AP Biology 2.10 Origins of Cell Compartmentalization Study Notes - New Syllabus Effective 2025
AP Biology 2.10 Origins of Cell Compartmentalization Study Notes- New syllabus
AP Biology 2.10 Origins of Cell Compartmentalization Study Notes – AP Biology – per latest AP Biology Syllabus.
LEARNING OBJECTIVE
Describe the processes that allow ions and other molecules to move across membranes.
Key Concepts:
- Origins of Cell Compartmentalization
2.10.A – Prokaryotes vs. Eukaryotes: Compartmentalization
🔍 Key Differences in Compartmentalization
| Feature | Prokaryotic Cells 🦠 | Eukaryotic Cells 🧫 |
|---|---|---|
| Organelles | No membrane-bound organelles | Have membrane-bound organelles |
| DNA Location | In the nucleoid region (no nucleus) | Inside a nucleus with double membrane |
| Membrane Systems | Basic internal membranes (if any) | Complex endomembrane system |
| Enzyme Organization | Enzymes float freely in cytoplasm | Enzymes compartmentalized in organelles |
| Efficiency | Simpler, less specialization | Higher efficiency, multiple reactions at once |
🎯 Similarity
- Both have plasma membranes, ribosomes, and cytoplasm
- Both regulate internal environments just with different complexity
✅ Summary
🔹 Prokaryotes: Simple cells with no membrane-bound compartments
🔸 Eukaryotes: Complex cells with specialized organelles that allow efficient compartmentalization of functions
2.10.A.1 – Origin of Mitochondria & Chloroplasts: Endosymbiosis
Mitochondria and chloroplasts evolved from ancient prokaryotes that were engulfed by larger cells.
🌱 What Is Endosymbiosis?
- Endosymbiosis is a theory that explains how eukaryotic cells got some of their organelles.
- Long ago, a larger prokaryote engulfed a smaller prokaryote, but instead of digesting it, they formed a mutual relationship.
🔋 Key Examples:
| Organelle | Came From… | Why We Know 🧪 |
|---|---|---|
| Mitochondria | Aerobic bacteria (used oxygen for energy) | Have their own DNA, double membrane, replicate independently |
| Chloroplasts | Photosynthetic bacteria (like cyanobacteria) | Also have circular DNA, ribosomes, double membrane, self-replicating |
🧠 Why It Matters
- Shows that some organelles were once free-living prokaryotes
- Helped eukaryotic cells evolve more complexity and efficiency
✅ Summary
Mitochondria and chloroplasts came from ancient prokaryotes through endosymbiosis, and their unique features (like DNA and membranes) still show this evolutionary origin.
2.10.A.2 – Internal Organization in Prokaryotes
Prokaryotic cells don’t have membrane-bound organelles, but they still organize certain functions using specialized internal regions.
🧱 No Membrane-Bound Organelles, But…
Prokaryotes are structurally simple, yet still functionally organized.
They don’t have:
- A nucleus
- Organelles like ER, Golgi, mitochondria, etc.
But they do have:
| Internal Region | Function ⚙️ |
|---|---|
| Nucleoid | Area where circular DNA is located |
| Ribosomes | Site of protein synthesis |
| Inclusion bodies | Store nutrients like glycogen or phosphate |
| Thylakoid-like membranes (in some bacteria) | Used for photosynthesis (e.g., cyanobacteria) |
🎯 Why It’s Important
- Make proteins
- Store materials
- Carry out photosynthesis (in some)
- Reproduce and survive in many environments
✅ Summary
Prokaryotes lack internal membrane-bound organelles but still have specialized regions that carry out essential life functions – proving that simplicity doesn’t mean inefficiency!
2.10.A.3 – Internal Membranes in Eukaryotic Cells
Eukaryotic cells use internal membranes to create separate, specialized regions for different functions.
🧱 What Does “Partition” Mean?
Partitioning = dividing the cell into functional zones.
Each membrane-bound organelle acts as its own workspace.
🧩 Examples of Specialized Regions
| Organelle | Specialized Function ⚙️ |
|---|---|
| Nucleus | Stores DNA & controls gene expression |
| Rough ER | Makes & folds proteins for export |
| Smooth ER | Makes lipids, detoxifies |
| Mitochondria | Makes ATP (energy) in its own space |
| Lysosomes | Break down waste with digestive enzymes |
| Golgi Apparatus | Modifies, packages, and ships materials |
🎯 Why It Matters
- Prevents interference between processes
- Creates ideal conditions for each task (e.g., pH, enzymes)
- Boosts efficiency and complexity
✅ Summary
Eukaryotic cells use internal membranes to create specialized regions, allowing multiple complex processes to happen at the same time in an organized way.