The Effect of Concentration, Ph and Temperature on Enzyme Activity

1 January 2017

We examined the reaction an enzyme has when its concentration, pH and temperature are altered. In order to do this, we added different levels of pH into different test tubes with the enzyme (sucrose), and substrate (sucrose), and we then inverted the tube. The higher pH produced more enzyme activity. Temperature effects enzyme activity by decreasing its stability when the temperature increases.

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Oppositely, low temperature levels resulted in little to no change or the enzyme denatured. Temperature variations were observed and recorded. Substrate concentration testing showed that as when the substrate increased, the activity of the enzyme also increased. Keyword: enzyme, substrate, sucrose, sucrose The Effect of Concentration, pH and Temperature on Enzyme Activity Introduction In this lab we explore enzyme activity and how it can be affected by changes to its environment. Enzymes are proteins that speed up the rate of chemical reactions.

Many important processes in the body involve the work of enzymes, including the digestion of nutrients such as carbohydrates, proteins and fats (Raven 45). Enzymes are also organic catalysts. A catalyst is a chemical that controls the rate of a reaction, but is itself not used up in the process. Reactions that are accelerated due to the presence of enzymes are known as enzyme-catalyzed reactions (Raven 112). The substrate is the reactant within the reaction that fits with the enzyme. Once the substrate enters the enzyme’s active site, the enzyme’s shape changes to form an enzyme-substrate complex.

The substrate is then metabolized or broken down, resulting in a product, which can be utilized to energize cells. Once the product is released from the active site, the enzyme returns to its original shape (Raven 117). The three factors that can affect the activity of an enzyme include temperature, pH, and concentration. The temperature effects enzyme activity. As the temperature increases, enzyme stability decreases. Therefore there are more collisions of the substrate with the active site and the formation of activated complex’s and product (Raven 52). The rate of reaction is increasing.

The optimal temperature is the highest rate of reaction. Greater temperature raises the kinetic energy of the enzyme atoms, resulting in the breakdown of bonds, and an alteration of shape of the active site. Most enzymes present in living tissue have their secondary protein structure denatured, at the temperature 40°C or above (Raven 53). Effects of enzyme concentration on enzyme activity were evident with the level of substrate concentration increased, so did enzyme activity. Conversely, this activity had a stop point where activity ceased suddenly (Raven 114).

Without enzymes, reactions may take place very slowly, but with enzymes the rate was directly proportional to the amount of enzyme that was present. Cells control the production of these enzymes, and if the breakdown of these enzymes exceeds synthesis, the rate slows down. But, if the synthesis exceeds the breakdown, the reaction rate increases (Silverthorn 91). Low substrate concentration is the least productive (Silverthorn 98). In the effects of pH on enzyme activity, the way a protein folds can be changed in the presence of various.

The pH also affects the rate of reaction of an enzyme catalyzed reaction at about or below the optimal pH; the rate decreases (Raven 116). The change in rate is because bonds are made and broken, which changes the shape of the active site and therefore decreases the rate of reaction. As the substrate concentration is increased, the rate of reaction increases. Further increases in substrate also increase the rate, but proportionately the rate is constant (Raven 117). Enzyme activity can be changed by enzyme concentration, pH, and temperature changes. Materials and Methods There are three parts to test concentration, pH, and temperature.

To begin, concentration is tested by collecting five test tubes and labeling each one 1-5 and placing them in a test tube rack. Next, a beaker is filled half way full of water and placed on a hotplate until it begins to boil. Afterward, different solutions are filled in each test tube: Test Tube 1: 2 ml of 1% sucrose and then add 2ml of pH buffer 4. 4. Test Tube 2: 2 ml of 1% sucrose and then add 2 ml of pH buffer 4. 4. Test Tube 3: 2 ml of 1% sucrose and then add 2 ml of pH buffer 4. 4. Test Tube 4: 2 ml of 1% sucrose and then add 2 ml of pH buffer 4. 4. Test Tube 5: 2 ml of 1% sucrose and then add 2 ml of pH buffer 4.

Consequently, predetermined amounts of enzyme and distilled water are added to each tube at room temperature: Test Tube 1: 0 ml sucrase and then add 3ml of water. Test Tube 2: 0. 5 ml sucrase and then add 2. 5 ml of water. Test Tube 3: 1 ml of sucrase and then add 2 ml of water. Test Tube 4: 1. 5 ml of 1% sucrase and then add 1. 5ml of water. Test Tube 5: 3 ml of sucrase and 0 ml of water. Each test tube is allowed to sit for five minutes. This stage is imperative to allow the sucrose to act upon the sucrose. Afterwards, 3 mL of Benedict’s reagent is added to each tube.

Each tube is placed in the boiling water for three minutes, and each tube is observed for color changes which are compared to the provided Benedict’s test for simple sugars, with results recorded. The second part of the experiment was targeted to determine the effects of temperature on the rate of enzyme activity. Four test tubes are labeled 1A-4A along with four additional tubes labeled 1B-4B. A beaker is filled ? full with water and brought to a boil. Test tubes 1A-4A is filled with 2 mL of both sucrose and a pH buffer. These four tubes are placed in the boiling water for fifteen minutes. Test Tube 1A: 0 C

Test Tube 2A: 30 C Test Tube 3A: 30 C Test Tube 4A: 100 C Measure and fill test tubes 1B-4B with 3 mL of enzyme. Test tube 1B-4B placed to water for 15 minutes. Test Tube 1B: 0 C Test Tube 2B: 30 C Test Tube 3B: 30 C Test Tube 4B: 100 C Put enzyme from B tubes into A tubes after fifteen minutes and place back into water for 5 minutes. Remove each tube from the water and add 3 mL of Benedict’s solution to each tube. Return each tube back into water and boil for 3 minutes. Results calculated and recorded. Lastly, part three of this experiment strives to understand the effects of pH on the rate of enzyme activity.

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