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