Prokaryotic vs. Eukaryotic Cells

Comparison of prokaryotic and eukaryotic cell structures

Written and reviewed by the Study Mondo Education TeamLast updated February 16, 2026

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🦠 Prokaryotic vs. Eukaryotic Cells

Cell Theory

All living things are composed of cells
The cell is the basic unit of life
All cells come from preexisting cells

Prokaryotic Cells

Characteristics:

No nucleus - DNA in nucleoid region
No membrane-bound organelles
Smaller (1-10 μm)
Examples: Bacteria, Archaea

Structures:

Nucleoid: region containing circular DNA
Ribosomes: protein synthesis (70S)
Cell wall: peptidoglycan (bacteria)
Plasma membrane: phospholipid bilayer
Capsule: protective outer layer (some)
Flagella: movement (some)
Pili: attachment, DNA transfer (some)

Eukaryotic Cells

Characteristics:

Nucleus with nuclear envelope
Membrane-bound organelles
Larger (10-100 μm)
Examples: Animals, plants, fungi, protists

Structures:

Nucleus: contains DNA
Membrane-bound organelles:
- Mitochondria
- Endoplasmic reticulum
- Golgi apparatus
- Lysosomes (animals)
- Peroxisomes
Ribosomes: 80S (larger than prokaryotic)
Cytoskeleton: structural support, movement

Plant vs. Animal Cells

Unique to Plants:

Cell wall: cellulose
Chloroplasts: photosynthesis
Central vacuole: storage, turgor pressure
Plasmodesmata: channels between cells

Unique to Animals:

Centrioles: organize spindle fibers
Lysosomes: digestion (rare in plants)

Surface Area to Volume Ratio

Importance:

Limits cell size
Larger cells have lower SA:V ratio
Less efficient diffusion as cells grow
Cells divide to maintain high SA:V

Calculation: For a cube with side length a:

Surface area = 6a²
Volume = a³
Ratio = 6a²/a³ = 6/a

As a increases, ratio decreases!

Key Concepts

Prokaryotes lack nucleus and organelles
Eukaryotes have nucleus and organelles
Plant cells have cell wall, chloroplasts, central vacuole
Surface area to volume ratio limits cell size
All cells have plasma membrane, ribosomes, DNA

📚 Practice Problems

1Problem 1easy

❓ Question:

Create a comparison table of prokaryotic and eukaryotic cells, addressing: (a) presence of membrane-bound organelles, (b) DNA organization, (c) cell size, and (d) examples of organisms in each category.

💡 Show Solution

Prokaryotic vs Eukaryotic Cells:

Feature	Prokaryotic	Eukaryotic
Nucleus	No true nucleus	Membrane-bound nucleus
DNA organization	Circular DNA in nucleoid region	Linear DNA in chromosomes, wrapped around histones
Membrane-bound organelles	Absent	Present (mitochondria, ER, Golgi, etc.)
Ribosomes	70S (smaller)	80S (larger) in cytoplasm; 70S in mitochondria/chloroplasts
Cell size	0.1-5.0 μm (smaller)	10-100 μm (larger)
Cell division	Binary fission	Mitosis/meiosis
Cytoskeleton	Simple (some have)	Complex (microtubules, microfilaments)
Cell wall	Peptidoglycan (bacteria)	Cellulose (plants), chitin (fungi), or absent (animals)

(a) Membrane-bound organelles:

Prokaryotic: ✗ No compartmentalization

All reactions occur in cytoplasm
Plasma membrane folds may increase surface area (mesosomes)

Eukaryotic: ✓ Extensive compartmentalization

Nucleus, mitochondria, ER, Golgi, lysosomes, peroxisomes
Allows specialized functions in separate compartments

(b) DNA organization:

Prokaryotic:

Single circular chromosome in nucleoid
No histones (except Archaea)
Plasmids (small circular DNA) common
Genes lack introns (continuous coding)

Eukaryotic:

Multiple linear chromosomes
DNA wrapped around histone proteins → chromatin
Genes contain introns and exons
Much more DNA (genome size 1000x larger typically)

(c) Cell size:

Prokaryotic: 0.1-5.0 μm

E. coli: ~2 μm long
Small size = high surface area to volume ratio
Efficient nutrient uptake

Eukaryotic: 10-100 μm

Human cell: ~10-30 μm
Larger, more complex
Require internal membrane systems

(d) Examples:

Prokaryotic:

Bacteria: E. coli, Streptococcus, Cyanobacteria
Archaea: Methanogens, Halophiles, Thermophiles

Eukaryotic:

Protists: Amoeba, Paramecium, Euglena
Fungi: Yeast, mushrooms
Plants: All plants
Animals: All animals

$\boxed{\text{Prokaryotes: simple, no nucleus; Eukaryotes: complex, membrane-bound organelles}}$

Explain using:

📋 AP Biology — Exam Format Guide

⏱ 3 hours📝 66 questions📊 3 sections

Section	Format	Questions	Time	Weight	Calculator
Multiple Choice	MCQ	60	90 min	50%	🚫
Free Response (Long)	FRQ	2	50 min	30%	🚫
Free Response (Short)	FRQ	4	40 min	20%	🚫

📊 Scoring: 1-5

Extremely Qualified

~14%

Well Qualified

~22%

Qualified

~24%

Possibly Qualified

~24%

No Recommendation

~16%

💡 Key Test-Day Tips

✓Focus on experimental design
✓Know data analysis
✓Practice graph interpretation

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🌍 Real-World Applications: Prokaryotic vs. Eukaryotic Cells

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Comparison of prokaryotic and eukaryotic cell structures

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