CELLULAR TRANSPORT

Homeostasis and Transport Homeostasis – the stable internal conditions of a living thing; maintaining a stable internal environment

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.

Passive Transport No energy is used by the cell to transport molecules across the cell membrane Molecules move along a concentration gradient – the difference in concentration of the molecules in a space. Diffusion, osmosis and facilitated diffusion

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

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.

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

Cells in ISOTONIC solution

Cells in HYPOTONIC solution

Cells in HYPERTONIC solution

Contractile vacuoles Organelle found in freshwater protista. Ameba, paramecium. Collects excess water continuously entering organism by osmosis. Vacuole bursts at cell surface expelling water without damaging the protista.

Facilitated Diffusion A process in which substances move down their concentration gradient across the plasma membrane with the help of transport (carrier) protein molecules. Sugars and amino acids

Active Transport Movement of molecules and ions against the concentration gradient Low  High Energy is used Transport proteins bind to ions, used energy to change shape, flipping ion into cell. Minerals from soil to plant, iodine from blood to thyroid glands.

CELL TRANSPORT PASSIVE ACTIVE DIFFUSION OSMOSIS FACILITATED DIFFUSION

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