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Cell Membrane

Cell Membrane. The Boundary of the Cell . Cell Membrane - Composition. Lipid bilayer Flexible structure Phospholipid Lipid tails Phosphate heads Barrier between cell & environment. Barrier between Cell and Environment. Proteins. Molecules embedded Many different types Fluid mosaic

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Cell Membrane

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  1. Cell Membrane The Boundary of the Cell

  2. Cell Membrane - Composition • Lipid bilayer • Flexible structure • Phospholipid • Lipid tails • Phosphate heads • Barrier between cell & environment

  3. Barrier between Cell and Environment

  4. Proteins • Molecules embedded • Many different types • Fluid mosaic • Form channels and pumps • Marker proteins • tag or identification card • cells can identify each other

  5. Cell Walls • Provide support and protection for cell • Composition • Cellulose • Carbohydrate • Protein • Porous – allows easy passing of substances • Found in plants, fungi, bacteria, and prokaryotes

  6. Diffusion Through Cell Boundaries • Many things cells need are dissolved in water • Cells are mostly water

  7. Diffusion • Particles in solution move constantly • Depends upon concentration • Move from higher concentration to lower concentration • equal concentration is equilibrium • requires no energy from cell • depends on random movement of molecules

  8. Osmosis • Diffusion of water across a selectively permeable membrane • Water easily passes through membranes • Works the same as diffusion (MMHCLC) • Large molecules will not pass through

  9. Osmotic pressure • Cells must balance water loss and intake • Build up of pressure (turgor) can burst cells

  10. Concentration • Hypertonic • Higher concentration outside cell • Moves out (cell shrinks) • Hypotonic • Lower concentration outside cell • Moves in (cell inflates) • Isotonic • Equal concentration inside and outside cell • No change in pressure

  11. Hypotonic Isotonic Hypertonic

  12. Facilitated Diffusion • Some molecules too large or too strongly charged to pass through membrane • Cell “needs” these substances • Protein channels provide passage through bilayer • MMHCLC – requires no energy from cell

  13. Active Transport • Molecular transport • Pumped across by proteins in membrane • small molecules • ions • Requires energy from cell • Can go across concentration gradient

  14. Endocytosis • Endo = into cell • Endocytosis • Materials entering cell • Membrane engulfs material • Forms vacuole • Vacuole opens and releases contents

  15. Exocytosis • Exo = out of cell • Exocytosis • Materials leaving cell • Vacuole membrane fuses with cell membrane • Vacuole opens and releases contents

  16. Phagocytosis • Engulfs food particle • Requires much energy • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html

  17. Pinocytosis • Pocket formed and fills with liquid • Pinched off to form vesicle

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