Cells
I.
The Discovery of Cells
A.
What are cells?
1.
the foundation for all life forms; all life functions begin with
cellular processes
2.
the smallest unit that retains all the characteristics of life
3.
A collection of organelles, each with particular function, held
together by a selectively permeable membrane
B.
The Cell Theory
1.
All organisms are composed of one or more cells
a.
unicellular: one cell
b.
multicellular: many cells, often organized into
specialized tissues, organs, systems
2.
The cell is the basic unit of structure and organization of
organisms
3.
All cells come from preexisting cells.
a.
cells divide to produce two identical daughter cells
b.
disputed previous beliefs of spontaneous generation,
homonculus, etc.
C.
How we arrived at what we know:
1.
384BC - Aristotle theorized that each germ must have come
from another
2.
1665 - Robert Hooke - an English scientist ; used a
light microscope to look at thin layers of cork.
Discovered small boxes that resembled rooms at a
monestary; called these "cellulae" (small rooms)
3.
1674 - 1683 - Anton von Leeuwenhoek - a dutch
scientist designed his own microscope and discovered
what he thought were living organisms in pond water,
milk, body fluids, scrapings of scum on his teeth, etc.
4.
a.
called them "animalcules"
b.
discovered bacteria and protozoans
1668 - Francesco Redi - disproved spontaneous generation
with maggot experiments
a.
one of the first scientific experiments conducted with
proper controls and isolated variables
b.
spontaneous generation - the idea that living organisms
can originate from non-living matter
5.
1802 - Lorenz Oken began the idea of the modern cell theory
by stating that all living organisms originate from and consist
of cells
6.
1833 - Robert Brown - observed plant cells and discovered, as
well as named, the nucleus: recognized that is an essential
organelle in cells and stressed its importance in reproduction
7.
1838 - Matthias Schleiden - German scientist that looked at
plant tissue and concluded that they were composed of cells;
cells are the basic building blocks of life
8.
1839 - Theodore Scwann - German scientist that observed
animal cells and reached same conclusions as Matthias
Schleiden; showed that plant and animal cells are
fundamentally similar. Determined that cells are the basic unit
of life.
9.
1855 - Rudolf Virchow - German scientist - published research
that cells come from preexisting cells
10.
1857 - Albert Von Kolliker - discovered mitochondria
11.
1860 - Louis Pasteur - French physician that developed germ
theory and said microorganisms cause disease. Supported idea
that cells come from preexisting cells.
12.
1869 - Friedrich Meischner - isolated DNA
13.
1879 - Walther Flemming - described chromosome behavior
14.
1960's - Lynn Margulis - An American scientist that proposed
that eukaryotic cells arose from a symbiotic relationship
between prokaryotic cells (mutualism); The Endosymbiant
Theory
D.
The Endosymbiant Theory: (endo = inner; symbiant = relationship)
1.
Observed unicellular organisms and noted that some bacteria
resemble chloroplasts in size, structure, and function
(photosynthesis); some bacteria resemble mitochondria in
structure and function (cellular respiration)
2.
Both chloroplasts and mitochondria contain their own unique
DNA similar to the DNA found in prokaryotes and not like the
DNA found in eukaryotic cells; also have their own ribosomes
and reproduce independently of the cells that contain them.
3.
Reasoned that one prokaryotic cell was engulfed by another;
once inside, the cell that was engulfed processed energy for
both cells; the cell that did the engulfing provided the food
sources broken down through respiration
4.
The same was true for prokaryotes that resembled
chloroplasts; a prokaryote capable of photosynthesis was
ingested by another prokaryote and ultimately carried on the
process for both cells; in exchange, a food source for
respiration, protection, etc. was provided for the inner cell.