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Cell Membrane

Cell Membrane. Cell Membrane. Boundary that separates the living cell from its’ non-living surroundings. Controls what enters and leaves the cell and provides protection and support . Selectively permeable- only allows certain things to enter and leave the cell Maintains homeostasis.

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Cell Membrane

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  1. Cell Membrane

  2. Cell Membrane • Boundary that separates the living cell from its’ non-living surroundings. • Controls what enters and leaves the cell and provides protection and support. • Selectively permeable- only allows certain things to enter and leave the cell • Maintains homeostasis

  3. Cell membrane

  4. Permeability • Permeable – anything can cross. • Impermeable–nothing can cross • Selectively permeable-(cell membrane)allows some substances to cross more easily than others.

  5. Concentration • The amount of solute (what is dissolving) per amount of solution. • The cytoplasm of the cell is one concentration • The outside of the cell is another concentration • They work to have the same concentration • Concentration gradient– occurs when there are differences in concentration. • When the concentration of the outside of the cell is the same as the concentration of the cytoplasm, the cell has reached equilibrium.

  6. Passive Transport-Diffusion/Osmosis • Osmosis occurs when water molecules move across a membrane from an area of high concentration to an area of low concentration. (with a concentration gradient). This occurs until equilibrium occurs. • Diffusion is the movement of particles from an area of high concentration to an area of low concentration. • Does not require energy.

  7. Passive Transport - Osmosis • The diffusion of water. • Hypertonic solution – a solution with a greater concentration of solute outside the cell than inside. What direction will water flow??

  8. Passive Transport - Osmosis • The diffusion of water. • Hypotonic solution– a solution with a lower concentration of solute outside the cell than inside the cell. What direction will water flow??

  9. Passive Transport - Osmosis • The diffusion of water. • Isotonic solution – a solution with a concentration of solute outside the cell equal to the concentration inside the cell. What direction will water flow??

  10. Passive Transport – Facilitated Diffusion • Diffusion of larger or highly charged molecules with the “help” of protein channels. • Does not require energy.

  11. Active Transport • Movement of particles across a membrane from an area of lower concentration to an area of higher concentration. (against the concentration gradient) • Requires energy!!

  12. Types of Active Transport • Small particles use protein pumps. • Larger particles require movement of the cell membrane. • Endocytosis– taking in material. • Phagocytosis – cell eating (taking in food) • Pinocytosis– cell drinking (taking in liquid) • Exocytosis – getting rid of waste.

  13. Structure of MembraneLipid Bi-layer *Membrane is composed of Phospholipids, Proteins, and Carbohydrates a. Phospholipids- an amphipathic molecule, which means it has both a hydrophilic region (attracts water) and a hydrophobic region (repels water). b. Proteins- embedded and dispersed throughout the membrane c. Carbohydrates

  14. proteins 2 major types: Peripheral- lies on the surface of the membrane. Transmits stimuli from outside the cell to inside the cell and influences cell shape Integral- extends through the membrane A. marker protein-(name tags) identifies cells B. Transport protein- (shipping/receiving) C. Receptor protein- (communication) interacts with other cells

  15. phospholipids Look like helium balloons They are not connected together They have a hydrophilic region (polar) which attracts water They have a hydrophobic region (non-polar) which repels water A bi-layer system Called a Fluid Mosaic Model- because it flows and has many parts that intermingle.

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