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Chapter 6 A Tour of the Cell

Chapter 6 A Tour of the Cell. Campbell and Reece. Cell Theory. All living organisms are made of cells Cells are the smallest unit of structure & function in living organisms All cells come from other cells. Microscopes. 1665: Hooke sees cell walls . Anton van Leewenhoek.

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Chapter 6 A Tour of the Cell

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  1. Chapter 6A Tour of the Cell Campbell and Reece

  2. Cell Theory All living organisms are made of cells Cells are the smallest unit of structure & function in living organisms All cells come from other cells

  3. Microscopes 1665: Hooke sees cell walls

  4. Anton van Leewenhoek made best lenses of his day pond water: animalcules

  5. Light Microscopy light goes through specimen and is refracted by glass lenses so image is magnified as it is projected toward eye magnification: ratio of image size to real size resolution: a measure of clarity , the minimum distance 2 pts can be separated & seen as 2 pts (can’t do better than 200 nm) contrast: accentuate pts in different parts of specimen

  6. Light Microscopy

  7. Electron Microscopy TEM SEM beam e- thru specimen beam e- across surfaces

  8. Size Range of Cells

  9. Cell Fractionation

  10. Common to all cells cytosol ribosomes DNA plasma membrane

  11. Compare & Contrast Prokaryotic Cell Eukaryotic Cell DNA concentrated in nucleoid smaller simpler (-) internal membranes older asexual reproduction DNA in nucleus larger more complex (+) internal membranes asexual or sexual reproduction

  12. Images Prokaryotic Nucleoid Eukaryotic Nucleus

  13. Cell Size Limitations

  14. Prokaryotic Cell Details

  15. Eukaryotic Cell Details: Plant Cell

  16. Eukaryotic Cell Detail: Animal Cell

  17. Nucleus contains most of the DNA 5 microns across on average enclosed by dbl membrane: nuclear envelope

  18. Chromatin

  19. Nucleolus Nucleus Nucleolus

  20. Ribosomes rRNA & proteins carry out protein synthesis free ribosomes or ribosomes embedded in membrane polysomes: string of ribosomes

  21. Ribosomes Polysomes

  22. Anatomy of a Ribosome

  23. The Endomembrane System • includes all membranes in cell • nuclear envelope • Endoplasmic reticulum • Golgi apparatus • vesicles, vacuoles • lysosomes • plasma membrane

  24. The Endomembrane System • functions: • synthesis of proteins (ribosomes in membrane) • transport of proteins into membranes & organelles (or out of cell) • movement of lipids • detoxification of poisons • all membranes “related” either by proximity or by transfer of membrane segments via vesicles

  25. The Endomembrane System

  26. Endoplasmic Reticulum >50% of membrane in a cell “endoplasmic” means within the cytoplasm” “reticulum” means little net made of network of tubules & sacs

  27. Endoplasmic Reticulum cisternae spaces contiguous with nuclear envelope

  28. RER & SER Contiguous

  29. RER ribosomes on outer surface of membrane most proteins made shipped out of cell as polypeptide grows (into cisternae) it folds into its 2’ then 3’ structure most secretory proteins are glycoproteins so that carbohydrate attachment is done by enzymes in RER membrane

  30. RER protein made for use in cytosol kept separate from those meant for export transport vesicles carry new secretory protein/glycoprotein away from RER

  31. Secretory Vesicles

  32. SER • functions: • lipid synthesis • metabolism of carbohydrates • detoxification of drugs & poisons • storage of Ca++

  33. SER • cells with lots SER: • endocrine glands • synthesize steroid hormones • ovaries, testes, adrenals • hepatocytes • detoxify by adding –OH, increases solubility  cleared by kidneys • alcohol, drug abusers (legal or not) have increased amts of SER in their hepatocytes (also increases drug tolerance)

  34. Detox by SER

  35. SER Stores Ca++ in Muscle Fibers

  36. Golgi Apparatus receives, sorts, packages, ships also does a little modifying of proteins extensive in cells that secrete made of flattened membranous sacs with a curve (has directionality cis & trans) internal space = cisternae

  37. Golgi Apparatus

  38. Golgi Apparatus • ER products modified on trip thru Golgi • cisternae membrane has unique “team”of enzymes that moves from cisto trans • modifies the monomers in carb part of glycoproteins • modifies phospholipids destined for membrane • makes some macromolecules: • polysaccharides

  39. Golgi Apparatus

  40. Golgi Apparatus Vesicles when leave trans vesicles have molecular ID tags that indicates where they are going vesicles have receptor proteins on external surface that “recognize” where vesicle is supposed to dock (other organelles, plasma membrane)

  41. Lysosomes membranous sac filled with hydrolytic enzymes digests macromolecules use acidic pH made in RER  Golgi  cytosol

  42. Lysosome Functions digest food vacuoles ingested by phagocytosis in protists or by macrophages (WBCs that ingest bacteria or debris and recycle nutrients in them) autophagy: hydrolytic enzymes in lysosomes recycle cell’s own organic material in worn out organelles

  43. Lysosomes

  44. Lysosmes

  45. Lysosomal Storage Diseases • autosomal recessive diseases • lack a functioning hydrolytic enzyme  whatever that enzyme would have chemically broken down builds up in lysosome (called a residual body)  lysosomes fill up interferes with cell functions • example: Tay Sachs disease • lipid-digesting enzyme malfunction • affects neurons

  46. Vacuoles • are large vesicles from ER or Golgi • solution inside different from cytosol due to its selectively permeable membrane • Types: • food vacuoles • contractile vacuoles • remove excess water • in plant cells act like • lysosomes • storage bins

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