Bio exam 2

Enzyme Study Guide

Key Concepts

  1. Purpose of Reaction Buffers

    • Buffers control the pH at which the reaction occurs.

  2. Enzyme Activity & Temperature

    • Enzyme activity is influenced by temperature. Use Excel to calculate mean and standard deviation to assess variability in experimental results.

  3. Role of Trypsin

    • Trypsin is a protease that breaks peptide bonds in dietary proteins, producing small peptides and amino acids.

  4. Importance of pH

    • Trypsin's activity significantly decreases when the buffer's pH lowers from pH 8 to pH 5 due to enzyme denaturation caused by broken hydrogen and ionic bonds.

  5. TCA in Enzyme Assays

    • Purpose: Stops enzyme activity after the reaction period.

    • Addition: Precipitates undigested substrate, enabling separation from reaction products.

  6. Spectrophotometer Usage

    • Measures the concentration of reaction products.

  7. Standard Deviation

    • Reflects variability among results for a specific experimental condition, such as temperature or salinity.

  8. Independent vs. Control Variables

    • Examples:

      • Independent: Salinity or Temperature

      • Control: pH, Temperature (if salinity is independent), Salinity (if temperature is independent).

Key Questions and Answers

Experimental Details

  • What happens if TCA is not added?

    • Absorbance would be unusually high.

  • What happens if the substrate is not added?

    • Absorbance would match negative controls.

  • What is the optimal temperature or pH for enzymes?

    • Analyze graphs to determine the point of highest activity.

Statistical Analysis

  • A p-value below 0.05 indicates significant differences between groups.

  • Why replicates are important?

    • Replicates help identify variability due to experimental errors or inconsistencies (e.g., uneven mixing or timing differences).

Dilutions

  • Example: Mixing 50 µL of reagent with 950 µL water creates a 1:20 dilution.

Enzyme Properties

  • Enzymes are proteins (not fats) that:

    • Speed up reactions.

    • May change shape during substrate binding.

    • Are sensitive to environmental changes like pH and temperature.

Real-World Enzyme Behavior

  • Why is trypsin secreted as trypsinogen?

    • Prevents digestion of pancreatic proteins, avoiding tissue damage.

Sample Calculations

Mean and Standard Deviation (Example at 10 °C):

Given:

  • Trial 1: 0.40

  • Trial 2: 0.35

  • Trial 3: 0.45

  • Trial 4: 0.50

  • Mean = (Sum of rates) / Number of trials

    • Mean=0.40+0.35+0.45+0.504=0.425\text{Mean} = \frac{0.40 + 0.35 + 0.45 + 0.50}{4} = 0.425Mean=40.40+0.35+0.45+0.50​=0.425

  • Standard Deviation = Measure of variability

    • Use Excel or statistical formulas to compute.

Important Steps in Enzyme Assays

  1. Add reaction buffer to maintain optimal pH.

  2. Include substrate and enzyme for proper reaction.

  3. Stop the reaction with TCA.

  4. Separate undigested substrate via centrifugation.

  5. Measure product concentration using a spectrophotometer.

Graph Interpretation Tips

  • Look for peaks in enzyme activity curves to determine optimal conditions (e.g., temperature or pH).

  • Compare activity at specific conditions (e.g., 50% max activity) to make predictions.