Cell Biology

3. Cell Theory:
2.All living things are
made of one or
more cells
3.Cells are the basic
units of structure
and function in
organisms
4.All cells arise from
existing cells

5. Development of the cell theory:
•Hooke in 1663, observed cork (plant): named the cell
•Brown observed and named nucleus
•Schwann in 1800’s states: all animals are made of cells
•Schleiden in 1800’s states: all plants are made of cells
•Pasteur’s work with bacteria ~ 1860 disproved idea of
spontaneous generation (living things from nonliving)
•Virchow observes cells dividing and states all cells come from
preexisting cells

6. • A cell is the simplest structural and functional unit of life.
There are no smaller subdivisions of a cell or organism that,
in themselves, are alive.
• An organism’s structure and all of its functions are ultimately
due to the activities of its cells.
• Cells come only from preexisting cells, not from nonliving
matter. All life, therefore, traces its ancestry to the same
original cells.
• Because of this common ancestry, the cells of all species have
many fundamental similarities in their chemical composition
and metabolic mechanisms.
Importance of Cell Theory

7. Cells are small

8. Small cells are more
efficient
Surface area to volume
ratio must remain high

10. Features Common to All Cells

12. Prokaryotic Cell

27. Cell Membrane Cell Membrane
Structure and TransportStructure and Transport

28. Cell Membrane
•Defines cell boundaries
•Controls interactions with other cells
•Controls passage of materials in and out of cell
(contributes to homeostasis)
• Fluid-Mosaic model

29. Fluid Mosaic Model of Membranes

30. Membrane Proteins

31. Membrane Fluidity

32. Membrane Permeability
•Cell membranes are selectively permeable (semi-permeable)
•Some solutes cross the membrane freely, some cross with assistance, and
others do not cross at all.

34. The diffusion of water molecules through a selectively The diffusion of water molecules through a selectively
permeable membranepermeable membrane
Osmosis will continue as long as there are more water Osmosis will continue as long as there are more water
molecules on one side of the membrane (“osmotic molecules on one side of the membrane (“osmotic
pressure”)pressure”)
Water will continue to diffuse until there are equal Water will continue to diffuse until there are equal
numbers of molecules inside and outside the cell numbers of molecules inside and outside the cell
(“osmotic balance”)(“osmotic balance”)
Osmosis

35. 60% H60% H
22OO 90% H90% H
22OO

36. Water will move out of to the left Water will move out of to the left
across the membrane until across the membrane until
osmotic balance has been reachedosmotic balance has been reached

37. 100% H100% H
22OO
80% H80% H
22OO

38. 90% H90% H
22OO
90% H90% H
22OO

39. 75% H75% H
22OO
90% H90% H
22OO
Water Water
leaves the leaves the
cell and it cell and it
shrinks. This shrinks. This
is called is called
plasmolysis plasmolysis
in plant cellsin plant cells