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