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Sec. 7.4, Cellular Transport

Sec. 7.4, Cellular Transport. Main idea: Cellular transport moves substances into and out of the cell. Passive Transport (No Energy). Diffusion is the movement of particles from an area of high concentration to low concentration.

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Sec. 7.4, Cellular Transport

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  1. Sec. 7.4, Cellular Transport • Main idea: Cellular transport moves substances into and out of the cell.

  2. Passive Transport (No Energy) • Diffusion is the movement of particles from an area of high concentration to low concentration. • Diffusion is caused by molecules moving in random motion and bumping into each other. • This is called Brownian motion.

  3. Facilitated Diffusion • Some substances cannot diffuse across the plasma membrane on their own. • Facilitated diffusion uses transport proteins to move ions or small molecules across the membrane.

  4. Osmosis • The diffusion of water across the plasma membrane is called osmosis. • Often, osmosis is necessary to help cells maintain homeostasis.

  5. Tonicity • The tonicity of a cell determines how osmosis will occur. • Water always moves across the membrane toward the higher concentration of solute. • Solutions can be isotonic, hypotonic, or hypertonic to a cell.

  6. Isotonic Solution • Iso means equal. • The concentration of solute inside and outside the cell is equal. • Water moves in and out in equal amounts. • Cell maintains regular shape.

  7. Hypotonic Solution • There is a higher concentration of solute inside the cell than outside. • More water will move into the cell than out. • Cell swells and possibly bursts.

  8. Hypertonic Solution • There is a lower concentration of solute inside the cell than outside. • More water will move out of the cell than in. • Cell shrivels.

  9. Active Transport (Needs Energy) • Active transport is the movement of substances against the concentration gradient, from lower to higher concentration. • This process requires energy.

  10. Transport of Large Particles • Some substances are too large to move across the plasma membrane at all. • They enter the cell through Endocytosis. • They leave the cell through Exocytosis. • Both are active transport and require energy.

  11. Endocytosis and Exocytosis • In endocytosis the cell surrounds a substance outside the cell, engulfs it and brings it inside. • Exocytosis is the reverse of Endocytosis and is used to expel waste.

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