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Cells

Cells. Ch 3a. Cell Theory. The cell is the smallest unit of life. All organisms are composed one or more cells. New cells arise from previously existing cells. The Nature of Cells. Basic Cell Structure. Each cell has four common components: Plasma membrane Region containing DNA

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Cells

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  1. Cells Ch 3a

  2. Cell Theory • The cell is the smallest unit of life. • All organisms are composed one or more cells. • New cells arise from previously existing cells.

  3. The Nature of Cells Basic Cell Structure • Each cell has four common components: • Plasma membrane • Region containing DNA • Cytoplasm • Biochemical molecules & biochemical pathways

  4. Cell Diversity

  5. Cell

  6. Plasma Membrane Fluid mosaic model: • Working model of the membrane • Protein molecules bobbing in phospholipid sea • Proteins determine membrane’s specific functions

  7. Structure of Cell Membrane Phospholipids Most abundant lipid Polar/hydrophilic head(attracted to water) Pair of nonpolar/hydrophobic tails(repelled by water)

  8. Phospholipids Hydrophilic head Hydrophobic tails

  9. Phospholipid Bilayer Polar heads, outside & inside Nonpolar tails in the interior cell membranes

  10. Specializations of the Plasma Membrane • Microvilli- intestinal cells • Membrane Junctions • Tight junctions (impermeable) • - stomach • Desmosomes (anchor) • - skin & heart muscle • Gap junctions(communication/electrical activity) • - heart & smooth muscle

  11. Plasma Membrane Function Selectively permeable- allows certain substances to pass through By 2 ways: active or passive transport Passive- downhill Active- uphill (needs energy)

  12. Passive & Active Transport • Passive: downhill reaction • Simple diffusion • Osmosis • Facilitated diffusion • Filtration • Active: uphill reaction, needs ATP • Exocytosis • Endocytosis • - Pinocytosis • - Phagosytosis

  13. Passive Diffusion No Barrier: Substances “spread out” High concentration to low concentration e.g.: Red dye placed in glass of water

  14. Passive Diffusion Biological membrane: Substances diffuse High concentration to low concentration Pores in membrane must be large “Down the concentration gradient” Dynamic equilibrium, equal rates in both directions

  15. Facilitated Diffusion • Carrier proteins: • Bind specific molecule & change shape • Pass molecule through middle of protein

  16. Passive Diffusion • Osmosis- diffusion of a water through a semi-permeable membrane • Moves down concentration gradient e.g., Two sugar solutions of different concentrations separated by porous membrane which lets water through but not sugar What will happen?

  17. Passive Diffusion: Terms & Osmosis More concentrated to less concentrated Until concentration same on both sides: isotonic

  18. Passive Diffusion: Terms & Osmosis Concentration of solute less: solution is hypotonic. Concentration of solute greater: solution is hypertonic.

  19. Passive Diffusion: Outcomes to Living Animal Cells Animal cells No cell walls Isotonic environment: Influx of water equals the efflux of water No change in cell shape

  20. Hypotonic solution: Water enters cell Bursts, or lyses Passive Diffusion: Outcomes to Living Animal Cells Hypertonic solution: Water leaves cell Shriveled, or crenate

  21. Passive Transport: Filtration Glomerular filtration

  22. ATP Passive Transport & Facilitated Diffusion Passive transport & facilitated diffusion do NOT require

  23. ATP Active Transport: DOES require the input of outside cell Transport proteins AGAINST concentration gradient inside cell

  24. ATP

  25. Role of ATP in Energy Metabolism ATP  ADP + Pi + Energy

  26. Endocytosis

  27. Exocytosis

  28. Secretion

  29. Exocytosis mucus nuclei

  30. 1 2 3 4 Membrane Permeability Cell membrane: selectively permeable 4 factors that determine permeability lipid solubility molecular size polarity charge

  31. Lipid solubility Most important factor Hydrophobic molecules Passively diffuse Hydrocarbons, carbon dioxide, & oxygen

  32. Molecular Size and Polarity - + Molecular Size Larger molecules, less permeable Lower kinetic energy Small pore sizes in the membrane Polarity Polar molecules hydrophilic, less permeable Very small, polar uncharged (water) molecules can diffuse

  33. Charge Charged molecules hydrophilic, less permeable Surrounded by coat of water (hydration shell), increases the size

  34. Cell Organelles

  35. Nucleus

  36. Nucleus

  37. Endoplasmic Reticulum Rough and Smooth ER

  38. Ribosomes

  39. Mitochondria

  40. Golgi Complex

  41. Function of the Golgi Complex

  42. Lysosome Function • Digest food • Autophagy • Autolysis

  43. Peroxisome • Rid body of toxic substances • Contains enzymes that can oxidize various organic substances Liver cell

  44. Centrosome • Centriole pair • Assemble microtubules • Assist in cell division • 9 clusters of microtubule triplets

  45. Cytoskeleton

  46. (c) Microtubules Hollow tubes of spherical protein subunits called tubulins Tubulin subunits 25 nm Microtubules appear as gold networks surrounding the cells’ pink nuclei in this photo. Figure 3.23c

  47. Cytoskeleton

  48. Cillia & Flagella- 9x2 arrangement 0.1 micrometer

  49. Cillia & Flagella- 9x2 arrangement

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