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Levels of Biological Organization
What is a cell?
Discovered by Robert Hooke, 1655Microscopic Analysis of cork sections
Tiny “Chambers” = “Cells”
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Wikipedia
What is the “Cell Theory”?
What defines something as “living”?
• Cells are the universal building blocks of life• Cells arise from pre-existing cells
How big is a cell?
A Sense of Scale
Figure 1-6
01_06_What can we see.jpg
“What can we see?”
“What can we see?”
Metric Units
• One meter - About Three Feet• One mm - 1/1000 of a meter• One µm - 1/1,000,000 of a meter• One nm - 1/1,000,000,000 of a meter• mm = 10-3 m• µm = 10-6 m• nm = 10-9 m
How to look at cells
• Light microscopy
• Electron microscopy
How to look at cells
• Light Microscopy– Resolution of about 0.2 m
• Resolution - How close two objects can be together and still be seen as 2 objects
Light Microscopy
Fixed and stained
Live cell
01_04_Early microscopes.jpg
The History of Cell Visualization:
Eduard Strasburger, 1880:
Modern day light microscopy:
How to Look at Cells
• Electron Microscopes• Two types:
– Scanning• 3-D image of cell’s surface• Resolution of 3 nm
– Transmission• Interior cell structure• Resolution of 2 nm
• Higher resolution because of shorter wavelength
SEM of a protozoan (single celled eukaryote)
Fig. 1-32
TEM micrograph of a killer T cell preparing to attack a large tumor cell
TEM Micrograph of Mammalian Cell
Basic Cell Anatomy
Basic Cell Anatomy
Plasma Membrane
Cytoplasm (cytosol: soluble portion)
Two major cell types
Prokaryotic
Eukaryotic
A Basic Distinction: Prokaryotic and Eukaryotic Cells “Pro” = before “Eu” = true
Distinguishing features:
The world of prokaryotes: Eubacteria and ArchaeaThe diversity of prokaryotes
The common bacterium: Escherichia
coli (E. coli)
Flagellum
Ribosomesin cytosol
DNA
PlasmaMembrane
Cell wall
Panel 1-2
Cells range in sizes
Plant vs animal vs bacterial cell size
The Eukaryotic Cell:
Nucleus
Mitochondria
(chloroplasts)
Internal Membranes generate intracellular compartmentsERGolgiLysosomesPeroxisomesVesicles
Cytosol
Cytoskeleton
Fig.1-5
Miniature Factory
Engine
• Unity within Diversity
• The role of microscopy in cell visualizationPanel 1-1, Page 8 (basics)
• The fundamental basis of cell classificationEukaryotic and Prokaryotic
• The subcellular components of the eukaryotic cellPANEL 1-2, Page 25
Key concepts you need to know
