See how different concentrations of Hydrogen Peroxide and water affects how much oxygen is given off in froth measured in volume (cm3), from 5cm3 of minced pigs liver (which contains catalyse) when mixed.
Biology Investigation - Hydrogen Peroxide and Enzymes.
Aim of my investigation
To see how different concentrations of Hydrogen Peroxide and water affects how much oxygen is given off in froth measured in volume (cm3), from 5cm3 of minced pigs liver (which contains catalyse) when mixed.
Background information
Catalase is an enzyme found in all living cells. It makes Hydrogen Peroxide decompose into water and oxygen.
You can represent this in the equation:
2H2O2 =2H2O + O2
Enzymes: Enzymes are able to increase the rate of reaction without actually being consumed in the process. In all, enzymes are very efficient. Small quantities at low temperatures are able to produce results, which would require high temperatures and a violent reaction from any normal chemical means. Although increases in temperature may speed up the reaction, enzymes are unstable when heated.
There are three important definitions that are used when talking about enzymes: -
The substance that enzymes act on is the substrate.
The substance formed by the reaction is the product
The site on which the enzyme takes place is called the active site.
Enzyme 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.
All enzymes have the following 4 properties:
· All enzymes are proteins
· Enzymes are catalysts
· Enzymes are denatured by high temperatures
· Enzymes work best at a certain pH (normally 7)
The Effect of Enzyme concentration:
As long as the concentration of the substrate is much higher than the enzyme concentration, the rate of reaction is directly proportional to the enzyme concentration. This is because, as the enzyme concentration rises, the number of active sites that are available to interact with the substrate also rises, this raises the rate of product formation: -
Enzymes are also used in fermentation where yeast is used to produce alcohol.
Previous knowledge from homework:
Enzymes are biological catalysts capable of speeding up biochemical reactions in the cells of living organisms or in industrial processes. They are very specific, which means fewer unwanted by-products. Because they can catalyze a specific reaction many thousands of times over, only very small quantities are needed. Enzymes can replace harsh chemicals and save energy and resources. Being by nature proteins means that they are fully biodegradable after use. (A catalyst is a chemical, which allows a reaction to occur more quickly, without being involved in the reaction itself)
Simple Terms: A Type of Proteins found in living cells that regulates chemical reaction in the body and also speed up the chemical reactions of such things as metabolism.
What Factors affects the rate of enzymes controlled reaction?
The increasing of enzyme's (amylase) concentration causes the time for the completion of an enzyme-controlled reaction to decrease. The temperature is also another factor, which affects the rate of a reaction; one of the main ways to give reaction energy is to heat it. There also needs to be the right PH for the reaction to be carried ...
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Simple Terms: A Type of Proteins found in living cells that regulates chemical reaction in the body and also speed up the chemical reactions of such things as metabolism.
What Factors affects the rate of enzymes controlled reaction?
The increasing of enzyme's (amylase) concentration causes the time for the completion of an enzyme-controlled reaction to decrease. The temperature is also another factor, which affects the rate of a reaction; one of the main ways to give reaction energy is to heat it. There also needs to be the right PH for the reaction to be carried out, normally slightly alkali.
The best conditions for Enzymes to work in.
An enzyme will work best at a particular temperature and pH,
called its optimum conditions. Enzymes usually work best in warm conditions (around 40 °C) unlike chemical catalysts, which often work best when they are very hot.
A graph of enzyme activity plotted against temperature is shown below. Enzyme activity is a measure of how well an enzyme works as a catalyst.
Above 45 °C, the enzyme starts to be destroyed and stops working. In these conditions the shape of the enzyme changes and it is said to denature. A graph of enzyme activity against pH would have a similar shape but the peak (the optimum conditions)
would be at a different pH for different enzymes.
Pepsin in the stomach works best at pH = 2.
Amylase in the mouth works best at pH = 7.
Synthesis occurs when an enzyme combines several smaller molecules into a large one. Common examples include enzymes that help simple sugars combine to form polysaccharides, amino acids to form proteins, and nucleotides to form nucleic acids. In biological processes, this almost always involves the formation of water molecules from the 'leftover pieces', and so is called dehydration synthesis.
Hydrolysis occurs when a large molecule is broken down into smaller ones. Water molecules are used to 'seal the edges' of the new smaller molecules, so synthesis is the opposite of dehydration synthesis. Synthesis is also known as digestion.
Plan
For my experiment I shall be using the concentration of Hydrogen Peroxide and water as variables as I already know that temperature and pH have an effect on the production substances. The total volume of the substance accumulated before the reaction occurs should equal to 25cm3 and the liver is not a variable meaning it will always be 5cm3. I shall use the concentrations of 0cm3 HP- 20cm3 H20, 5cm3 HP- 15cm3 H20, 10cm3 HP- 10cm3 H20, 15cm3 HP- 5cm3 H20, 0cm3 HP- 20cm3 H20 so that there is a range of high to low results. From each result I will measure the amount of oxygen produced in the reaction by measuring the volume of froth using units of cm3. Each of these I shall repeat at least twice and then get an average. To make it a fair test, I will clean and dry the equipment used at every interval between concentration changes. I will keep the temperature and PH level the same throughout the experiment and making sure volume always measures up to 25Cm3.
Prediction
I predict that as I increase the concentration of undiluted hydrogen peroxide (more HP then water) the amount of oxygen produced should increase accordingly. I also have a theory that temperature affects the rate of reaction, the warmer the conditions to its threshold (approx 40oC) the faster the reaction. If you succeed 40oC, I would think it would begin to be denatured, but this is not to be dealt with in this experiment but I will come back to this later.
Apparatus
* 50cm3 Minced Liver (divided into 10 different experiment)
* 1 Bottle of 3 Hydrogen Peroxide
* 2 Measuring cylinders
* Safety goggles
We use the safety goggles to eliminate the risk of getting hydrogen peroxide in the eye. We use measuring cylinders to make measuring the amount of oxygen produced in froth easier as well as the amount of water and Hydrogen peroxide. There are variations of size in the measuring cylinders, I intend to use the 150Ml for the lower Hydrogen Peroxide experiments and will extend to the 250Ml measuring cylinders for the higher amount of hydrogen peroxide present in experiments.
Diagram
Safety
Risk
Preventative Actions
Hydrogen Peroxide irritant
Wear goggles, Care when dispensing, Mop up spillages, wash of spillages quickly.
Tube breakages
Wear goggles, clear up immediately after breakage occurs.
Rushing and carelessness
Take time with procedures and pour and observe cautiously.
Method
I shall start by setting up my apparatus as in the diagram below. I would then put 5cm3 of minced liver into measuring cylinder A and put to one side. I would then get measuring cylinder B and insert the first variable, which would be the amount of hydrogen peroxide. I would do this by putting in pipette fills into the measuring cylinder until the desired amount is met which in our first experiment is 5cm3. I would then go over to my water supply and fill the amount left over to reach the deficit which in this case would be 15cm3. Once this is done we then pour the contents of measuring cylinder B into measuring cylinder with our goggles worn. I then measure the volume of oxygen produced in froth triggered by the reaction by looking at the centimetre markings on the cylinder and record it. Once this is done I wash out all the contents and dry to its original state. I then carry out the exact same procedure changing the amount of each variable, one this is done I carry out each experiment again and record the results and look out for any anomalies.
A B
Measuring cylinder
Results
Results table
VOLUME OF 2H202 (CM3)
VOLUME OF WATER (CM3)
VOLUME OF CATALASE (CM3)
VOLUME OF OXYGEN PRODUCE (CM3)
ST RESULTS 2ND RESULTS 3RD RESULTS
0
20
5
2
.5
5
5
5
27
26
26.5
0
0
5
55
70
62.5
5
5
5
64
68
66
20
0
5
78
75
76.5
Analysis and conclusion
I have found out that the higher the concentration of hydrogen peroxide, the higher amount of oxygen produced. We can see this from out graphs and results table. From looking at our results table we can see a fairly steady pattern with a slight blip, which I will come onto in my evaluation. It show that the more diluted the concentration is, the weaker or slower the reaction, and less oxygen is produced on sight. This is because as the concentration of hydrogen peroxide is increased, there is a larger surface area on which the enzyme (catalyse) can work upon..
Now, if we look back to my prediction we will see that there were no differences from my prediction and my actual results, this was because I used the right amount of each substance and my experiment went well enough to produce the results I expected.
If we examine the line of best fit we can see it is a beautiful curve and shows the experiment went well, we see the steady increase of oxygen produced as the hydrogen peroxide levels are increased, a very pleasing result.
Evaluation
The experiment went well, this is because I had only single anomalous result, and the general results agreed with my prediction. I think I had accurate results as they were as I predicted and also there were no abnormal patterns that occurred. If I were to make one improvement on my method, it would be to have a larger range of concentrations of hydrogen peroxide and water to prove that the results continue proportionally. I feel the reason for my anomaly must have been a lapse in concentration and the repercussion of this is an abnormal result. We can clearly see this does not fit with the general chain of results and can clearly be defined as an anomaly. I feel that if I had used a larger amount of catalyse for my experiment such as 10cm3- 20cm3, I would see if the same pattern happens and to see if the general reaction is the same with larger amounts of the liver (catalyse)
Future investigation
I could further my understanding on factors which affects catalyse reactions by doing an experiment on temperature Influence.
My prediction would be that the enzyme will become denatured, and therefore will work at a slower rate after 40 - 45oC. I think the reason for this prediction is because every enzyme has a temperature range of optimum activity. Outside that temperature range the enzyme is rendered inactive. This occurs because as the temperature changes enough energy is supplied to break some of the molecular bonds. When these forces are disturbed and changed the active site becomes altered in its ability to accommodate the substrate molecules it was intended to catalase. Most enzymes in a human body shut down beyond certain temperatures. This can happen if body temperature gets too low (hypothermia), or too high (hyperthermia).
My aim would be to find the affect of temperature on enzymes, using a potato as a catalyst. The source of catalase is in the potato cells.
The key variables would be:
- Heat
- pH
- Time for a dye to reach a certain mark
- Concentration of enzyme of substrate
- Potato
- The surface area of the potato
I hope to carry out this experiment in the near future and fully understand another factor that affects enzyme activity.
By Arif Shahed Sidique Zaman 10HR
