1. A Tour of the Cell
Chapter 6

2. You Must Know
Three differences between prokaryotic and eukaryotic cells.
The structure and function of organelles common to plant and animal cells.
The structure and function of organelles found only in plant cells or only in animal cells.

3. How We Study Cells
Biologists use microscopes and the tools of biochemistry to study cells

4. Size range of cells
Note that light microscopes can not magnify as well as electron microscopes

5. Light Microscopy (LM) vs. Electron Microscopy (EM)

6. Comparisons of Scopes Light Electron
Visible light passes through specimen
Refracts light so specimen is magnified
Magnify up to 1000X
Specimen can be alive/moving
Color
Focuses a beam of electrons through/onto specimen
Magnify up to 1,000,000 times
Specimen non-living and in vacuum
Black and white

7. Electron Microscopy Transmission (TEM) Scanning (SEM) 2-D
4/21/2017
Electron Microscopy
Transmission (TEM)
Scanning (SEM)
2-D
Creates a flat image with extreme detail
Can enhance contrast by staining atoms with heavy metal dyes
3-D
Used for detailed study of surface of specimen
Gives great field of depth

8. Studying cell structure & function
Cell fractionation - take apart cells, separate major organelles
Ultracentrifuge - applies force 1 million times the force of gravity to separate further the cell organelles with the most dense at the bottom

9. 2 Types of Cells:
Prokaryotes: Domain Bacteria & Archaea
Eukaryotes (Domain Eukarya): Protists, Fungi, Plants, Animals

10. A Prokaryotic Cell (bacteria)

11. Prokaryote Vs. Eukaryote
“before” “kernel”
No nucleus
DNA in a nucleoid
Cytosol
No organelles other than ribosomes
Small size
Primitive
i.e. Bacteria & Archaea
“true” “kernel”
Has nucleus and nuclear envelope
Cytosol
Membrane-bound organelles with specialized structure/function
Much larger in size
More complex
i.e. plant/animal cell

12. Cells must be small to maintain a large surface area to volume ratio
Large S.A. allows  rates of chemical exchange between cell and environment

13. Surface Area Example (Animal):
Small Intestine: highly folded surface to increase absorption of nutrients
Villi: finger-like projections on SI wall
Microvilli: projections on each cell

14. Folds  Villi  Microvilli

15. Surface Area Example (Plant):
Root hairs: extensions of root epidermal cells; increase surface area for absorbing water and minerals

16. Nucleus Continuous with the rough ER Function: control center of cell
Contains DNA
Surrounded by double membrane (nuclear envelope)
Continuous with the rough ER
Nuclear pores: control what enters/leaves nucleus
Chromatin: complex of DNA + proteins; makes up chromosomes
Nucleolus: region where ribosomal subunits are formed

17. Nucleus Continuous with the rough ER Contains DNA
Function: control center of cell
Surrounded by double membrane (nuclear envelope)
Continuous with the rough ER
Nuclear pores: control what enters/leaves nucleus
Chromatin: complex of DNA + proteins; makes up chromosomes
Nucleolus: region where ribosomal subunits are formed

18. Ribosomes
Function: protein synthesis
Composed of rRNA + protein
Large subunit + small subunit
Types:
Free ribosomes: float in cytosol, produce proteins used within cell
Bound ribosomes: attached to ER, make proteins for export from cell

19. Regulates protein traffic & performs metabolic functions
Endomembrane System:

20. Endoplasmic Reticulum (ER)
Network of membranes and sacs
Types:
Rough ER: ribosomes on surface
Function: package proteins for secretion, send transport vesicles to Golgi, make replacement membrane
Smooth ER: no ribosomes on surface
Function: synthesize lipids, metabolize carbs, detox drugs & poisons, store Ca2+

21. Endoplasmic Reticulum (ER)

22. Golgi Apparatus Cis face: receives vesicles Trans face: ships vesicles
Function: synthesis & packaging of materials (small molecules) for transport (in vesicles); produce lysosomes
Series of flattened membrane sacs (cisternae)
Cis face: receives vesicles
Trans face: ships vesicles

23. Lysosomes
Function: intracellular digestion; recycle cell’s materials; programmed cell death (apoptosis)
Contains hydrolytic enzymes

24. Vacuoles
Function: storage of materials (food, water, minerals, pigments, poisons)
Membrane-bound vesicles
Eg. food vacuoles, contractile vacuoles
Plants: large central vacuole -- stores water, ions

28. Parts of plant & animal cell p 108-109

30. Mitochondria Function: site of cellular respiration
Double membrane: outer and inner membrane
Cristae: folds of inner membrane; contains enzymes for ATP production; increased surface area to  ATP made
Matrix: fluid-filled inner compartment

31. Chloroplasts Function: site of photosynthesis Double membrane
Thylakoid disks in stacks (grana); stroma (fluid)
Contains chlorophylls (pigments) for capturing sunlight energy

32. Endosymbiont theory Double-membrane structure Have own ribosomes & DNA
Mitochondria & chloroplasts share similar origin
Prokaryotic cells engulfed by ancestors of eukaryotic cells
Evidence:
Double-membrane structure
Have own ribosomes & DNA
Reproduce independently within cell

33. Peroxisomes Functions: break down fatty acids; detox alcohol
Involves production of hydrogen peroxide (H2O2)

34. Cytoskeleton: network of protein fibers
Function: support, motility, regulate biochemical activities

35. 3 Types of Cytoskeleton Fibers:
Microtubules
Microfilaments
Intermediate Filaments
Protein = tubulin
Largest fibers
Shape/support cell
Track for organelle movement
Forms spindle for mitosis/meiosis
Component of cilia/flagella
Protein = actin
Smallest fibers
Support cell on smaller scale
Cell movement
Eg. ameboid movement, cytoplasmic streaming, muscle cell contraction
Intermediate size
Permanent fixtures
Maintain shape of cell
Fix position of organelles

36. Also called microtubule organizing center
Centrosomes: region from which microtubules grow
Also called microtubule organizing center
Animal cells contain centrioles

37. Cilia & Flagella Flagella: long and few; propel through water
Cilia: short and numerous; locomotion or move fluids
Have “9+2 pattern” of microtubules

38. Extracellular Matrix (ECM)
Outside plasma membrane
Composed of glycoproteins (ex. collagen)
Function: Strengthens tissues and transmits external signals to cell

39. Intercellular Junctions (Animal cells)
Tight junctions: 2 cells are fused to form watertight seal
Desmosomes: “rivets” that fasten cells into strong sheets
Gap junctions: channels through which ions, sugar, small molecules can pass

40. Plant Cells Composed of cellulose
Cell wall: protect plant, maintain shape
Composed of cellulose
Plasmodesmata: channels between cells to allow passage of molecules