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CELLS
 Misc.:
–The smallest unit that can carry on
the process of life
–Unicellular: one celled organism
(bacteria)
–Multicellular: organism composed of
more than one cell.
CELLS
Cell Discovery
 Robert Hooke, 1665: first to name cells
observed in a thin slice of cork. “Little boxes”
reminded him of the cells monks lived in.
Observed plant cells
 Anton van Leeuvenhoek, 1675: Observed
living creatures in pond water
 Mattias Schleiden, 1838: concluded all
plants composed of cells
CELLS
Cell Discovery
 Theodor Schwann, 1839: concluded animals
composed of cells
 Rudolph Virchow, 1858: concluded that cells
come from other cells
CELLS
Cell Theory
 All living things are made up of one
or more cells
 Cells are the basic unit of structure
and function
 All cells arise from existing cells
CELLS
Cell Diversity
 Size:
– Range from 2 m long (nerves in a giraffe’s
neck) to .2 micrometers long (bacteria)
– All cells are three dimensional
– Shape is limited in size by the ratio
between volume and surface area.
 Volume increases faster than surface
area
CELLS
Cell Diversity
 Internal Organization
– Nucleus- directs all cellular activity
– Organelles- Components in cells that perform specific
functions in the cell
 Eukaryotes
– Have a nucleus and membrane bound organelles
 Prokaryotes
– No nucleus or membrane bound organelles
– Contain ribosomes