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Osmosis & Diffusion

Osmosis & Diffusion. Unit 4. Diffusion Through Cell Membranes. Every living cell exists in a liquid environment. One of the functions of the cell membrane is to regulate the movement of molecules from one side of the membrane to the other.

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Osmosis & Diffusion

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  1. Osmosis & Diffusion Unit 4

  2. Diffusion Through Cell Membranes • Every living cell exists in a liquid environment. • One of the functions of the cell membrane is to regulate the movement of molecules from one side of the membrane to the other. • Diffusion-The movement of molecules from an area where they are more concentrated to an area where they are less concentrated.

  3. Diffusion

  4. Diffusion Continued • In solutions particles constantly and randomly move. • Concentration- The concentration of a solute in a given volume of solution. M/V (Examples: 12g/3L, 4g/1L) • Diffusion moves particles from an area where they are more concentrated (4g/1L) to areas of less concentration (2g/1L). • Diffusion depends upon random particle movements. • Substances diffuse without using energy. • Diffusion uses the concentration gradient to move particles instead of using energy. • The concentration gradient is the differences in concentrations from one area to another.

  5. Osmosis • Osmosis- The diffusion of water (and dissolved substances) through a selectively permeable membrane. • Works like diffusion (moves from higher to lower concentration, without energy) • The selectively permeable membrane lets some things pass through it (water) and not others (sugar). • Osmosis continues until the concentration on both sides of the membrane is the same (no gradient). • When this happens the two solutions are said to be Isotonic.

  6. Solutions • Hypertonic- High concentration of particles in solution. • Hypotonic-Low concentration of particles in solution. • Isotonic- When the concentration of particles in two solutions are the same (equal). • Osmotic Pressure- Produces net movement, this is created by the pressure on the hypertonic side of the membrane.

  7. Facilitated Diffusion • The diffusion of (larger) substances with the aid of protein channels. • Happens at a faster pace then regular diffusion. • Hundreds of different protein channels have been found, each is specific to the substances they move. • Even though facilitated diffusion is fast and specific via protein channels, it still requires a concentration gradient and doesn’t use energy.

  8. Active Transport • The movement of materials against the concentration gradient • Requires Energy • Generally carried out by transport proteins called protein pumps, that are found in the membrane. • The movement of large molecules or clumps of material can be done using this process.

  9. Types of Active Transport • Endocytosis- The process of taking material into the cell by means of inner folds, or pockets inthe cell membrane. • Exocytosis- The release of large molecules or material, vacuole membrane fuses with the cell membrane forcing the material out. • Phagocytosis- Process in which an extension of the cytoplasm surrounds and engulfs a particle. • Pinocytosis- The process of forming fluid filled vacuoles along the membrane.

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