Prokaryotic and Eukaryotic Cells
Compare prokaryotic and eukaryotic cells, including DNA location, organelles, and relative complexity. Explain why compartmentalization increases cellular efficiency.
A lesson of Biology, in Cells and Cellular Processes, about 10 minutes.
By the end of this lesson, you will be able to compare and contrast prokaryotic and eukaryotic cells, distinguish plant and animal cells, and explain the evolutionary significance of compartmentalization.
The Fundamental Division
Prokaryotic cells — no membrane-bound nucleus:
- Domain Bacteria and Domain Archaea
- 1–10 μm typical size
- Circular DNA in nucleoid region (not enclosed by membrane)
- No membrane-bound organelles
- Ribosomes present (smaller, 70S)
- Cell wall (peptidoglycan in bacteria)
- Many have flagella, pili, plasmids
Eukaryotic cells — membrane-bound nucleus:
- Domain Eukarya (animals, plants, fungi, protists)
- 10–100 μm typical size
- Linear DNA in nucleus
- Membrane-bound organelles
- Larger ribosomes (80S)
Plant vs. Animal Cells
| Feature | Plant | Animal |
|---|---|---|
| Cell wall | Yes (cellulose) | No |
| Chloroplasts | Yes | No |
| Central vacuole | Large | Small or absent |
| Centrioles | No (in most) | Yes |
| Lysosomes | Rare | Common |
| Shape | More regular | More variable |
The Importance of Compartmentalization
Membrane-bound compartments in eukaryotes create specialized microenvironments:
- Nucleus: separates DNA replication and transcription from translation
- Mitochondria: concentrate ATP synthesis machinery
- Lysosomes: isolate digestive enzymes that would destroy the cell
- ER and Golgi: sequential processing of proteins
Why this matters: compartmentalization allows different chemical environments (pH, ion concentration) in the same cell without interference — enabling greater metabolic complexity.
The Endosymbiotic Theory
Mitochondria and chloroplasts likely originated as free-living prokaryotes engulfed by ancestral eukaryotic cells.
Evidence:
- Both have their own circular DNA (like prokaryotes)