تجربة نشاط الإنزيمات

Enzyme Activity Experiment

• Enzyme Definition: A biological catalyst that accelerates chemical reactions in living organisms by reducing activation energy without being consumed.
• Enzyme Structure: Mostly proteins with a 3D (globular) shape.
• Enzyme Specificity: Enzymes catalyze only one specific type of reaction.
• Enzyme Nomenclature: Enzyme names often end with "-ase".
• Enzyme Function in Catalysis: Enzymes lower the activation energy required for reactions, allowing bonds to break in reactants and new bonds to form in products.
• Enzyme-Substrate Complex: Formed when a substrate binds to an enzyme's active site. The active site is the region where the substrate binds and the chemical reaction occurs. This is an intermediate step.
• Substrate Specificity: Enzymes are substrate-specific, meaning they catalyze specific reactions.
• Catalase: An enzyme found in most living organisms, including chopped potatoes in the lab experiment, and in human livers, which breaks down hydrogen peroxide (H₂O₂). This reaction produces water and oxygen, and is used to remove the toxic effects of this substance. The reaction is 2H₂O₂ → 2H₂O + O₂.
• Variables Affecting Enzyme Activity:
  • Enzyme Concentration: Increasing enzyme concentration increases reaction rate up to a certain point (saturation), where all available substrate is bound.
  • Substrate Concentration: Increasing substrate concentration increases reaction rate until it reaches a maximum (saturation). After this, increasing substrate concentration does not affect the reaction rate due to the substrate becoming the limiting factor (not enough enzymes to react with all substrate).
  • Temperature: Enzyme activity increases with temperature up to an optimum temperature, at which it is highest. Extremes in either direction (too high or too low temperatures) can denature the enzyme, reducing its activity.
  • pH: Enzyme activity is highest at an optimum pH, which varies depending on the specific enzyme, for most enzymes this is around 7. Extreame pH can change the enzyme's shape decreasing its activity.

Practical Procedure

• Materials required: Test tubes, racks, hydrogen peroxide, water, potato extract (source of catalase), dropper.
• Procedure Overview: The experiment involved testing the effect of varying enzyme and substrate concentrations, and temperature on the reaction rate of an enzyme-catalyzed reaction. Measurements were made to observe how the reaction rate changed in response to these conditions.
• Experiment design: In one experiment using a dropper, varying amounts of substrate (H₂O₂) and enzyme (potato extract) were added to separate tubes. Changes in the foaming reaction were observed and measured. In another experiment, varying temperatures were maintained for different test tubes and then the H₂O₂ was added and the results recorded.

Results and Observations

• The experiment showed a positive correlation between enzyme concentration and reaction rate up to a saturation point. Likewise, the correlation between the substrate concentration and reaction rate was positive and ceased at the saturation point.
• The experimental data from various variables such as temperature or pH will be recorded, analyzed and interpreted in the report.