Prokaryotic and Eukaryotic Cells
Levels of Organization
Biology 4(A), Biology 10(C)
Prokaryotic and Eukaryotic Cells
Learning Objectives
• Relate the levels of organization to each other and to
the whole system
• Compare and contrast prokaryotic and eukaryotic cells
(Ch. 7 of text)
Levels of Organization
• Ecologists use nested levels of organization to make
interactions clear
– Atom (hydrogen atom) Molecule (DNA molecule, water molecule) 
Cell (epithelial cell)  Tissue (similar cells working together, epithelial layer)
 Organ (different tissues working together, stomach)  Organ system
(digestive system)  organism  population  community 
ecosystem  biome  biosphere
Prokaryotic and Eukaryotic Cells
All living cells can be divided into two groups:
• Prokaryotic cells – simple cells
– Single-celled organisms (eubacteria, archaebacteria and bluegreen algae)
• Eukaryotic cells – more complex cells
– Members of Kingdoms Protista, Fungi, Plantae and Animalia
are all eukaryotes!
– Single-celled organisms (most protists)
– Compose multi-cellular organisms (few protists, fungi, plants
and animals)
Prokaryotic and Eukaryotic Cells
Eukaryotes contain
• Well-defined nucleus
• Membrane-bound
organelles
Prokaryotes contain
• No nucleus
• No membrane-bound
organelles
Nucleus
Eukaryotic Cell
Prokaryotic Cell
Similarities Between Prokaryotic
and Eukaryotic Cells
Both prokaryotic and eukaryotic cells contain
• Cell (plasma) membrane
• Cytoplasm
Cytoplasm
Cell Membrane
Eukaryotic Cell
Prokaryotic Cell
Similarities Between Prokaryotic
and Eukaryotic Cells
Both contain DNA material
• Eukaryotes – organized into chromosomes in nucleus
• Prokaryotes – circular segment of DNA in cytoplasm
and sometimes plasmids
Eukaryotic Cell
Prokaryotic Cell
Similarities Between Prokaryotic
and Eukaryotic Cells
Both prokaryotic and eukaryotic cells contain
• Ribosomes - sites of protein synthesis, composed of
RNA
Ribosomes
Eukaryotic Cell
Prokaryotic Cell
Similarities Between Prokaryotic
and Eukaryotic Cells
All prokaryotic and some eukaryotic cells contain a cell wall
• Eukaryotes – plant cell walls contain cellulose, fungi cell walls
contain chitin
• Prokaryotes – bacterial cell walls composed of amino acids and
sugars (peptidoglycan in Eubacteria)
Cell Wall
Eukaryotic Cell
Prokaryotic Cell
Similarities Between Prokaryotic
and Eukaryotic Cells
Some prokaryotic and some eukaryotic cells have flagella
• Flagella – long, hair like structures on the surface of the
cell that aids in locomotion
Flagellum
Flagellum
Eukaryotic Cell
(Euglena, Kingdom Protista)
Prokaryotic Cell
(bacteria)
Differences Between Prokaryotic
and Eukaryotic Cells
Prokaryotic Cells
• No nucleus
• No nuclear membrane
• No mitochondria
• No Golgi apparatus
• No lysosomes
• No plastids
Eukaryotic Cells
• Membrane-bound
organelles:
–
–
–
–
–
–
Nucleus
Nuclear membrane
Mitochondria
Golgi apparatus
Lysosomes
Plastids
Eukaryotic Cell Organelles
Cellular Control Center:
• Nucleus: contains DNA
*DNA in prokaryotes is found
in the cytoplasm!
Organelles that Capture
energy:
– Chloroplasts: convert
solar energy to chemical
energy stored in food
(PLANTS)
– Mitochondria: convert
chemical energy to usable
compounds
Organelles that store, cleanup and support:
– Vacuoles and vesicles:
store materials
– Lysosomes: break down
and recycle
macromolecules (rare in
plants)
– Cytoskeleton: maintains
cell shape, moves cell
parts, helps cell move
– Centrioles: cell division
(ANIMAL)
Eukaryotic Cell Organelles
Organelles that Build
Proteins:
– Ribosomes: synthesize
proteins (ALL CELLS)
– Endoplasmic Reticulum:
assembles proteins and
lipids
– Golgi Apparatus:
modifies, sorts and
packages proteins and
lipids for storage or
transport out of the cells
• Cell Boundaries:
– Cell wall: shapes,
supports and protects
cells (plant, prokaryotes,
Fungi)
– Cell Membrane:
regulates materials
entering and leaving cell;
protects and supports
cell (ALL CELLS)
Prokaryotic and Eukaryotic Cells
Greatest evolutionary advantage of eukaryotes
• Chromosomal organization of the DNA material
– Enables mitosis and meiosis to occur
• Mitosis was a prerequisite for multicellular organisms
Prokaryotic cells suited for their environment and niche
Cell Complexity
Prokaryote – “before nucleus,” simple cell
lacking nucleus
• Example: bacteria
Eukaryote – “true nucleus,” more complex
cell containing nucleus
• Example: plant cell
Which cell type evolved first?
• Theory: Prokaryotes
Bubble Theory
How did the first prokaryotes evolve?
• Theory: Bubble Theory (coacervates)
Scientific explanation:
Bubble Theory – bubble-like structures (coacervates) form
hollow spheres in water
• Form because of chemical properties
• Organic molecule produced
– Primitive cell membrane?
First Eukaryotes
How did complex eukaryotes evolve?
• Theory: Prokaryotes evolved into eukaryotes
Scientific explanation:
• Origin of nucleus and endoplasmic reticulum
– Bacteria have inward foldings of outer membranes extending
into cytoplasm
– Serve as passageways to surface
First Eukaryotes
Scientific explanation:
• Origin of nucleus and endoplasmic reticulum
– Endoplasmic reticulum –
network of internal membranes
• Evolved from these infoldings
– Nuclear envelope – extension of
ER network that isolates
and protects the nucleus
First Eukaryotes
Scientific explanation:
• Origin of mitochondria and chloroplasts
– Endosymbiotic bacteria – bacteria that live within other cells
and perform specific functions for host cells
– Endosymbiotic Theory – suggests critical stage in evolution of
eukaryotic cells involved endosymbiotic relationships with
prokaryotes
• Energy-producing bacteria reside in larger bacteria, eventually evolving
into mitochondria
• Photosynthetic bacteria live within larger bacteria, leading to evolution
of chloroplasts
First Eukaryotes
Support for endosymbiotic theory
• Presence of numerous symbiotic relationships
• Present-day mitochondria, chloroplasts, and centrioles
contain their own DNA
– Similar to DNA of bacteria in size and character
Prokaryotic and Eukaryotic Cells
Learning Objectives
• Compare and contrast prokaryotic and eukaryotic cells