Chapter 8 Study Guide

Section A: Metabolism, Energy, and Life

1. Metabolic Pathways

   • Metabolism: The totality of an organism’s chemical reactions.

   • Catabolic pathways: Break down complex molecules, releasing energy (e.g., cellular respiration).

   • Anabolic pathways: Build complex molecules, requiring energy (e.g., photosynthesis).

2. Energy Transformation

   • Energy: The capacity to do work.

   • Potential energy: Stored energy (e.g., gravitational energy).

   • Kinetic energy: Energy of motion (e.g., heat, movement).

3. Laws of Thermodynamics

   • First Law: Energy cannot be created or destroyed, only transformed.

   • Second Law: Every energy transformation increases entropy (disorder).

   • Organisms require free energy (ΔG) to function.

4. Types of Reactions

   • Exergonic: Releases energy (ΔG negative, spontaneous, catabolic).

   • Endergonic: Requires energy input (ΔG positive, nonspontaneous, anabolic).

   • Equilibrium (ΔG = 0): Cells cannot reach equilibrium or they will die.

5. ATP and Cellular Work

   • ATP (Adenosine Triphosphate) stores energy in phosphate bonds.

   • ATP powers mechanical, transport, and chemical work.

   • ATP hydrolysis releases energy; ATP regeneration requires energy input.

Section B: Enzymes

1. Activation Energy

   • Enzymes speed up reactions by lowering activation energy.

   • Catalysts reduce the energy needed to start a reaction.

2. Enzyme Structure and Function

   • Substrate: Reactant that binds to an enzyme.

   • Active site: Pocket on enzyme where the reaction occurs.

   • Induced fit: Enzyme adjusts shape to fit the substrate.

3. Factors Affecting Enzyme Activity

   • Temperature and pH influence enzyme shape and function.

   • Cofactors: Non-protein helpers (e.g., zinc, iron, vitamins).

   • Inhibitors:

     • Competitive: Bind to the active site, blocking the substrate.

     • Non-competitive: Bind elsewhere, changing enzyme shape.

     • Allosteric regulation: Activators or inhibitors bind to a site other than the active site.

4. How DNA Controls Metabolism

   • DNA directs enzyme production, which regulates metabolic pathways.