1. Bio 178 Lecture 6 Cell Structure Sui Huang and Donald E. Ingber, http://w3.mit.edu/i-m/image2big.htm

2. Reading Chapter 5 Quiz Material Questions on P 104 Chapter 5 Quiz on Text Website (www.mhhe.com/raven7)

3. Outline Characteristics of cells Microscopy

4. Characteristics of All Cells 1. Hereditary Material Prokaryotes Nucleoid - DNA not surrounded by a membrane. Eukaryotes Nucleus - DNA is surrounded by the nuclear envelope. 2. Cytoplasm Cell matrix.

5. Characteristics of All Cells 3. Phosopholipid Bilayer boundary Plasma membrane is 5-10 nm thick and contains embedded proteins.

6. Modern Cell Theory 1. All organisms are composed of one or more cells. 2. A cell is the smallest living entity. 3. New cells arise only via division of pre-existing cells. SchleidenSchwann

7. Cell Size Most eukaryotic cells are 5-20 µm Reasons Surface to Volume Ratio 1.Cells need a large a S:V to allow transport of nutrients, gases, & waste across the plasma membrane. 2.Much easier to achieve if an organism is made of numerous small cells rather than few large cells. One Command Center per Cell The nucleus can more easily provide for the cell if the cell is small.

8. Cell Size How do large cells overcome these problems? Syncytium Skeletal Muscle http://www8.nos.noaa.gov/coris_glossary/index.aspx?letter=s

9. Cell Size How do large cells overcome these problems? Syncytium (cntd.) Soybeet syncytium induced by nematode parasite Heterodera glycines. http://www.apsnet.org/education/IllustratedGlossary/PhotosS- V/syncytium.htm

10. Cell Size How do large cells overcome these problems? Cell Shape http://www.nature.com/news/2004/040531/images/nerve_180.jpg http://web.sfn.org/content/Publications/BrainBackgrounders/communicat ion.htm

11. Cell Size How do large cells overcome these problems? Large Nuclei ES gland of Otostrongylus circumlitus (copyright J. Elson-Riggins)

12. Microscopy Resolution The minimum distance between 2 points at which they can be distinguished as separate objects. Human Eye: ~ 100 µm Light Microscope: 0.2 µm (in theory) Electron Microscope: 0.1 nm

13. Microscopy Resolution (R) R = 0.61  = 1/2 angular width cone of light rays collected by objective lens n sin  n = refractive index of medium separating object from objective and condenser lenses = wavelength William H. Heidcamp, http://homepages.gac.edu/~cellab/chpts/chpt1/figure1-3.html What limits the resolution of the light microscope?

14. LM of O. circumlitus Anterior End Copyright J. Elson-Riggins

15. Electron Microscope Transmission Electron Microscope (TEM) Electrons are transmitted through the specimen (thin section). http://euch3i.chem.emory.edu/~nmr/apk/inst rumentation.html http://www.barrettresearch.ca/teaching/ nanotechnology/nano02.htm (light) = 0.53 µm (electrons) = 0.004 nm

16. TEM (O. circumlitus ES Gland) Copyright J. Elson-Riggins

17. Scanning Electron Microscope (SEM) Electrons are reflected off the surface of the specimen - gives 3D images. Ant head http://www.ucmp.berkeley.edu/esem/gallery.html

18. Staining Specimens for Microscopy Staining increases contrast (cells are 70% water  little to impede passage of light rays/electrons). O. Circumlitus ES gland stained with PAS and aniline blue-black. Copyright J. Elson-Riggins Specific stains are used to visualize structures.

19. Staining Specimens for Microscopy Immunocytochemistry Antibodies are labeled with fluorescent molecules (or other substances) and used to stain specific structures. NANCY KEDERSHA / IMMUNOGEN / SCIENCE PHOTO, LIBRARY http://www.sciencephoto.com/images/imagePopUpDetails.html?id=771320363 Squamous carcinoma cells. Blue = Nuclei, Red = Cytoplasm, Green = Plasma membrane

23. Characteristics of Principle Cell Types 2 structurally different types of cells: PROKARYOTEEUKARYOTE True Nucleus? Membrane bound organelles? Kingdoms