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 one molecule is altered in a series of defined steps, each 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, movement of molecules).
Potential energy: Stored energy based on location or structure (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 not created or destroyed.Second Law (Entropy):
Every energy transformation increases entropy (disorder) in the universe.
Life maintains order internally by contributing disorder to the surroundings.
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 transformation is 100% 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 comes in different forms and flows according to the laws of thermodynamics.
Life runs on chemical energy—and energy transformations fuel everything from muscle movement to DNA replication.