Animals use enzymes in their digestive systems to break down foods into their simpler components so that the body can readily absorb them. Plants use enzymes in photosynthesis, the process by which plants obtain their food from sunlight. Enzymes also help plants and animals get energy from food. Energy is freed from digested food by oxidation in the individual cells of a plant or animal. In this process, oxygen, usually obtained from air, receives electrons from the breakdown products of sugars, fats, or proteins to liberate the energy they contain. In living things, oxidation must take place slowly to minimize destructive heat. It does so through a series of enzyme-controlled reactions that release heat and energy step-by-step in small amounts.
Since enzyme molecules are far larger than those of their substrates, their catalytic action occurs only at a small active site on the enzyme. The substrate and the enzyme fit together at the active site like a lock and a key. This accounts for an enzyme's specificity for a particular substrate. Then the chemical bond holding the substrate together is weakened in the enzyme-substrate activated complex, and the substrate molecule is broken down into smaller products. After disengagement, the enzyme is free to perform its catalytic action again. If a coenzyme is needed to reduce a substrate it floats to the basic enzyme molecule when a reaction is about to take place, links with the enzyme and substrate, and then disengages itself from the enzyme when the biochemical task is finished.
Many enzymes are catalysts in reactions that build molecules. In a similar lock-and-key fashion, they fasten smaller molecules together.
Enzymes are formed at cell sites called ribosome’s. Amino acids, the building blocks of proteins, are brought to the ribosome’s and strung together in a precise manner to form the enzymes. These then float free within the cell or into nearby body areas where they are needed. The genetic code that determines protein structure also directs the amino-acid sequence of enzymes. The genes of a species control the kinds of enzymes its members make. (See also Genetics.)
Enzymes that exist in nature are usually named for their substrates, with the suffix -ase added on. The enzyme lipase, for example, acts on fatty lipids. However, some of the first enzymes discovered were not named in this way. Among them was the enzyme pepsin, which breaks down proteins.
Enzymes are divided into six categories based on their function. The hydrolase’s usually split their substrates with the aid of water. The lyases split their substrates without aid. The transferases transfer chemical groups between different molecules. The isomerases rearrange the molecules of their substrates. The oxidoreductases transfer hydrogen ions. The ligases, or synthetases, help release energy.
In the 1980s it was discovered that two new agents previously unassociated with enzymes, RNA (ribonucleic acid) molecules and antibodies could be manipulated to act like enzymes. American researchers Sidney Altman and Thomas R. Cech were awarded the 1989 Nobel prize for chemistry for uncovering the fact that catalytic RNA molecules, called rimzymes, could cut and splice themselves. Antibodies that act like enzymes to speed up reactions within the human body were detected by researchers in California and were named abzymes. In 1988 researchers at a Canadian biotechnology firm, who discovered that the enzymes remain stable at very high temperatures, isolated two new enzymes of the cyclodextrin glycosyltransferase kind. (See also Biochemistry; Digestive System; Organic Chemistry; Fermentation.)
This information above is from an interactive encyclopaedia.
Predictions
I made two different predictions for my experiment. I will tell what they were and my reasons for choosing them.
- I think if you increase the temperature, it will increase the reaction in the experiment. I thought this prediction would be a good educated guess of what I thought was going to happen in the experiment because usually when you increase the temperature in a number of different objects the molecules inside will become excited causing more activity. This is what I thought was going to happen in this experiment. I have drawn a graph of what I think will happen at the end of this experiment for this prediction.
- I think that the experiment will work best at 37°C. I have said this because 37°C is usually the temperature of body heat. With catalase being an enzyme in the body it will be designed to work best at body temperature, this is my reason for picking this prediction. I have drawn a graph of what I think will happen at the end of the experiment for this prediction.
This graph of prediction 2 could do two things so I have drawn them both on, labelling them 1st possibility and 2nd possibility.
Procedure
Fair Test
I made my experiment a fair test by doing different things. In the following information it will explain how I made it a fair test and why did the procedure made it a fair test. Here is a list of how I made it a fair test:-
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I used the same amount of H2O2 - which was 50cm² - so that I gave each experiment a fair chance to give off possible different readings, but in the same procedure.
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I used the same amount of potatoes. The length for each potato was 41/2 cms and I used three of them. I made sure that they were all the same length by measuring them with a ruler. I made sure they were all the same thickness by cutting them with a cork borer.
- I also used the same amount of time in each experiment to see how much oxygen would be captured from the potatoes. Five minutes seemed a sufficient amount of time because its not too short so that insufficient oxygen would be caught and not too long that it seemed like forever to get one piece of information and was prolonging the procedure to an unacceptable level.
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I used the same types of apparatus in each experiment. If I used different types of equipment I might have got different results, for example if I used a different sized beaker with the same amount of pieces of potatoes and H2O2 in, the H2O2 might have only covered the bottom of the beaker, therefore only touching the bottom of the pieces potatoes which might have effected the reading of oxygen.
Safety
For the safety it was different because it wasn’t just me I was thinking about, I was in a classroom full of students so I had to think about their safety as well as mine. I did the usual safety procedures such as:-
- I wore goggles to protect my eyes.
- My tie was tucked into my shirt so that I didn’t knock anything over.
- I was being sensible, which would help the other students concentrate causing them to make fewer mistakes. Me not messing about also helped me a lot too because it meant that I could move onto the next experiment much quicker.
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I washed my hands straight away if I got H2O2 on them.
- I had all the equipment I needed close to me so I didn’t have to stretch to reach for any of them.
As well as the normal safety procedures you have to follow whilst working in the laboratory, I did the extra safety procedures that were appropriate for this experiment. These are a list of the extra safety procedures I followed:-
- I sat near a sink so that I would not have to walk very far with a full container of water, causing less chance of spilling the water, which means no one will slip over and injure themselves.
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After I had done each experiment I emptied the beaker containing the potato pieces and the H2O2 into a jug instead of pouring it down the sink. If I did pour it down the sink it could have caused a blockage.
The Experiment
Results/Conclusion
I did this experiment three times because I had problems with the results I obtained. Now I will tell you what problems I encounted and how I overcame them.
My first set of results weren’t very accurate and didn’t show any relationship between them at all as you can see in this table of results:-
I have no idea of what went wrong. The only thing I can think of is that it was the first time I had done the experiment and I didn’t know what to do.
I then decided to repeat the experiment completely and start again the second set of results were better than first but not as good as I would have hoped for:-
As you can see it was going good up until 40°C, but then it started to increase again. I think I left the timer on longer than five minutes, which would have corrupted my experiment.
I decided to do the experiment a third time but if I do something wrong this time I would not start the whole project again I’ll just repeat the one(s) that are not right. These set of results were the best ones:-
These results were perfect apart from a couple. I only repeated the ones that were wrong, so I had constructed a very accurate table of results from which I can draw a good graph.
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Here is the graph for results 3:-
Evaluation
Equipment Used
2 Plastic containers.
A glass container.
A glass-measuring beaker.
A long, thin, plastic measuring container.
A rubber cork.
A straight, thin tube.
A straight, thin tube with a bend going up at a 45° angle.
A straight, thin tube with a thistle shape in the end.
A rubber bandage type device that connects two things together.
Method
I will now tell you in what order and what way I did my experiment:-
- I got all the apparatus I needed to complete my experiment.
- I filled the two plastic containers with water, one with cold water and one with water at the correct temperature for that part of my experiment.
- I then stood a glass beaker inside the plastic container holding the warm water.
- I cut the pieces of potato and put them into the glass beaker that was standing in the warm water.
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I measured 50 cm2 of H2O2 and poured it into the glass beaker with the potato pieces in, bubbles came off the pieces of potatoes all at once, I waited until the rapid bubbling had finished. Then I put the long, thin measuring beaker over the thin tube with a bend at the end to measure the amount of oxygen caught. The way this happens is the long, thin measuring beaker is full of water, turned upside down over a tube that lets oxygen into the long beaker forcing water out of the thin beaker and into the plastic container. The following diagram shows how the experiment was carried out and how the equipment was set up.
- I restricted the timing of the experiment to five minutes for each test. I took the thin tube, but carefully keeping it under the water not letting any of the oxygen escape. Then I took the reading and recorded it into a table.
Analysis of the results obtained.
The results I obtained the first and second time I did the experiment were not how I would have liked them to be. The first set of results were not very accurate and didn’t show any relationship between them at all. They were all over the place. The second set of results was better but again not acceptable for what I wanted to do with them. The third set of results were the best because they showed the amount of oxygen given off increasing, peaking and then decreasing. There were two results that didn’t quite meet my expectations so I decided to repeat those ones. I got good enough results from those minor tests and was able to produce a really good set of results, which means that I will be able to produce an accurate graph with at least six points.
Were my predictions right?
When I compared my predictions with my results it seemed that my second prediction was right. The graph of my results did peak at around the 37°C but then dropped, which is what I said would happen on the second possibility that I drew on the graph titled prediction 2.
What I learned from the experiment?
The things I learned from this experiment are:-
- Perseverance, if something happens differently than what you had planned, keep trying and eventually you get what you had hoped for.
- If you put your mind to it you can produce a good set of results, graph and a good piece of coursework.
- Safety comes first in every experiment that you do.
- It helps to plan everything before you do it.
Exctracted from Compton’s Interactive Encyclopedia.
