NDA Biology · Cell Biology
Prokaryotic vs Eukaryotic Cells
Prokaryotic cells (bacteria) have no membrane-bound nucleus — just a 'nucleoid' of naked circular DNA — and no membrane-bound organelles; eukaryotic cells (plants, animals, fungi) have a true nucleus and organelles like mitochondria.
Why this matters
A tight, high-frequency 5-PYQ cluster, all single-fact recall. The bank tests the same handful of points: prokaryotes lack a true nucleus (they have a nucleoid), lack membrane-bound organelles (no mitochondria), have a single circular chromosome, and their DNA is 'naked' (no histone proteins). All EASY or MODERATE.
Concept 1 of 2: Prokaryote vs eukaryote — the contrast table
Definition
The key differences between the two cell types:
- Nucleus — eukaryotes have a true membrane-bound nucleus; prokaryotes have only a nucleoid (no membrane).
- Organelles — eukaryotes have membrane-bound organelles (mitochondria, ER, Golgi); prokaryotes have none.
- Both have a cell wall, plasma membrane and ribosomes — so these do NOT distinguish them.
- 'Exclusively present in a eukaryote' = the mitochondrion (a membrane-bound organelle).
- 'NOT present in a prokaryote' = the nucleus (and other membrane-bound organelles).
Both have a wall, membrane and ribosomes. Only the eukaryote has a true nucleus and membrane-bound organelles.
| Feature | Prokaryote | Eukaryote |
|---|---|---|
| Nucleus | Nucleoid (no membrane) | True membrane-bound nucleus 'Not present in a prokaryote' → the nucleus. |
| Mitochondria | Absent | Present 'Exclusively in eukaryotes' → mitochondria (membrane-bound). |
| Cell wall | Present | Present (plants/fungi) |
| Plasma membrane | Present | Present |
| Ribosomes | Present (70S) | Present (80S) |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Cell Biology · Prokaryotic vs Eukaryotic Cells
Cell wall is NOT eukaryote-exclusive
Concept 2 of 2: The nucleoid and 'naked' bacterial DNA
Definition
Prokaryotic DNA facts:
- The membrane-less region holding the DNA is the nucleoid (not nucleolus, not nucleosome).
- Bacterial DNA is called 'naked' because it is NOT associated with histone proteins (eukaryotic DNA is wound around histones).
- Most prokaryotes have a single circular chromosome — chromosome number = 1 (plus optional plasmids).
| Term | Meaning |
|---|---|
| Nucleoid | The membrane-less DNA region of a prokaryote Nucleoid — not nucleolus (eukaryotic) or nucleosome (DNA+histone unit). |
| 'Naked' DNA | Bacterial DNA NOT bound to histone proteins 'Naked because not associated with' → proteins (histones). |
| Chromosome number | Usually 1 (a single circular chromosome) |
Practice this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 2 · Cell Biology · Prokaryotic vs Eukaryotic Cells
Nucleoid vs nucleolus vs nucleosome
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Prokaryote vs eukaryote — the contrast table5 rows
| Feature | Prokaryote | Eukaryote |
|---|---|---|
| Nucleus | Nucleoid (no membrane) | True membrane-bound nucleus 'Not present in a prokaryote' → the nucleus. |
| Mitochondria | Absent | Present 'Exclusively in eukaryotes' → mitochondria (membrane-bound). |
| Cell wall | Present | Present (plants/fungi) |
| Plasma membrane | Present | Present |
| Ribosomes | Present (70S) | Present (80S) |
The nucleoid and 'naked' bacterial DNA3 rows
| Term | Meaning |
|---|---|
| Nucleoid | The membrane-less DNA region of a prokaryote Nucleoid — not nucleolus (eukaryotic) or nucleosome (DNA+histone unit). |
| 'Naked' DNA | Bacterial DNA NOT bound to histone proteins 'Naked because not associated with' → proteins (histones). |
| Chromosome number | Usually 1 (a single circular chromosome) |
Watch out for (2)
- Cell wall is NOT eukaryote-exclusive→ Prokaryote vs eukaryote — the contrast table
- Nucleoid vs nucleolus vs nucleosome→ The nucleoid and 'naked' bacterial DNA
Test yourself on Cell Biology
15 past NDA questions from this chapter, timed at 15 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.