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
- Time Interval
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
- 50cm3 beakers
- 5cm3 syringe
- Stop watch
- Lead nitrate
- pH buffer
- Distilled water
- Universal indicator
- Data logger
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.
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
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A strong base was formed when urease was added to solution 1 and 2, for the urease catalyzed the reaction of urea and water whiles the buffer offered an acidic channel in order to get the reaction to respond. In solution 1 the urea and the distilled water has provided ammonia with the aid of the urease enzyme. In solution 1 and 2 we see that the solution becomes stronger as the time increases but solution 1 became stronger as the time was increased to 20 minutes this shows that the addition of thiourea brought the pH of the base produced a little and not too much so then the activity of the urease was not in anyway affected by thiourea because the urease still catalyzed the reaction of urea and distilled water. Solution 3 started out as a strong acid, the pH of solution 3 rose above solution 1 and 2 due to the presence of distilled water, which made the urease react properly with urea and the ammonia, which dissolved in water to produce a strong base. Solution 4 started out as a weak acid but the addition of urease neutralized it, the pH of 3 did not rise as much as 1 and 2 due to the absence of the distilled water in order for the urease to properly react with the urea and the ammonia to dissolve in the water and produce a strong base. The product of the reaction was also not able to properly stabilize to become a strong base due to the absence of water. Unlike the thiourea, lead nitrate had a major effect on the activity of urease, although 4th and 5th test turned peachy, they have different pH. The 6th test, which was the control, the 5th test was lower than it.
I contemplate that, overall the experiment was fair. There might have been some measurement errors but it wasn’t that serious in order to make the experinment erroneous and unrealiable.
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