Prokaryotic vs. Eukaryotic Cells
Comparison of prokaryotic and eukaryotic cell structures
🦠 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
2Problem 2easy
❓ 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
3Problem 3easy
❓ 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
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