• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

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

Extracts from this document...

Introduction

An experiment to investigate the effect of chloride ion concentration on the activity of amylase PLAN Introduction Amylases are a group of enzymes which hydrolyse starch (A glucose polymer) linked by ?-1,4 and ?-1,6 glycosidic bonds to maltose (a disaccharide). Fungal salivary amylase requires the addition of a cofactor, this is a chemical species that does not directly undergo chemical reaction but is required to maintain the shape the active site or aid the activation of certain molecules. This allows regulation of activity for specific enzymes. Objectives To determine how the concentration of chloride ions affects the rate in which salivary amylase hydrolyses starch Independent variable Chloride ion concentration (sodium chloride) Hypothesis The reaction velocity will increase in direct proportion to concentration of chloride ions present until a point where the graph will plateau and no further increase in rate will be observed. Theory Of Hypothesis Some enzyme molecules can exist in two different states. Either the molecule is relaxed (R-state), or tense (T-state) This is caused by a difference in the three-dimensional shape. In the R-state it has a greater affinity to the substrate than the T-state. This type of enzyme is referred to as an allosteric enzyme, and they contain a site to which the cofactor fits changing the enzyme from the T to the R state. With allosteric enzymes, they are all in the T-state before the substrate (or cofactor) is added. Using the induced fit model of the enzyme-substrate complex, the substrate causes the enzyme to change from T to R state. As such some activity will occur without the presence of cofactors. ...read more.

Middle

The pH affects the reaction velocity by ionisation of the side chain when the pH varies from it's optimum. This changes the shape of the active site, and high or low pH causes the enzyme to denature. Amylase concentration must remain the same for each experiment. This can be achieved using a fixed volume of a set concentration of amylase in each experiment. This must be maintained as an increased/decreased number of enzymes in solution will cause an increase/decrease in reaction velocity irrespective of whether they are in the R-state or T-state. Initial starch concentration again must be maintained for each experiment. As above a change in starch concentration will change the rate of the reaction due to an increased number of collisions between enzyme and substrate. A set volume and concentration can be used to maintain this variable. Temperature will be kept at a constant and known level throughout all the experiments. This can be done by placing the test tubes of enzyme and substrate in a water bath which is at room temperature. The high specific heat capacity of water will compensate for any small changes in room temperature that occur during the experiment. The test tubes will be left in the water bath for a minimum of 5 minutes prior to the beginning of the experiment. The effect of temperature is to increase the kinetic energy of the enzyme and substrate thereby increasing the number of successful collisions and increasing the reaction velocity. Hence it must be kept constant. No inhibitors / other promoters will be used . ...read more.

Conclusion

Using the iodine method the change in colour is often very slow, particularly in the reactions with a low concentration of chloride ions the difference in colour over a 15 second interval is almost undistinguishable. It is also possible that the perception of the endpoint colour could change over the span of several days in which the experiments took place. This could account for the apparent increase in rate from one day to the next. Another possible source of error could be from the solutions of amylase. The powdered form used was several years old and its activity may have diminished unevenly throughout. As a result of this the solutions used may have varied, and although the up-most care was taken to accurately produce consistent solutions, variation is most probable. In the time available a repeat of each experiment was possible which further validates the conclusions in the above analysis, however at least one more repeat would be suitable to provide proof that the trend described is correct. Overall it is possible to say that the experimental evidence is adequate to corroborate the conclusions made above. Further work to be considered other than repeating the experiment, would be to quantify the numbers of enzymes present in solution by calculating the relative molecular mass, and consequently analysis of the numbers of active sites present per enzyme molecule. This would also allow specific calculations of the equilibrium constant 'L' (the ratio of R - T state enzymes) to be made. Other allosteric proteins should also be investigated such as human haemoglobin to confirm that the hypothesis relates to all allosteric enzyme. ?? ?? ?? ?? Matt Wilson 1 01/01/02 ...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

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. Experiment to Investigate the Effect of Copper Ions on a Solution of Amylase and ...

    Once the enzyme and the substrate are joined they form an enzyme-substrate complex. The formation of an enzyme-substrate complex makes it possible for substrate molecules to be brought together to form a product. The product is released and the enzyme is free again to take part in another reaction.

  2. The Effect of Starch Solution on the Activity of Amylase

    Also what I noticed that the diluted to a tenth amylase solution had the longest time to reach its achromatic point. Thus showing that an increase in the concentration of amylase solution, the shorter the time it takes for it to reach its achromatic point.

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

    I predict that if an increasing concentration of NaCl is used with no change in volume of enzyme used, a saturation point may be reached. This is where the rate of reaction reaches a maximum and then it levels off due to saturation of enzyme active sites.

  2. for this experiment my main aim is to investigate the effect of temperature on ...

    For my experiment, my enzyme concentration is going to be constant. pH Concentration: pH is a measure of the acidity or hydrogen ion concentration of a solution. It is measured on a scale of 0-14 with pH values below 7 being acidic, values above 7 being basic and a value around 7 is neutral.

  1. How does the concentration of starch (substrate) affects the activity of amylase (the enzyme).

    After that, any further increase in temperature will result in the denaturation of the enzyme, and a steep drop in activity. The lock and key theory suggests that the substrate slots into the active site of the enzyme, and a reaction takes place which turns the substrate into its product.

  2. 'Investigating how temperature affects the rate action of the amylase enzyme on starch.'

    not be functioning (starch is still present; it's not being digested)-and so must be denatured. This proves that starch is present. If the starch was not present then the colour of the iodine would be brown. Gradually as the starch is digested the colour of the iodine when testing progresses from blue/black to brown.

  1. The effect of pH on an enzyme - Fungal amylase.

    The variables: There are four factors that affect the rate of the reaction. Increasing or decreasing any one of them has an effect on the rate of the reaction and the time taken for the reaction to be completed. They are: 1.

  2. The Effect of Substrate Concentration on the Rate of Reaction with Amylase

    The independent variable and the dependent variable. The independent variable is manipulated by the experimenter; in this experiment it is the substrate concentration. The dependent variable, on the other hand, should theoretically change in accordance to the value of the independent variable. In this experiment the dependent variable is the change in colour of the iodine when the enzyme-substrate mixture is added.

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