Effect of different size beads on the activity of immobilised catalyse

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Effect of different size beads on the activity of immobilised catalyse

Aim: To find out how varying the size of beads containing yeast varies the rate of activity of catalase in a fermentation reaction of hydrogen peroxide with immobilised enzymes.

A catalyst is a substance that speeds up the rate of a chemical reaction, without itself being used up in the process however it maybe affected physically i.e. degradation of the surface of the catalyst. Catalysts work by reducing the activation energy needed for a particular reaction by offering a different path for the reaction to take place. Activation energy is the energy, which needs to be supplied before a reaction can occur, basically the amount of energy needed to overcome the bonds between the molecules and atoms.

Catalysts are usually specific to one reaction, that is, different reactions need different catalysts. This is the lock and key theory however there is another theory as well called the induced fit theory. Since a catalyst is not used up during a chemical reaction, it can be used over and over again to convert reactants to products. 

In this experiment I will be using the immobilised enzyme yeast. When an enzyme is immobilised in this case it is encapsulated in a sodium alginate gel. When an enzyme is immobilised it is in a more stable state, they are better able to resist alteration to shape and activity. In particular they are less likely to be inactive or denatured by changes in pH, presence of other chemicals, or high temperatures. Immobilised enzymes can also be used for longer periods before their activity reduces which is useful in the experiment as the rate must stay the same otherwise after a certain amount of the time the results would become invalid as some enzymes rates would decrease at a slower rate then others.

Lock and Key theory

Enzymes are specific to a particular substrate molecule or a restricted group of substrate molecules.

Surface area to volume

Smaller organisms have larger surface area to volume ratio’s (surface area divided by volume) than larger ones. In principle the greater the surface area, the more active site in contact with the substrate therefore it increases the rate of reaction, and the thinner the separating layers. Another factor to consider is the larger the volume of the drop the more enzymes it contains inside it.

BACKGROUND:

Catalase (the enzyme) is found in yeast, it breaks down hydrogen peroxide (the substrate) into water and oxygen according to this equation.

2H2O2(aq) -------------------> 2H2O(l) + O2(g) + catalase(aq)

One molecule of catalase can break 40 million molecules of hydrogen peroxide each second.

Factors that affect the rate of reaction

  • Increasing the temperature increases the kinetic energy at which the enzyme and substrate collide. Increasing the average energy of each particle meaning that more particles have enough energy for the particles to collide and bond. However this effect is short lived as most catalysts have a specific heat temperature range above or below that will slow down the rate of reaction, or even cause denaturisation where the active site of the enzyme in this case is changed beyond repair and wont bond with the substrate.

  • Increasing the concentration of substrate or enzyme means that the number of enzymes/substrate with enough energy to collide and bond together increases.
  • Changing the ph to the optimum ph can also effect the rate of reactivity of the Catalase enzyme the ph affects the electronic charge on the active site; the charge helps attract the substrate to the active site.
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Prediction: Increasing the bead size decreases the rate of reaction i.e. proportional assuming no other limiting factors. Graph above

I aim to keep all of the variables the same. There are many factors, which can increase the rate at which an enzyme works at. These include the following:

  • Light (which pigment of light) green, red or blue
  • Size of beads and ration it is made at
  • Wind, no wind in classroom
  • Experiment placed in water-bathes to control the temperature.
  • The concentration of enzyme yeast and the amount of hydrogen peroxide
  • Use a stopwatch ...

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