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Cytology

Cytology. The Study of Cells. Themes. Emergent properties : interactions among cell components produces ‘life’ Structure and function : cell processes based upon ordered structures Interactions : exchange and respond to external environment Evolution : adaptations of structure.

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Cytology

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  1. Cytology The Study of Cells

  2. Themes • Emergent properties: interactions among cell components produces ‘life’ • Structure and function: cell processes based upon ordered structures • Interactions: exchange and respond to external environment • Evolution: adaptations of structure

  3. Relative sizes

  4. How Cells Are Studied • Microscope: # 1 tool • 1665 Robert Hooke; “Cells” • Magnification= how much larger object is made to appear • Resolution= minimum distance between 2 points that can still be seen as 2 points; ‘focused’

  5. How Cells Are Studied • Two types of microscopes: • Light: 1500x; light passes through lens • Electron Microscope: electrons instead of light waves (smaller) electromagnets aim electron beam

  6. How Cells Are Studied • 3 types of electron microscopes: • Transmission Electron Microscope; TEM; electrons pass through subject, 100,000x • Scanning Electron Microscope; SEM; electrons bounce off a thin gold plate on the surface of the object; 60,000x; 3d • Scanning-tunneling STM; 1,000,000 x

  7. TEM SEM

  8. How Cells Are Studied • Cell Fractionation: • Disrupt cell; centrifuge organelles to the bottom • ‘Pellet’ • Separate and isolate pellets • Study function independently

  9. Prokaryote Bacteria No nucleus (nucleoid) No membrane-bound organelles Ribosomes Eukaryote Animal, plants, fungi, protists Nucleus (DNA) Membrane-bound organelles Panoramic View of the Cell

  10. Eukaryotic Cells • Cell membrane • Cytoplasm= region (matrix) between cell membrane and nucleus • Cytosol = semi-fluid medium in the cytoplasm

  11. Eukaryotic Cells • Eukaryotes more complex than prokaryotes • More DNA • More organelles • Enables larger size due to more efficient metabolism (specialized organelles)

  12. Size of Cells • Limited by surface area /volume ratio -Volume increases 8 x faster than S.A. - Problems with diffusion • Limited by the amount of DNA • DNA must be able to keep up with demands of the cytosol

  13. Eukaryotic Cells • Compartmentalization: • Eukaryotic cells have 1000x the volume of prokaryotic cells • Need way to process cell activities • How can you create more area? • Internal membranes!!!!

  14. Increase surface area; • Specialized molecules are embedded within so they can carry on some metabolism; (chemiosmosis) • Partitions create compartments to isolate chemical reactions • Structure and function

  15. Nucleus • Nucleus:2 parts: • DNA • Nuclear envelope

  16. Nucleus • Nuclear envelope: • Phospholipid bilayer • Pores • Most of the genes • Mitochondria, chloroplasts

  17. Nucleus DNA: • Chromatin = DNA wrapped around protein (histone) • Chromosomes = coiled, condensed chromatin • Genes = sections of DNA that code for proteins

  18. Nucleus • Nucleolus: large, obvious structure in non-dividing cells • Composed of ribosomes in production • May have 2 or more per cell

  19. Nucleus • Protein synthesis: • mRNA transcribed in Nucleus • Through nuclear pores into cytoplasm • Attaches to ribosomes to be translated into amino acid sequences (primary structure)

  20. Ribosomes • Protein synthesis • Non-membrane bound (prokaryotes) • Prokaryotes have slightly different ribosome molecular structure (antibiotics tetracycline, streptomycin)

  21. Ribosomes • Free ribosomes; float in cytosol; proteins within the cell; muscle • Bound ribosomes(ER); proteins for secretion; pancreas, liver, etc

  22. Endomembrane System • Vesicles • Nuclear envelope • Endoplasmic reticulum • Golgi • Lysosomes • Vacuoles • Plasma membrane

  23. Endomembrane System • Membranes vary in structure and function • Dynamic; constantly changing in composition, behavior, and thickness

  24. Endomembrane System • Vesicles= membrane-enclosed sacs that are pinched off portions of membranes moving from one membrane to another

  25. Endomembrane System • Endoplasmic reticulum (ER) • Endo = within; reticulum = network • Network of tubules and sacs (cisternae) • Creates passages, chemical ‘laboratories’ • Continuous with outer nuclear membrane

  26. Endoplasmic Reticulum • 2types: SmoothandRough • Smooth - Makes lipids,steroidsphospholipids; adrenal glands; gonads, skin oil glands • Carbohydrate metabolism; liver, enzyme converts glycogen into glucose • Detoxifies poisons/drugs: adds OH • Store Ca for muscle contraction

  27. Endomembrane System • Rough ER: make proteins

  28. Endomembrane System • Golgi = stacked, flattened discs; sacs (cisternae) • Stores, modifies and routes products from ER • Enzymes modify products of ER • Manufactures some macromolecules (pectins) • Sorts products for secretion

  29. Endomembrane System • Lysosomes= membrane-bound organelle with hydrolytic enzymes • Lipases, carbohydrases, proteases, nucleases • Intracellular digestion - phagocytosis; • Amoeba, macrophages • Recycle - worn out organelles • Remodeling - metamorphosis

  30. Lysosome formation

  31. Endomembrane System • Vacuoles:membrane-bound sac, larger than a vesicle • 2 types and functions: • Food vacuole: phagocytosis; intracellular digestion • Water vacuoles – store water and excrete water

  32. Endomembrane System • Contractile vacuole; fresh-water protozoa (paramecium) • Excretes excess water out; osmosis

  33. Central Vacuole • Large vacuole found in plant cells • Tonoplast; membrane around vacuole • Storage - minerals, water (turgor pressure), poisons • Helps provide shape, rigidity in plant cells

  34. Other Membranous Organelles • Mitochondria and chloroplasts • Peroxisomes

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