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Chapter 5

Chapter 5. A Closer Look At Cell Membranes. Cell Membranes. Basically similar in all membranes Fluid mosaic model Mixed composition Lipids not fixed in place, can move. Cell membranes. Phospholipids Glycolipids Proteins Glycoproteins Sterols. phospholipids. Polar head, non-polar tail

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Chapter 5

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  1. Chapter 5 A Closer Look At Cell Membranes

  2. Cell Membranes • Basically similar in all membranes • Fluid mosaic model • Mixed composition • Lipids not fixed in place, can move

  3. Cell membranes • Phospholipids • Glycolipids • Proteins • Glycoproteins • Sterols

  4. phospholipids • Polar head, non-polar tail • Majority of membrane • Provides fluidity

  5. glycolipids • Carbohydrate + Phospholipid • Recognition sites

  6. sterols • Decrease membrane’s fluidity • Developmental signaling • Cholesterol • Hormones

  7. Proteins & glycoproteins • Glycoprotein = Carbohydrate + Protein • Multiple functions within cell membranes

  8. glycoproteins • Peripheral proteins • Only on surface • Cell receptor sites

  9. glycoproteins • Integral proteins • Within the membrane • Channel/Transport Proteins—allow molecules to pass across • Active • Na/K transport failure obesity • Passive • Cystic fibrosis • Adhesion Proteins—connect similar cells into tissues

  10. Glycoproteins • Communication Proteins—channels between cells • Gap junction • Receptor Proteins—Docks for chemicals that signal cell activities • Pygmies • Recognition Proteins—ID self vs. non-self • Blood tranfusion • Organ transplant

  11. glycoproteins

  12. Membrane specializations

  13. Membrane permeability • Selectively permeable • Depends on… • Size • Charge • Polarity • Concentration gradient

  14. Membrane transport • Passive—no energy used • Diffusion—movement of molecules from high to low concentration • Osmosis—movement of WATER from high to low • Concentration gradient • Active—energy used • Movement against gradient • Usually requires carrier molecule

  15. Membrane transport • Endocytosis—creating vesicle to move things into cell • Exocytosis—moving things out of cell by merging vesicle into membrane

  16. Passive tRansport • Diffusion • Movement of molecules • High to low • Simple & Facilitated • Lipid solubility

  17. Passive Transport • Osmosis • Movement of water • High to low • Semipermeable membrane • Based on solute

  18. Diffusion vs. osmosis

  19. Tonicity • Isotonic—Same solute concentration in cell & solution • Hypertonic—More solutes in solution than cell • Hypotonic—Less solutes in solution than cell

  20. tonicity

  21. Tonicity • Plants • Plasmolysis • Turgor pressure • Animals • Crenation • Lysis

  22. Active transport • Requires energy • ATP • Against a gradient • Single movement • Calcium pump • Cotransport • Sodium-potassium pump

  23. Passive vs. active

  24. Surface transport • Exocytosis • Movement of things out of cell • Vescicles • Golgi bodies

  25. endocytosis • Receptor-mediated • Substance binds to receptors, vesicle forms • Phagocytosis—“cell eating” • Engulf food • Pinocytosis—“cell drinking” • Engulf dissolved particles

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