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Diffusion and Osmosis: How does stuff get into and out of a cell?

Diffusion and Osmosis: How does stuff get into and out of a cell?. The Cell in its Environment Ch 7, Section 2 L3 Biology. Molecules are always moving. Molecules move randomly and bump into each other and other barriers. Diffusion.

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Diffusion and Osmosis: How does stuff get into and out of a cell?

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  1. Diffusion and Osmosis: How does stuff get into and out of a cell? The Cell in its Environment Ch 7, Section 2 L3 Biology

  2. Molecules are always moving • Molecules move randomly and bump into each other and other barriers

  3. Diffusion • Movement of molecules from an area of high concentration to an area of lower concentration • Continues until equilibrium is reached.

  4. Diffusion

  5. Diffusion • Occurs without control or energy use – it is called Passive Transport • Affected by: • Size of molecules • Size of pores in a membrane • Temperature • Stirring

  6. Simple Diffusion

  7. Cell Membranes are Semipermeable • Let some molecules pass through and not others. • Small molecules pass through – ex: water • Large molecules can’t pass through – ex: proteins and complex carbohydrates

  8. Which molecules will diffuse? 1 2 3 4 5 6

  9. How long does diffusion continue? • Until equilibrium is reached: • This means there will be an equal distribution of molecules throughout the space – this is why odors smell strong at first, then seem to disappear

  10. Osmosis – A Special kind of Diffusion • Diffusion of water across a selectively permeable membrane • Cytoplasm is a solution of water and solutes (stuff dissolved in the water). • Water moves into and out of cells because of the different concentrations of the solutes. • Different kinds of cells react differently to osmosis, depending on the solution they are in:

  11. Blood in different solutions:

  12. Active Transport – uses carrier molecules to move molecules from an area of lower concentration to an area of higher concentration

  13. Endocytosis • Very large molecules or substances must enter the cell by the membrane pinching inward:

  14. Pinocytosis • The cell takes in liquid droplets and forms a vacuole

  15. Phagocytosis • The cell takes in large particles

  16. Exocytosis • The cell gets rid of secretions or wastes

  17. Phagocytosis in action – phagocyte (white blood cell) going after a bacteria cell The End

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