pH Power WorksheetpH Power Mapping Enzyme Efficiency Name: __________________________ Date: ___________ Period: _______ Essential Question: How does the concentration of hydrogen ions (pH) affect the tertiary structure and catalytic function of enzymes? Figure 1: Comparison of Digestive Enzymes pH Level Reaction Rate PEPSIN AMYLASE TRYPSIN 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 DENATURATION DENATURATION Optimum pH: The specific pH value where an enzyme shows its maximum rate of reaction. Denaturation: Extreme pH levels break bonds, causing the active site to change shape. Graph Interpretation 1. Identify the optimum pH for each enzyme shown in Figure 1. Pepsin: Amylase: Trypsin: 2. Based on the graph, explain why Pepsin cannot function in the small intestine (where pH is approximately 8). 3. Design Challenge: Sketch a curve for an enzyme found in a hot alkaline spring (pH 10). How would its position differ from the ones above? Sketch your curve centered over the pH 10 mark on the x-axis above.
pH Power Answer KeyTeacher Resource Answer Key pH Power Answer Key Grading Guide for Enzyme Investigation Graph Interpretation Key Pepsin: Optimal pH is ~2. Operates in the acidic stomach environment. Salivary Amylase: Optimal pH is ~7. Operates in the neutral mouth environment. Trypsin: Optimal pH is ~8-9. Operates in the basic small intestine environment. 1. Identify the optimum pH for each enzyme shown in Figure 1. Pepsin: pH 2 Amylase: pH 7 Trypsin: pH 8.5-9 2. Based on the graph, explain why Pepsin cannot function in the small intestine (where pH is approximately 8). Pepsin is highly active at pH 2 but its activity drops to zero long before pH 8. In the small intestine's basic environment, Pepsin's structure is denatured (unfolded) because the high pH disrupts the ionic bonds holding its shape together, making it non-functional. 3. Chemical Reasoning: How does a change in pH specifically affect the "Active Site" of these enzymes? pH changes alter the concentration of H+ and OH- ions. These ions interact with the R-groups (side chains) of the amino acids in the active site. This can change the charge distribution or break hydrogen and ionic bonds, causing the active site to change shape (denature). If the active site is no longer complementary to the substrate, the enzyme cannot catalyze the reaction. 4. Design Challenge: Sketch a curve for an enzyme found in a hot alkaline spring (pH 10). How would its position differ from the ones above? The curve should be shifted to the right of Trypsin, with a peak (Optimum) centered exactly over the pH 10 mark on the X-axis. This shows the enzyme is adapted to function best in highly alkaline conditions. Teaching Tips Common Misconception: Students often think enzymes "die" at high pH. Clarify that enzymes are not alive; they are complex molecules that denature or unfold. Connection: Relate this to how antacids work (changing pH can shut down enzymes in the stomach temporarily). Visual Aid: Use the "Lock and Key" model to show how the "Lock" (active site) changes shape when pH changes.
pH Power SlidespH Power How Environmental Chemistry Controls Biological Catalysts Enzymes as Catalysts Enzymes are protein catalysts that speed up chemical reactions by lowering activation energy. Highly specific (Lock and Key) Reusable molecules Fragile structure The Active Site Shape = Function Understanding pH ACIDIC 0 - 6 High concentration of H+ ions Stomach Acid, Lemon NEUTRAL 7 Balanced ions Pure Water, Blood (~7.4) BASIC 8 - 14 High concentration of OH- ions Bleach, Small Intestine The pH Response Curve pH Level Reaction Rate OPTIMUM pH 0 2 4 6 8 10 12 14 DENATURED DENATURED What is Denaturation? Charged ions (H+ or OH-) interact with the R-groups of the amino acids. 1 Hydrogen/Ionic bonds break. 2 The protein unfolds and loses its 3D shape. 3 The Active Site is destroyed. UNFOLDING = FAILURE Comparative Enzyme Profiles 0 2 4 6 8 10 12 14 Pepsin (Stomach) pH 2.0 Amylase (Mouth) pH 7.0 Trypsin (Intestine) pH 8.5 Check Your Knowledge Q: If an enzyme's optimum pH is 7, what would happen to its reaction rate at pH 12? Take 60 seconds to discuss with your partner...
