Rucete ✏ Campbell Biology In a Nutshell
Unit 2 THE CELL — Concept 8.1 An Organism’s Metabolism Transforms Matter and Energy
Cells aren’t just tiny bags of molecules—they’re bustling factories of chemical reactions. All of these reactions together make up an organism’s metabolism, the engine that transforms matter and energy to keep life going.
1. What Is Metabolism?
- Definition: Metabolism is the sum of all chemical reactions within a living organism.
- These reactions are organized into metabolic pathways, where each step is catalyzed by a specific enzyme.
2. Catabolic vs. Anabolic Pathways
- Catabolic pathways:
- Break down complex molecules into simpler ones.
- Release energy.
- Example: Cellular respiration breaks down glucose to generate ATP.
- Anabolic pathways:
- Build complex molecules from simpler components.
- Consume energy.
- Example: Protein synthesis from amino acids.
3. Forms of Energy in Biology
- Kinetic energy: Energy of motion (e.g., heat, molecular movement).
- Potential energy: Stored energy based on structure or position (e.g., in chemical bonds).
- Chemical energy: A form of potential energy stored in molecules like glucose; released during reactions.
4. Thermodynamics: Energy Principles of Life
- First Law (Conservation of Energy): Energy can be transferred or transformed but cannot be created or destroyed.
- Second Law (Entropy): Energy transformations increase entropy (disorder) in the universe. Life maintains order internally by increasing disorder around it.
5. The Flow of Energy in Life
- Energy enters ecosystems as light and exits as heat.
- Cells use chemical energy to do work, but some energy is always lost as heat—no energy transfer is perfectly efficient.
In a Nutshell
- Metabolism is the sum of all chemical processes in an organism.
- It includes catabolic (breaking down) and anabolic (building up) pathways.
- Energy exists in many forms and follows the laws of thermodynamics.
- Life runs on chemical energy—and these energy transformations fuel everything from muscle contraction to DNA replication.