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CELL TRANSPORT
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Homeostasis and Transport
Homeostasis – the stable internal conditions of a living thing; maintaining a stable internal environment
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Maintaining a Balance Cells must keep the proper concentration of nutrients and water and eliminate wastes. Cells die without homeostasis. The plasma membrane is selectively permeable – it will allow some things to pass through, while blocking other things.
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Passive Transport Molecules move along a concentration gradient – the difference in concentration of the molecules in a space. 3 Types of transport: Diffusion, osmosis and facilitated diffusion
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Diffusion Diffusion – the random movement of molecules from an area of high concentration to an area of low concentration until dynamic equilibrium is reached Perfume, food coloring, O2, CO2
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Osmosis The diffusion of water across a selectively permeable membrane, from an area of higher concentration to an area of lower concentration until dynamic equilibrium is reached.
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3 types of solutions/cell environments
The direction of osmosis is determined by the type of solution a cell is in: Hypertonic – the concentration of solute molecules is higher outside the cell than inside, Hypotonic – the concentration is higher inside than outside, or Isotonic – the concentration is the same
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Cells in ISOTONIC solution
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Cells in HYPOTONIC solution
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Cells in HYPERTONIC solution
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Facilitated Diffusion
A process in which substances move down their concentration gradient across the plasma membrane with the help of transport (carrier) protein molecules. Examples: Sugars and amino acids
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Active Transport Movement of molecules and ions against the concentration gradient Moves in the direction of Low High Energy is used Example: Transport proteins bind to ions, used energy to change shape, flipping ion into cell.
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CELL TRANSPORT PASSIVE ACTIVE DIFFUSION OSMOSIS FACILITATED DIFFUSION
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Diffusion Osmosis Facilitated diffusion Active transport Takes energy? With or against the concentration gradient? Requires a protein? What kind of molecules
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Cell Membrane Organized as double layer of phospholipids called a lipid bilayer.
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Cell Membrane Phospholipids have a hydrophilic head and a hydrophobic tail Hydrophillic – water “loving” Hydrophobic – water “fearing” These interactions results in a selectively permeable membrane This helps determine what substances enter and leave the cell
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Cell Membrane Proteins are also embedded in the lipid bilayer of the cell membrane This helps recognize substances, which can pass through the cell
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