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Aim: To investigate Urease activity and the effect of two other chemicals which are Lead Nitrate, and Thiourea (CS (NH2)2
Urease is an enzyme that catalyzes the hydrolysis of urea as shown below:
CO (NH2)2 + H20 CO2 + 2NH3
Ammonia releases and dissolves in water to form ammonium hydroxide, which is a strong base.
NH3 + H20 NH4+ OH-
The level of alkali can be then used as a measure of the speed of the reaction. Universal Indicator solution will be used to measure this.
What is the effect of lead nitrate and thiourea activity?
Volume of urea, urease, lead nitrate, thiourea, distilled water, Temperature
I predict that at the conclusion of the experiment Thiourea will function as a modest inhibitor. Because it has a similar molecular formula to Urea, the substrate for the enzyme, so then there will not be sufficient substrate created or even there will not be any substrate formed at all for the Thiourea that would prevent the urea from reacting with the urease. Still, with the addition of Lead Nitrate, increasing the concentration will lead to excess substrate. The lead nitrate will then attach to the urea to destroy the active site to counteract any more ammonia from forming.
Materials and apparatus
6 Boiling tubes
Test tube rack
Label boiling tubes from 1-6
In the boiling tube labeled 1, add 2cm3 of buffer solution, 5cm3 of Urea and 5cm3 of distilled water.
In the boiling tube labeled 2, add 2cm3 of buffer solution, 5cm3 of Urea, 2.5cm3 Thiourea and 2.5cm3 of distilled water
In the boiling tube labeled 3, add 2cm3 buffer solution, 5cm3 of Urea and 5cm3 of distilled water.
In the boiling tube labeled 4, add 2cm3 buffer solution, 5cm3 of Urea, 2.5cm3 of lead nitrate and 2.5cm3 of distilled
In the boiling tube labeled 5, add 2cm3 of buffer solution, 5cm3 Urea and 5cm3 of lead nitrate.
In the boiling tube labeled 6, add 2cm3 of buffer solution, 5cm3 of Urea and 10cm3 of distilled water
Add 5 drops of the universal pH indicator to each boiling tube
Add 5cm3 to the boiling tubes labeled 1-5 and mix completely
Using the color scale, find the pH changes in the course of the experiment
Record pH changes in each container using the pH probe with the data logger at a 5 minute interval or20 minutes
Mix the content of each boiling tube from time to time
Record all the other relevant observations.
Table showing the results of the effect of the addition of lead nitrate and thiourea on urease activity
pH in each boiling tube
Graph showing the results of the effect of the addition of lead nitrate and thiourea on urease activity
Before Urease was added pH was 5.3.When Urease was added to the first boiling tube it turned green after 5 minutes with a little fizzling at the top of the solution, also the pH in the first boiling tube increased as the time increased. When urease was added to the 2nd boiling tube it also turned green with after 5 minutes with no fizzling at the top of the top of the solution. As time increased so did the pH in the second boiling tube. When urease was added to the 3rd boiling tube it turned green within 5 minutes and also as the time increased with the urease inside the boiling tube its pH also increased with a little fizzling at the top of the solution. When urease was added to the 4th boiling tube it turned peachy orange and also as the urease was being check for its pH it decrease as the time was increased with a lot of fizzling in the boiling tube. When urease was added to the 5th boiling tube