The Tour of the Cell

1. The Tour of the Cell Chapter 6

2. The Fundamental Units of Life • All living things composed of cells • Cell structure correlated to cell function • All cells descend from existing cells

3. Microscopy • Light microscope = visible light through specimen magnified by lenses • Up to 1000X

4. Electron microscopes (EMs) • Scanning EM (SEM) focus beam of electrons onto surface  3-D image • Transmission EM (TEM) • focus beam of electrons through specimen •  internal structures

5. Gills of fish yeast • HIV

7. Cell Fractionation centrifuge separates cell components

8. TECHNIQUE Homogenization Tissue cells Homogenate Differential centrifugation

9. TECHNIQUE (cont.) 1000 g 10 min Homogenate Pellet Supernatant Supernatant poured into next tube 20,000g 20 min 80,000g 60 min 150,000g 3 hr Nuclei, debris  mitochondria  membranes  ribosomes

10. Prokaryoticcells= Archaea and Bacteria • No nucleus, no membrane-bounded organelles • DNA in nucleoidregion 0.5 µm

11. Eukaryotic cells = Plants, Animals, Fungi, Protista • DNA in nucleus • Organelles • Membrane bounded • Cytoplasm = fluid + organelles • Cytosol = fluid

12. Featured scientist: Robert Hooke 1635-1703

13. Micrographia was a best seller Best CLM of its time!

14. The famous slide: . . . I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular. . . . these pores, or cells, . . . were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this. . .

15. Features of cells 1. The plasma membrane = selective barrier allows passage of oxygen, nutrients, waste etc • Composed of phospholipid bilayer

16. 2. Surface to Volume ratio high • Small cells have greater surface area relative to volume • Larger organisms do not have larger cells than smaller organisms Human Rat

19. The Eukaryotic Cell

21. 1. The Nucleus Hela cells

22. A. Nuclear envelope (NE) • Double membrane; each a bilayer • Poresregulate entry and exit of molecules from nucleus

24. Nuclear lamina fibrous proteins maintain shape of nucleus Lamin A and lamin B can bind histones – may have role in chromosome organization

25. B. Chromatin= DNA + proteins • Chromosomes = strands of chromatin

26. C. Nucleolus • Assembles ribosomes

27. D. Nucleoplasm • Viscous fluid of nucleus

28. 2. Ribosomes: Protein Factories • Assemble amino acids into polypeptides • cytosol (free ribosomes) • RER/NE (bound ribosomes)

29. 3. The Endomembrane System • Components • Nuclear envelope • Endoplasmic reticulum (ER) • Golgi apparatus • Lysosomes • Vacuoles • *Plasma membrane

30. A. The Endoplasmic Reticulum • >half of total membrane • continuous with nuclear envelope • Smooth ER • lacks ribosomes • Synthesizes lipids • Metabolizes carbohydrates • Detoxifies poison • Stores calcium

31. Rough ER (RER) • Ribosomes assemble proteins thread through ER lumen  transport vesicles • Membrane factory

33. B. The Golgi Apparatus • flattened membranous sacs called cisternae • cis and trans face trans face (“shipping” side of Golgi apparatus)

34. Functions of the Golgi apparatus: • Modifies proteins from ER • Sorts and packages protein into transportvesicles Golgi makes polysaccharides in plants

35. Nucleus Rough ER SmoothER cisGolgi • Where do the vesicles go? Plasma membrane trans Golgi

36. Virtual cell Note: Ribosome, RER, vesicle, Golgi

37. C. Lysosomes • membranous sac of enzymes that digest macromolecules • What do they do? recycle cell components (autophagy) get rid of phagocytosed invaders form food vacuoles How do they work?

38. phagocytosis A cell engulfs another cell to form a food vacuole • lysosome fuses with food vacuole and digests molecules

39. D. Vacuoles • Food vacuoles formed by phagocytosis • Contractile vacuoles • freshwater protists • store or/and pump excess water out of cells

40. Central vacuoles • found in many plant cells • hold organic compounds and water

41. 4. Mitochondria Outer membrane • cellular respiration generates ATP (energy) • contain mtDNA • all eukaryotic cells have mt • Some have 1, some 1000s Cristae

42. mitochondrion

43. Mitochondria • outer membrane and inner membrane fold into cristae • large surface area for enzymes that synthesize ATP

44. 5. Chloroplasts (plastid) • found in plants and algae • sites of photosynthesis • green pigment chlorophyll, enzymes, other molecules

45. 6. Peroxisomes • detoxify catalase 2 H2O2 2H2O + O2 (toxic)

46. Bioflix Tour of animal cell – the big picture • Note: • Sticky extracellular matrix • Plasma membrane • Cytoskeleton • Mitochondria- ATP, surface area • Nucleus and nuclear envelope with pores • DNA and protein wrappings, code for protein • Ribosome builds protein • Endomembrane system = RER and SER + Golgi

47. 7. Cytoskeleton • Network of protein fibers organize structures and activities in cell • Anchors organelles • Maintains cell shape

48. Cytoskeleton • interacts with motor proteins to transport cargo or for movement

50. 10 µm Column of tubulin dimers 25 nm Tubulin dimer  