1. Cell Theory Simple statements, powerful concept:
All living organisms are made of cells
All Cells come from pre-existing cells
The organization of living things
The continuity of life

2. The Size of Cells How big is a cell??? Range from 1µm to 1mm
Which cell!!!
Range from 1µm to 1mm
What limits size?
Transport substances into and out of cells
Limited by surface area of cell
Surface area to volume ratio
Decreases as size increases

3. SA/V Cell radius (r) 1 unit 10 units 3 Surface area (4r2)
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SA/V
Cell radius (r)
1 unit
10 units 3
Surface area (4r2)
12.57 units2
1257 units2
0.3
Volume (4/3r3)
4.189 units3
4189 units3

4. Cell Types At the most basic level, cells come in one of two flavors:
Prokaryotic
Eukaryotic
These are vastly different cell types
Simple definition: presence/absence of membrane bound nucleus
Later, look at relationship to organization and evolution of life

5. Prokaryotic Cells Divided into two domains: Tend to be small (1-10 µm)
Bacteria (also called eubacteria)
Archaea
Tend to be small (1-10 µm)
Dominant life forms on the planet
Biomass
Diversity
Consider similarities of structure briefly

6. Prokaryotic Structure
No nucleus, but genetic material still compartmentalized: nucleoid
Cytoplasm: soluble cytosol and suspended particles
Few organelles: ribosomes, the universal organelle
Have Cell Wall composed of peptidoglycan (bacteria)
Have plasma membrane
May be infolded

7. Fig. 5.5 (TEArt) Pili Nucleoid (DNA) Ribosomes Flagellum Capsule
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Fig. 5.5 (TEArt)
Pili
Nucleoid (DNA)
Ribosomes
Flagellum
Capsule
Cell wall
Plasma
membrane
Cytoplasm

8. Eukaryotic Cells
All cells that contain a membrane bound nucleus (genetic material)
Animal cells
Plant cells
Fungal Cells
Protists
We will consider general features

9. Compartmentalization
The most striking feature of eukaryotic cells is compartmentalization
Different compartments perform different functions
Usually membrane bound
Organelles
“Little organs” subcellular components with a specific function
Single organism may have many specialized cell types

10. Fig. 5.8 (TEArt) Golgi apparatus Microvilli Plasma membrane
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Fig. 5.8 (TEArt)
Golgi
apparatus
Microvilli
Plasma
membrane
Actin filament
Cytoskeleton
Microtubule
Centriole
Intermediate
filament
Peroxisome
Smooth
endoplasmic
reticulum (SER)
Lysosome
Ribosomes
Nuclear
envelope
Mitochondrion
Nucleolus
Rough
endoplasmic
reticulum (RER)
Nucleus
Cytoplasm

11. Nucleus Structure: Function:
Nuclear envelope: double membrane (two bilayers)
Inner not the same as outer
Outer connected to endomembrane system
Has pores to control traffic with cytoplasm
Function:
Houses genetic information
Storage of information
Expression of genetic information starts here

12. Fig. 5.10a (TEArt) Nuclear Nucleolus envelope Nuclear pores Nuclear
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Fig. 5.10a (TEArt)
Nucleolus
Nuclear
envelope
Nuclear
pores
Nuclear
pore
Inner
membrane
Outer
membrane
Nucleoplasm

13. Fig. 5.10b

14. Endomembrane System Internal system of membranes
Endoplasmic Reticulum (ER)
Smooth (SER): no ribosomes
Lipid synthesis, synthesis of new membrane
Rough (RER): has ribosomes on surface
Protein synthesis, modify proteins
Golgi Complex
Processing and packaging of proteins
Vesicles: small sacs that “bud off” ER

15. Fig. 5.13a (TEArt) Ribosomes Rough endo- plasmic reticulum Smooth
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Fig. 5.13a (TEArt)
Ribosomes
Rough
endo-
plasmic
reticulum
Smooth
endo-
plasmic
reticulum

16. Fig. 5.13b

17. Secretory vesicles trans face cis face Transport vesicles
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Secretory
vesicles
trans face
cis face
Transport vesicles

18. Mitochondria/Chloroplasts
Involved in energy metabolism
Mitochondria is site of respiration
Chloroplast is site of photosynthesis
Structure related to function
Have double membrane
Creates internal compartment
Both arose by endosymbiosis
Once free living
Now part of “modern” cell

19. Back to Phospholipid Structure
Phospholipids are amphipathic: they have hydrophobic and hydrophilic regions
Hydrophilic regions (phosphate) orient towards water
Hydrophobic regions (hydrocarbon) orient away from water
Hydrophobic regions orient towards each other
Leads to bilayer structure

20. extracellular fluid
cytoplasm

21. Permeability of Pure Phospholipid Bilayer
What kinds of material should be able to pass through phospholipid bilayer?
Nonpolar
Small polar
What kinds of things should not be able to pass through phospholipid bilayer?
Large polar
Charged

22. Membrane Permeability
nonpolar
(hydrophobic)
O2, N2
benezene
small polar
(hydrophilic)
H2O, CO2,
urea, glycerol
large polar
(hydrophilic)
glucose, sucrose
H+, Na+, Ca2+, Mg2+, Cl-,
ions
(hydrophilic)

23. What else is in a Membrane?
Early physical analysis indicated that membranes contain proteins
Now distinguish two kinds of proteins
Integral: span the membrane
Transmembrane proteins have intra and extracellular domains
Peripheral: on one surface of membrane
Proteins necessary for function
Control traffic across membrane
Proteins allow signaling across membrane

24. Fluid Mosaic Model for Membrane
The current view of the plasma membrane was first named the Fluid Mosaic Model
Membrane lipids are not fixed, but rather are a fluid structure
Integral membrane proteins are floating in this sea of lipids
Peripheral proteins are on surface of membrane
Dynamic structure

25. Transmembrane Protein
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Extracellular fluid
Cytoplasm
Integral Protein
Transmembrane Protein
Peripheral Protein
Microfilament