1. Chapter 4: Cell Structure/Function

2. Compound Light Microscopy

3. Magnification Resolution capacity to distinguish as separate 2 adjacent points. Max resoultion of light microscope is 0.2 micrometers (2 points closer than 0.2 apart appear as one) Refractive Index measure of speed at which light passes through a material (staining increases the difference between refractive indexes of specimen and the medium…so contrast is increased) Brightfield illumination

4. Some microorganisms are pigmented. Most are not. Green algae Purple phototrophic bacteria

5. Staining Basic dyes (positive ion colored) Positive stains Acidic dyes (negative ion colored) Negative stains

6. Steps in smear preparation and staining

7. The Gram Stain (a differential stain)

8. Gram Stain…Positive cocci and Negative rods

9. Darkfield microscopy (specimem appears light against a black background) (good for seeing motility and very small or thin microbes) Phase Contrast (enhances differences in refractive indexes of structures, so…yields increase contrast) (good for seeing internal structures of living cells)

10. DarkfieldPhase contrastBrightfield

11. Cyanobacteria stained with fluorescent dye

12. Three-Dimensional Imaging

13. Differential Interference Contrast Microscopy

14. Atomic Force Microscope (AFM)

15. Confocal Scanning Laser Microscopy

16. Electron Microscopy

17. TEM Transmission Electron Microscopy

18. SEM Scanning Electron Microscopy

19. CELL SIZE (an upper limit is imposed by surface to volume ratio)

20. Prokaryotes and Eukaryotes compared Similarities –Genetic material –Cellular chemistry and metabolic pathways –Some structures and functions

21. Prokaryotes and Eukaryotes compared Differences (compartmentalization) –Prokaryotes DNA NOT enclosed by membrane No membrane-bound organelles No histone proteins associated with DNA Complex cell walls Division by binary fission –Eukaryotes DNA with a nucleus Membrane-bound organelles Histone proteins Cell walls absent or simple Division by mitosis

22. BASIC SHAPES Coccus Rod Spiral

23. CELL STRUCTURES

24. Cytoplasmic Membrane Phospholipid bilayer studded with proteins (Fluid Mosaic Model) Selectively permeable barrier Membrane strengthening agents Sterols in eukaryotes Hopanoids in some bacteria Archaea contain very different lipids than Eukarya and Bacteria

27. Transport across membranes Passive processes Diffusion/osmosis Facilitated diffusion Active processes

28. Cell Wall Peptidoglycan A polysaccharide which is the major component of cell walls in bacteria Archaea cell walls do not contain peptidoglycan Structure: Polysaccharide chains (glycans) cross-linked by peptide chains of amino acids. Two subunits N-Acetylglucosamine (G) and N-Acetylmuramic acid (M)

30. Gram Positive Cell Wall Thick layer peptidoglycan Teichoic acid Lipoteichoic acid

31. Gram Negative Cell wall Outer Membrane LPS-lipopolysaccharide (Endotoxin) Porins Periplasm

32. Genetic Material Nucleoid = area of the cell in which the DNA is aggregated Single circular chromosome Haploid Plasmids

33. Motility

34. Flagella Filament Hook Basal Body

35. Rotational movement of the flagella

36. Peritrichous Polar (monotrichous) Polar (lophotrichous)

38. Taxis Phototaxis Chemotaxis Positive taxis Negative taxis

39. Phototaxis: Figure shows movement of an entire colony of bacteria toward a light source at the right of the photo (not shown)

40. Ribosomes Site of protein synthesis Some structural differences between prokaryotic and eukaryotic ribosomes A major site of attack for antibiotics

41. Surface Structures

42. Fimbriae and Pili

43. S-Layers A surface layer made of protein found in many bacteria

44. Capsules and Slime Layers Glycocalx – polysaccharide-containing material outside of the cell

45. Inclusions/Storage Bodies/Granules Function in storage of energy molecules or as a reservoir of structural building blocks

46. PHB (poly-B-hydroxybutric acid) A carbon/energy storage polymer

47. Glycogen (energy storage) Metachromatic granules (inorganic phosphate reserves)

48. Sulfur Granules

49. Magnetosomes Iron-oxide crystals which allow the bacteria to respond to a magnetic field

50. Gas Vesicles Small gas filled protein structures that function to confer bouyancy on cells EM of gas vesicles  Cyanobacteria “bloom” on lake surface

51. Endospores Hardiest of all life forms For escape from unfavorable environmental conditions Germination = return to the vegetative state from the spore state NOT reproductive (1 cell forms 1 endospore which return to reform 1 cell)

54. Endosymbiont theory of Eukaryotic evolution Evidence in support of the hypothesis Mitochondria and chloroplasts contain their own DNA They contain their own ribosomes which are very similar to prokaryotes They divide independent of the cell and by binary fission Size, etc. etc