1. Cell Structure and Function
Chapter 7

2. Cell History Robert Hooke (1635-1703)
Viewed slices of cork under a crude compound microscope
He saw boxes which reminded him of cells that monks lived in
Hence the name “cell”

3. Hooke’s Microscope

4. Cell History Anton van Leeuwenhoek (1632-1723)
Designed an early microscope
First to see living organisms in a drop of water

5. Cell History Robert Brown (1773-1858)
Used special stains and dye to view nucleus

6. Cell History Theodor Schwann, zoologist, (1810-1882)
Rudolph Virchow, physician ( )
Mathias Schleiden, botanist ( )

7. Cell Theory
Schleiden, Schwann and Virchow each contributed to the cell theory (1838-9):
Cells are the basic unit of structure and function of all living things
All living things are composed of one or more cells
New cells are produced from existing cells

8. Cell Types Prokaryotic Eukaryotic
First appear in fossil record 3.5 BYA
No membrane bound organelles
Bacteria
Eukaryotic
Evolved 1.5 BYA
Have membrane bound organelles
Protists, fungi, animals, plants

9. Cell Structures Cell Wall
Found in plants, fungi, algae, and most bacteria
Rigid
Provide structure and protection
Composed of cellulose or chitin

10. Cell Structures Cell Membrane Selectively permeable Flexible
Regulates what goes in and out
Flexible
Provides protection and support
Made of a lipid bilayer

11. Cell Membrane
Regulates what goes in and out of the cell – SELECTIVE PERMEABILITY
Wastes and cell products need to exit
CO2, O2 (in plants), hormones
Nutrients need to enter
Sugar, O2, CO2 (in plants), amino acids
Lipid Bilayer

12. Phospholipids Fatty acid tails are non-polar Heads are polar
Tails don’t want to be near water because water is polar
Polar ♥ Polar
Non-polar ≠ Polar

13. Cell Membrane Fluid Mosaic Model
Fluid: in motion -Mosaic: different stuff
Outside
of cell
Inside
(cytoplasm)
Cell
membrane
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains

14. Cell Transport Substances need to cross the CM
Some molecules are small and non-polar → don’t require energy
O2, CO2
Some molecules are polar or too big to cross CM → do require energy
Proteins, sugars

15. Diffusion
Movement of molecules from an area of high concentration to low concentration
Small, non-polar molecules will diffuse across CM
DOES NOT REQUIRE ENERGY!! = Passive Transport

16. Dynamic Equilibrium Dynamic = changing, moving Equilibrium = balanced
Molecules will diffuse until dynamic equilibrium is reached
Molecules will continue to move

17. Osmosis
Diffusion of water across a membrane

18. Osmosis High water to low water Fresh water to salt water

19. Hypotonic Solution ‘Hypo-’ means less
Concentration of solute (dissolved solids) is less outside of cell than inside
Water will enter cell
Cell may lyse (burst)
Cell wall prevents lysis in plant cells

20. Hypertonic Solution ‘Hyper-’ means more
Concentration of solute is higher outside of cell
Cell will lose water
Plasmolysis results in plant cells

21. Isotonic Solution ‘Iso-’ means equal
Solute concentration is the same outside and inside the cell
No change in cell size
Animals prefer this

22. Facilitated Diffusion
Large molecules moving down their concentration gradient use a protein to facilitate (help) their crossing the CM
Diffusion = no energy!

23. Facilitated Diffusion

24. Active Transport Requires energy
Used for large molecules or substances moving against their concentration gradient (low to high)
Exocytosis – exiting cell
Endocytosis – entering cell

25. Active Transport

26. Endo- and Exocytosis

27. Levels of Organization