C

BIO NOTES CHAPT 5,6 3/24/25

  • Energy Transformations

    • The first law of thermodynamics states that energy cannot be created or destroyed; it only changes forms.

    • In biological terms: energy before transformation = energy after transformation.

  • Reactions Overview

    • Catabolic Reactions: Breakdown molecules releasing energy (e.g., cellular respiration).

    • Anabolic Reactions: Build or synthesize molecules, requiring energy (e.g., protein synthesis).

    • Delta G (9;Gibbs Free Energy Change9;): Positive for anabolic reactions and negative for catabolic reactions.

  • Enzymatic Regulation

    • Enzyme-Substrate Complex: Enzymes bind substrates, transforming them into products which releases the enzyme for reuse.

    • Inhibitors: Substances that reduce enzyme activity.

      • Irreversible Inhibitors: Bind and permanently deactivate enzymes (e.g., nerve agents like sarin).

      • Reversible Inhibitors:

        • Competitive Inhibitors: Bind to active site, preventing substrate access but can be dislodged.

        • Non-competitive Inhibitors: Bind elsewhere, altering the enzyme's shape and preventing substrate interaction.

  • Factors Affecting Enzyme Activity

    • Enzyme activity is influenced by pH, temperature, and substrate concentration.

    • Optimal temperature ranges vary among organisms; mammals maintain a narrow range (36-38°C).

    • Enzymes have a V_max which is the maximum rate of reaction; saturation occurs when all active sites are occupied by substrate.

  • Cellular Respiration

    • Takes place in mitochondria (eukaryotes) and cytoplasm (prokaryotes).

    • Equation for Aerobic Respiration:

      • C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP