Enzymes are biological catalysts that speed up chemical reactions, without being used up or changed. Catalase is a globular protein molecule that is found in all living cells. A globular protein is a protein with its molecules curled up into a ‘ball’ shape. All enzymes have an active site. This is where another molecule(s) can bind with the enzyme. This molecule is known as the substrate. When the substrate binds with the enzyme, a product is produced. Enzymes are specific to their substrate, because the shape of their active site will only fit the shape of their substrate. It is said that the substrate is complimentary to their substrate.
When the substrate binds with the enzyme, it forms an enzyme-substrate complex. The reaction happens immediately after and the substrate is broken down in to either two or more products causing a catabolic reaction. Or two or more substrates are bonded to make one product causing an anabolic reaction.
There are five factors that effect enzyme activity. They are:
The factor I am changing is surface area of potato containing Catalase. By increasing the surface area of the potato, you make more Catalase molecules be exposed to hydrogen peroxide. This will result in the rate of reaction increasing because it increases the chance of more successful collisions between the enzyme and the substrate.
... the Hydrogen Peroxide and Catalase solution, the less effective the reaction will be. THE EQUATION SUBSTRATE ENZYME PRODUCTS 2 HO Catalase 2 HO + O ... as much as it would with a lower temperature. Enzyme molecules can take a little while to denature, even over ... are the faster the reaction. The same can be said for reactions controlled by enzymes, but because enzymes are proteins if the temperature ...
Catalase is an enzyme found in food such as, potato. It is used to break down a poisonous by-product of metabolism called hydrogen peroxide. hydrogen peroxide is a compound that can kill cells therefore; it is essential that our body can break it up. Catalase breaks down hydrogen peroxide into oxygen and water.
Below is the reaction equation for the decomposition of hydrogen peroxide.
To increase the surface area of potato, I will be cutting them into smaller pieces. Therefore, I predict that the greater the surface area of potato, the greater the rate of reaction. If you increase the surface area, you are exposing more Catalase molecules to the hydrogen peroxide. This increases the chances of successful collisions between the enzyme and the substrate. It can also be said, that if I was to double the surface area, I would double the rate of reaction.
However, there is a certain extent when there will be no further reaction. This is because a substrate molecule will occupy all the enzyme’s active sites. Therefore, it will not matter how much you increase the surface area, there is not enough substrate molecules, to bind with the active site. This statement is only in theory.
As mentioned before, there are five factors that effect enzyme activity.
Temperature – The temperature is partly responsible for how slow or how fast as chemical reaction takes place. If you increase the temperature, the faster the molecules move. This causes more enzyme and substrate molecules to collide. The more collisions there are, the higher the chance of a substrate molecule temporarily binding with the active site of the enzyme. It could be said that the higher the temperature, the faster the rate of reaction. This is true, until a certain temperature. This is known as the optimum temperature. The optimum temperature is where the conditions are perfect for the enzyme to work. Therefore, the result of the optimum temperature is the maximum amount of product created.
There are two different ways in which a substrate can bind to an active site. The first way is through the lock and key model. Certain substrates can bind only to certain active sites in the lock and key model. This is called the lock and key model because the active site is like the lock and the key is the substrate. Only certain keys can open certain locks. This accounts for the specificity; not ...
Once the optimum temperature is reached, the rate of reactions decreases. This is because the temperature is too high and the enzyme molecules begin to vibrate so violently that the delicate bonds break. These broken bonds are irreversible because it changes the shape of the enzyme. The substrate can no longer fit with the enzyme and so no reaction occurs. This is known as the enzyme being denatured.
Most human enzymes have an optimum temperature of 40ºC. Therefore, it will be important to keep temperature below 40ºC. I will be conducting the experiment in a classroom, so it will be unlikely that the temperature will rise that high. However, temperature difference can affect the experiment. To prevent this, I will conduct the experiment at the same time of day if more than one day is needed. This is because it is generally colder in the mornings and evening than the afternoon.
Also, I will hold the test tube by the tip. If I were to grab the test tube with my whole hand, my body heat would be passed onto the test tube causing a temperature increase. Therefore, not creating a reliable set of results.
pH – Enzymes also have an optimum pH level. The pH of a solution affects the enzyme’s secondary and tertiary structures. These bonds make the shape of an enzyme’s active site. So, if these bonds are broken, the shape of the active site changes and is distorted. If there is no active site, there is no reaction resulting in no products. If the enzyme is put in a pH that is very different from the optimum pH, it can cause the enzyme to denature.
Most enzymes have an optimum pH of around 7, which is fairly neutral. To ensure the experiment is a fair test, I will use the same pH of hydrogen peroxide in every test.
Inhibitors – As mentioned earlier, enzymes have an active site specific to the substrate molecules. However, it is possible for other molecules similar to enzyme’s substrate to bind with the enzyme’s active site and therefore, inhibit the enzyme’s task.
When the inhibitor binds with the enzyme’s active site for a short space of time it is known as competitive inhibition because it is competing against the substrate for the active site. It can be said for this inhibitor to be reversible because if you increase the concentration of the substrate it is more likely that the substrate will collide with an active site, not in use.
Write an explanation of how any two factors affect the rate of an enzyme-controlled reaction. How do these factors affect the chemical structure and properties of the enzyme. Many things can affect the rate of enzyme activity. The temperature of the enzyme, the pH of the solution, the concentration of the enzyme, substrate and the product. Also, another affector is the number of competitive and ...
There are also inhibitors that remain permanently bonded to the enzyme’s active site. Therefore, it is not accessible to the substrate resulting in no reaction. These are known as non-competitive irreversible inhibitors. This is because it does not matter how much substrate is added, their active sites are still occupied by another molecule.
Some inhibitors can bind to another part of the enzyme rather than the true active site. This can disturb the normal arrangement of hydrogen bonds causing a change in the shape of the enzyme. Therefore, the substrate can no longer fit in the active site of the enzyme. This can be reversible or irreversible. It depends on whether the inhibitor bonds with the enzyme briefly or permanently.
To ensure a fair test, no extra products will be added to the solution. Only hydrogen peroxide and potato will be present. This should prevent any molecules inhibiting the enzyme’s activity.
Substrate concentration – The general rule for substrate concentration is, the more substrate present in solution, the faster the initial rate of reaction. The initial rate of reaction is the first 30 seconds of the reaction. This tends to be the steepest part of the graph when the results are displayed. This is because when the enzyme and substrate are first mixed together there are large quantities of both present.
After the initial rate of reaction, the reaction will begin to slow down. This is because as the reaction takes place, the amount of substrate available gets fewer. The reaction gets increasingly slower until it eventually stops.
There is a certain point when it does not matter how substrate you add to the solution. This is because all the enzyme’s active sites are already occupied. It can be said that the substrate molecules are ‘queuing’ up, waiting for an active site to become vacant. The enzyme is currently working at its maximum rate. This is known as its Vmax.
To make sure that the substrate concentration stays constant, I will use the same bottle of hydrogen peroxide, with the same concentration. This is to prevent any changes in my results that are not part of the experiment.
Effect of changes in substrate concentration on the reaction rate of an enzyme IB biology Internal Assessment 3/23/12 Research Question: Effect of changes in substrate concentration amount on the reaction rate of an enzyme Introduction: In this experiment, the substrate is hydrogen peroxide. The purpose of this investigation is to find out the relationship between the substrate concentration and ...
Enzyme concentration – The general rule for enzyme concentration is, the more enzymes present in the solution, the faster the initial rate of reaction. The amount of product produced will be steepest in the initial rate. This is because at the beginning of the reaction, this is where the concentration of both the enzyme and the substrate are the highest.
I do not want to vary the enzyme concentration in this experiment because that is not what I want to be testing. I will be using the same mass of potato for each experiment. I will use the same equipment to create the same mass of potato. All I will be changing is the surface area. I will be keeping change to a minimal because the fewer things you change, the more likely your results will be accurate.
Scalpel/cork borer- These pieces of equipment are sharp and come with a protective cover. When the protective cover is removed for the experiment, great care should be taken when using it to prevent injury to others and myself.
Glassware- All glassware can be easily broken so it is essential to take great care when handling it.
Hydrogen Peroxide- Hydrogen peroxide is an oxygen agent. This means that when it decomposes, oxygen is released. So, when putting the cap back on the bottle, it is important to leave it silently off. If it was done up tightly, the bottle would explode. Also, hydrogen peroxide is irritable on the skin and eyes so care will be taken not to spill any.
Safety Goggles- These will be worn when handling the hydrogen peroxide to prevent the solution from going into our eyes.
Laboratory Coat- This will prevent hydrogen peroxide spilling onto my clothes and some of my skin.
Doing a preliminary experiment is important because this is the time when you can see how accurate your method is. Preliminary work will indicate to me what size potatoes I should use, how much hydrogen peroxide to add for the reaction, and how often I should take down a reading. These are just some of the things preliminary work checks for. I did not do the whole experiment in my preliminary work because it was not necessary. I did the part of the experiment that would produce the smallest amount of oxygen (5cm length).
An investigation to compare the reaction rates between potato and hydrogen peroxide against liver and hydrogen peroxide through loss in mass. Background information: Catalase is an enzyme that is found in all cells. This means that it is an intracellular enzyme. And enzyme is a biological catalyst. A catalyst is some thing that speeds up a reaction without being changed itself. Because of this ...
This is because it would take the longest time to produce any oxygen. This will give me a good indication on how much time should be spent on each test.
Looking at my results, the first thing I noticed was the first results of 1.7ml”. This figure is considerably higher than the other results. This could be due to when I put the bung on the boiling tube the air that is already present in the delivery tube gets pushed out. This has obviously affected the results. Therefore, the next time I do the experiment I will have to place the bung on first, then put the delivery tube in the burette.
I believe that taking a reading at every minute is not good enough. The next time I do this experiment I will be taking a reading every thirty seconds. This will show a better scale of how the rate of reaction increases.
I believe that a 5cm length is a good length because the reaction did not happen too quickly that I was not able to take a good reading. Also, it wasn’t too small because I was able to receive a substantial reading.
The amount of hydrogen peroxide I used was a good amount and I will be using that for my experiment. I know is was a good amount because after I had stopped timing, the reaction was still going because I could still see bubbles of oxygen being released. I made sure that the hydrogen peroxide covered the potato fully to ensure that all the exposed pieces of potato were available to the solution.
Bung- Prevents oxygen from being lost into the atmosphere. It ensures that any oxygen given off goes through the delivery tube.
Delivery Tube- Delivers the oxygen from the boiling tube to the burette.
Boiling Tube- The reaction between the potato and hydrogen peroxide takes place here. I decided to use a boiling tube rather than a test tube because a boiling tube is bigger. Therefore, more area of the potato is available to the hydrogen peroxide. Also, it ensures that all pieces of potato can fit into the tube.
Light reactions in photosynthesis involve the absorption and use of light. The reactions take place in the thylakoid membrane where chlorophyll and other kinds of smaller organic molecules are present. There are two types of photosystems, photo system I and photo system II. The reaction center in photo system I is knon as P700 and the reaction center in Photosystem II is P680. The splitting of a ...
Clamp Stand- Hold the burette securely in its place.
Burette- Collects oxygen from the reaction. I chose to use this piece of apparatus because it measures accurately to 0.1ml”.
Cutting Tile- Safe area to cut potato onto. Prevents me from cutting the table or myself.
Cork Borer- Cuts the potato in a cylinder shape. This is the most accurate way of cutting the potato because the circumference stays the same all the way through. The diameter of the cork borer will always be 14mm.
Scalpel- This is a sharp but accurate piece of apparatus. This is better than a normal knife because it has no teeth. With teeth this would increase the surface area making the experiment an unfair test.
Ruler- Measures length of potato accurately. The potato needs to be cut at different lengths for different tests.
Tub- Fill the tube with water.
Distilled Water- I used distilled water rather than normal water from the tap. This is because water from the tap collects bubbles on the side of the burette. This can make it harder to record results as shown in the preliminary work.
Stop watch- This will time accurately how long the experiment will go on for.
Syringes- Accurately measures the volume of hydrogen peroxide solution to add for the reaction. Therefore, the volume of the solution will be the same in each test.
Potato- In the potato is the enzyme Catalase. Without the potato, there would be no reaction. Different amounts of potato will be used for this experiment because I am going to be testing for surface area. A total length of potato will always be 5cm.
Hydrogen Peroxide- This is the substrate used in this experiment. 20cm” of this solution will be used for each test.
·Put on and wear any safety equipment.
·Set up apparatus and fill the tub with water.
·Fill the burette with distilled water making sure that tap on the burette is closed. Turn the burette upside down and into the water. Use the clamp stand to hold securely.
·Place the potato on the cutting tile and cut a cylinder of potato out using the cork borer.
·Using the ruler cut the potato to the right length. At this point make sure that there is no skin on the potato because this will affect the results of the experiment.
·Use the syringe to measure 20cm” of hydrogen peroxide and put in the boiling tube.
·Place the potato in the boiling tube and push the bung into the boiling tube.
·Put the delivery tube under the burette.
·As soon as this is done, immediately start the stopwatch.
·Record the volume of oxygen collected every 30 seconds for a total of 5 minutes.
·Once the first set of results has been collected, discard the contents of the boiling tube.
·Repeat the tests until all the different ranges of surface area have been covered.
·When the equipment is completed once, repeat each surface area again to obtain a reliable set of results. So, there should be three sets of results for each surface area.
·Once you have completed the whole equipment and you are happy with the results, clear up apparatus.
Once the results are collected, knowing the initial rate of reaction can be used for the analysis of the results. There are two ways of working out the initial rate of reaction. For both methods you have to first display the results in a graph with time on the x-axis and total volume of oxygen collected on the y-axis. Once this is done, you can either, calculate the slope of a tangent to the curve as close to time 0 as possible. Or the simplest way is to read off the graph the amount of oxygen released in the first 30 seconds of the reaction.