Overview
This lecture introduces the basics of energy metabolism and enzymes, focusing on how organisms convert and use energy through metabolic pathways, and explains core concepts including anabolic/catabolic reactions, types of energy, and Gibbs free energy.
Energy Flow in Living Systems
- Most energy for life originates from the Sun and is captured by plants via photosynthesis.
- Energy transfers through producers, consumers, and decomposers, with some lost as heat at each step.
- Bioenergetics is the study of energy flow through living systems.
Metabolism & Metabolic Pathways
- Metabolism includes all chemical reactions in a cell or organism.
- Anabolic reactions (anabolism) build larger molecules from smaller ones and require energy input.
- Catabolic reactions (catabolism) break down large molecules into smaller ones, releasing energy.
- Metabolic pathways convert substrates into final products through a series of biochemical reactions.
- All organisms share some metabolic pathways, indicating a common evolutionary origin.
Energy Types in Biology
- Kinetic energy is energy of motion; potential energy is stored energy with the capacity to move.
- Chemical energy is potential energy stored in chemical bonds (e.g., glucose, gasoline).
- Diffusion demonstrates both potential (before movement) and kinetic (during movement) energy at a cellular level.
Gibbs Free Energy & Chemical Reactions
- Gibbs free energy (ΔG) is the usable energy in a system after accounting for energy lost as heat.
- Gibbs free energy equation: ΔG = ΔH – TΔS (change in enthalpy minus temperature times change in entropy).
- Exergonic reactions release energy (ΔG < 0), are spontaneous, but not necessarily fast.
- Endergonic reactions require an energy input (ΔG > 0), leading to products with more energy than the reactants.
- Exergonic reactions are linked to catabolic processes; endergonic reactions are linked to anabolic processes.
Key Terms & Definitions
- Bioenergetics — the study of energy flow through living systems.
- Metabolism — all chemical reactions within a living organism.
- Anabolism — metabolic pathways that build larger molecules and require energy.
- Catabolism — metabolic pathways that break down molecules and release energy.
- Metabolic Pathway — a series of chemical reactions converting substrates to products.
- Kinetic Energy — energy of motion.
- Potential Energy — stored energy with the potential to do work.
- Chemical Energy — energy stored in chemical bonds.
- Gibbs Free Energy (ΔG) — usable energy available to do work in a system.
- Exergonic Reaction — a reaction that releases energy (ΔG < 0).
- Endergonic Reaction — a reaction that requires energy input (ΔG > 0).
Action Items / Next Steps
- Review chapter 6 in the textbook.
- Watch the next video on activation energy.