An investigation into the rate of reaction of the enzyme urease.

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An investigation into the rate of reaction of the enzyme urease

Introduction

Enzymes are protein molecules produced in living cells. They act as biological catalysts. They are specific to certain reactions, and so they only operate within narrow temperature and pH ranges.

Urease is an enzyme that breaks the carbon-nitrogen bond of urea to form ammonia and carbon dioxide.

This can be represented in the equation:

Urea                         urease                  ammonia         +         carbon dioxide

(NH2)2CO                 urease                   NH3                +                CO2

The rate of reaction of the enzyme can be affected by the following variables:

a) pH: at too high pH, the enzyme is denatured due to the loss of H+ ions. The same applies for too low a pH level, where too many H+ ions would attach to the negative regions of the enzyme, changes its shape and causing it to denature.

b) Concentration of enzyme: The higher the concentration, the higher the rate of reaction will be. With a larger number of urease molecules, the chance of successful collisions between enzyme (urease) and substrate (urea) will be increased. This is the factor which I will be investigating in my experiment.

c) Surface area: Again, the greater the surface area, the greater the rate of reaction will be. So with a larger surface area, there is more chance of successful collisions between the urea and the urease taking place.

d) Temperature: An increase in temperature will speed up the rate of reaction because the reacting molecules have more kinetic energy, so more collisions are likely to take place. However, enzymes have an optimum temperature range, beyond which the kinetic energy of the enzyme and water molecules is too great for the structure of the enzyme molecule. This starts to disrupt its shape and denatures the enzyme. The optimum temperature is usually around 45°C.

Prediction

I predict that as the concentration of the urease becomes weaker, the time taken for the reaction to be completed will increase, ie the rate of reaction decreases as the concentration is more diluted. This means that as the concentration is increased, the rate of reaction also increases.

As the enzyme concentration is diluted so that there is a greater substrate concentration, the rate of reaction will decrease. This is because the number of active sites available will all be reacting with a substrate with the maximum number of reactions being done at once. Any extra substrate molecules have to wait until some of the active sites become available, until which, the rate of reaction will no longer go up.

The way in which enzymes function can be explained by the lock and key hypothesis. The active site of an enzyme (the lock) has a specific shape in which only the precise amount of substrate (the key) will fit – forming an enzyme-substrate complex, therefore producing a product.

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The substance that enzymes act on is the substrate. The substance formed by the reaction is the product and the site on which the enzyme takes place is called the active site.

The diagram below shows how the enzyme and substrate work together to form a product:

I will produce graphs to display my findings which will help me to analyse my results and draw suitable conclusions. I have prediction that the rate of reaction will increase as the concentration is increased. I also predict that ...

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