The Cell Theory
1. All living things are made of one or more cells.
2. Cells are the basic units of structure and function in organisms.
3. All cells arise from existing cells.
Things all cells have in common:
1. Cell membrane
2. Cytoplasm
3. DNA
Cell Types
 Prokaryotes
– Bacteria
 Eukaryotes
– Unicellular (Protozoa)
– Fungi
– Plants
– Animals
Prokaryotes
Unicellular organisms (bacteria)
No nucleus
No membrane-bound organelles
Circular DNA
Reproduce quickly – 20 minutes
Relatively small in size
Peptidoglycan cell wall
4. Ribosomes
5. Cytoskeleton
Eukaryotes
Can be single-celled or multicullular
Nucleus
Many membrane-bound organelles
Linear DNA
Cells reproduce slowly – 24+ hours
Relatively larger in size
Cell Wall (Fungi, Plants) or Not (Animals)
– Not made of peptidoglycans
Plasma/Cell Membrane = “Gatekeeper”
 Lipid Bilayer
 Filters what goes in and out
– Active Transport (Sodium)
– Facilitated Transport (Glucose)
– Passive Diffusion (Water)
 Communication with environment
Cell Wall = “Retaining wall”
 Peptidoglycans in Prokaryotes
– Targeted by antibiotics like penicillin
– Three types in bacteria:
 Gram + (Strep throat)
 Gram – (E. coli)
 Acid fast (tuberculosis)
 Also in fungi and plants
– Different chemistry (cellulose in plants)
– Provides rigid support
Nucleus = “Brain of the cell”
 Consists of:
– Nuclear membrane
– Chromatin (DNA + proteins)
– Nucleolus (rRNA  ribosomes)
 DNA replication and transcription occurs in the nucleus
 Controls all cell activities.
Centrioles = “Construction Foremen”
 Found only in animal cells
 Directs construction of the spindle during cell division
 Composed of 9 triplets of microtubules arranged in a circle.
 Come in pairs
Mitochondria = “Powerhouse of the Cell”
 ATP (energy) production occurs here
 All mitochondria come from mother
 Contain own enzymes and DNA
 Inner and Outer membrane space with Cristae in between
 May have originally been a “captured” bacterium put to use by cell
Ribosomes = “Factories of the Cell”
 Found free in cytoplasm or attached to ER
 Translate mRNA (from DNA) into protein
 Two subunits
– 50S and 30S  70S in prokaryotes
– 60S and 40S  80S in eukaryotes
– Made up of proteins and rRNA
 Not a true organelle (found in prokaryotes)
Endoplasmic Reticulum (ER) = “Highways of the Cell”
 Rough (with ribosomes)
– Membrane protein synthesis
– Transport and Vesicle formation
 Smooth (no ribosomes)
– Synthesis and metabolism of lipids
– Detoxification (lots in liver cells)
Golgi Apparatus = “UPS for the Cell”
 Processes, Packages, and Distributes
– Processing of proteins to final form
– Packaging into vesicles
– Distribution of vesicles to final destinations (secretion, membranes, etc.)
Lysosomes and Peroxisomes = “Garbage Disposal of the Cell”
 Lysosomes
– Highly acidic
– Have pH sensitive enzymes that break down proteins and lipids

Peroxisomes
– Produce and metabolize H2O2
– May impact aging? (get/leak more as you age)
Vesicles = “Transport Bins of Cell”
 Bud off of and merge with membranes
 Endocytosis – forms vesicle carrying substance into the cell
 Exocytosis – vesicle carries (secretes) substance out of the cell
Cytoskeleton = “Skeleton and motion of cell”
Three basic types:
– Microtubules
– Actin filaments
– Intermediate filaments
Centrosomes serve as microtubule organizing center
– In animals, the centrosome has two centrioles, which play role in cell division
forming the mitotic spindle
Cytosol (cytoplasm) =“Soup of the Cell”
 Made up of water, ions, and macromolecules of the cell
 Organelles float within cytosol
 Many reactions and signaling cascades take place within the cytosol
Chloroplasts =“Solar Cells of Plants”
 Synthesize Sugar from Sunlight (Photosynthesis)
 Stacked grana and thylakoid membranes filled with Chlorophyll (green pigment)
 Energy stored via the Calvin (Dark) Cycle using carbon dioxide to form sugar
Vacuoles = “Water Tower in Plants”
 Small (3 or 4) in animals; used for storage
 Membrane surrounds water or other storage materials
 Also supplies “turgor pressure” against cell wall of plants to allow them to stand up
provide structural strength
 If depleted, plants wilt
Plant Cells vs. Animal Cells
Plant Cells
Animal Cells
Have cell wall (made of
cellulose)
Have chloroplasts
No cell wall
Large central vacuole
Many small vacuoles
No centrioles
Pair of centrioles
No chloroplasts