Download The Cell Theory

The Cell Theory
Microscopes Provide the Windows
to the World of the Cell
The Men
• Anton Van
Leeuwenhoek
(1600’s)
• Credit for the first
microscope
• Looked at pond
water and saw
“wee beasties”
Robert Hooke
• Observed plant
stems, wood, and
cork (1600’s)
• Saw all the tiny
chambers and called
them CELLS
• What cell part did
Hooke observe?
• Cell Wall
Robert Brown (1833)
• Observed that cells had a dark structure
within plant cells
• Brown observed the nucleus
Matthias Schleiden (1838)
• Stated that all
plants are made of
Cells
• Made many
observations of
plants around the
area
Theodor Schwann (1839)
• Stated that all animals are made of Cells
• Observed many animal tissues
Rudolf Virchow (1855)
• Stated that all cells come from pre-existing
cells
• Cells arise from the division of pre-existing
cells
The Cell Theory
• All living things are
composed of cells
• Cells are the basic
unit of structure and
function in living
things
• All cells come from
pre-existing cells
Exceptions to the Cell Theory
• Viruses – are not cellular
• Mitochondria and chloroplast – each
contain genetic material and can reproduce
Endosymbiotic Theory
• What is this?
• Concerns the origins of mitochondria and
plastids (chloroplasts) from prokaryotic
cells
• Endosymbiont
• Cell that lives within another cell
Endosymbiotic Theory
• Endosymbionts gained entry to cell as
undigested prey items or parasites and began a
mutually beneficial relationship
• Occurred by endocytosis (cell parts are
engulfed)
• Over time this would turn into a single organism
whose parts are inseparable
Endosymbiotic Theory
Evidence
• Mitochondria & Plastids
• Have enzymes and transport systems that
are the same as in plasma membrane of
prokaryotes
• Also replicate by same process as certain
prokaryotes
Endosymbiotic Theory
Evidence Cont’d
• Both organelles have DNA, have
mechanisms to transcribe /translate
proteins
• Size, Nucleotide Sequence, & Sensitivity
to antibiotics are similar to prokaryotes