Enzymes, which are organic catalysts in the body, serve to enhance metabolic reactions while maintaining their chemical integrity through an active site.
This is a region, typically a depression or cleft, where another molecule can attach. The molecule that attaches here is known as the substrate and it usually corresponds specifically with the active site of the enzyme that decomposes it. Substrates generally cannot fit into any other active sites except for the one intended for the enzyme. This analogy can be compared to a lock and key model, where each lock and key are distinct from one another. However, enzymes possess multiple instances of identical locks and keys.
Proteins have a structure resembling lock and key shapes, including enzymes that usually have one active site but sometimes have more. Some cellular reactions produce hydrogen peroxide, an acidic compound that can harm cells.
The decomposition of hydrogen peroxide usually results in the formation of hydrogen and oxygen: 2H2O2 → 2H2O + O2. However, this process is time-consuming. Cells possess the enzyme catalase, which significantly accelerates the breakdown of hydrogen peroxide. catalase: 2H2O2 → 2H2O + O2. This kind of reaction, referred to as a catabolic reaction, breaks down molecules into smaller fragments. To investigate the impact of temperature on catalase activity, I will measure the amount of oxygen released during the decomposition of hydrogen peroxide.
It is important to control variables such as pH and enzyme concentration because they greatly affect the rate of a reaction. High pH levels can cause the enzyme to become denatured by losing H+ ions, while low pH levels can alter its shape due to an excess of H+ ions. Furthermore, increasing the concentration of the enzyme improves the reaction rate.
Increasing the number of catalase molecules will enhance the likelihood of successful enzyme-substrate collisions. To maintain consistency, I will use the same volume of catalase-containing tissue (potato) for every experiment. The same principle applies to the surface area. Additionally, it’s important to consider that different potatoes, even if equally sized pieces are cut, will have varying masses.
Different potatoes will not have the exact same water and catalase content. The mass, surface area, and enzyme concentration will be kept constant. Arefin Khan predicts that as the temperature increases, the rate of reaction will also increase up to a certain point. This is because the particles gain kinetic energy, leading to more vigorous movement.
The enzyme-substrate collision rate increases with higher kinetic energy and increased frequency of particle collisions. Enzymes have a specific shape maintained by ionic and hydrogen bonds. Excessive motion can break these bonds and denature the enzyme.
As the enzymes undergo denaturation, their activity rate decreases due to the loss of their specific three-dimensional shape. Typically, the enzymes begin to denature at temperatures above 40°C, which is usually their optimal temperature for activity. Beyond this temperature, the reaction rate is likely to decline further. It is expected that at 60°C, no reaction would occur since the enzymes would most likely be fully denatured by then.
*(Above from: Source, Page 47)
Methodology:
1. Wear goggles for protection, and lab coat if available.
2. Arrange apparatus.
3. Take a 250cm3 beaker and add water to it until it reaches the 150cm3 mark. To achieve the desired temperature, you can either cool the water using ice or heat it with a Bunsen burner.
While heating the water, you can shape the potato into a cylinder using a cork borer. Start by placing the potato on a tile and holding it firmly with one hand. Then, press down firmly with the cork borer until you achieve the desired cylindrical shape. To remove the potato cylinder from the cork borer, use the flat end of a pencil to push it out.
5. Take the potato cylinder and use a ruler to trim it down to a length of three centimeters. Next, divide this three centimeter cylinder into six equal pieces that are each 5 millimeters in width. Remember to keep your eyes level with the ruler to prevent any potential parallax error.
Using the cork borer ensures that the diameter of the cylinder remains constant. Additionally, put the potato pieces into a boiling tube and set it aside.
Using a 50cm3-measuring cylinder, pour 30ml of hydrogen peroxide into a boiling tube. Obtain two boiling tubes, one containing hydrogen peroxide and the other containing potato.
When the desired temperature is reached, place both the potato and hydrogen peroxide in a water-filled beaker. You can achieve this by either heating or cooling the water. Let the hydrogen peroxide and water bath reach the same temperature. Once they are at equal temperatures, attach a boiling tube filled with hydrogen peroxide to a clamp stand after both the potato and hydrogen peroxide have reached equal temperatures.
First, insert the potato into the test tube that already has hydrogen peroxide. Then, place a bung on top of the test tube. Ensure that the test tube, now containing both potato and hydrogen peroxide, is placed in a beaker of water.
Next, measure the amount of water being displaced from the 100cm3 measuring cylinder every thirty seconds using a stopwatch.
The instructions for the investigation are to take readings every thirty seconds for five minutes. Once completed, repeat the same steps at different temperatures. The risk assessment for this experiment involves the use of catalase from potato cells to accelerate the breakdown of hydrogen peroxide.
Hydrogen peroxide, an oxidising agent, releases oxygen when reacting, which can enhance the combustion of fires. Therefore, precautionary measures should be taken to avoid exposing the Bunsen burner’s flame directly to oxygen while heating water. Furthermore, direct contact with hydrogen peroxide can cause severe eye injuries.
Hence, wearing goggles and lab coats is necessary. The sharpness of the cork borer can also be a potential risk. When cutting a piece of potato, ensure to place it on a tile for safety.
The methodology details the process of cutting the potato, including the use of a potentially hazardous blade that needs careful handling due to its sharpness. Additionally, caution should be exercised when handling glass apparatus to prevent breakage.
If the reactants do have another hazard, it should also be cleared up and disposed of appropriately. Fair testing is essential during the experiment, and it is important to control certain variables to ensure fairness. One variable that needs to be kept constant is the PH of the reactants.
This will be easy to ensure as the pH of the reactants remains relatively constant throughout the reaction. However, maintaining a constant temperature for the reactants poses a more challenging task.
There will be a beaker of 150cm3 of water at the appropriate temperature. The boiling tube containing the reactants will be immersed into the beaker once their temperatures have equalised and stabilised. This will ensure that the temperature of the reactants remains stable for a longer period as the larger volume of water in the beaker retains its temperature for longer. Additionally, the same volume of water will be added to the beaker for each new test to avoid any variations in the duration of heat retention.
When taking readings off measuring cylinders and thermometers, it is important to ensure that the graduated markings are at eye level. This helps minimize the risk of inaccurate readings.
After using boiling tubes, they must be washed thoroughly with water to minimize the chance of contamination.
Arefin Khan5. Ensuring that all potato pieces are uniformly cut in width and diameter will regulate the potato’s surface area. During the experiment, it is crucial to prioritize accuracy as it directly impacts the reliability of the results. Consequently, this will strengthen evidence for or against my prediction on enzyme activity in relation to temperature.
The aforementioned methods of accurate measurement will be utilized in their original form as they are deemed most suitable for the given situation. Time factors and equipment availability play significant roles in the implementation of these methods. The experiment will involve the usage of the following apparatus: Cork borer (size four), potato, hydrogen peroxide, water, blade, ruler (15cm), stopwatch, test tube rack, boiling tubes, delivery tube and rubber bung, water container, measuring cylinders (100 cm3 and 50cm3), goggles, cutting tile, clamp and stand, beaker (250cm3), graduated pipette (5ml), ice, and thermometer (0 ?C-100 ?C). The apparatus will be set up according to the following diagram during the experiment. In preliminary work, it was determined that the 100 cm3 measuring cylinder was the most suitable for measuring the water displacement caused by oxygen formed during the reaction. This is because it is graduated in millilitres, allowing for precise measurement of water displacement to the nearest 0.
Five millilitres of hydrogen peroxide can be measured accurately with a 50cm3 measuring cylinder. The cylinder’s size ensures that the volume of oxygen produced during the reaction does not exceed its capacity. Boiling tubes are suitable containers for this reaction due to the relatively small volume of oxygen produced.
Therefore, the displacement of water in the measuring cylinder by the oxygen produced will be faster, compared to using a conical flask. Additionally, I noticed a significantly slow breakdown of hydrogen peroxide at room temperature without a catalyst. There was no release of oxygen throughout the duration of my observation for any reaction.
However, I did not test if this was also applicable at higher temperatures. If it was not, then there might be significant flaws in how the experiment was conducted. Source: Arefin Khan
Background information utilized in this study was obtained from Cambridge Advanced Sciences. Biology 1 – endorsed by OCR: Chapter 3.
(Page 42 onwards.) The information on variables was derived from the concepts learned in AS chemistry: (Salters Horners Advanced Chemistry)
