few glucose units (maltose). These can then be broken down by water so that the entire starch polymer is degraded to glucose. The glucose concentration that will be produced in a fixed time by the action of diastase on starch can be measured to find out the rate of hydrolysis of starch, as the equation below shows: STARCH DIASTASE GLUCOSE + MALTOSE The reaction between starch + water = glucose is called hydrolysis. In the chemical reaction that occurs, water is introduced into the bond between two glucose units with a -OH becoming part of one side of the bond and a hydrogen (H-) becoming attached to the other glucose molecule. Rate of hydrolysis of starch ? concentration of glucose produced (In the above relation time is kept constant) Glucose concentration can be measured by titrating glucose solution with quantitative Benedict solution having sodium carbonate in it. 25ml of quantitative Benedict solution+10 grams of sodium carbonate can be titrated with a solution having glucose in it. This titration gives us the volume of glucose solution used to carry out the titration. Subsequently we can find out the rate of hydrolysis of starch by comparing the concentration of glucose produced in one minute. So, lesser the volume of glucose solution used greater the concentration of glucose and faster the rate of hydrolysis of starch. ...read more.

Middle

pH Volume of reaction mixture used Rate of the reaction = 1/ volume of reaction mixture used 4 10.24 ml 0.0976 4.8 9.65 ml 0.104 5 9.35 ml 0.107 7 11.00 ml 0.0909 9 11.67 ml 0.0857 A graph of the rate of hydrolysis of starch against ph is shown below pH affects the three-dimensional structure of all enzymes. Enzymes are made up of amino acids. Each amino acid has a -NH2 group and a -COOH group, not to mention certain amino acids that have an extra -COOH group (e.g. aspartame) or an extra -NH3+group (e.g. asparagines). PH is all about concentration of H+ ions. At low pH and high H+ concentration the predominant forms of these groups will be -COOH and -NH3+ or the "protonated forms". At neutral pH the predominant forms will be -COO and -NH3+. At high pH the predominant forms will be -COO- and -NH2. However the actual pH at which each group becomes ionised depends on the particular amino acid and also the environment in which the enzyme is found. The usual way of expressing this is the pK value: this pK is the pH at which half of the groups are ionised. Interactions between these positive and negative charges are a very important part of what holds the structure together in an enzyme. These links are known as salt links, salt bridges or electrostatic interactions and involve a + to - attraction. Changing the pH therefore alters the properties of these salt bridges. Even a small shift away from optimum pH might mean one of these salt bridges is affected and therefore the shape and activity and stability of the protein will also be affected. ...read more.

Conclusion

Following results were obtained from these titrations. Titration readings using 1% starch solution. Titration no Initial reading Final reading Volume of solution used 1 1.00 13.6 12.6ml 2 13.6 25.7 12.7ml 3 25.7 38.4 12.7ml Mean volume of solution used = 12.6+12.7+12.7 = 12.67ml 3 Titration readings using 2% starch solution. Titration no Initial reading Final reading Volume of solution used 1 1.00 13.3 12.3ml 2 13.3 25.6 12.3ml 3 25.6 37.8 12.2ml Mean volume of solution used = 12.3+12.3+12.2 = 12.27 ml 3 Titration readings using 3% starch solution. Titration no Initial reading Final reading Volume of solution used 1 1.00 13.3 12.3ml 2 13.3 25.5 12.2ml 3 25.5 37.8 12.3ml Mean volume of solution used = 12.3+12.2+12.3 = 12.27ml 3 Effect of change in the concentration of starch on the rate of hydrolysis of starch Concentration of starch Volume of solution used Rate of hydrolysis of starch = 1/ volume of solution used 1% 12.67ml 0.0789 2% 12.27ml 0.0815 3% 12.27ml 0.0815 A graph of concentration of starch against rate is shown below These results shows that increasing the concentration of starch increases the rate of the reaction. This is because there are more molecules of starch present to be broken down, increasing the rate. However there comes a certain point whereby increasing the concentration of starch will no longer affect the rate of the reaction. From my results I can observe that this optimum stage at where this happens is when the concentration of the starch is at 2 and 3 percent. The reason for this is because all the active sites of the diastase enzyme were busy in breaking down the starch molecules, leaving no available active sites for new starch molecules. Therefore increasing the concentration of starch did not effect the rate of the reaction. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.

Found what you're looking for?

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

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 GCSE Patterns of Behaviour essays

  1. Rates of Reaction - The Iodine Clock

    ]0 [ H2O2 ]1 [ I- ]1 The reaction is therefore second order overall. Error analysis: Error introduced by temperature: Although I endeavoured to perform the reactions at a constant temperature, due to fluctuations in room temperature this was largely impossible to achieve.

  2. Rates of Reaction- Hydrolysis of Urea by Urease

    'pH' simply means 'power of hydrogen', and is a measurement of the concentration of hydrogen ions H+ in a solution. It is usually on a scale of 0 to 14 but a negative pH is possible. A pH of 0 to 6 is considered as acidic and has a high

  1. The effect of enzyme concentration on the rate of amylase and starch reaction.

    If the concentration of substrate is low, enzymes will bind with all the substrate. The remaining enzymes will be unable to bind with any substrate and the reaction rate will not increase until more substrate is added. The diagram below demonstrates this: Fair Testing Key Variables I will keep these variables constant: -Concentration of starch -Concentration of amylase.

  2. Enzymes - show how substrate concentration affects the rate of reaction for an enzyme ...

    In order to be aware of the fact that the hydrogen peroxide is prepared to the actual extent of 2.00 mol/dm� which is required in order to carry out the experiment. Temperature If the room temperature increases then the rate of reaction will increase.

  1. THE EFFECT OF BILE SALT ON THE ACTION OF THE ENZYME LIPASE

    lipase to breakdown the lipids, whether or not this is correct will be observed by the duration taken for the pH to drop becoming more acidic once the bile salt has reacted with the cream emulsifying the fats thereby allowing the lipase to work more efficiently breaking down the lipids into single fatty acids.

  2. Factors Affecting Enzyme Activity

    Also, if the pH is not the right ph for the specific enzyme then there will either be too many OH- ions or too many H+ ions which will disrupt hydrogen bonds thus denaturing the enzyme. Key factors investigating the rate of enzyme activity After conducting extensive research into the

  1. The effect of concentration on the activity of catalase.

    Figure 1 illustrates the action of increasing the concentration. The reaction of the decomposition of the hydrogen peroxide by catalase is a redox reaction. This experiment uses catalase as the enzyme. Catalase is an enzyme that is present in the cells of plants, animals and aerobic bacteria.

  2. Does the Volume of Amylase Affect the Rate of Reaction between Amylase and Starch?

    All the other variables I will keep the same. I will also make sure that I keep my apparatus the same throughout the experiment. Apparatus: Colorimeter Micro pipette Iodine solution Test tube Amylase Stopwatch Measuring cylinder Starch Filter 470 (For the colorimeter) Colorimetery: A colorimeter will be used to measure the reaction rate between amylase and starch.

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