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Understanding Cell Membrane Transport: Diffusion, Osmosis, and Active Processes

This review explores the mechanisms by which materials move across cell membranes, focusing on diffusion, osmosis, and active transport. All cells have a cell membrane that regulates the entry of necessary materials for processes like photosynthesis and cellular respiration, as well as the exit of waste products. Diffusion allows small molecules to move from high to low concentration areas, while osmosis specifically refers to water movement. Active transport requires energy to move larger molecules against concentration gradients. Understanding these processes is crucial for grasping cellular function.

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Understanding Cell Membrane Transport: Diffusion, Osmosis, and Active Processes

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  1. Materials can move across the cell’s membrane Chapter Two – Section Three

  2. Quickie Review • All cells have a cell membrane surrounding them • Cells need STARTER materials to do different processes (photosynthesis and cellular respiration) • Cells need to get rid of Waste products and items that they make for the body

  3. Colored Water Demonstration • Describe what you saw…. • Animation: How Diffusion Works

  4. Some materials move by DIFFUSION • Diffusion is when molecules spread out from where there is a lot – to where there is not a lot. • It happens because molecules are in Constantmotion in all directions (everywhere) • Examples: • Any scent that “travels” through air • Food dye through water • Water, CO2, O traveling in and out of cells

  5. “Concentration” – page 57 • Diffusion is movement from areas of High “concentration” to areas of Low “concentration” until there is EQUILIBRIUM (balance) • The greater the difference in concentration, the faster the movement (diffusion) • Adding Salt to Ocean Water…slow diffusion • Adding Salt to Fresh Water…fast diffusion

  6. Diffusion in cells happens the same way • Small molecules (like O, H2O, CO2) can move through the cell membrane without problem • Diffusion across a Cell Membrane • This is called PASSIVE TRANSPORT – Movement with out Energy required

  7. Passive Transport in cells –No Energy needed • Most Passive Transport happens with smaller molecules (O, H2O, CO2) • Some Molecules are Large (C6H12O6) and require special “doors” to move through called “Passive Transport Proteins”

  8. H2O • H2O H20 H2O • H20 H2O • H2O H2OH2O • H2O H2O • H20 • BALANCE THIS PICTURE

  9. Second Type of Passive Transport • Osmosis • It is the “Diffusion” of Water ONLY across the cell membrane • It move on its “own” until there are the sameamount of H2O’s on each side (Equilibrium) • Example: Page 59 – Wilting plants

  10. Active Transport in cells • Opposite from Passive in that this molecule movement needsENERGY Movement from areas ofLow Concentration to areas ofHigh Concentration • This usually happens when the molecules are very LARGE in size, or when more molecules have to get out of the cell, or come in the cell • Example: Page 60 – Iguanas • Active Transport Animation

  11. Two types of Active Transport • Endocytosis • When molecules that are too big to go through the cell membrane, need to get IN the cell • Exocytosis • When molecules that are too big to go through the cell membrane, need to get OUT of the cell • Example: Plastic Bag demo • Amoeba eating

  12. end

  13. Cell Size will affect how molecules move • Almost all cells are small • Average human cell is .005mm in diameter • Lots of things need to go in and out of cell for jobs to be done. • Surface Area is needed • More surface – more exchange can take place

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