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Maintaining a constant cell environment

Maintaining a constant cell environment . I. Cells must maintain Homeostasis – (Internal State of Balance) In order to maintain homeostasis cells must be able to obtain needed materials and get rid of waste. This is accomplished through movement through the membrane known as

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Maintaining a constant cell environment

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  1. Maintaininga constant cell environment

  2. I. Cells must maintain Homeostasis – (Internal State of Balance) In order to maintain homeostasis cells must be able to obtain needed materials and get rid of waste. This is accomplished through movement through the membrane known as Cell Transport

  3. A. The job of the Cell Membrane: Controls what enters and leaves and provides protection and support This is accomplished by the lipid bilayer which is semi-permeable Double layer of lipids

  4. In addition to lipids the bilayer contains carbohydrate chains and proteins which serve as channels (tunnels) or pumps that move things across the membrane that can’t move by themselves.

  5. II. Passive Transport: If something happens automatically and does not require energy we refer to it as passive. Therefore, movement across the membrane that happens automatically and requires no work is called passive transport. So what causes something to move if it is not work Differences in concentration between 2 substances in contact.

  6. High Concentration (Molecules are close together or crowded) Low Concentration (Molecules are spread out) Far apart Permeable Membrane

  7. A. Diffusion Describe what happened to the concentration of molecules in the animation Molecules moved from high concentration (crowded) to low concentration (not crowded or spread out) across the membrane until both sides were equally distributed. The cell membrane did nothing to make this happen. This type of passive transport is Called DIFFUSION

  8. Going from High to Low does not require work or lots of energy. Think about going down the stairs or falling– no problem Gravity is a force which makes things go from high height to low height. Diffusion is a force which makes things go from high concentration to low concentration.

  9. Diffusion Only happens with molecules that are small enough to fit through the membrane!!!!! Large molecules need to find another way through the membrane.

  10. B. Osmosis is a special type of diffusion involving water • How can water have different concentrations? • Plain water is a high concentration of water molecules. • Water with another substance in it (known as a solute) such as salt is a low concentration of water • The more solute (stuff in it) the lower the concentration of the water.

  11. The water will move from high concentration to low concentration until all areas are equal (ie.. reach equilibrium) Osmosis or movement of water into or out of cell depends on the differences in concentration of water inside and outside of the cell.

  12. The cell membrane is completely permeable to water If the water in the cytoplasm of a cell contains 5% salt and the water outside contains 10% salt, which way will the water move? Out! Less salt means higher concentration of water inside the cell and therefore water will go from high to low and the cell will shrink.

  13. Remember “salt sucks”

  14. Low salt Concentration inside causes cells shrink. High salt Concentration inside causes cells to swell. Equal salt Concentrations means no change in volume

  15. Chloroplasts Vacuole

  16. Vacuoles shrunk

  17. Vacuoles Enlarged

  18. Remember Diffusion and Osmosis are both types of passive transport which means they do not require energy (ATP) from the cell

  19. C. Facilitated Diffusion Is a type of diffusion (movement from high concentration to low concentration that does not require energy) in whicha protein channel is required to help the molecule through the membrane. Sugar or glucose moves through the membrane by facilitated diffusion

  20. III. Active Transport Active transport is movement through a membrane that requires cell energy (ATP). The material needed by the cell has to be carried against the “flow” or against the concentration. Material moves from low to high

  21. Think about the work involved in going from low to high in this building. That takes work, which requires energy (ATP)

  22. Examples of active transport in cells: • 1.Sodium/Potassium Pump • Cells pump Sodium (Na+) out against forces of diffusion • Potassium (K+) in against diffusion

  23. 2. Endocytosis & Exocytosis Endocytosis is a process where the cell takes in material by infolding or making pockets in the cell membrane. Exocytosis is a process where the cell releases material

  24. All of these processes help maintain HOMEOSTASIS State of internal balance How? By bringing in the materials the cell needs and by releasing wastes

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