Lecture #8
Unicellular
Multicellular
Cell 1660 Robert Hooke
Protoplasm 1839
Johannes Purkinje
Cell Theory 1839
Matthias Schleiden and
Theodor Schwann
Continuity of Cells 1855
Rudolph Virchow
All cells existing today
can trace their ancestry
back to the earliest
living things.
1880 August Weismann
cell culture or
tissue culture
culture medium
Animal cells in tissue
culture do NOT differentiate.
Plant cells in tissue
culture DO differentiate.
Ross Harrison 1907
Nerve cells from a
salamander in a drop of
blood plasma
Organelles occur regularly
in cells, they are permanent
and they are metabolically
active.
Inclusions occur irregularly
in cells, they are not
permanent and they are
not metabolically active.
Organelles:
1. cell membrane
How things get into and
out of cells:
A. bulk flow
B. diffusion is the
movement of molecules
from an area of high
concentration to an area
of low concentration.
gradient”
Freely permeable membrane
Impermeable membrane
Selectively permeable membrane
Diffusion of a dissolved
substance through a
selectively permeable
membrane is called
dialysis.
Osmosis is the dialysis
of water.
Osmotic pressure is a
measure of the tendency
of water to flow into a
solution.
A solution with the same
osmotic pressure as the
intracellular fluid in a
cell is isotonic.
A solution with a higher
osmotic pressure than the
intracellular fluid in a
cell is hypertonic.
A solution with a lower
osmotic pressure than the
intracellular fluid in a
cell is hypotonic.
turgor pressure